During chronic dieting, the body goes into a metabolic conservation mode. During starvation, metabolic rate slows and appetite increases, which makes it difficult to sustain long low-calorie diets.
Calorie shifting is a weight-loss strategy consisting of periods of low-calorie dieting followed by several days of normal eating patterns. The theory behind this strategy is that metabolic control mechanisms never enter the starvation mode.
An Iranian study discovered that caffeine supplements encouraged weight loss and prevented weight regain during calorie-shifting dieting. Caffeine prevented reductions in resting metabolic rate and helped suppress hunger.