Roseanne Barr was watching repeats of her TV sitcom with her son Buck when he asked: 'Mom, did you know you were that fat?' She recalls: 'I said to him: "I had no idea."'

The comedienne, who once weighed in at a staggering 26st, is a shadow of her former self at just over 12st.

I had my entire digestive system removed, so I should look thinner!

While most celebrities might try to claim that their slimmer figure is due to healthy eating and exercise alone, Roseanne admits to having had her stomach stapled in a desperate bid to overcome the weight problem she'd battled for many years.

'I had my entire digestive system removed, so I should look thinner!' the mother-of-five says of her new figure.

'I still can't find any clothes to fit in LA because everyone's a size zero, but I do feel good.'

Roseanne was out of hospital after three days

The surgery, known as a gastric bypass, involved the actress having a section of her stomach stapled to create a small pouch – which means she feels fuller quicker and therefore eats less.

In addition, a Y-shaped section of her small intestine was attached to the stomach pouch, allowing food to bypass part of the small intestine to decrease the absorption of calories.

The operation is performed under general anaesthetic and Roseanne was out of hospital after three days – although the technique isn't without side effects. Surgical risks, although rare, include infection, internal bleeding and spleen injuries.

The stomach can be made smaller or bigger over time

But since Roseanne's gastric bypass in March 1998, a safer alternative has been developed. Known as laproscopic gastric band surgery, it's the most commonly performed 'stomach stapling' procedure in the UK.

Performed via keyhole surgery, it's less invasive and involves a tube being inserted around the stomach to create a small pouch, with the same results as stomach stapling. Because the small intestine isn't bypassed, the absorption of minerals and nutrients isn't affected and the band's adjustability means the stomach can be made smaller or bigger over time.

Obesity surgery is a last resort

But surgeons are keen to point out that it isn't a miracle cure that will overcome the emotional and psychological compulsion to overeat from which obese patients often suffer.

'Obesity surgery is a last resort and, although a powerful tool in keeping obesity under control, it's by no means a cure,' says Dr David Ashdown of the Healthier Weight Centre, which offers surgical and non-surgical treatments to tackle obesity. 'Success is dependent on diet and exercise to manage long-term weight loss.'

Rachael Woolston