this is a copy paste (sorry)
Why dieting is bad for your health
MENTAL
Dieting creates an unrealistic relationship with food. This means you will “crack” and regain the weight you lost.
Restricting calories lowers your energy levels. This can reduce your “cognitive capacity” or brain power.
Numerous studies link chronic dieting with feelings of depression, low self-esteem and increased stress. Since nobody can stay on a diet permanently, you are setting yourself up to fail.
Believing that being thin will give you more “worth” as a person reflects the attitude that your self-esteem is dependent on your weight. Dieting doesn’t solve self-esteem problems; it could make them worse.
Dieting disconnects you from your appetite. You don’t eat when you are hungry. You then lose the ability to recognise when you are full and should stop eating.
PHYSICAL
Yo-yo dieting can cause long-term damage to the body’s major organs such as the kidneys, heart and liver, as well as to muscle tissue.
Constant dieting reduces the levels of the body’s natural killer cells. These are vital for fighting off diseases such as cancer.
Dieting can also lead to skin problems, headaches, hair loss, light-headedness, menstrual irregularities, sleepiness, gallstones and constipation.
Going on a diet can starve your body of essential nutrients. It is impossible to stay on a diet permanently without causing some damage to your body.
A single episode of sudden weight loss, followed by rapid weight gain, can increase the likelihood of you developing heart disease.