Have you ever wondered if there’s a natural way to lower your high blood pressure, guard against Alzheimer's, lose weight, and feel better? Well as it turns out there is. Michael Greger, M.D. FACLM, founder of NutritionFacts.org, and author of the instant New York Times bestseller “How Not to Die” celebrates evidence-based nutrition to add years to our life and life to our years.

Evidence-Based Weight Loss

Today on the show I get to talk about one of my favorite topics, which happens to be the subject of my new book, How Not to Diet.

This episode features audio from Evidence-Based Weight Loss – Live Presentation. Visit the video page for all sources and doctor’s notes related to this podcast.


Have you ever noticed that every month seems to bring a trendy new diet? And yet obesity rates continue to rise and with it a growing number of health problems. That’s why I wrote my new book How Not to Diet. Check it out at your local public library. Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger.

Today on the show I get to talk about one of my favorite topics which happens to be the subject of my new book How Not to Diet.

(Introduction of Dr. Greger)

Surely, if there was some safe, simple, side-effect-free solution to the obesity epidemic, we would know about it by now, right? I’m not so sure.

It may take up to 17 years before research findings make it into day-to-day clinical practice. To take one example that was particularly poignant for my family: heart disease.  You know, decades ago, Dr. Dean Ornish and colleagues published evidence in one of the most prestigious medical journals in the world that our leading cause of death could be reversed with diet and lifestyle changes alone; yet, hardly anything changed. Even now, hundreds of thousands of Americans continue to needlessly die from what we learned decades ago was a reversible disease. In fact, I had seen it with my own eyes. My grandmother was cured of her end-stage heart disease by one of Dean’s predecessors, Nathan Pritikin, using similar methods.

So, if effectively the cure to our number-one killer of men and women could get lost down some rabbit hole and ignored, what else might there be in the medical literature that could help my patients, but that just didn’t have a corporate budget driving its promotion? Well, I made it my life’s mission to find out. That’s why I became a doctor in the first place and why I started my nonprofit site, NutritionFacts.org.

Everything on the website is free. There are no ads, no corporate sponsorship. It’s strictly noncommercial, not selling anything. I just put it up as a public service, as a labor of love, as a tribute to my grandmother. (Applause) New videos and articles nearly every day on the latest in evidence-based nutrition—what a concept.

Ok, so, what does the science show is the best way to lose weight? If you want testimonials and before-and-after pictures, you have come to the wrong place. I’m not interested in anecdotes; I’m interested in the evidence. When it comes to making decisions as life-and-death-important as the health and well-being of yourself and your family, there’s really only one question: What does the best available balance of evidence show right now?

The problem is that even just sticking to the peer-reviewed medical literature is not enough as, “False and scientifically misleading unsupported beliefs about obesity are pervasive” even in scientific journals. The only way to get at the truth, then, is to dive deep into the primary literature and read all the original studies themselves. But, who’s got time for that? There are more than half a million scientific papers on obesity with a hundred new ones published every day. Even researchers in the field might not be able to keep track beyond their narrow domain. But that’s what we do at NutritionFacts.org. We comb through tens of thousands of studies a year so you don’t have to. Very nice!

And indeed, we uncovered a treasure trove of buried data, like today I’ll cover simple spices, for example, proven in randomized, double-blind, placebo-controlled trials to accelerate weight loss for pennies a day, but with so little profit potential, it’s no wonder those studies never saw the light of day. The only profiting I care about, though, is your health. That’s why 100 percent of all the proceeds I receive from all of my books, and DVDs, and speaking engagements are all donated to charity. I just want to do for your family what Pritikin did for my family.

But wait, isn’t weight loss just about eating less and moving more? I mean, isn’t a calorie a calorie? That’s what the food industry wants you to think. The notion that a calorie from one source is just as fattening any other is a trope broadcast by the food industry as a way to absolve itself of culpability. Coca-Cola itself even put an ad out there emphasizing this “one simple common-sense fact.” As the current and past chairs of the Harvard’s nutrition department put it, this “central argument” from industry is that the “overconsumption of calories from carrots would be no different from overconsumption of calories from soda” If a calorie is just a calorie, why does it matter what we put in our mouths?

Let’s explore that example of carrots versus Coca-Cola. It’s true that in a tightly controlled laboratory setting, 240 calories of carrots (10 carrots) would have the same effect on calorie balance as the 240 calories in a bottle of Coke, but this comparison falls flat on its face out in the real world. You could chug those liquid candy calories in less than a minute, but eating 240 calories of carrots would take you more than two-and-a-half hours of sustained constant chewing. (Laughing) Not only would your jaw get sore, but 240 calories of carrots is like five cups. You might not even be able to fit them all in.

Our stomach is only so big. Once we fill it up, stretch receptors in our stomach wall tell us when we’ve had enough, but different foods have different amounts of calories per stomachful. Some foods have more calories per cup, per pound, per mouthful than others. This is the concept of calorie density, the number of calories in a given amount of food. Three pounds is about what the average American eats in a day. For example, oil has a high calorie density, meaning a high calorie concentration, lots of calories packed into a small space. Drizzling just a tablespoon of oil on a dish adds over a hundred calories. For those same calories, you could have instead eaten about two cups of blackberries, for example, a food with a low calorie density. So, these two meals have the same number of calories. You could swig down that spoonful of oil and not even feel anything in your stomach, but eating a couple of cups of berries could start to fill you up. That’s why yes, biochemically a calorie is a calorie, but eating the same amount of calories in different foods, can have different effects.

