There are lots of things we want to do in life. Climb a mountain, write a song, watch our grandchildren grow up. But guess what? We can’t do any of those things if we don’t have our health.
Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger. And I’m here to bring you evidence-based research that takes the mystery out of the best way to live a healthier, longer life.
Today on the show, part 2 of my Keto Diet Series. Today we continue our examination of some new Keto diet research.
In our first story we ask might the appetite-suppressing effects of ketosis improve dietary compliance?
The new data is said to debunk “some, if not all, of the popular claims made for extreme carbohydrate restriction.” But what about ketones suppressing your hunger? In the tightly-controlled metabolic ward study where the ketogenic diet made things worse, everyone was made to eat the same number of calories. So yes, eat the same number of calories on a keto diet, and lose less body fat, but out in the real world, maybe all those ketones would spoil your appetite enough that you’d end up eating significantly less overall. On a low-carb diet, people ended up storing 300 more calories of fat every day. But outside the laboratory, if you were in a state of ketosis, maybe you could offset that if you were able to sustainably eat significantly less.
Paradoxically, people may experience less hunger on a total fast compared to an extremely low-calorie diet. This may be thanks to ketones; in this state of ketosis, when you have high levels of ketones in your bloodstream, your hunger is dampened. How do we know it’s the ketones? Because if you inject ketones straight into people’s veins, even those who are not fasting lose their appetite, sometimes even to the point of getting nauseated and vomiting. So, ketones can explain why after a few days you might feel hungrier on a low-calorie diet than on a total zero-calorie diet (a fast).
Can we then exploit the appetite-suppressing effects of ketosis by eating a ketogenic diet? If you ate so few carbs to sustain brain function, couldn’t you trick your body into thinking you’re fasting, and get your liver to start pumping out ketones? Sure! But is it safe, and is it effective?
A meta-analysis of 48 randomized trials of various branded diets found that those advised to eat low-carb diets and those told to eat low-fat diets lost nearly identical amounts of weight after a year. Now obviously, “high attrition rates and poor dietary adherence” complicate comparisons of efficacy, I mean, they weren’t actually put on these diets; they were just told to eat that way. But you can see how even just moving in each respective direction can get rid of a lot of CRAP, which is Jeff Novick’s beloved acronym for Calorie-Rich And Processed foods. After all, the four largest calorie contributors in the American diet are refined grains, added fats, meat, and added sugars. Low-carb diets cut down on 1 and 4, and low-fat diets tend to cut down on 2 and 3. So they both tell people to cut down on doughnuts. Any diet that does that already has a leg up.
I figure a don’t-eat-anything-that-starts-with-the-letter-D diet could also successfully cause weight loss if it caused people to cut down on doughnuts, danishes, and Doritos even if makes no nutritional sense to exclude something like dill.
The secret to long-term weight loss success on any diet is compliance. Diet adherence is difficult, though, because any time you try to cut calories, your body ramps up your appetite to try to compensate. This is why traditional weight-loss approaches, like portion control, tend to fail. For long-term success, measured not in weeks or months but in years and decades, this day-to-day hunger problem must be overcome. On a wholesome plant-based diet, this can be accomplished thanks in part to calorie density. You’re just eating so much food. On a ketogenic diet, it may be accomplished with ketosis.
In a systematic review and meta-analysis entitled “Do ketogenic diets really suppress appetite?” the answer, they found, was yes. Also, ketogenic diets offer the unique advantage of being able to track dietary compliance in real time with ketone test strips you can pee on to see if you’re still in ketosis. There’s no pee stick that will tell you if you’re eating enough fruits and veggies. All you have is the bathroom scale.
Keto compliance may be more in theory than practice, though. Even in studies where ketogenic diets are being used to control seizures, after a few months, dietary compliance may drop to under 50 percent. This can be tragic for those with intractable epilepsy, but for everyone else, the difficulty in sticking to ketogenic diets long-term may actually be a lifesaver.
In our next story we look at the effects of ketogenic diets on nutrient sufficiency, gut flora, and heart disease risk.
Given the decades of use of ketogenic diets to treat certain cases of pediatric epilepsy, a body of safety data has accumulated. Nutrient deficiencies would seem to be the obvious issue. Inadequate intake of 17 micronutrients—vitamins and minerals—has been documented in those on strict ketogenic diets.
