Nutritionist Describes Effects of Extreme Calorie Restriction on Metabolism

Registered dietitian Lindsay Allen said extreme calorie restriction can slow or stop weight loss by lowering the body's metabolic rate. "Eating too little over time slows your weight loss or stops it completely because your body lowers its metabolic rate and preserves energy for your survival," Allen told GB News.

Allen explained that the body interprets prolonged low food intake as a famine and activates protective mechanisms. She said this response decreases metabolic rate and thyroid hormones while increasing processes that store fat.

Allen stated that severe restriction also affects hunger and fullness signals. "You become leptin resistant while your hunger hormone, ghrelin, goes up," she said. She added that muscle tissue can decrease because the body draws amino acids from muscle when dietary intake is low.

Allen listed common signs of under-eating, including frequent hunger, difficulty feeling satisfied after meals, trouble sleeping, low energy, mood changes, hair loss, and brittle nails.

Allen said focusing on food quality and exercise is more effective than counting calories. "When you couple high-quality foods with the right exercise, you can lose weight effortlessly without tracking a single calorie or macro," she advised.