Long-term low-carbohydrate diet may cause the following problems: 1. Ketosis: Excessive restriction of carbohydrates will cause the decomposition of fat in the body, produce elevated ketone bodies, and cause ketosis. 2. Malnutrition: Long-term reduction of carbohydrates will lead to energy deficiency, fatigue, muscle atrophy, etc. 3. Affects memory and thinking ability: The body relies on glucose for energy, and long-term low-carb diet may affect memory and thinking ability.