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A crash diet is generally thought to be an unhealthy way to lose weight. The process is essentially starving one's self of calories and fat for a short period of time in order to lose weight fast. It is sometimes done in conjunction with other unhealthy weight loss methods, such as exercising for many hours per day or taking diet pills, which increases negative health risks even more. Crash diets can cause problems in the areas of mental health, organ and body system damage, lowered metabolism and gaining weight back quickly.
One risk of a crash diet is the creation of mental health problems from the body receiving too few calories and nutrients. The brain needs food in order to operate optimally, and a crash diet restricts intake to levels where the brain is not getting what it needs. This might cause depression, anxiety, anorexia, bulimia or other mental health problems to develop. An individual already suffering from a mental health problem might exacerbate his or her symptoms by restricting food intake. Less-severe mental problems that can affect daily life include lack of concentration, lack of sleep and a negative mood from not eating enough.
Restricting the body to a crash diet can cause damage to body organs and systems from lack of vitamins, minerals, proteins, fats and carbohydrates. If certain substances in the body become too low, there is a risk for a heart attack, stroke, liver problems, kidney damage and other body system failure. The body's immune system is also weakened because of the lack of nutrients, which makes an individual more likely to get sick. Women might experience problems with menstruation during crash diets, which can lead to problems with fertility.
A major risk in a crash diet is gaining back the weight that was lost immediately after cessation of the diet. The diet is not sustainable over time, so as soon as an individual begins eating regularly again, he or she will gain back most or all of the weight that was lost. Metabolism might also become lower because the body feels the need to store more calories as fat to prevent starvation, so an individual might actually gain more weight than was lost while on the diet. An individual might find it impossible to lose more weight past a certain point, even while on the diet, because of the slowing of metabolism.