Beware of crash diets, you might lose more than you bargained for! Crash dieting can cause hair loss.

How does dieting affect hair growth?
Healthy hair, amongst other things is dependent on a balanced diet. The cells of the hair follicle are some of the most active cells in the body. Extreme calorie restriction with subsequent inadequate energy supply of the hair matrix is thought to be a cause of hair loss.
In the context of weight loss, whether it is due to calorie restriction, nutritional restriction or excessive exercise, energy that is normally available for hair growth is redirected to more essential needs. Therefore any diet that restricts calories or certain food groups to the extent that you are missing out on certain nutrients may affect hair growth. Additionally, diet pills can cause a change in metabolism and consequently hair loss.
The physical stress exerted on your body by weight loss can trigger a condition called Telogen effluvium, which results in increased hair shedding and loss. Usually full hair growth will return once imbalances are corrected but it may take several months.
There are many recognised diets that will enable you to achieve safe weight loss whilst maintaining a healthy nutritional intake and healthy hair.