The average human stomach can expand to fit about four cups of food; so, a single stomachful of strawberry ice cream, for example, could max out our caloric intake for the entire day. For the same two-thousand calories, to get those same two thousand calories from strawberries themselves you’d have to eat forty-four cups of berries. That’s eleven stomachfuls. As delicious as berries are, I don’t know if I could fill my stomach to bursting eleven times a day. So some foods are just impossible to overeat. They are so low in calorie density, you just physically couldn’t eat a enough to even maintain your weight. In a lab, a calorie is a calorie, but in life, far from it.

Traditional weight-loss diets focus on decreasing portion size, but we know these “eat less” approaches can leave people feeling hungry and unsatisfied. A more effective approach may be to shift the emphasis from restriction to positive “eat more” messaging of increasing intake of healthy, low-calorie-density foods, but you don’t know, until you  put it to the test.

Researchers in Hawaii tried putting people on more of a traditional Hawaiian diet with all the plant foods they could eat, unlimited quantities of fruits, vegetables, whole grains, and beans. And, the study subjects lost an average of seventeen pounds in just twenty-one days. Calorie intake dropped by 40 percent, but not because they were eating less food. They lost seventeen pounds in three weeks eating more food, in excess of four pounds a day. How could that be? Because whole plant foods tend to be so calorically dilute, you can stuff yourself without getting the same kind of weight gain. They lost seventeen pounds in three weeks eating more food. That’s why “Low in Calorie Density” is on my list of the 17 ingredients for an ideal weight loss diet.

As noted before, Americans appear to average about three pounds of food a day. So, if you stuck with mostly these foods, you can see how you can eat more food and still shed pounds.

A landmark study found that, even when presented with the same number of calories, and the same salt, sugar, fat, fiber and protein, processed foods led to weight gain, two pounds gained over two weeks; and unprocessed foods led to weight loss, two pounds down in the same two weeks. Here’s one of their processed food meals which is probably healthier, actually, than what most people eat. Non-fat Greek yogurt, baked potato chips, sugar-free diet lemonade with a turkey sandwich has the same number of calories as this: what the unprocessed-meal-food folks were eating, kind of a southwest entrée salad with black beans, avocados, nuts. That’s the calorie density effect. Same calories but there’s just more food. No wonder it satisfied their hunger.  And they ended up four pounds lighter in two weeks eating more food.  So, how can you decrease the calorie density of your diet? Well, just a quick peek at the two extremes should suggest two methods: abandon added fats and add abandoned vegetables.

Method number one: Covertly put people on a relatively low-fat diet, and they tend to lose body fat every day even though they can eat as much as they want. If you instead give those same people the same meals, but this time sneak in enough extra fats and oils to change it to a high-fat diet, they gain body fat every day.

In fact, in a famous prison experiment in Vermont, lean inmates were overfed up to ten thousand calories a day to try to experimentally make them fat. This turned out to be surprisingly difficult. Most starting dreading breakfast and involuntarily threw it up. The researchers learned how difficult it was to have people to gain weight on purpose, unless you feed them lots of fat. To get prisoners to gain thirty pounds on a regular diet, it took about 140,000 excess calories per certain amount of body surface area. To get the same thirty-pound weight gain just by adding fat to their diets, all they had to do was feed them about an extra 40,000 calories. When the extra calories were in the form of straight fat, it took as many as a hundred thousand fewer calories to gain the same amount of weight. A calorie is not a calorie. It depends on what you eat. In this case, lowering fat content effectively made up to 100,000 calories, disappear. That’s why “Low in Added Fat” is on my list of ideal weight loss ingredients as well.

There are, however, two important exceptions. Processed foods with “reduced-fat claims” are often so packed with sugar that they can have the same number of calories as a higher fat product. SnackWell’s fat-free cookies, for example, at seventeen hundred calories per pound are as calorie-dense as a cheese danish.

The other exception is to the low-fat rule is that vegetables are so calorically dilute that even a high-fat veggie dish, like some oily broccoli with garlic sauce, tends to be less calorie dense overall, which brings us to the second strategy for lowering calorie density: instead of sneaking out fat, sneak in vegetables.

The biggest influence on calorie density is not fat, but water content. Since water adds weight and bulk without adding calories, the most calorie-dense foods and the most calorie-dense diets tend to be those that are dry. Some vegetables, on the other hand, are more than 95 percent water, and not just you know, iceberg lettuce. Cucumbers, celery, turnips, cooked napa cabbage, bok choy, summer squash, zucchini, bean sprouts, and bamboo shoots can top out at 95 percent water. They’re basically just water in vegetable form. A big bowl of water-rich vegetables is practically just a big bowl of trapped water. The effect on calorie density is so dramatic the food industry wants in on the action. They figure they could use nanotechnology to “structure a solid processed food similar to a celery stalk with self-assembled, water-filled, nanocells or nanotubes.” No need, as Mother Nature beat you to it.

