Media playback is unsupported on your device Media caption Lee Donald says fitness has changed her life

Lee Donald didn't think she would see her 21st birthday.

She had struggled with an eating disorder from the age of 13 and at her lowest point made herself sick more than 10 times a day.

But she successfully hid her problem throughout her teenage years because her weight was considered normal.

She explains: "I maintained a normal weight for years and that's very common with bulimics in particular, to be able to maintain a normal weight."

Now 37, Lee believes many eating disorders go unnoticed because they are so commonly associated with being a low weight.

"There's no definitive eating disorder weight," she says, adding that for her, the illness was "not really about weight".

Instead, it was "much more about control and self harm".

Image copyright Lee Donald Image caption Lee now lives with her wife, daughter and newborn son in Aberdeen

Binge eating and bulimia are the most common types of eating disorders in the UK with studies showing that 80-85% of people with eating disorders are not underweight.

Despite this, two in three adults are more likely to name being thin as a sign of an eating disorder, according to a survey by the charity Beat.

Rebecca Willgress, from Beat, says: "It is important that we challenge stigma and stereotypes, educating that eating disorders are serious mental illnesses, not physical, can affect people of all ages, genders and backgrounds and that you cannot spot an eating disorder by simply looking at someone.

"The sooner someone gets treatment for an eating disorder, the better their chances of a rapid recovery, and it is essential that no one is denied care because they are deemed 'not thin enough'."

'Bulimia cost me my job'

For Lee, it wasn't until she had significantly dropped weight in the space of a year for friends to realise something was wrong.

She was 19 at the time and working as a water sports instructor in France.

Lee recalls: "I was thinking I was being sneaky being sick after meals, but actually my friends who were concerned about me followed me and they realised I was being sick.

"They told the centre manager and I got sent home. It was the worst thing that could possibly happen.

"I wasn't deemed safe in case I passed out when I've got kids doing water sports."

But Lee continued to be in denial about her bulimia despite the shock of losing her job.

She did not manage to get her eating disorder under control until she was 29.

Image copyright Lee Donald Image caption Lee Donald believed her "normal weight" helped her to disguise the fact that she was bulimic

When her health started to deteriorate, she realised she had to address her problem. She had always been a physically active person but she began to struggle to maintain this.

"My energy was very low. I found it very difficult to feel full - if I had food in my stomach and I felt full, I really, really struggled with it. I had to be sick."

She describes beginning to feel faint regularly and not being able to think about anything other than being sick, which also led to her losing four front teeth.

"I was so sick of being sick."

But getting better was a more difficult task than she thought it would be: "I remember speaking to my sister, she was one of the first people to know, and she would ask 'how many days have you managed now?' and I'd count the days.

"I'd say 'I've not been sick for five days', 'I've not been sick for six days', and then I'd be sick again."

Lee sought help from counsellors, psychiatrists, a life coach, as well as being an outpatient and attending group meetings.

But it wasn't until she qualified as a personal trainer that she was able to get her life back on track.

Lee, who is married with two children, uses her experience to help others beat their eating disorders.

She says: "If people are overweight, others seem to just think 'you're eating too much', whereas they actually could be really struggling with an eating disorder. In essence, regardless of whether somebody is overweight or obese, it is an eating disorder at the same time.

She adds: "People who have issues with bingeing and being sick, it's totally normal for them to have a healthy weight. That doesn't mean to say they don't have an eating disorder and they're not having lots of problems."

If you need help or support to do with any of the issues raised in this article you can take a look at the BBC Advice pages or talk to Beat - a charity that helps people with eating disorders - on their helpline on 0808 801 0677.