According to the U.S. Department of Agriculture, adults should consume from 1,200 to 2,600 calories per day depending on their gender, age, and activity level. Many extreme diets encourage people to lose weight through calorie restrictions that fall well below these requirements. If you're considering an extreme diet, you should ensure that you have a full understanding of the health risks and side effects of cutting calories and restricting your food choices.
Fatigue and Mood Changes
The first symptoms dieters on low calorie diets may experience are a lack of energy and mood changes. As you cut calories, your body will have less food to convert to energy. The levels of sugar in your blood will typically drop, and this can lead to fatigue, irritability, and even food cravings. Some people who plan to cut back on food actually find themselves cheating on their diet because of the strong cravings for unhealthy foods that can result from extreme hunger.
As your body experiences a calorie deficit and energy levels drop, your metabolism will naturally slow in order to conserve energy. This can actually stall weight loss and lead to the loss of muscle tone. Your body will conserve fat deposits and produce muscle-wasting; if your goal is to slim down and tone up, you may find that you retain almost the same body fat levels but experience a loss of muscle tone.
Changes in Digestion and Gallstones
Proper digestion requires sufficient fiber and water, which your body obtains from a variety of foods such as fruits, vegetables, and grains. When you restrict calories and food groups, it can lead to slowed digestion, constipation, and even bloating. In addition, gallbladder function can be adversely affected by lowered calories and decreases in cholesterol levels, and this can lead to the formation of gallstones.
A wide variety of medical organizations, including the Mayo Clinic and the National Institutes of Health, encourage dieters to forego extreme dieting in favor of more balanced, nutritious diet plans. These organizations note that very low calorie diets are only recommended for obese individuals and should only be followed under the supervision of a doctor. If you hope to lose a relatively small amount of weight, you can construct a healthy diet plan by consulting with your doctor about your personal calorie needs and any individual health concerns you may have.