Anorexia Nervosa's an eating disorder that affects around 5% of young women, with most cases starting at around 16-17 years-old. Teenage men can also suffer but the numbers are a lot lower at around 0.5%.

People with Anorexia Nervosa limit the amount they eat and drink to control how their body looks. As the body and brain become increasingly starved, the ability to think rationally about food is affected, and they develop a distorted view of their body - seeing themselves as fat, when they're anything but. Aside from extreme weight loss, anorexic people may suffer:

• Dizzy spells and fainting
• Feeling cold and poor blood circulation
• Rough, dry skin
• Constipation, tummy swelling and abdominal pain
• Irregular or no periods
• Weakened bones
• Lack of sex drive

In the long term, it can make getting pregnant more difficult and increase the risk of developing osteoporosis (brittle bones). A few cases even lead to death.

The most obvious sign of anorexia is extreme weight loss, but other things like mood swings, secrecy, an obsession with calories, food and thinness, and making excuses not to eat are also good clues.