Biochemical and animal research shows HMB has a role in protein synthesis and might improve muscle growth and overall body composition as a supplement. However, double-blind human research suggests that HMB may only be effective when combined with an exercise programme in people who are not already highly trained athletes. Double-blind trials found no effect of 3 to 6 grams per day HMB on body weight, body fat, or overall body composition in weight-training football players or other trained athletes.^{1, 2, 3, 4, 5} However, one double-blind study found that 3 grams per day HMB increased the amount of body fat lost by 70-year old adults who were participating in a strength-training programme for the first time.⁶ A double-blind study of young men with no strength-training experience reported greater improvements in muscle mass (but not in percentage body fat) when HMB was used in the amount of 17 mg per pound of body weight.⁷ However, another group of men in the same study given twice as much HMB did not experience any changes in body composition.