When dozens of common foods, pitted head-to-head for for their ability to satiate appetites for hours, the characteristic most predictive was not how little fat or how much protein it had, but how much water it had. That was the number one predictor of how filling a food is. That’s why “High in Water-Rich Foods” is on my list, too.

Water-rich foods like vegetables, topping the charts with most more than 90% water by weight, followed by most fresh fruit, coming in around the 80s. Starchier vegetables, whole grains, and canned beans are mostly 70s, meaning three-quarters of their weight: pure water. In general, when it comes to water-rich foods, most whole plant foods float towards the top, most animal foods fall somewhere in the middle, and most processed foods sink to the bottom.

In a famous series of experiments, researchers at Penn State decided to put water-rich vegetables to the test. Study subjects were served pasta and told to eat as much or as little as they’d like. On average, they consumed about 900 calories of pasta. What do you think would happen if, as a first course, you gave them a hundred calories of salad composed largely of lettuce, carrots, cucumber, celery, and cherry tomatoes? Would they go on to eat the same amount of pasta and end up with a thousand calorie lunch, 900 plus 100? Or would they maybe eat a hundred fewer calories of pasta, effectively canceling out the added salad calories? It was even better than that. They ate more than 200 fewer calories of pasta. Thanks to the salad, a hundred calories in, 200 calories out. So, in essence, the salad had negative 100 calories. Preloading with vegetables can effectively subtract a hundred calories out of a meal. That’s how you can lose weight by eating more food.

Of course, the type of salad matters. The researchers repeated the experiment, this time adding a fatty dressing and extra shredded cheese, which quadrupled the salad’s calorie density. Now, eating this salad as a first course didn’t turn the 900-calorie meal into one with less than 800 calories. Instead, it turned it into a meal with calories in the quadruple digits. It’s like preloading pizza with garlic bread you could end up with more calories overall.

Okay, so, what’s the cut-off? Studies on preloading show that eating about a cup of food before a meal decreases subsequent intake by about 100 calories; so, to get a “negative calorie” effect, the first course would have to contain fewer than a hundred calories per cup. This includes most fresh fruits and vegetables, but having something like a dinner roll would not work.

But, hey, give people a large apple to eat before that same pasta meal, and rather than consuming two hundred calories less, it was more like three hundred calories less. So, how many calories does an apple have? It depends on when you eat it. Before a meal, an apple could effectively have about negative 200 calories.

You can see the same thing giving people vegetable soup as a first course. Hundreds of calories disappear. One study tracked people’s intake throughout the day even found that overweight subjects randomized to pre-lunch vegetable soup not only ate less lunch, but deducted an extra bonus hundred calories at dinner, too, a whole seven hours later. So, the next time you sit down to a healthy soup, you can imagine calories being veritably sucked out of your body with every spoonful.

Even just drinking two cups of water before a meal immediately caused people to cut about 20 percent of calories out of the meal, taking in more than 100 fewer calories. No wonder overweight men and women randomized to two cups of water before each meal lost weight 44 percent faster. Two cups of water before each meal, 44 percent faster weight loss. That’s why so-called “Negative Calorie Preloading” is on my list of weight loss boosters: which all the things I could find that can accelerate weight loss regardless of what you eat the rest of the time. Negative calorie preloading just means starting a meal with foods containing fewer than a hundred calories per cup. That would include many fruits, vegetables, soups, salads, or simply, a tall glass of water.

Anything we can put on that first-course salad to boost weight loss even further? Well, in my “Amping AMPK” section I talk about ways to activate an enzyme known as the “fat controller.” Its discovery is considered one of the most important medical breakthroughs in the last few decades. You can activate this enzyme through exercise, fasting, and nicotine, but is there any way to boost it for weight loss without sweat, hunger, or the whole dying-a-horrible-death-from-lung-cancer thing?

Well, Big Pharma is all over it. After all, obese individuals may be “unwilling to perform even a minimum of physical activity,” wrote a group of pharmacologists, “thus, indicating that drugs mimicking endurance exercise are highly desirable.” So, “it’s crucial that oral compounds with high bioavailability are developed to safely induce chronic AMPK activation” for “long-term weight loss and maintenance.” But, there’s no need to develop such a compound since you can already buy it at any grocery store. It’s called vinegar.

When vinegar, acetic acid is absorbed and metabolized, you get a natural AMPK boost. Enough of a boost to lose weight at the typical dose you might use dressing a salad? Well, I mean vinegar has evidently been used to treat obesity for centuries, but only recently has it been put to the test.

A randomized, double-blind, placebo-controlled trial on the effects of vinegar intake on the reduction of body fat in overweight men and women. The subjects were randomized to drink a daily beverage, one or two tablespoons of apple cider vinegar or a controlled drink developed to taste the same as the vinegar drink, but prepared with a different kind of acid so it didn’t have any actual vinegar in it. Three months in, the fake vinegar group actually gained weight (as overweight people tend to do), whereas the genuine vinegar groups significantly lost body fat, as determined by CT scan. A little vinegar every day led to pounds of weight loss achieved for just pennies a day without removing anything from their diet. That’s why one of my 21 tweaks to accelerate weight loss, is two teaspoons of vinegar with each meal, either sprinkled on your salad or even just added to tea with some lemon juice.

