A double-blind placebo controlled trial into the impacts of HMB supplementation and exercise on free-living muscle protein synthesis, muscle mass and function, in older adults

Taking HMB supplements does not significantly increase muscle growth in people who already eat enough protein, but might slightly affect muscle growth when calorie intake is very low or training intensity is extremely high.

In healthy men aged 67 to 69, taking 3 grams of HMB-free acid daily while doing strength training led to a slightly greater increase in thigh muscle mass compared to a placebo, though the difference was not large enough to be considered statistically certain.

Taking HMB-free acid supplements raised levels of HMB in the blood of older men, showing the body absorbed it, but this did not lead to meaningful health improvements except for a minor gain in thigh muscle mass.

In older men doing strength training, taking HMB-free acid may temporarily boost muscle protein synthesis in the first two weeks, but this effect disappears after that and is not different from taking a placebo.

In older men, doing resistance exercises such as weightlifting increased muscle strength, muscle size, and lean tissue in the thighs, even without taking HMB supplements, indicating that the exercise itself was the main factor driving these changes.

In older men doing strength training, taking HMB-free acid supplements for six weeks did not lead to measurable improvements in strength, muscle size, or maximum force production compared to a placebo, even if there was a slight increase in lean mass.