Identical twins Kelly Acres and Stacey Warren loved gorging on Chinese takeaways and fish and chips together.
The obese sisters both tipped the scales at 20st and struggled to stick to diets.
But all that changed when Stacey was offered a gastric bypass in November 2010 and shed a staggering 10st in two years.
Stacey was only given the op due to health problems - leaving Kelly watching enviously as the pounds fell off her twin.
As Stacey slimmed to 8st and a trim size 8, Kelly became increasingly jealous and begged her doctor for a gastric bypass.
Size 26 Kelly, from Exeter, says: "Doctors told me I had to lose weight through diet and exercise. I didn't think it was fair and watching Stacey lose weight was tough.
"She was posting pictures of her slim figure on Facebook and I felt like she was rubbing my nose in it. People no longer believed we were twins, which was hurtful."
But defiant Kelly kept pestering her doctor until she was also eventually given the go ahead for a gastric band after developing arthritis.
And once Kelly has had her surgery this summer the unrepentant twins, now aged 42, will together have cost the NHS £30k.
Retail supervisor Kelly, now 18 stone, says: "I'm entitled to it! I'll be saving the NHS money in the long run because I won't need treatment for obesity-related illnesses.
"I was so dissapointed when I was initially turned down - I thought I deserved a gastric bypass as much as my sister.
"I can't wait to have a slim figure and lose ten stone so I can look like my twin again."
Stacey - who is 5ft 2 - adds: "I felt bad when I had the surgery because I knew how much Kelly wanted it.
"But I was suffering from a hormone imbalance which made it hard for me to lose weight. I'm pleased she's having the op, I know how much it'll change her life."
Stacey and Kelly had always been big and were bullied throughout childhood.
Kelly - who has a BMI of 44 (18-25 is the healthy range) - says: "We were called the 'fat twins'. It was really upsetting.
"We ate healthy meals but had big appetites and our dad's side of the family was big. By the age of 10 we weighed 9st."
Kelly and Stacey continued to pile on the pounds through their teens.
Kelly explains: "We got part time jobs at 14 and spent our wages on crisps and fizzy drinks. We loved food and didn't do any exercise."
But it was in her 20s, after having two children, Matthew, now 24, and Tristan, 20, that Kelly's weight spiralled out of control.
She says: "After having the boys I weighed 20st. I hated my body but I carried on eating huge portions of pie and chips or Chinese takeaways for dinner."
Over the next decade, Kelly continued gorging on junk food and yo-yoed between 20 and 26st.
She says: "Stacey's weight stayed around 20st while mine fluctuated.
"We were both unhappy and tried diets like WeightWatchers together, but we'd always put the weight back on.
"We saw each other most Fridays after work and treated ourselves to takeaways, we were a bad influence on each other."
In 2008, aged 36, Kelly - who has since split with the father of her children and has a new boyfriend Muhammed Choudhury, 28 - started thinking about having a gastric bypass.
She says: "We were both 20st at that point and I was at the end of my tether.
"Strangers would say I had an 'a*se like the back of a bus' and one woman whispered to her friend that I must be an over eater.
"It was really hurtful. I kept managing to lose a bit of weight and putting it on again. I needed help.
"I told Stacey I was thinking about surgery and she was supportive, but said she wanted to lose weight naturally."
Kelly approached her GP who told her she needed to try diet and exercise before being given surgery.
But a few weeks later, Stacey was offered the operation because she was suffering from health problems.
Stacey explains: "I'd been to see the doctor because I had a hormone imbalance in my pituitary gland, which was making it difficult for me to lose weight.
"He told me I was at risk of developing type 2 diabetes and suggested a gastric bypass.
Kelly felt it was a bit unfair, as she's always been bigger but was told she had to do to try dieting and exercise.
She says: "I was nervous about the op at first, but when I realised how much weight I could lose I was excited."
Stacey was instructed to lose 2st in order to make the surgery in November 2010 safer and began a healthy eating program.
She says: "It took me two years to lose the weight by eating lots of protein and salads.
But two months after the op, Stacey had already lost a further 2st.
"She looked incredible," Kelly says.
"It was hard watching her lose weight. She gave me her old clothes and I felt like the fat, frumpy twin."
Kelly begged her GP for the same surgery, but was told she needed to diet and exercise instead.
It was only after developing arthritis in her right foot as a result of her weight, leaving her unable to exercise, that she was granted the op last August.
She has since lost 2st in preparation for surgery in the summer.
She explains: "I lost the weight through healthy eating and occasionally skipped meals in the evening. The surgery was my motivation.
"My friends are supportive and Muhammed knows the op will be good for my health, although he likes my bigger figure.
"I can't wait until I feel confident about my body and look as good as my twin."
Stacey adds: "I'm looking forward to Kelly having more energy and feeling healthier.
"We're still really close but it'll be nice to go clothes shopping together again and have people recognise us as twins."