The Amino Acid Leucine May Preserve Muscle Mass When Losing Weight

One of the problems with adopting a calorie-restricted diet to lose weight is you not only lose fat, but you shed muscle as well. This is especially true if you don’t do resistance training. When you lose muscle mass, it slows down your metabolism and does little to improve your overall physique. The ideal situation would be to lose body fat while preserving lean body mass. Is there a way to do this?

Preserving Lean Body Mass While Losing Fat

One way to preserve lean body mass while restricting calories is to strength train to build more lean muscle. The other is to eat a diet that contains adequate amounts of protein while not restricting calories too severely. According to new research, the amino acid leucine found in protein-rich foods may help preserve lean body mass while dieting.

Leucine: Does It Help to Maintain Lean Body Mass When Restricting Calories?

Leucine is an amino acid, one of the fundamental building blocks of protein. It’s an essential amino acid, meaning the body requires it but can’t synthesize it on its own. This means you need to get it through diet.

In a study carried out at the University of Utah, researchers supplemented the diet of mountain climbers with leucine by giving them three food bars that contained the amino acid during their 6 to 8-week climb. They wanted to see whether the leucine-enhanced bars would help the climbers preserve lean body mass at high altitudes when they weren’t consuming enough calories. What did they find? After measuring their fat and muscle mass using an ultrasound device, they discovered that leucine worked well for this purpose.

Other research also shows that leucine preserves lean body mass by stimulating muscle protein synthesis and helping to reduce its degradation. Leucine is a branched-chain amino acid along with two other amino acids, isoleucine, and valine. Several studies have looked at the effect of branched-chain amino acids on protein synthesis. They suggest that consuming them before endurance exercise helps to reduce protein breakdown and preserve muscle glycogen stores while working out.

Studies also show that branched-chain amino acids boost the loss of visceral abdominal fat tissue while on a low-calorie diet. Other research shows that branched-chain amino acids reduce muscle damage after endurance exercise.

The Problem with Taking Amino Acid Supplements

Some bodybuilders take branched-chain amino acid supplements including leucine. The problem with taking isolated amino acid supplements is high quantities may interfere with the absorption of other essential amino acids you need through diet. Amino acids are absorbed by amino acid transporters in the small intestines. If you overwhelm those carriers with too much of a single amino acid, other essential amino acids may not be able to bind to the transporters, and they won’t be absorbed. This could lead to a deficiency of one or more amino acids.

The Bottom Line?

The amino acid leucine may help to preserve lean body mass when you’re restricting calories. But it’s best to get leucine and other amino acids by eating a diet that contains moderate amounts of protein. This will help to avoid an imbalance of amino acids. Good food sources of leucine include lean meats, soybeans, nuts, seeds, and egg whites. Enjoy these foods, and get your leucine naturally.

References:

J. Sports Med. Phys. Fitness. 2000 Sep; 40(3): 240-8.
Sports Med. 1999. Jun; 27(8): 347-58.
Nutraingredients.com. “Leucine May Help to Burn Fat but Spare Muscle Wastage”

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