How starvation mode work?
Caloric deficit and starvation mode are 2 separate entities. A caloric deficit is simply a shortage of calories which causes the body to tap into its fat stores to satisfy the deficit. Starvation mode is when a deficiency in a vital nutrient (usually carbs or protein) forces the body to cannibalize its living tissue (usually muscle) to satisfy the deficiency. For example, the brain and kidneys need carbs to function. In a shortage, the body will break down muscle for the amino acids to make carbs (gluconeogenesis) for these functions. Also, the body needs protein to make enzymes and to maintain internal organs. If it is lacking protein, it will take protein from muscles for these functions. The loss of lean mass will lower the resting metabolic rate. Starvation can happen in a caloric deficit, a caloric equilibrium, or even a caloric surplus (where the person is getting fatter while starving to death). For example, if someone eats 6000 calories/day exclusively from fats, the person is