Dieting is a particularly important time to make sure you’re meeting all your essential nutrient requirements, since you may be taking in less food. Ketogenic diets tend to be so nutritionally vacuous that one assessment estimated that to get a sufficient daily intake of all essential vitamins and minerals. you’d have to eat more than 37,000 calories a day.
That’s one of the advantages of more plant-based approaches. As the editor-in-chief of the Journal of the American Dietetic Association put it: “What could be more nutrient dense than a vegetarian diet?” Choosing a healthy diet may be easier than sticking 50 sticks of butter in your coffee.
And we’re not talking about just not reaching your daily allowances. Children have gotten scurvy on ketogenic diets, and some have even died from selenium deficiency (which can cause sudden cardiac death). The vitamin and mineral deficiencies can be solved with supplements, but what about the paucity of prebiotics, the dozens of types of fiber and resistant starches found concentrated in whole grains and beans that you’d be missing out on?
Not surprisingly, constipation is very common on keto diets, but as I reviewed before, starving our microbial self of prebiotics can have a whole array of negative consequences. Ketogenic diets have been shown to reduce the richness and diversity of our gut flora. Microbiome changes can be detected “within 24 hours” of switching to a high-fat, low-fiber diet. The lack of fiber starves our good gut bacteria, but we used to think dietary fat itself was nearly all absorbed in the small intestine. But based on studies using radioactive tracers, we now know that about 7 percent of the saturated fat in a fat-rich meal can make it down to the colon, which may result in detrimental changes in our gut microbiome, weight gain, increased leaky gut, and pro-inflammatory changes. For example, a drop in beneficial bifidobacteria and a decrease in overall short-chain fatty acid production, both of which would be expected to “increase the risk of gastrointestinal disorders.”
Okay, but striking at the heart of the matter, what might all that saturated fat be doing to our heart? If you look at low-carbohydrate diets and all-cause mortality, those who eat lower-carb diets suffer “a significantly higher risk of all-cause mortality,” meaning they live, on average, significantly shorter lives. From a heart disease perspective, though, it matters if it’s an animal fat or plant fat. Based on the famous Harvard cohorts, eating more of an animal-based low-carb diet was associated with higher death rates from cardiovascular disease, a 50 percent higher risk of dying from a heart attack or stroke, But, no such association was found for lower-carb diets based on plant sources.
And it wasn’t just from Harvard. “Low carbohydrate dietary patterns favouring animal protein and fat, from sources such as red meat and chicken, were associated with higher mortality. Whereas those favoring plant protein and fat from things like vegetables, nuts, peanut butter, and whole grains, were associated with lower mortality.”
Cholesterol production in the body is directly correlated to body weight. Every pound of weight loss by nearly any means is associated with about a one-point drop in cholesterol levels in the blood. But put people on very low-carb ketogenic diets and the beneficial effect on LDL bad cholesterol is blunted or even completely neutralized. Counterbalancing changes in LDL size or HDL (what we used to think of as good cholesterol) are not considered sufficient to offset this risk. You don’t have to wait until cholesterol builds up in your arteries to have adverse effects, though. Within three hours of eating a meal high in saturated fat, you can see a significant impairment of artery function. Even with a dozen pounds of weight loss, artery function worsens on a ketogenic which appears to be the case with low-carb diets in general.
In our final story today, we ask does a Ketogenic diet help diabetes or make it worse?
Ketogenic diets can certainly lower blood sugars, better than conventional diets So much so, there is a keto product company that claims ketogenic diets can “reverse” diabetes. But they are confusing the symptom, high blood sugars with the disease, which is carbohydrate intolerance. People with diabetes can’t properly handle carbohydrates, and this manifests as high blood sugars. Sure, if you stick to eating mostly fat, your blood sugars will stay low, but you may be actually making the underlying disease worse, at the same time.
We’ve known for nearly a century that if you put people on a ketogenic diet, their carbohydrate intolerance can skyrocket within just two days. One week on an 80 percent fat diet, and you can quintuple your blood sugar spike in reaction to the same carb load, compared to a week on a low-fat diet. Even a single day of excessive dietary fat intake can do it. If you’re going in for a diabetes test, having a fatty dinner the night before can adversely affect your results. One meal high in saturated fat can make the cause of diabetes, carbohydrate intolerance worse within four hours.
