Why increase calories gradually?
After a prolonged calorie deficit, resting metabolic rate often falls below the level predicted by body composition alone — a phenomenon sometimes called adaptive thermogenesis or metabolic adaptation. Rapidly returning to pre-diet maintenance calories may produce a larger-than-expected calorie surplus before metabolic rate recovers, leading to faster fat regain than a gradual approach. Increments of 50–150 kcal per week give the body time to adjust.