But instead of treating herself to a slice of cake or a yoghurt, Ellie takes two packets of laxatives from her bag and swallows the lot – 40 tablets in all.

The 28 year old is so addicted to laxatives, she takes as many as 100 in a day.

“I suffer agonising stomach cramps and spend hours rushing to the loo,” says Ellie, a full-time mum from Pembrokeshire.

“I often feel weak and dizzy and I know what I do is wrong, but I can’t help myself.”

In the past five months, Ellie, who is 5ft 6in, has lost a third of her body weight, dropping from 15st 7lb to just 10st 7lb.

Her problems started in September 2004 with the traumatic birth of her son Joey, now three.

Ellie wanted a natural birth, but after a difficult 18-hour labour, she had to have an emergency Caesarean.

Ellie developed severe post-natal depression and was prescribed antidepressants, and for the first time ever began worrying about her size.

“I’d been big all my life but had never worried about it.

"By the time I conceived Joey, I was a size 22 and weighed 16st 7lb,” she says.

“But after he was born my weight became an obsession, and losing it felt like the only thing in my life I could control.”

Ellie started skipping meals and making herself sick, losing a worrying 5st in four months.

In August 2005, her weight plateaued at 10st 7lb but by then Ellie was addicted to slimming and, because she hated making herself sick, turned to laxatives to lose even more weight.

At first she took four or five tablets a day, unbeknown to her husband Jason, a 38-year-old teacher, who joined friends and family in complimenting her on her new slimmer figure.

When she fell pregnant again in November 2005, Ellie was a size 10-12.

During her second pregnancy she ate normally, stopped taking laxatives and antidepressants, and looked forward to her second chance at a natural birth.

But to Ellie’s horror, her baby stopped moving in the final days of pregnancy and Ellie had to have another emergency Caesarean.

Grace was born healthy, but over the next few months Ellie’s life spiralled out of control.

She began taking 10 laxatives every time she ate, and by last Christmas had upped her daily dose to 40.

She was now at risk from serious malnutrition and dehydration, which can cause heart failure.

“I finally confessed to Jason,” she says. “He was horrified and vowed to help me get better.”

But despite her husband’s support, by January this year, Ellie was taking an incredible 100 laxatives a day, spending about £30 a week on them at the supermarket.

“It had started as a way of controlling my life, but now they controlled me,” admits Ellie.

In February, she sneaked out of the house in the early hours and went to her local beach, where she sat crying for hours.

Jason woke to find a note beside him in which Ellie said she couldn’t cope any longer.

“I wasn’t planning on killing myself, but I felt so full of despair that I wanted to get away from my life,” she explains.

Worried sick, Jason phoned and texted and eventually persuaded Ellie to come home where she collapsed in tears.

It was the trigger for Ellie to seek help. Mother’s Voice, a support group, and her local health visitor have become involved, and Ellie is now on a waiting list to see a psychologist.

She weighs 10st 7lb now and is a size 10, but Ellie’s still taking between 60 and 100 laxatives several times a week, depending on her mood.

With Jason’s support, she’s trying to cut down.

Ellie says: “My addiction affects every aspect of my life – I rarely leave the house any more, but despite everything I still hope I’ll get the help I need, and that one day I’ll be able to enjoy motherhood as much as I’d thought I would.”

Dr Hilary says: “Laxatives are commonly taken by anorexics and other obsessional dieters in the mistaken belief that it is a healthy way to control weight loss. But chronic abuse is dangerous and can lead to dehydration, muscle weakness, stomach cramps, malnutrition, anaemia, even fatal heart failure.”

Would you consider taking laxatives as a way to control your weight? Do you think about the wider health implications behind doing this? Should taking laxatives be considered as serious an eating disorder as anorexia or bulimia?

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For support with post-natal depression, log on to mothersvoice.org.uk; Photography: Sian Trenberth; Hair and Make up: Charley B at Gingersnap