A lack of food can cause the body to go into starvation mode over time. Starvation mode is a metabolic response to the body being deprived of food, which may occur during periods of famine or economic depression, when using a fad diet, or when suffering from anorexia nervosa. A variety of specific signs and symptoms affect those whose body has gone into starvation mode.
Reducing calories to a very low level prevents the body from obtaining proper nutrients and energy. As a result, fatigue is common because the body does not have ample energy to function. The body breaks down muscles to be used as fuel as it attempts to keep vital organs like the heart and lungs functioning. Vitamin and mineral deficiency is another result of a lack of food, and can lead to anemia, diarrhea, rashes, edema and heart failure. Testosterone and estrogen levels decrease during starvation mode, so sexual drive also diminishes. The primary drive in a food-deprived body is to eat to regain energy and nutrition, not to reproduce. In women, irregular menstruation or a complete absence of a menstrual cycle may occur.
Depression and Anxiety
In a landmark 1950's study by Dr. Ancel Keys, published in the book “The Biology of Human Starvation," subjects who were placed on a starvation diet experienced psychological changes. Depression was one such symptom. Dr. Keys found that those who ate the least calories were the most depressed. Anxiety is another psychological symptom of not consuming enough calories. Dr. Keys noted nervousness and impatience among the participants in the study. Some participants even avoided eating because they were fearful of gaining weight.
Food obsession is another symptom of starvation mode, as found in Dr. Keys’ study. The deprived body focuses on food because it needs the energy and nutrients to survive. A person in starvation mode may spend much time talking about food, thinking about food and searching for food. In developed countries, people in starvation mode -- such as dieters or people with anorexia nevosa -- may also spend much time watching cooking shows, looking at recipes or shopping for food.
A reduction in the intake of food leads to a reduced metabolic rate, or a decreased rate in burning calories. This decrease in metabolic rate increases your weight gain. Once you begin to eat more, you often experience an increase in appetite, while your metabolic rate stays at a low level, according to a study conducted by Dr. Abdul Dulloo that was reported in the March 1997 issue of “American Journal of Clinical Nutrition.” As a result, you can regain all the lost weight and may even gain more weight than when the starvation started. Additionally, the weight that you put on is mostly fat tissue.