Youngsters consumed less than half the recommended five portions of fruit and vegetables a day, according to the interim report "Food: an analysis of the issues".

Researchers found a quarter of 11 to 15 year-olds were now classed as obese and revealed soaring rates of type 2 diabetes among children.

While the British public is more obsessed with food than ever – with growing numbers of cookery shows cramming the TV schedules and a plethora of chefs' books on sale – few people manage to cook from scratch.

Carina Norris, a Fife-based author and the nutritionist for Channel 4's Turn Back Your Body Clock, said the prevalence of TV chefs had failed to teach adults how to cook for their families.

"People are watching celebrity chef shows for entertainment rather than trying to cook for themselves," she said. "It is more a spectator sport than an activity."

She also said some recipes promoted by TV chefs were too indulgent for daily life.

"If you look at some of the ingredients, they are very much 'treat' meals rather than routine ones. Maybe that's because, if you had celebrity chefs making basic home-cooked food, then it would not be seen as entertainment."

Ms Norris is researching children's eating habits for her PhD and has found that young people consume the majority of their calories in between meals, through "grazing".

A glance at some of the recipes promoted by celebrities for families shows many contain far more calories and fats than the daily recommended allowance.