Helena and Murray have been married for around 22 years, but their weight gain is concerning them. Helena believes that her weight gain is down to the menopause, but Murray is at a loss to explain why he's also gained weight. The surveillance cameras follow their every move to try and discover the truth.

Engaged couple Ronnie Derrett and Stuart Ellaway from Farnborough want to solve the riddle of why they're putting on weight.

Sisters Lauren and Stephanie from Essex are 20something siblings mystified by their weight gain. They've each put on two stone over the last two years, tipping the scales over into the overweight category. Lauren is even training for the marathon but has yet to lose a pound. The girls think they eat healthily, but Stephanie's grab-and-go habits and Lauren's social suppers suggest otherwise. Once they learn the shocking truth of what they're really eating, will they be able to stick to a healthy eating plan, nip their weight gain in the bud and lead a healthier lifestyle in the future? Plus, when it comes to eating, once we pop most of us can't stop, so in this episode the secret cameras record mischievous and tasty traps set for the public, proving just how easy it is for anyone to succumb to secret eating.

Lovebirds 22 year old Katie and 24 year old Michael from Kent are a young couple who can’t understand why they’ve piled on the pounds. Not only have they grown up together but they’ve also grown outwards and in the last 4 years they’ve put on a massive 8 stone between them. To find out why their weight is spiraling out of control Katie and Michael agree to surveillance cameras being rigged inside their home to monitor what they eat and in order to get the full picture they are also tracked outside the home by a crack PI team.

Glyn, Louise and Sue are 3 people whose family fortunes have increased by more than just a few pounds and they’re desperate to understand why they can’t shed their weight.

Good friends Daryl and Kat from Essex are desperate to lose weight, but think they eat healthily. Daryl's breakfast blowouts and Kate's serial snacking suggest otherwise.

Lorraine and Cori are dieting mother and daughter from south London, whose massive weight gain is a total mystery to them. They agree to let surveillance cameras being put inside their home to monitor what they eat.

The Castle family from Welwyn Garden City are mystified - how can they be putting on weight when they eat mostly healthy, home-cooked food? Using surveillance from cameras in their home, plus private investigators following them outside the house, the Castles are shown what they're really eating. Anna Richardson is on hand to guide them through their discovery, as well as put them on a ten-week healthy-eating regime. Plus, a group of office workers test the theory that by putting sweet treats out of sight, they can be kept out of mind and - more importantly - mouth.

Faye and Laura are shocked by their weight gain as they've been working overtime in the gym in an effort to lose weight, but with little success. They are put under 24-hour-camera surveillance in the hope of finding out if their diets reveal any clues as to those puzzling extra pounds.

This week, Dawn and Mike, a married couple from Hull and their best friend and lodger, Gareth, want to solve the riddle of why they're putting on weight.

The White Oliver family are desperate to find out how to live a healthier, more balanced diet for the sake of daughter Ellie who is very over weight.

Sister and brother Emma and Matthew from Camberley in Surrey are under the spotlight this time. Matthew is very sporty, mountain-biking at weekends and going to the gym three times a week, while Emma restricts her food intake on weekdays to just a few hundred calories a day. So why are these two putting on weight? They're convinced they're making the right choices with their food, but Emma's habit of picking while cooking, and Matthew's willingness to indulge in chocolate cake immediately after exercise, seem to suggest otherwise. Once they learn the shocking truth of what they're really eating, will these siblings be able to stick to a healthy eating plan, start winning their fight with the flab and look forward to a healthier future?