PPARGC1A and obesity due to melanocortin 4 receptor deficiency: Elevated PGC‐1α in muscle dramatically protects against the sarcopenia, obesity, and diabetes that normally accompanies aging.42 Therefore, the use of l‐citrulline to increase PGC‐1α expression may be useful in the management of diseases such as obesity, diabetes, and sarcopenia, as well as in the enhancement of exercise performance.