The beauty of the vinegar studies is that they were not just randomized, controlled trials, but placebo-controlled trials. Some studies aren’t controlled at all. Women asked to eat a ripe tomato before lunch every day for a month lost about two pounds, but without a control group you don’t know if the tomato had anything to do with it. Just being enrolled in a weight-loss study where you know they’re going to come back and weigh you again in a month can have people to change their diets in other ways. I mean it’s certainly possible. A tomato is 95 percent water; so, you’d be filling up a fist-sized portion of your stomach with only about fifteen calories before a meal, so it’s certainly possible, but we’d need a better study to prove it for weight loss.

Stronger studies have control groups. At least, for example, randomize people to a weight-loss diet with or without one to two cups of low-sodium vegetable juice and those drinking the vegetable juice lose significantly more weight. Or, split people into two groups and give half about two tablespoons of goji berries a day, and forty-five days later, the goji group appeared to cut two-and-a-half inches off their waistline compared to no change in the control group. But, any time you have one group do something special, you don’t know how much of the benefit is due to the placebo effect. In drug trials it’s easy: you give half the people the actual medication and the other half a placebo, an identical-looking sugar pill placebo. Both groups are then doing the same thing, taking identical-looking pills so, if you see any difference in outcomes, we can suspect it’s the due to the actual drug. But what would placebo broccoli look like? That’s the problem.

You can’t stuff cabbage into a capsule, but there are some foods so potent that you could actually fit them into a pill to pit them against placebos: spices. Want to know if garlic can cause weight loss? Give people some garlic powder compressed into tablets versus placebo pills. And? Garlic worked, resulting in both a drop in weight and in waistlines within six weeks. They used about a half teaspoon of garlic powder a day, which would cost less than four cents.

Four cents too steep? How about two cents a day? A quarter teaspoon of garlic powder a day, about a hundred overweight men and women were randomized to a quarter teaspoon worth of garlic powder a day or placebo, and those unknowingly taking that two cents worth of garlic powder a day lost about six pounds of straight body fat over the next fifteen weeks.

Now, if you can splurge up to three cents a day, there’s black cumin. A meta-analysis of randomized, controlled trials shows weight-loss efficacy again with just a quarter teaspoon a day. Not regular cumin, this is a completely different spice known as black cumin. What is black cumin? You obviously haven’t been reading your bibles. Described as a “miracle herb,” besides the weight loss, there are randomized controlled trials showing daily black cumin consumption significantly improves cholesterol and triglycerides significantly improves blood pressure and blood sugar control. But I use it, just cause it tastes good. I just put black cumin seeds in a pepper grinder and grind it like pepper.

With more than a thousand papers published in the medical literature on black cumin, some reporting extraordinary results like dropping cholesterol levels as much as a statin drug, why don’t we hear more about it? Why weren’t we taught about it in medical school? Presumably because there’s no profit motive. Black cumin is just a common, natural spice. You’re not going to thrill your stockholders selling something that you can’t patent, that costs three cents a day.

Or you can use regular cumin, the second most popular spice on Earth. Those randomized to a half of a teaspoon at both lunch and dinner over three-months lost about four more pounds and an extra inch off their waist, found comparable to the obesity drug known as orlistat. That’s the “anal leakage” drug you may have heard about, though the drug company evidently prefers the term “fecal spotting” to describe the rectal discharge it causes. The drug company’s website offers some helpful tips, though, “it’s probably a smart idea to wear dark pants and bring a change of clothes with you to work.” You know, just in case their drug causes you to crap your pants at work. I think I’ll stick with the cumin.

Cayenne pepper can counteract the metabolic slowing that accompanies weight loss and accelerate fat burning as a bonus. Ginger powder! Over a dozen randomized controlled trials starting at just a quarter teaspoon of ground ginger a day showing significantly decreased body weight for just pennies a day. Proven in placebo-controlled trials to work, but you probably never heard about any of this because they can’t make enough profit. Don’t get me started.

But let me go back to the Coke versus carrots example. A calorie is not a calorie because drinking this, is not the same as eating this. But even if you consumed the same number of calories, chewed for hours to pack in all those carrots, a calorie may still not be a calorie, because it’s not what you eat, it’s what you absorb. And, as anyone who’s ever eaten corn can tell you, some bits of vegetable matter can pass right through you. A calorie may still be a calorie circling your toilet bowl, but flushed calories aren’t going to make it onto your hips.

That’s where fiber comes in. If you bump people’s fiber intake up, even to just the recommended minimum daily intake they start losing weight, because they experience about a 10% drop in daily caloric intake. Why should more fiber mean fewer calories? Well first, it adds bulk without adding calories. Cold-pressed apple juice, for example, is basically just apples minus fiber. And you could chug a bottle of juice in a couple of seconds, but, I mean to get the same number of calories, you would have to eat about five cups of apple slices. That’s the difference fiber can make, but it’s not just a calorie density thing.

Imagine what happens next: The apple juice would get rapidly absorbed as soon as it spilled out of your stomach into the gut, spike your blood sugars, whereas the sugar trapped in the mass of chewed apple slices would be absorbed more slowly along the length of your intestines. Nutrients can only be absorbed when they physically come in contact with the side of your intestine, with your gut wall. Fiber never gets absorbed; so, it can act as a carrier to dilute or even eliminate calories out the other end. And fiber doesn’t just trap sugars. It acts as a fat- and starch-blocker, too.

