WeightWatchers is discarding its famous fat and calorie-based points plan in favour of a new system that allows alcohol and the odd fast food binge.
The international dieting company said it was adopting the new "ProPoints" system because "science had moved on" and the previous style of calorie-counting had been proven to be inaccurate and "outdated", The Grocer magazine reported.
The new plan, set to be announced on Monday, will centre on the amounts and types of protein, carbohydrate, fibre and fat in food, while the old calorie-based point system has been recalibrated to factor in the energy used in chewing and digesting the food.
In an added bonus, followers will for the first time be granted extra "real living" points so they can treat themselves to their favourite drink and fast foods, while all fruit and most vegetables will carry zero points.
Dieters will be allowed a typical daily allowance of up to 29 of the recalculated ProPoints, compared with 18 points previously, plus the weekly bonus of 49 "real living" points.
A gin and low-calorie tonic will account for two ProPoints, a pint of lager adds six points and a Big Mac costs 12 points.
WeightWatchers spokesman Chris Stirk told The Grocer that the changes to the 15-year-old system would help consumers lose weight while living in the real world. While he denied the changes were an admission that the old system was flawed, he admitted it had needed to be updated to keep pace with the latest scientific thinking.
Mr Stirk said: "Points have been phenomenally successful but science has moved on. 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."
WeightWatchers dietician Zoe Hellman added: "We've taken all the best nutritional science from around the globe and distilled it down into one simple, easy-to-follow plan to give healthy, sustainable weight loss for life."
Manufacturers who will have to make changes to their WeightWatchers packaging to carry the new ProPoints system include Heinz, Yoplait, Greencore and Warburtons.