Losing Weight

Hello and welcome to Nutrition Facts – the podcast that brings you the latest in evidence-based nutrition research. I’m your host Dr. Michael Greger.

I’m often asked what my opinion is about one food or another. I know what people are asking, but you know, I’m not interested in opinions. I’m not interested in beliefs. I’m interested in the science. What does the best available balance of evidence published in the peer-reviewed medical literature show, right now. That’s why I wrote my book “How Not to die” – and why I created my nonprofit site NutritionFacts.org – and now this podcast.

Today we’re going to talk about something we’ve probably all tried – with varying degrees of success: losing weight. Anyone can lose weight in the short term on nearly any diet, but diets don’t work in the long term almost by definition because you go on them and then off of them.

So what we need is a life-long pattern of healthy eating.

In our first story we find that Americans eating meat-free diets average higher intakes of nearly every nutrient, while maintaining a lower body weight, perhaps due in part to their higher resting metabolic rates.

We know that vegetarians tend to be slimmer, but there’s this perception that veg diets may be somehow deficient in nutrients, so how’s this for a simple study—let’s just analyze the diets of 13,000 people and compare the nutrient intake of those eating meat to the those eating meat-free.

They found that those eating vegetarian were getting higher intakes of nearly every nutrient: more fiber; more vitamin A; more vitamin C; more vitamin E; more of the B vitamins (thiamin, riboflavin, & folate); more calcium, magnesium, iron, and potassium; while, at the same time, eating less of the harmful stuff, like saturated fat and cholesterol. And, yes, they got enough protein.

And, some of those nutrients are the ones Americans really struggle to get enough of—fiber, vitamins A, C, and E, calcium, magnesium, potassium—and those eating vegetarian got more of all of them. Even so, though, just because they did better than the standard American diet isn’t saying much—they still didn’t get as much as they should have. I mean, yes, those eating vegetarian ate significantly more dark green leafy vegetables—but, that comes out to just two teaspoons of greens more.

In terms of weight management, the vegetarians were consuming, on average, 363 fewer calories every day. That’s like what people do when they go on a diet and restrict their food intake. But, that seemed just like what vegetarians ate normally. So, a vegetarian diet could be considered an all-you-care-to-eat version of a calorie-restricted weight-loss diet, naturally inducing weight loss, and also helping “maintain healthy weight status long-term.” So, “[J]ust following a vegetarian diet alone, without focusing on calorie reduction, could result in…weight loss.”

How sustainable are more plant-based diets, long term? They are, in fact, among the only type of diets that have been shown to be sustainable long-term—perhaps because not only do people lose weight, but they often feel so much better.

And, there’s no calorie counting, or portion control. In fact, vegetarians may burn more calories in their sleep! Those eating more plant-based diets appear to have an 11% higher resting metabolic rate. Both vegetarians and vegans in this study just naturally seemed to have a revved-up metabolism, compared to those eating meat.

Having said that, the vegetarian diet pattern in this study included eating eggs and dairy. So, while they were significantly slimmer than those eating meat, they were still, on average, overweight. As we’ve seen before, the only dietary pattern associated with, on average, an ideal body weight was a strictly plant-based one.

Still… this study does help dispel the myth that meat-free diets are somehow nutrient deficient. In fact, in response the editor-in-chief of the Journal of the American Dietetic Association asked, what could be more nutrient dense than a vegetarian diet?

So we wanted to know – what role has inactivity played in the obesity epidemic and how much should we be exercising? Let’s look at the facts.

Right now, almost two-thirds of Americans are overweight, and by 2030 more than half our population may be clinically obese. Childhood obesity has tripled, and most of them will grow up to be overweight as well. The United States may be in the midst of raising the first generation, since our nation’s founding, that will have a shorter predicted life span than that of the previous generation.

The food industry blames inactivity. We just need to move more, but what is the role of exercise in the treatment of obesity?

