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Your body burns more fat with BCAA isoleucine

Consuming protein and carbs before and during a training session boosts muscle growth that's nothing new. But if fat loss is your goal, you're probably not so keen on this strategy. In this case, BCAA supplements might be an idea. According to an animal study done by researchers at Oita University in Japan, the BCAA isoleucine [structural formula shown below] enhances the body's fat burning.

Leucine, isoleucine and valine, all BCAAs, play a key role in muscle tissue during physical exercise. Introduce them into an athlete's body during a workout and less muscle tissue is broken down and the anabolic stimulus of the training increases. When the muscle cells are faced with an energy shortage, they'll convert the BCAAs into energy instead of their own proteins. At the same time, the muscle cells' anabolic or anticatabolic mechanisms work harder the more leucine the cells absorb.

That BCAAs also help fat loss is a relatively new discovery. An epidemiological study has shown that people whose diet contains high amounts of BCAAs are thinner than people who consume lower amounts. This is partly due to the effect that leucine supplementation has: it raises the metabolic rate. But the Japanese discovered that leucine is not the only slimming factor in BCAAs.

The Japanese fattened mice for 6 weeks by putting them on a fat-rich diet. For the last 4 weeks half of the mice were given isoleucine as well, in their drinking water. The researchers gradually increased the concentration of isoleucine up to 2.5 percent.

The supplementation reduced weight gain and fat tissue growth. The amount of fatty acids in the muscles and the liver also decreased, indicating that the organs burned more fat. This was because isoleucine stimulates the fat sensor PPAR alpha in the liver and muscles, and deactivates the same PPAR alpha in fat tissue. More PPAR means that cells absorb and burn more fatty acids.

Your body burns more fat with BCAA isoleucine

Your body burns more fat with BCAA isoleucine

But isoleucine does more: it also activates the proteins UCP2 and UCP3, which boost the metabolism.

Strength athletes who use high doses of BCAAs during workouts 10 to 20 g per session often notice that they are getting ripped more easily. Mention this to a biochemist and he's likely to frown in puzzlement. That's understandable. BCAAs contain calories too, and if muscles cells convert some of the BCAAs consumed into energy, you'd expect that they burn less fat.

This Japanese study makes the stories from the gym more plausible.

J Nutr. 2010 Mar; 140(3): 496-500.

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