Which of the following effects has been associated with HMB on lean body mass (LBM)?

HMB, or beta-hydroxy-beta-methylbutyrate, is a metabolite of the amino acid leucine, and it has been studied extensively for its effects on muscle mass and strength. The association between HMB and stimulation of protein synthesis is well supported by scientific research.

When HMB is ingested, it can enhance the anabolic processes in the body, contributing to an increase in muscle protein synthesis. This is particularly important during periods of muscle loss, such as during caloric restriction, aging, or after intense exercise. By promoting protein synthesis, HMB helps to preserve lean body mass and can even contribute to increases in muscle mass over time, especially in individuals who are undergoing resistance training or have experienced muscle-wasting conditions.

The effectiveness of HMB in stimulating protein synthesis is closely tied to its ability to mitigate muscle protein breakdown as well. Therefore, its role in promoting a positive balance between protein synthesis and breakdown is significant in maintaining or increasing lean body mass.

This specific action makes it clear why stimulation of protein synthesis is the correct answer concerning the effects of HMB on lean body mass.