The new system, which will be introduced on Sunday (7 November), updates the science on which the company's diet regime is based.
Instead of points measuring food by calories and saturated fat, the new ProPoints measure food by carbohydrate, fat, fibre and protein.
There will also be a new "real life" points allowance that gives people the chance to push the boat out occasionally.
Zoe Hellman, company dietician at Weight Watchers, said: "We like to call the weekly allowance the 'real living' allowance. It's there to give people the flexibility to include social occasions and special events, to let you indulge in your favourite food, manage unexpected invitations, or simply to treat yourself, without undermining your weight loss."
Weight Watchers, which describes the change as its biggest innovation for 15 years, is planning to back the campaign with a media spend of £28m to the end of 2011.
A direct mail push has started already with teaser marketing. Weight Watchers uses agencies Orchid and Gecko for its direct marketing work.
The campaign will span TV and press, created by McCann Erickson, and online, created by Plan.net and Razorfish. Media planning and buying is by OMD.