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Branched-Chain Amino Acids and Weight Loss

By Tracey Roizman, D.C. ; Updated July 18, 2017

Branched-chain amino acids -- leucine, isoleucine and valine -- serve numerous functions in your body, including promoting protein production, decreasing protein breakdown and speeding recovery from endurance exercise. Because of their influence on protein metabolism, scientists have investigated the potential benefits of branched-chain amino acids for weight loss. Consult your doctor before using branched-chain amino acids for weight reduction.

Fat Promotion

The amino acid leucine promotes growth of adipose tissue, according to a study published in the April 2011 issue of the journal "Age." In a study on laboratory animals, long-term consumption of a diet composes of 15 percent protein supplemented with 4.5 percent leucine did not impair insulin sensitivity in muscle but did impair insulin sensitivity in adipose tissue. Transport of glucose into muscle increased without resulting in increased muscle mass on the leucine diet, whereas fat deposits around the kidneys increased. The researchers concluded that leucine's promotion of excess adipose tissue production did not increase overall insulin resistance and did not influence weight levels, in this preliminary animal study.

Lean Muscle

Leucine promotes protein production in skeletal muscle and prevents muscle from breaking down when consumed before exercise, according to a study published in the February 2006 issue of "The Journal of Nutrition." The end result may be a leaner body with greater ability to exercise and less resultant fatigue or muscle damage, a trend that can lead to overall weight loss. A study published in the October 2007 issue of "Biochemical Journal" reported that branched-chain amino acids suppressed weight loss in laboratory animals, largely by promoting increased protein production and decreased protein breakdown via numerous pathways


Branched-chain amino acids combined with exercise may be the ideal approach to weight loss using this form of protein, according to a study published in the January 2003 issue of the "Journal of Nutrition." In the study, the participants, all adult women aged 40 to 56, consumed one of two weight loss diets for 10 weeks. Each diet consisted of 1,700 calories and equal amounts of fat; one diet contained a higher percentage of leucine and a lower level of carbohydrate, and the other contained a lower percentage of leucine and a higher level of carbohydrate. Both groups showed similar weight loss, with the higher protein group showing a marginally higher level of weight loss. In another phase of the study, the same diets combined with exercise resulted in significantly more weight loss in the higher leucine group. The higher leucine group lost more fat and retained more lean mass. The researchers concluded that the protein-preserving effect of leucine may have contributed to the weight loss and improved body composition that resulted from the high-leucine diet.

Altered Metabolism

Obese people may have altered mechanisms of processing branched-chain amino acids, resulting in an inability to utilize them and their consequent accumulation in the blood, suggests a study published in the October 2007 issue of "The American Journal of Physiology, Endocrinology and Metabolism." Researchers increasingly view branched-chain amino acids as playing a role in regulation of appetite, blood sugar levels and body weight. Animal studies of obese laboratory rodents found a loss of the ability to process branched-chain amino acids. Also, fasting in animals and surgical weight loss intervention in humans reduced levels of circulating branched-chain amino acids.

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