WeightWatchers, the international dieting empire, is exchanging its fat and calorie-based points system for a new one that allows treats.

The company is calling this system `ProPoints', stating that "science has moved on" from the previous style of calorie counting, which has recently been proven inaccurate.

The ProPoints plan will focus on the amounts and the types of carbohydrates, fibre, fat and protein in foods, rather than just fat and calorie content.

In the old system a dieter could calculate their point quota based on age, gender, weight and height. Whereas the average daily allowance was 18, the new system has jacked it up to 29.

The deal closer is the `fund' of 49 `real living' points, which dieters are allowed to dip into on special occasions. These might be a big night out or a fast food dinner.

Another change is that fruit and most vegetables will be point-free, encouraging dieters to snack on healthy foods.

The company's spokesman, Chris Stirk, said that these changes are intended to help consumers lose weight while living in the real world.

"We have learned so much more about how we metabolise the food we eat and how we can give people the best programme for sustainable weight loss success."

This change does not undermine the good name of WeightWatchers. A study found that dieters attending NHS-funded weekly WeightWatchers sessions lost an average of 15 pounds in a year-double the amount of those receiving weight-loss advice from their GP.