Those on a Standard American Diet lose about 5 percent of their calories through their waste every day, but on a higher-fiber diet we can double that. It’s not what you eat, but what you absorb; so, you can lose weight on a high-fiber diet eating the exact same number of calories simply because some of those calories get trapped, get flushed down the toilet, and never make it into your system.

And it’s not just the calories in the high-fiber foods themselves that are less available. High-fiber foods trap calories across the board. So, eat a Twinkie on a high-fiber diet and you absorb fewer Twinkie calories. It’s like every calorie label you look at gets instantly discounted when you are eating lots of fiber-rich foods, which is why it makes it onto my list.

My section on other fat-blocking foods starts out with a command to “Eat Your Thylakoids”, doctor’s orders. What on earth is a thylakoid? Just the source of nearly all known life and, the oxygen we breathe, no biggie. Thylakoids are where photosynthesis takes place, the process by which plants turn light into food. Thylakoids are the great green engine of life, microscopic sac-like structures composed of chlorophyll-rich membranes concentrated in the leaves of plants.

When we eat thylakoids, when we bite into a leaf of spinach, or something, those green leaf membranes don’t immediately get digested. They last for hours in our intestines and that’s when they work their magic. Thylakoid membranes bind to lipase.  Lipase is the enzyme that our body uses to digest fat; so, you bind the enzyme – you slow fat absorption.

But, if all the fat is eventually absorbed, what’s the benefit? Location, location, location. There’s a phenomenon known as the ileal brake. The ileum is the last part of the small intestine before it dumps into your colon. When undigested calories are detected that far down in your intestines, your body thinks “I must be full from stem to stern,” and puts the brakes on eating more by dialing down your appetite. This can be shown experimentally. If you insert a nine-foot tube down people’s throats and drip in any calories: fat, sugar, or protein, and you can activate the ileal brake. So, then you sit them down to an all-you-can-eat meal and, compared to the placebo group who had only gotten a squirt of water down the tube, people eat over a hundred calories less. You just don’t feel as hungry. You feel just as full, eating significantly less. That’s the ileal brake in action.

This can then translate into weight loss. Randomize overweight women on a diet to “green-plant membranes” (in other words, just covertly slip them some powdered spinach) and they get a boost in appetite suppressing hormones, a decreased urge for sweets. Yes indeed, spinach can cut your urge for chocolate. And boom, accelerated weight loss. All thanks to eating green, the actual green itself, the chlorophyll-packed membranes in the leaves.

Now, the researchers used spinach powder just so they could create convincing placebos, but you can get just as many thylakoids eating about a half cup of cooked greens, which is what I recommend people eat two times a day in my Daily Dozen checklist of all the healthiest of healthy things I encourage people to fit into their daily routine.

In the journal of the Society of Chemical Industry, a group of food technologists argued that given their fat-blocking benefits, “thylakoid membranes could be incorporated in functional foods as a new promising appetite-reducing ingredient” or you can just get them in the way Mother Nature intended.

Which greens have the most? You can tell just by looking at them. Because thylakoids are where the chlorophyll is, the greener the leaves, the more potent the effect. So, go for the darkest-green greens you can find; where I shop that’s the lacinato (a.k.a. dinosaur) kale.

Now, if you overcook greens too long, right. You know how they turn that drab olive brown? That’s the thylakoids physically degrading, but blanched for fifteen seconds or so in steaming or boiling water, you know how greens get an even brighter green that actually translates into a boost in the fat-blocking ability. So, you can gauge thylakoid activity in the grocery store, in your kitchen with your own two eyes by going for the green.

Though thylakoids eventually get broken down, fiber makes it all the way down to our colon. While it’s technically true that we can’t digest fiber, that’s only applicable to the part of us that’s actually human. Most of the cells in our body are bacteria. Our gut flora, which weigh as much as one of our kidneys, as metabolically active as our liver, has been called our “forgotten organ,” and it’s an organ that runs on MAC, Microbiota-Accessible Carbohydrates. So, when you see me write “Eat Lots of Big MACs” I don’t want anyone to get the wrong idea. MAC is just another name for prebiotics, what our good gut flora eat, in other words, fiber. There’s that fiber again.

What do our good bacteria do with the fiber? We feed them and they feed us right back. They make short-chain fatty acids that get absorbed from the colon into our bloodstream, circulate through our body, and even make it up into our brain. That’s like the way our gut flora communicates with us, dialing down our appetite, all the while increasing the rate at which we burn fat and boosting our metabolism at the same time. All thanks to fiber.

Check this out. Put people on a brain scan and show them a high-calorie food like a donut and the reward centers in their brains instantly light up. But, if you repeat the experiment, but this time, secretly deliver fiber-derived short-chain fatty acids directly into their colon, you get a blunted reward center response and subjects report that high-calorie foods just seemed less appetizing, and subsequently ate less of an all-you-can-eat meal. But fiber supplements like Metamucil don’t work, which makes sense because they are nonfermentable, meaning our gut bacteria can’t eat them; so, yeah, they can improve bowel regularity but can’t be used by our good bacteria to make those compounds that can block our cravings. For that, we have to actually eat real food.

