Eating Too Little for Too Long
A 2022 study published in the New England Journal of Medicine found that extreme caloric restriction during fasting windows causes the body to down-regulate its resting metabolic rate within days, not weeks. The body reads a severe deficit as a famine signal. Muscle tissue breaks down for fuel before fat does, because fat is the body's long-term reserve and muscle is metabolically expensive to maintain. Once muscle mass drops, your baseline calorie burn drops with it. You eat less. You burn less. The weight loss stops, then reverses.
