How are ACTN3 and weight loss related?

The provided context does not contain information about ACTN3 and weight loss. ACTN3 encodes α-actinin-3, a protein expressed in fast-twitch muscle fibers. A common loss-of-function variant (R577X) is associated with reduced sprint and power performance but has no established direct link to weight loss. Evidence is mechanistic and population-based, not from clinical trials. Weight loss depends on energy balance, diet, and physical activity; ACTN3 genotype may modestly influence exercise response but is not a determinant of weight loss. Consumers should be cautious of direct-to-consumer claims that overstate the role of this gene in weight management.