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Diabetes isn’t just about the amount of body fat, but the distribution of body fat. Check out these cross-sections of two different thighs from two different patients. This is an MRI, so the fat shows up as white, and the black is the thigh muscle. At first glance, it looks like the one on the bottom has more fat. That’s the subcutaneous fat, under the skin. But if you look at the top one, see how their muscle is more marbled in the middle with fat; those white streaks? That’s not gristle; that’s fat, like one of those really fatty Japanese beef steaks. That’s the fat infiltrating into the muscle, colored in red here. The green is the fat between your muscles, and then the yellow is the fat outside of the muscles under the skin. And if you add up all three types, both of those thighs actually have the same amount of fat—just distributed differently. And that seems to be the critical factor in terms of determining insulin resistance, the cause of type 2 diabetes. The subcutaneous adipose tissue, the fat right under the skin, was not associated with insulin resistance. So, it’s healthier to have this thigh. Is it possible a more plant-based diet also affects a more healthy distribution of fat? We didn’t know … until, now. “The effect of a vegetarian vs conventional diabetic diet on thigh fat distribution in subjects with type 2 diabetes.”

Researchers decided to put it to the test. Seventy-four diabetics were randomly assigned to either follow a vegetarian diet or conventional diabetic diet. Both diets were calorie-restricted down to the same number of calories. The vegetarian diet was also egg-free, and dairy-limited to a max of one serving of low-fat yogurt a day, and the reduction in the more benign subcutaneous fat was comparable, about the same in both groups. But the more dangerous fat, the fat lodged inside the muscle itself, was reduced only in response to the more plant-based diet. So, even on the same number of calories, there can be a healthier weight loss on a more plant-based diet.

Those eating strictly plant-based also had lower levels of fat stuck inside the individual muscle fibers themselves—what’s called intramyocellular lipid, which may help explain why vegans in particular are often found to have the lowest odds of diabetes. And it’s not just because they’re slimmer. Even if you match subjects pound-for-pound, there’s significantly less fat inside the muscle cells of vegans compared to omnivores, as measured in one of their calf muscles, which is a good thing, since storing fat in muscle cells “may be one of the primary causes of insulin resistance,” which is what’s behind both prediabetes and type 2 diabetes. Whereas if you put someone on a high-fat diet, in just a single week the fat in their muscle cells shoots up 54 percent.

And go on a high-protein diet, and you may undermine one of the principal benefits of weight loss: eliminating the weight-loss-induced improvement in insulin action, the improvement in insulin resistance. Obese individuals were put on a calorie-restricted diet, less than 1400 calories a day, until they lost 10 percent of their body weight. Half were getting more of a regular protein intake, 73 grams a day, and the other half a higher-protein diet. Now, normally you lose 10 percent of your body weight and your insulin resistance improves—that’s why it’s so critical for obese type 2 diabetics to lose weight. But the beneficial effect of 10 percent weight loss was eliminated by the high protein intake. Those extra 32 grams of protein a day abolished the weight loss benefit. “The failure to improve…insulin sensitivity in the [high-protein weight-loss] group is clinically important because it reflects a failure to improve a major [cause-and-effect] mechanism involved in the development of type 2 diabetes.” In summary, they concluded that they demonstrated that “the protein content of a weight loss diet can have profound effects on metabolic function.”

All protein? Any kind of protein? If you split it up between animal versus plant protein, following people over time, animal protein intake is associated with an increased risk of diabetes in most studies, whereas plant protein intake appears to have either a neutral or protective association with diabetes. Yes, but these were just observational studies. People who eat lots of animal protein might have lots of unhealthy behaviors. But you see the same thing in randomized, controlled, interventional trials where you can improve blood sugar control just by replacing sources of animal protein with plant protein.

We think it may be the branched-chain amino acids concentrated in animal protein. Higher levels in the bloodstream are associated with obesity and the development of insulin resistance. We may be able to drop our levels by sticking to plant proteins. But, you don’t know if that has metabolic effects until you put it to the test.

I hate it when titles ruin the suspense, but indeed: Decreased Consumption of Branched-Chain Amino Acids Improves Metabolic Health. They demonstrated that a moderate reduction in protein intake rapidly improves metabolic health, improving blood-sugar control while also decreasing BMI and body fat. Check this out. The protein-restricted group was eating literally hundreds more calories per day, significantly more calories than the control group; so, they should have gained weight, right? But no, they lost weight. After about a month and a half, they were eating more calories, but lost more weight, about five pounds more than the control group eating fewer calories. And this “protein restriction”? They were just having people eat the recommended amount of protein a day; so, that’s about 56 grams a day. So, they should have just called that 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. And, as a bonus, just sticking to the recommended protein intake doubled the levels of a pro-longevity hormone called FGF21, but that’s for another video.

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