There is considerable debate in the medical literature today about whether physical activity has any role whatsoever in the epidemic of obesity that has swept the globe since the 1980s. The increase in calories per person is more than sufficient to explain the U.S. epidemic of obesity. In fact, if anything, the level of physical activity over the last few decades has actually gone up in both Europe and North America.

This has important policy implications. Yes, we still need to exercise more, but the priorities for reversing the obesity epidemic should focus on the overconsumption of calories. To work off the increased calorie intake, which for kids is like an extra can of soda and small fries compared to what they were eating back in the 70s, and for adults about an extra big mac. To work that off, we’d have to walk 2 hours a day, seven days a week. So exercise can prevent weight gain, but the amount required to prevent weight gain may be closer to twice the current recommendations.

Public health advocates have been experimenting with including this kind of information. The fast food menu labeled with calories and the number of miles to walk to burn those calories appeared the most effective in influencing the selection of lower calorie meals.

Now exercise alone may have a small effect, and that small effect can make a big difference on a population scale. A 1% decrease in BMI nationwide might prevent millions of cases of diabetes and heart disease and thousands of cases of cancer.

But why don’t we lose more weight from exercise? It may be because we’re just not doing it enough. The small magnitude of weight loss observed from the majority of exercise interventions may be primarily due to low doses of prescribed exercise. People tend to overestimate how many calories are burned by physical activity. For example, there’s this myth that a bout of sexual activity burns a few hundred calories, so hey, you could get a side of fries with that. But if you actually hook people up and measure energy expenditure during the act, and your study subjects don’t get too tangled up with all the wires and hoses, though it may be nearly the metabolic equivalent of calisthenics, given that the average bout of sexual activity only lasts about 6 minutes, a young man might expend approximately 21 calories during sexual intercourse.

Of course, he would have spent roughly one third of that just lying around watching TV, just basal metabolism, so the incremental benefit is plausibly on the order of 14 calories. So maybe we could have one fry with that.

Turning now to a story about brown adipose tissue. What you may ask is that? Well – it’s a unique organ in the body that burns fat to create heat, improving temperature regulation in infants and weight loss in adults.

During World War I, it was discovered that many of the chemicals for the new explosives they were working on had toxic, or even lethal, effects on the workers in the munitions factories. Chemicals such as dinitrophenol, or DNP. It boosts metabolism so much, workers were found somewhere along the road after work, covered in sweat, with a temperature of 106º Fahrenheit, or even 109º before they died. And then even after death, their temperatures kept going up, like a total body meltdown. But at subacute doses, workers claimed to have grown thin to a notable extent after several months working with the chemical.

That got some Stanford pharmacologists excited about the “promising metabolic applications” of DNP. One dose and our resting metabolic rate jumps up 30%—an actual fat-burning drug. People started losing weight with no apparent side effects as a result of their weight-reducing treatment. On the contrary, they felt great – until thousands of people started going blind and users started dropping dead from hyperpyrexia, fatal fever from the heat created by the burning fat. Of course, it continued to be sold. “Here, at last, is a weight-reducing remedy that will bring you a figure men admire and women envy, without danger to your health or change in your regular mode of living. No diet, no exercise!” It did work, but the therapeutic index was razor thin—a razor thin difference between the effective dose and the deadly dose. It was not until thousands suffered irreversible harm that it got pulled from the market. Until, of course, it was brought back by the internet for those dying to be thin.

There is a way our body naturally burns fat to create heat, though. When we’re born, we go from a nice tropical 98.6º in our mother’s womb straight to room temperature, where we’re all wet and slimy. This represents a challenge for thermoregulation—for maintaining our warm body temperature. As an adaptive mechanism, the appearance of a unique organ around 150 million years ago allowed mammals to maintain our high body temperatures.

That unique organ is called brown adipose tissue, or BAT, whose role is to consume fat calories by generating heat in response to cold exposure. The white fat in our bellies stores fat, but the brown fat, located up between our shoulder blades, burns fat.

