The Hairy Bikers are now the Hairy Dieters having accepted that years of overindulgence has taken its toll. The boys have been determined, however, to enjoy great food while losing weight. They've been reinventing the food they love making it big on flavour but low on calories.

In this final episode, Dave and Si's challenge is to reinvent the indulgent party treats they adore and celebrate their new svelte frames with their families and friends. They boys know that most people on a diet avoid parties where temptation is everywhere but Si and Dave are determined to prove that you can have a good time and shed the pounds.

In this episode they create slimline fairy cakes, crack a delicious low-cal quiche, reinvent the full-fat chilli taco and shed the paella of the fat stuff. And they meet up with wine expert, Ollie Smith, who has himself shed three-and-a-half stones in just a few months. Ollie gives the boys some much desired tips on what type of wine is better for you when you are on a diet.

With their families supporting all the way, the boys work hard to reach their goals. Dave wants to win his bet with his step-daughter Iza and get into his 20-year-old jeans and then slip into an off-the-peg designer suit. Si wants to get his top off without feeling embarrassed. Reflecting on their weight-loss adventure, the boys realise how much happier they feel and how important losing weight is for them and their families.

The boys catch-up on the progress of the Big Eaters - fellow foodies who are also going all-out to reduce their weight while worshipping good food. Their lives have also been transformed. Only chef Andrew, who didn't follow the Bikers low-cal regime, has had a tougher time shedding weight.

Finally, with one last visit to Professor Roy Taylor, the boys discover how successful their low-cal regime has been, and upstairs in dietician Professor Ashley Adamson's office they are confronted with the amount fat they've lost in total. The boys can't quite believe they used to carry all that lard around with them every day. Show less