Her generous derriere helped her find fame and fortune.

But having previously championed the fuller figure, Jennifer Lopez has now decided to cash in on the slimming industry.

The American singer claims to have come up with a diet supplement that can help women shed 10 per cent of their body fat in a matter of weeks.

It has been available in the US, but this week arrived in Britain, going on sale at high street shop Superdrug.

Mother of two Miss Lopez, 46, claims her BodyLab supplement is different from other weight loss products because it was developed specifically for women rather than adapting a formula designed for men.

She said this means it is better at targeting the way women’s bodies store and burn fat. In clinical trials, some women lost two inches off their waists and hips in as little as five weeks.

But some nutritionists were sceptical, pointing out that you still need to eat well and exercise to get in shape.

And Patrick Holford, a weight loss expert and author of Burn Fat Fast, warned it was more ‘hype’ than a healthy way to lose weight.

The BodyLab Metabolise capsules, which cost £19.99 for a two-week course, contain sinetrol, a natural fat-burning product made from extracts of citrus fruits such as grapefruit and red orange.

Ingredients also include guarana, a plant that contains caffeine, and biotin, a vitamin that is said to boost the metabolism and help skin, hair and nails stay healthy.

The tablets are meant to be topped up with a two-week ‘jump-start kit’ – which claims to improve liver function and energy levels with a mixture that includes garlic, turmeric and radish – and additional ‘replenish’ pills, made from live bacteria, elderberry and fennel seed, that are taken after seven days to improve digestion.

Dr Amy Heaton, director of scientific affairs at BodyLab, said most research on nutrition is carried out on men and recommendations are simply ‘scaled down’ for women.

But often these are not suitable as men and women’s bodies work differently.

So BodyLab looked specifically at how the female metabolism operates, which Dr Heaton said means their supplement is better than others at helping women improve muscle tone and burn fat while exercising.

She added that other supplements contain more protein than women need for maintaining muscle, ‘effectively loading excess calories and thereby compromising weight loss’.

The American singer claims to have come up with a diet supplement that can help women shed 10 per cent of their body fat in a matter of weeks

Hilary Kingston, a Harley Street nutritionist, said the BodyLab pills ‘have some nice ingredients’ that could work – but for women who are already healthy.

She added: ‘Like all supplements, what works for some women won’t necessarily work for others.’

Mr Holford agreed, saying that while there was evidence some of the ingredients do help burn fat, ‘the best way’ to lose weight is through exercise and a healthy diet.

He added: ‘Four out of the five of the ingredients in BodyLab Metabolise are sources of caffeine or similar stimulants, which are known to suppress appetite temporarily and possibly help weight loss, but it’s not a healthy or sustainable way to achieve that goal.

I’d say it’s more hype than a healthy weight loss supplement.’

Miss Lopez, who has eight-year-old twins Maximilian and Emme with ex-husband Marc Anthony, said: ‘I’m extremely proud of the fact our formulas were designed by women, for women. No bulky muscles.

No ingredients that wreak havoc on your hormones. Simply unique blends created with plant-based compounds to help women get lean and feel amazing.’