Hairy Bikers Si and Dave embark on a campaign to lose two-and-a-half stones in three months. The duo face up to some home truths about themselves and their eating habits, and with the support of their families and advice from a weight-loss clinician, become the Hairy Dieters. They join forces with a group of overweight foodies looking to shed pounds themselves.

Hairy Bikers Si and Dave tackle a slimline cooked breakfast and a roast chicken family dinner. Having swapped their famous motorcycles for bicycles, a final challenge awaits. Can they tempt two hungry rugby teams to forgo their post-match curry in favour of a low-calorie French cassoulet?

Si and Dave try to redesign the pie, one of the nation's favourite comfort foods and one of their fellow big eaters' favourite treat. The duo also learn that though their diet is starting to take full effect, they'll need to reduce their calorie intake to an even lower 1,200 per day. Moreso, they'll need to boost their exercise as they travel to Windermere.

As their campaign comes to an end, Dave and Si reinvent indulgent party treats to celebrate their new svelte frames with their families and friends. They meet newly slender wine expert Ollie Smith who reveals what wine is best for those on a diet. Si and Dave also catch-up on the progress of their fellow dieting foodies and discover that many have had their lives transformed.