Now, with enough weight loss by any means; whether from cholera or bariatric surgery, type 2 diabetes can be reversed. But a keto diet for diabetes may not just be papering over the cracks, but actively throwing fuel on the fire.
I’ve been trying to think of a good metaphor. It’s easy to come up with things that just treat the symptoms without helping the underlying disease, like giving someone with pneumonia aspirin for their fever, instead of antibiotics. But a keto diet for diabetes is worse than that, because it may treat the symptoms while actively worsening the disease. So maybe it’s more like curing the fever by throwing that pneumonia patient out into a snow bank. Or maybe “curing” your amputated finger by amputating your hand. No more unsightly finger stub! One of the co-founders of masteringdiabetes.org suggested it’s like a CEO that makes their bad bottom line look better by just borrowing tons of new cash. The outward numbers look better, but on the inside, the company is just digging itself a deeper hole.
Remember “The Club”? Maybe I just watched too much late-night TV growing up, but it’s a car anti-theft device that attaches to your steering wheel and locks it in place, so the steering column can only turn a few inches. Imagine you’re in a car at the top of a hill with the steering wheel locked. Then the car starts rolling down the hill. What do you do? Oh, did I mention there’s also something stuck under your brake pedal too? The keto-diet-equivalent-response to this situation is who cares if you’re barreling down into traffic with no brakes and a locked steering wheel. Just stick to really straight deserted roads without any stop signs or traffic lights. If you do that, problem solved! Yeah, the longer you go, the more speed you’ll pick up, and so if you should hit a dietary bump in the road, or start to veer off the path, the consequences could get more and more disastrous with time. But if you stick to the keto straight and narrow, you’ll be A-OK. In contrast, the non-keto response would be to just unlock the steering wheel and dislodge whatever’s under your brake. In other words, fix the underlying problem, instead of just whistling past and then into the graveyard.
The reason keto proponents claim they can “reverse” diabetes is that they can successfully wean type 2 diabetics off their insulin. That’s like faith healing someone out of the need for a wheelchair by making them lie in bed the rest of their life. No need for a wheelchair if you never move. Their carbohydrate intolerance isn’t gone; their diabetes isn’t gone. It could be as bad or even worse. Type 2 diabetes is reversed when you can wean people off insulin eating a normal diet like everybody else. Then and only then do you not have diabetes anymore. A true diabetes reversal diet is practically the opposite of a ketogenic diet; diabetics off their insulin within a matter of weeks, eating more than 300 grams of carbs a day.
The irony doesn’t stop there. One of the reasons diabetics suffer such nerve and artery damage is due to an inflammatory metabolic toxin known as methylglyoxal that forms at high blood sugar levels. Methylglyoxal is the most potent creator of advanced glycation end products, so-called AGEs, which are implicated in degenerative disease from Alzheimer’s disease and cataracts to kidney disease and strokes. You get AGEs in your body from two sources: eating them preformed in your diet, or making them internally from methylglyoxal if you have high blood sugar levels. On a keto diet, one would expect high exposure to the preformed AGEs, since they’re found concentrated in animal-derived foods high in fat and protein. But we would expect less internal new formation due to presumably low levels of methylglyoxal, given lower blood sugars not eating carbs. Dartmouth researchers were surprised to find more methylglyoxal, though. A few weeks on the Atkins diet led to a significant increase in methylglyoxal levels, and those in active ketosis did even worse; doubling the level of this glycotoxin in their bloodstream. It turns out high sugars may not be the only way to create this toxin.
One of the ketones you make on a ketogenic diet is acetone (known for its starring role in nail polish remover). Acetone does more than just make keto dieters fail breathalyzer tests and develop what’s been described as “rotten apple breath.” Acetone can oxidize in the blood to acetol, which may be a precursor for methylglyoxal. That may be why keto dieters can end up with levels of this glycotoxin as high as those with out-of-control diabetes, which can cause the nerve damage and blood vessel damage you see in diabetics. That’s another way keto dieters can end up with a heart attack. So, the irony of treating diabetes with a ketogenic diet may extend beyond just making the underlying diabetes worse, but by mimicking some of the disease’s dire consequences.
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Thanks for listening to Nutrition Facts. I’m your host, Dr. Michael Greger.