Our good gut bugs are trying to help us, but when we eat a diet deficient in fiber, we are in effect starving our microbial self. Less than 5 percent of Americans reach even the recommended minimum daily adequate intake of fiber, no surprise since the number one sources are beans and whole grains, and 96% of Americans don’t even reach the recommended minimum intake of legumes (which are beans, split peas, chickpeas, and lentils), and 99% don’t reach the recommended minimum for whole grains.

Most people don’t even know what fiber is. More than half of Americans surveyed think that steak is a significant source of fiber. However, by definition, fiber is only found in plants. There is zero fiber in meat, eggs, or dairy, and typically little or no fiber in processed junk, and therein lies the problem.

But wouldn’t at least the protein in that steak fill you up? Surprisingly, even a review supported by the meat, dairy, and egg industries acknowledged that protein intake does not actually translate into eating less later on, whereas you eat a fiber-rich whole grain for supper, and it can cut your calorie intake more than 12 hours later at lunch the next day! You feel full a hundred calories quicker the following day because, by then, your good gut bugs are feasting on the same bounty and dialing down your appetite.

Today, even our meat could be considered junk food. For more than a century, one of the great goals of animal agriculture has been to increase the carcass fat content of farm animals. Take chicken, for example. A hundred years ago, the USDA determined chicken was about 23 percent protein by weight and less than 2 percent fat. Today, chickens have been genetically manipulated through selective breeding to have about ten times more fat. Chicken Little has become Chicken Big and may be making us bigger too.

Meat consumption in general is associated with weight gain, but poultry appeared to be the worst. Even just an ounce a day that’s like a single chicken nugget, or like one chicken breast every ten days, was associated with weight gain compared to eating no chicken at all.

You know, it’s funny, when the meat industry funds obesity studies on chicken, they choose for their head-to-head comparison, foods like “cookies and sugar-coated chocolates.” This is a classic drug industry trick to try to make your product look better by comparing it to something worse. (Apparently, just regular chocolate wasn’t enough to make chicken look better.) But what happens when chicken is pitted against a real control, like chicken without the actual chicken? Chicken chickens out.

Both soy-based proteins and Quorn, a plant-based meat made from the mushroom kingdom, were found to have stronger satiating qualities than chicken. Feed people a chicken and rice lunch, and four-and-a-half hours later, they eat 18 percent more of a dinner buffet than had they instead been given a chicken-free chicken and rice lunch. These findings are consistent with childhood obesity research that found that meat consumption seemed to double the odds of schoolchildren becoming overweight, compared to the consumption of plant-based meat products. Whole-food sources of plant protein such as beans did even better though, associated with cutting in half the odds of becoming overweight. So, that’s why I consider these kinds of plant-based meats more of a useful stepping stone towards a healthier diet, rather than the end-game goal / ideal.

Part of the reason plant-based meats may be less fattening is that they cause less of an insulin spike. A meat-free chicken like Quorn causes up to 41 percent less of an immediate insulin reaction. It turns out animal protein causes almost exactly as much insulin release as pure sugar. Just adding some egg whites to your diet can increase insulin output as much as as 60 percent within four days. And fish may be even worse.

Why would adding tuna to mashed potatoes spike up insulin levels, but adding broccoli instead cut the insulin response by about 40 percent? It’s not the fiber, since giving the same amount of broccoli fiber alone provided no significant benefit. So, why does animal protein make things worse but plant protein makes things better?

Plant proteins tend to be lower in the branched-chain amino acids which are associated with insulin resistance, the cause of type 2 diabetes. You can show this experimentally. Give some vegans branched-chain amino acids, and you can make them as insulin resistant as omnivores. Or, take some omnivores and put them through even a “48-hour vegan diet challenge,” and, within two days, you can see the opposite, significant improvements in metabolic health.

Why? Because decreased consumption of branched-chain amino acids improves metabolic health. Check this out. Those randomized to restrict their protein intake were averaging literally hundreds more calories a day; so, they should have become fatter right? But no, they actually lost more body fat. Restricting their protein enabled them to eat more calories, while at the same time they lost more weight. More calories, yet a loss in body fat. And this magic “protein restriction”? They were just having people eat the recommended amounts of protein. So, maybe they should have just called this group the normal protein group, or the recommended protein group, and the group that was eating more typical American protein levels and suffering because of it, the excess protein group.

Given the metabolic harms of excess branched-chain amino acid exposure, leaders in the field have suggested the invention of drugs to block their absorption, to “promote metabolic health and treat diabetes and obesity without reducing caloric intake.” Or, we can just try not to eat so many branched-chain amino acids in the first place. They are found mostly in meat, including chicken and fish, dairy products, and eggs, perhaps explaining why animal protein has been associated with higher diabetes risk, whereas plant protein appears protective. So, defining the “appropriate upper limits” of animal protein intake “may offer a great chance for the prevention of T2D and obesity,” but it need not be all or nothing. Even an intermittent vegan diet has been shown to be beneficial.

