Is weight cycling clinically harmful?

Worldwide, approximately half of the general population is actively attempting to lose weight. However, weight loss is typically followed by substantial weight regain, often leading to repeated cycles of loss and gain of bodyweight. Weight cycling has been suggested to be metabolically harmful, in that it could lead to greater rebounds in fat mass and smaller regains in lean (muscle) mass, thereby promoting sarcopenia, lowering metabolic rate, and exacerbating obesity and its metabolic complications (eg, glucose intolerance). In this Personal view, we critically evaluate evidence from studies in humans and animals investigating whether weight cycling has adverse effects on bodyweight, body composition, energy metabolism, and metabolic function. We also briefly discuss potential strategies to mitigate weight regain and its consequences. Overall, the current evidence does not support a causal link between weight cycling per se and clinical harm in people with obesity. Most of the adverse effects reported are likely circumstantial, possibly because of ageing, unintentional weight loss, reverse causality, earlier onset of obesity, repeated obesogenic exposures, or longer cumulative exposure to obesity. Available evidence suggests that the benefits of intermittent weight reduction-such as improved metabolic markers, cardiovascular health, and quality of life-outweigh the potential risks associated with weight fluctuation.