1. Weight Watchers - loved by Patsy Kensit
How it works: Sign up and follow joined Weight Watchers' ProPoints plan. Every food is worth a different number of 'points', all of which add up to your weekly limit. Your limit will depend on your personal health and weight loss goals.
The expert says: “Weight Watchers is nutritionally sound and gets the thumbs up from docs. You're encouraged to eat lots of fruit and vegetables and nothing's banned.
"Instead you think about the quality of what you eat in terms of how it curbs your hunger rather than just counting calories. There's a big emphasis on group support too which helps a lot of people.”