Weight regained after a period of weight loss reflects coordinated biological responses rather than a failure of discipline, according to a growing body of research on how the brain monitors and defends body energy stores. The newest contribution comes from mice, not people, and that distinction matters for how much weight to give it.
The broader account draws together several decades of work on what researchers call a defended body weight. The core observation is that after weight loss, appetite-related signaling increases, energy expenditure falls by more than body size alone would predict, and neuroendocrine signals shift in ways that favor restoring lost tissue.
