What happens if you don't eat enough carbohydrates?

Fatigue is one of the most common symptoms of not eating enough carbohydrates. Carbohydrates supply energy for the body to use during physical activity by storing glycogen. If glycogen is depleted, the body uses protein to supply energy, and this breaks down muscle tissue.

Ketosis is a process in which the body breaks down fat to provide energy in the absence of carbohydrates. Ketosis typically occurs when the body receives less than 20 grams of carbohydrates a day. Ketosis causes ketones to build up in the body, causing headaches and nausea. A low-carbohydrate, high-protein diet is an effective way to lose weight, but experts do not agree on whether it is healthy.