Lack of carbohydrates can cause low blood sugar and ketosis. Many people avoid carbohydrates due to concerns about weight gain, but carbs are needed for the body to function. Carbohydrates are your body’s main energy source and necessary for you to think and remain active.etosis. Eating less than 130 grams of carbohydrates a day can cause a buildup of ketones, which are partially broken-down fats in the blood. This condition is known as ketosis, according to the Weight-Control Information Network, a service of the National Institute of Diabetes and Digestive and Kidney Diseases.