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Diet that's high in BCAAs will keep you slim

Men and women aged between 40 and 60 are slimmer the more BCAAs their diet contains. Researchers at the University of North Carolina at Chapel Hill discovered this after studying data on 4429 Japanese, Chinese, British and Americans.

The study, which has been published in the Journal of Nutrition, is based on data gathered for the International Study of Macro- and Micronutrients and Blood Pressure [Intermap]. Nutritionists are trawling the data in the search for substances that keep blood pressure healthy.

While doing so, these researchers stumbled on a link between the amino acid composition of protein in the diet and bodyweight: the more BCAAs there were in the diets of the four thousand men and women, the less often they were overweight.

The researchers divided their subjects up into quartiles according to their BCAA intake. The first quartile is the 25 percent with the lowest BCAA intake, and the fourth quartile the 25 percent with the highest intake.


When they set the chance of overweight at 1 for the first quartile, they saw that the same chance in the fourth quartile was 0.8. That means the chance of overweight is 20 percent less for the people in the fourth quartile than for those in the first quartile.

Diet that's high in BCAAs will keep you slim

Diet that's high in BCAAs will keep you slim

The likelihood of extreme overweight obesity is reduced by about the same amount in the fourth BCAA quartile too, as the table above shows.

The researchers went on to do a literature study, from which they conclude that of the 3 BCAAs valine, isoleucine and leucine it's leucine that has the most slimming effect. One human study that shows this is one in which three groups of wrestlers were put on a diet for 19 days. The group of wrestlers that, despite the reduced calorie intake, still got high levels of BCAA lost the most weight in the study. The wrestlers lost 4 kg fat and their fat percentage went down by 17 percent. [Int J Sports Med. 1997 Jan; 18(1): 47-55.]

A possible mechanism here is that meals containing lots of leucine cause an increase in leptin emission. [Am J Physiol Endocrinol Metab. 2006 Sep; 291(3): E621-30.] This is the hormone that tells the body that it has consumed enough energy, increases energy burning and suppresses appetite.

The average earth dweller consumes 6 g of leucine a day. This can safely be increased to 20 g, by increasing protein intake or taking supplements. The researchers are optimistic that an intervention like this could help reduce the obesity epidemic.

J Nutr. 2011 Feb;141(2):249-254.

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