The so-called 'diet' and 'light' brands of food products that claim to make people slim are no more effective than normal grub, according to consumer watchdogs 'Which?'.
After analysing calorie, fat and sugar levels in such products, Which? found that they offered little benefit over standard versions.
They tested weight-loss claims across a range of foods sold by Asda, Morrisons, Sainsbury's, Tesco, M and S and Waitrose.
And the results indicated that Kellogg's Special K, which is marketed as a slimming cereal, contained equal calories at 171 per 30g as the company's Corn Flakes and even more than its Bran Flakes.
Weight Watchers' thick-sliced white bread, at 68kcal per 29g slice, was revealed to be nutritionally similar to Warburtons Toastie sliced white (69kcal per 29g slice) and Asda Danish white (63kcal per 25g slice).
While McVitie's Lights digestive biscuits had less fat than their Originals, but it contained more sugar. This comes out to be a difference of just 4kcal between the two.
An M and S "Count On Us" lasagne contained 440 calories, less than their standard range's 620kcal. On the other hand, a normal Morrisons lasagne had 464kcal and Waitrose's 468kcal, little more than M and S's "healthy" option.
"If you're looking for a quick fix to shed a few pounds, weight-loss products are not the answer," The Sun quoted Nikki Ratcliff, of Which?, as saying.
But Kellogg's hit back: "Consumers aren't stupid. The reason Special K is one of the UK's biggest selling cereals is because it works."