But experts are warning they are risking their health.

Insulin helps people with diabetes absorb glucose

Sarah was 21 when she was diagnosed with type 1 diabetes.

The news kick-started a seven-year battle with her weight.

"I was like any normal 21-year-old. I liked going out, travelling and drinking.

"But all of a sudden I was told I had this condition and I had to start controlling my diet and managing my diabetes."

After starting her daily injections of insulin, she found her weight started increasing - insulin helps patients to absorb glucose better.

From weighing about 9st before her diagnosis, she soon reached 12st.

It was hard. There is all this pressure on girls to remain thin, from magazines, from advertising Sarah, diabetes patient Diabetes eating disorder warning

Sarah, who is now 28 and lives in London, said: "It was hard. There is all this pressure on girls to remain thin, from magazines, from advertising.

"I supposed I just freaked out. I started missing some of my doses. I would just take one in the evening and miss all the others I should have been taking with my meals.

"The doctors and nurses were telling me what harm I was doing, but I would just not listen."

Sarah's behaviour has led to her being admitted to hospital three times in the last six years after infections - or on one occasion food poisoning - prompted her blood sugar levels to dangerously high levels.

Weight

"I would have a scare and then start having the injections, but I would soon relapse. It didn't matter, I just thought I had to lose weight."

At points her weight dropped to 6.5st, but Sarah's perspective changed last year when she found herself in hospital a few days before her 27th birthday in June.

"I suppose I just started thinking what I was doing. My eyesight had started to suffer and I had nerve damage at the bottom of my legs. The doctors said I would never be able to reverse the damage.

"I guess I just realised I could end up doing myself a lot of harm and that one-day it would go too far and I might die."

Sarah is now taking her four-daily insulin doses, but she says it is still a battle.