Retatrutide

Physics limits

• The body defends its weightAs weight falls, hunger hormones rise and energy use drops, so loss plateaus after about a year. When treatment stops, most people regain much of it: in one trial, about two-thirds within a year.
• Part of the weight lost is muscleRoughly a quarter to a third of the weight lost on these drugs is lean mass, not fat. In older people that loss of muscle and bone can matter more than the weight itself.
• Glucagon is a double-edged signalGlucagon burns energy but also raises blood sugar and heart rate. Balancing it against the other two hormones sets a ceiling on how hard the drug can push without side effects.