Betsy Sanchez was just 12 when she became the world's youngest gastric sleeve patient.
Now 14, she claims the risky weight-loss surgery transformed her life, and says having 70 per cent of her stomach removed has helped her beat cruel bullies who teased her because of her size.
In the two years since her op, Betsy, from Mexico, has dropped five stone from 15 stone to 10 stone, and is exercising and taking part in activities like horse-riding for the first time.
Betsy's mum Ana Sanchez, 39, believes taking the drastic step at a young age prevented her daughter following the same heart-breaking path as British teen Georgia Davis, 19, whose food addiction caused her weight to balloon to 63 stone.
"Diet and exercise didn't work for Betsy - she was addicted to food, only surgery would work," says Ana.
He claims the benefits are not only improving a child's health and preventing medical issues such as diabetes and liver disease, but enabling them to gain confidence, have a more active childhood and happy school life.
Dr Alvarez, who receives patients from across the USA, Britain and Europe, has since operated on other children, but sets a lower age limit of 12.
Betsy says: "When my uncle said he could make me thinner I was so excited. I can still eat whatever I want but smaller portions.
I can have McDonald's, but much smaller portions, only two chicken nuggets and chips. I'm much happier.
"I now go horse-riding and I have lots of friends."
Betsy's weight problems began at the age of three when she started asking for extra portions and demanding snacks between meals, causing her weight to rise to four stone.
Ana and Betty's dad Guillermo, 44, a furniture dealer, had treats in the house for their two other children, aged 13 and nine.
"Betsy would have four cookies and four crackers between meals. If I tried to stop her, she'd have a tantrum. She was always hungry," explains Ana. "I tried serving healthy food and cutting portions, but Betsy was out of control."
Ana and Guillermo took her to see a paediatrician and she underwent tests for an under-active thyroid but no medical reason was found for her weight issues. Nutritionists and psychologists also failed to find a solution.
By the age of seven, Betsy was eating up to 3,000 calories a day - double the recommended intake for her age - and by the time she was nine she was a size 20 and weighed 13 stone.
"When I asked mum for seconds she gave in. I used to comfort eat because I was bullied," says Betsy. "My parents took me to see lots of doctors and nutritionists but nothing helped me lose weight. I was worried I was going to get so fat I'd end up bed-ridden."
By the time she was 12, Betsy was 15 stone and had a BMI of 41, making her morbidly obese. Her parents took her to see Dr Alvarez, who is Ana's second cousin, anxious that Betsy might be suffering from depression and could develop medical issues such as diabetes and high cholesterol.
Dr Alvarez explained all young patients undergo a psychological evaluation to ensure they understand the implications of weight-loss surgery. They are put on a nutrition and exercise program which continues after the operation.
He was able to operate on Betsy in 2008 after studies showed the benefit of surgery on young people. Betsy is believed to be the youngest patient ever to undergo the gastric sleeve.
"It is very controversial to operate on children," he explains.
But I see the benefits of helping children in cases where parents have tried everything but nothing else seems to control their eating problem. It has changed Betsy's life. She now goes to a new school where no-one even knows she used to be overweight.
"Betsy is like a different girl," agrees Ana. "She is still shy, but she is blossoming into a beautiful young woman, making friends, and enjoying her teenage years. I think surgery is definitely worth considering in some cases for children like her."
12 years old. What do you think?