Final answer:
Very low calorie diets may cause nutrient deficiencies, require the use of supplements, and lead to very low caloric intake with potential starvation response. These diets can result in a reduced basal metabolic rate (BMR), lack of energy due to inadequate protein, and severe forms of malnutrition and muscle wastage.
Step-by-step explanation:
Problems associated with very low calorie diets can be significant and serious. One major problem is that they are not entirely evidence-based and often lack comprehensive nutritional balance, leading to potential nutrient deficiencies. With the restriction of calories, the body may not receive adequate amounts of vitamins and minerals. Because of this, individuals on very low calorie diets frequently require supplements.
Another concern is that these diets can lead to very low caloric intake, which might cause the body to enter a state of starvation. This can result in various physiological changes, such as a reduction in the basal metabolic rate (BMR), which can drop significantly during periods of low food intake. For instance, starvation or abrupt calorie reduction can reduce BMR by up to 30%, and restrictive diets may lead to a 20% decrease in BMR. This change in metabolism can cause the body to become more efficient at conserving energy, making weight loss more difficult over time.
Moreover, a lack of energy is often experienced because very low calorie diets may not provide sufficient protein, leading to muscle loss and general fatigue. This can have a cascade of negative effects, including weakness, irritability, and a reduction in physical activity levels. Prolonged adherence to such diets, especially without proper medical supervision, can lead to severe forms of malnutrition, muscle wastage, and even organ damage, as the body starts breaking down its own tissues for energy in a process called catabolysis. In women, such restrictions can cause amenorrhea, the cessation of menstruation, which has its own set of health implications.