Joanna Blythman: Don't fall for the low-cal trick

Don't rush to applaud fast food restaurants for displaying calorie counts on their Big Macmenus. This move, which comes as part of a deal between the Government and the food industry, might look enlightened, but it is no more than a marketing ploy that will yield no rewards for the nation's health.

As legions of dieters can testify, calorie counting is a useless way to lose weight. This is why Weight Watchers, the world's largest diet organisation, recently ditched its long-standing calorie-based points system. Foods can be low-cal, but have a poor nutritional profile. Seen through the calorie lens, popcorn and bagels, for instance, can be mistaken for health foods, eggs, dairy and meat, despite being naturally rich in life-sustaining macro and micro nutrients, can look like dietary demons. However, the finger of blame for obesity increasingly points not at whole foods containing natural fats, but at processed foods laden with refined carbohydrates and sugar, which rapidly turn into body fat.

The whole calorie theory already looks like the last half century's bankrupt nutritional paradigm. But it has served junk food barons well, creating a bonanza for profitable value-added processed foods and low-grade convenience meals. The sooner we wise up to this, the better.