Plummeting sales of slimming milkshakes and cereal bars has dragged the whole slimming foods market down 27 per cent in the last five years to a value of £81m, market research group, Mintel, says.

The figures make unpleasant reading for brands such as SlimFast, once a star of the weight loss sector, but herald a new era for healthy foods viewed as natural.

Dairy firms could reap advantages from this trend because of the natural image generally associated with their products.

Katy Child, Mintel market analyst, said it was surprising to see slimming foods on the wane when obesity rates stood at an all time high in the UK.

"But the market has suffered negative press with many health professionals seeing them only as a quick fix, that will not help people maintain a healthy weight in the long-term."

She added slimming foods had also fallen foul of the 'mega-trend' away from artificial ingredients.

More than a third of consumers asked by Mintel said they would not consider using slimming foods and preferred more natural ways of losing weight.

Unilever, which has owned the SlimFast brand since 2000, re-launched the range last year with new products and packaging in order to tempt consumers back.

But market value for slimming milkshakes and cereal bars is expected to almost halve again over the next five years, according to Mintel. That would mean a fall in value from around £90m in 2001 to around £16m in 2011.