If there was one piece of advice, it would be: “Wall Off Your Calories.” Animal cells are encased only in easily digestible membranes, which allows the enzymes in our gut to effortlessly liberate the calories within a steak, for example. Plant cells, on the other hand, have cell walls that are made out of fiber, which present an indigestible physical barrier; so, many of the calories remain trapped. Now, processed plant foods; however,  fruit juice, sugar, refined grains, even whole grains if they have been powdered into flour have had their cellular structure destroyed, their cell walls cracked open and their calories are free for the taking. But when you eat structurally intact plant foods, chew all you want, you’re still going to end up with calories completely surrounded by fiber, which then blunts the glycemic impact, activates the ileal brake, and delivers sustenance to your friendly flora. So, bottom line, try to make sure as many of your calories as possible, your protein, your carbs, your fat are encased in cell walls, in other words from whole, intact plant foods.

That’s what nature intended to happen. Millions of years before we learned how to sharpen spears and mill grains and boil sugar cane, our entire physiology is presumed to have evolved in the context of eating what the rest of our great ape cousins eat: plants. The Paleolithic period, when we started using tools, only goes back about two million years. We and other great apes have been evolving since back in the Miocene era, more like twenty million years ago. So, for the first 90 percent of our hominoid existence, our bodies evolved on mostly plants. It’s no wonder then that our bodies may thrive best on the diet we were designed to eat. So, maybe we should go back to our roots. (clears throat)

With enough portion control, anyone can lose weight. Lock someone in a closet, and you can force them to lose as much body fat as you want. Chaining someone to a treadmill could probably have a similar effect. But, what is the most effective weight-loss regimen that doesn’t involve calorie restriction or exercise or a felony? I scoured through the medical literature and all the randomized controlled trials and the single most successful strategy to date is a diet of whole plant foods. The single most effective weight loss intervention like that ever published in the peer-reviewed medical literature, a whole food, plant-based diet. That works better than anything else studied to date. And, no wonder given what we just learned about fiber and branched-chain amino acids.

I mean, we’ve known for more than forty years that those eating predominantly plant-based diets weigh, on average, about thirty pounds less than the general population, but you don’t know if it’s the diet itself, until you put it to the test.

In 2017, a group of New Zealand researchers published the BROAD study, a twelve-week randomized controlled trial in the poorest region of the country with the highest obesity rates. Overweight individuals were randomized to receive either standard medical care or semi-weekly classes offering advice and encouragement to eat a low-fat diet centered around fruits, vegetables, whole grains, and legumes. And that’s all it was, just empowerment, and information, empowerment with knowledge. No meals were provided, the intervention group was merely informed about the benefits of plant-based living and encouraged to fit it into their own lives at home.

No significant change in the control group, but the plant-based intervention group, even though there were no restrictions on portions and being able to eat freely all the healthy foods they wanted, lost an average of nineteen pounds by the end of the three-month study. Nineteen pounds is a respectable weight loss, but what happened next? At the end of those twelve weeks, class was dismissed, and no more instruction was given.

The researchers were curious to see how much weight the subjects had gained back after being released from the study; so, everyone was invited back at the six-month mark to get re-weighed. The plant-based group had left the three-month study nineteen pounds lighter on average. But, you know, six months later they were only down about twenty-seven pounds! They got better. The plant-based group had been feeling so good both physically and mentally and had been able to come off so many of their medications, that they were sticking to the diet on their own and the weight continued to come off.

What about a year later? Even in studies that last a whole year, where people are coached to stay on a particular diet for the entire years’ time, by the end of the year, any initial weight lost typically tends to creep on back. The BROAD study only lasted three months, yet after it was all over, those who had been randomized to the plant-based group not only lost dozens of pounds, but they kept it off.

They not only achieved greater weight loss at six and twelve months than any other comparable trial that was months after the study had already ended! A whole food, plant-based diet achieved the greatest weight loss ever recorded compared to any other such intervention published in the scientific literature. You can read the record-breaking study yourself for free, in full, at nature.com/articles/nutd20173.

Any diet that results in reduced calorie intake can result in weight loss. Dropping pounds isn’t so much the issue. The problem is keeping them off. A key difference between plant-based nutrition and more traditional approaches to weight loss is that people are encouraged, on plant-based diets, to eat ad libitum, meaning eat as much as they want. No calorie counting, no portion control just eating. The strategy is to improve the quality of the food rather than restricting the quantity of the food.

If you put people on a diet packed with fruits, vegetables, whole grains, and beans and allow them to eat as much as they want, they end up eating about 50% fewer calories than they might have otherwise. Just as full on half the calories. Wait, how can you keep people satisfied cutting more than a thousand calories from their daily diet? By eating more high-bulk, low-calorie-density foods (vegetables, fruits, whole grains, and beans) and fewer calorie-dense foods, like meats, cheeses, sugars, and fats.

But it may not just be the calories-in side of the equation; those eating more plant-based appear to be effectively burning more calories in their sleep. The resting metabolic rate of those eating more plant-based may be 10% higher, or more; a boosted metabolism that can translate into burning off hundreds of extra calories a day more without doing a thing. Eating more plant-based you burn more calories just existing. So, no wonder why those who eat more plant-based tend to be slimmer. Start packing your diet with real foods that grow out of the ground, and the pounds should come off naturally, taking you down towards your ideal weight.