It’s essential for the thermogenesis, the creation of heat in newborns, but has been considered unnecessary in adults, who have higher metabolic rates and increased muscle mass for shivering to warm us up if we get cold.

So, we used to think it just shrank away when we grew up. But if it were there, then it could potentially make a big difference for how many calories we burn every day—but supposedly we outgrew it.

But when PET scans were invented to detect metabolically active tissues like cancer, oncologists kept finding hot spots in the neck and shoulder regions that on CT scans turned out to be not cancer, just fat. Then, some observant radiologists noticed they appeared in patients mostly during the cold winter months, and when we looked closer at tissue samples taken from people who had undergone neck surgery, we found it: brown fat in adults.

The common message from these studies is that BAT is present and active in adults, and the more we have, the more active it is, and the thinner we are. And we can rapidly activate our fat-burning brown fat by exposure to cold temperatures. For example, if you hang out in a cold room for two hours in your undies and put your legs on a block of ice for four minutes every five minutes, you can elicit a marked increase in energy expenditure, thanks to brown fat activation. So, these studies point to a potential “natural” intervention to stimulate energy expenditure: turn down the heat and burn calories (and reduce your carbon footprint in the process!).

But thankfully, for those of us who would rather not lay our bare legs on blocks of ice, our brown fat can also be activated by some food ingredients.”

Here’s more about those food ingredients that can activate brown fat.

Until about ten years ago, brown adipose tissue was considered to be biologically active only in babies and small children, generating heat by burning fat, but there is now no doubt that active brown fat is present in adult humans, involved in cold-induced increases in whole-body calorie expenditure, and thereby, the control of body temperature and how fat we are.

In 2013, researchers showed that one could activate brown adipose tissue by chilling people out long enough: two hours of cold exposure every day for six weeks, which can lead to a significant reduction in body fat. Although they demonstrated the effective recruitment of human brown fat, it would seem difficult to increase exposure to cold in daily life. Thankfully, our brown fat can also be activated by some food ingredients, such as capsaicin, the compound that makes hot peppers hot.

Whereas increased physical activity is usually recommended to increase energy expenditure, specific food components, such as capsaicin, are known to burn off calories and fat.

There was a significant rise in energy expenditure within 30 minutes of eating the equivalent of a jalapeno pepper.

Normally, when we cut down on calories, our metabolism slows down, undercutting our weight loss attempts. But sprinkling a third of a teaspoon of cayenne pepper powder onto our meals counteracts that metabolic slowdown and promotes fat burning. They wanted to try giving them more, to try to match some of the studies done in Asia, but they were working with Caucasians. There is a difference in maximum tolerable dose of red chili pepper between Asians and Caucasians. Take some Japanese women, and you can boost the fat burned after a high-fat meal too, adding over a tablespoon of red pepper powder.

We’ve known for decades that cayenne pepper increases metabolic rate, but we didn’t know how. But now, we have studies showing that this class of compounds increases energy expenditure in human individuals with brown fat, but not those without it, indicating that they increase expenditure straight off the bat. And there’s all sorts of structurally similar flavor molecules in other foods, like black pepper and ginger, which we expect to activate thermogenesis as well, but they haven’t been directly tested.

All these results suggest that the anti-obesity effects of pepper compounds are based on the heat-generating activity of recruited brown fat. Thus, repeated ingestion can mimic the chronic effects of cold exposure without having to freeze ourselves.

Consumption of spicy foods may help us lose weight, but what about the sensory burn and pain on our tongues, and sometimes in our stomach as well as further on down? So, are our only two options for boosting brown fat to freeze our legs or burn our butts?

Arginine-rich foods may also stimulate brown adipose tissue growth and development through a variety of mechanisms, which just means eating more soy foods, seeds, nuts, and beans.

Thanks for listening to this episode of Nutrition Facts. 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 videos I highlighted with links to all the sources cited.

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Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.