Taking 3 grams of HMB daily for four weeks or longer may be linked to a very small increase in lean body mass in athletes, but this effect is not statistically significant and may only occur if protein intake is less than 1.6 grams per kilogram of body weight per day.

Taking HMB supplements at 3 grams per day for 4 to 12 weeks while doing resistance training does not lead to meaningful changes in strength, body weight, muscle mass, or fat mass in trained athletes.

HMB, a supplement used by athletes, may only help increase fat-free mass in those who eat less than 1.6 grams of protein per kilogram of body weight each day. For athletes consuming more protein, HMB does not appear to provide additional benefit.

Taking HMB supplements does not lead to a meaningful change in fat mass among athletes, based on data from multiple studies combining 128 participants.

Taking 3 grams of HMB daily may increase muscle growth in resistance-trained adults only when they are under high training stress or not consuming enough calories; in well-fed, trained individuals, it typically has little to no effect on muscle growth.

Taking HMB supplements does not lead to a meaningful change in total body weight for athletes, based on data from multiple studies.