OK, so that’s what I spent the first half of the book doing, laying out the optimum weight-loss diet, “Plant Yourself.” Then I spend the second half of the book on all the tools I unearthed to drive further weight loss for any stubborn pounds that remain.

We already learned that a calorie is not necessarily a calorie. A hundred calories of chickpeas has a different impact than a hundred calories of chicken or Chiclets, based on factors like absorption and appetite, but in the second half I go a step further and explore how even the exact same foods eaten differently can have different effects. Even if you eat the same amount, even if you absorb the same amount, a calorie may still not be a calorie. It’s not only what we eat, but how and when.

Just to give you a taste, the exact same number of calories at breakfast are significantly less fattening than the same number of calories at dinner. What?! That’s just mind-blowing. Same calories, different weight loss. A diet with a bigger breakfast causes more weight loss than the same diet with a bigger dinner. So, my recommendation to stop eating after 7 PM is not just because, you know, I’m afraid people are mindlessly snacking on the couch or something. The same snack at night is literally more fattening than eating the exact same snack during the daytime, all thanks to our circadian rhythms, our “Chronobiology.” Something I spend a whole chapter on.

Some of the sleep data is really crazy too. Overweight adults were randomized to eight weeks of either a calorie-restricted diet or the same diet combined with five days a week of just one less hour of sleep a night. Now, they ended up sleeping an hour later on the weekends. So, overall, they just cut three hours of sleep out of their week. Now, surely 3 hours a week of sleep difference is not going to change how much weight they lost, right? And on the scale that was true. But in the normal sleep group, 80 percent of the weight loss was fat, whereas in the group missing just a few hours of sleep, it was the opposite, with 80 percent of the loss being lean body mass. So, you snooze you lose fat! A few hours of missed sleep seemed to totally flip fat loss on its head, but just looking at the scale you wouldn’t know it.

It’s like when people fast. Stopping eating completely for a week or two can cause more weight loss than just restricting your calories, but paradoxically, it may actually lead to less loss of body fat. Wait, how can eating fewer calories lead to less fat loss? Because during fasting your body starts cannibalizing itself and burning your own protein for fuel.

The scale made it look as though they were doing better when they were fasting, but the reality is they were doing worse. They would have lost more body fat if they had kept eating; they would have lost more body fat, eating more calories. Short-term fasting can interfere with body fat loss, not accelerate it, and you see the same thing, with the keto diet.

Body fat loss actually slows down when you switch to a ketogenic diet. Just looking at the bathroom scale, though, the keto diet seems like a smashing success, losing less than a pound a week on a regular diet to boom three-and-a-half pounds in seven days after switching to keto, but what was happening inside their bodies told a totally different story. On the ketogenic diet, their rate of body fat loss was slowed by more than half; so, most of what they were losing was water, but they were also losing protein, they were also losing lean mass. That may help explain why the leg muscles of CrossFit trainees placed on a ketogenic diet can shrink as much as 8 percent within two months.

Of course, even if keto diets worked, the point of weight loss is not to fit into a skinnier casket. People whose diets even tend to trend that way appear to significantly shorten their lives. On the other hand, even just drifting in the direction of eating more healthy plant foods is associated with living longer. Those going the other way, though, those who start out more plant-based but then add meat to their diet at least once a week not only appear to double or triple their odds of diabetes, stroke, heart disease, and weight gain, but may also suffer an associated 3.6-year drop in life expectancy. That’s going from no meat to just once-a-week meat or more.

Low-carb diets have been shown to impair artery function and worsen heart disease. Whereas, whole food, plant-based diets have been shown to actually reverse heart disease that’s what Ornish used. So, what appears to be the most effective weight-loss diet just so happens to be the only diet ever proven to reverse heart disease in the majority of patients. If my grandma didn’t have to die like that, no one’s grandma has to die like that. If that’s all a plant-based diet could do, reverse the number-one killer of men and women shouldn’t that be kind of the default diet until proven otherwise? And the fact that it can also be so effective in treating, arresting, and reversing other leading killers, like type 2 diabetes and high blood pressure, would seem to make the case for plant-based eating simply overwhelming. Only one diet has ever been shown to do all that: a diet centered around whole plant foods. You don’t have to mortgage your health to lose weight. The single healthiest diet also appears to be the most effective diet for weight loss.

After all, permanent weight loss requires permanent dietary changes healthier habits just have to become a way of life. And if it’s going to be life-long, you want it to lead to a long life. Thankfully, the single best diet proven for weight loss may just so happen to be the safest, cheapest way to eat, for the longest, healthiest life. Thank you.


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To see any graphs charts, graphics, images or studies mentioned here, please go to the Nutrition Facts Podcast landing page. There you’ll find all the detailed information you need plus links to all of the sources we cite for each of these topics.

For recipes, check out my How Not to Diet Cookbook. It’s beautifully designed, with more than 100 recipes for delicious and nutritious meals. And all proceeds I receive from the sales of my books goes to charity.

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Everything on the website is free. There’s no ads, no corporate sponsorship. It’s strictly non-commercial. I’m not selling anything. I just put it up as a public service, as a labor of love, as a tribute to my grandmother whose own life was saved with evidence-based nutrition.  Thanks for listening to Nutrition Facts. I’m your host, Dr. Michael Greger.

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