The new series starts with tears and tantrums as 21-stone Louise Hayes swaps with Josh Evan, whose diet barely features a proper meal. Louise is determined to get through the swap as deep down she's terrified her five-year-old son is picking up her supersize habits and will end up as big as her. She gets a personal message from America, from 41-stone Texan Karen Ferguson, who is so disabled by her weight that she's been forced to move into a care home. Louise is also flown out to America to witness first hand the horrors of being super-obese.

In the feeding clinic, supersize Amy Green, who tips the scales at a staggering twenty-stone plus, swaps with superskinny Ami Walsh, who only weighs seven stone ten . Twenty-one-year old comfort eater Amy gorges on enough food for three women and is terrified that she's going to pass on her poor eating habits to her baby daughter. Meanwhile 18-year-old Ami is always too busy to eat, and her poor diet has left her lacking in energy and confidence. It's an emotional week for both women, who are desperate to turn their eating habits around. Also, throughout this series, the show follows the ongoing story of women with eating disorders. This time, dietician Ursula Philpot urges the group to face their fear of foods head on in the supermarket.

It's war in the feeding clinic as Dawn goes into meltdown when calorie-counting Charlene doesn't eat her mountainous meals. Meat addict 47-year-old Dawn Grant tips the scales at a whopping eighteen stone four lbs. Over a year Dawn wolfs down 208 whole chickens, 1716 rashers of bacon, 3800 sausages, 36,000 slices of deli meat, and 36 kilos of minced beef. Charlene Sequiera weighs less than six stone. Her diet is so restrictive that she lacks energy and is constantly sleeping. This is seriously affecting her life at uni. Charlene desperately needs to eat more, but it's one excuse after another until Dr Christian gives her a stern dressing down. Dietician Ursula Philpot challenges the regular group of eating-disordered women to have 3-D plaster casts of their torsos made to face the reality of what their dangerous eating habits have done to their bodies.

It's a first for the show with a double swap as mother and daughter Janet and Tara Wells swap diets with too-busy-to-eat Joanne Evans and Keith Linage. Janet and Tara weigh in at nearly half a ton. Their diet of cholesterol-crammed Chinese meals and cakes aplenty have left them both morbidly obese. Joanne and workaholic Keith have no time for food in their hectic lifestyles. But, with a gallery of superskinny horrors, Dr Christian shocks them into realising the potential dangers of their deficient diets. And the show's group of eating disordered people bravely face their food fears head-on as they attempt to confront the overwhelming choices offered at a breakfast buffet.

It's an emotional rollercoaster in the feeding clinic as Supersize cheese addict Stu Preston takes on Superskinny portion controller Alice Duran. At 27 stone 13lbs Stu is digging himself an early grave with a knife and fork and desperately needs help. Twenty-five-year-old mum of two Alice weighs a lightweight 7 stone 13lbs by obsessively controlling her diet and weighing her food but she's hiding a supersize secret, she once weighed a staggering 17 stone. Stu's deadly diet of fast food and excess cheese pushes Alice into meltdown and Dr Christian wades in to confront her about her food phobias. Plus eating disorder dietician Ursula Philpot asks the show's group of eating disordered people to look back to childhood times when eating was enjoyable, which forces the girls to face up to the fact food should be fun.

Forty-two-year-old Mark's daily diet of mountains of greasy food has left him 11 stone overweight. He goes head-to-head with self-conscious food casualty Dale who weighs less than ten stone. Mark Hughes is a heart attack waiting to happen. His continuous consumption of greasy mountains of food has left him weighing 22 stone 3lbs. He's not slept in the marital bed for seven years because of his loud snoring, and relations with his wife are becoming tense. He's checked into the feeding clinic as a last ditch attempt to shift some pounds and start becoming an active dad again. Mark's diet-swap partner is 21-year-old Dale who's been running his body on empty and now weighs a lightweight nine stone six lbs. His skinny frame has knocked his self confidence and left his family worried. Dale wastes no time getting stuck into Mark's colossal portions but the mountains of grease and fat soon turn his stomach - and he just can't keep it down! This sickening wake up call helps Mark realise just how appalling his diet really is. Plus the show's eating disordered group are challenged to confront their distorted body images with a day of clothes shopping. It's a struggle for all of the girls but particularly the youngest member of the group Erin, who has an emotional realisation about the extent of her illness.

Sugar junkie Danni Brooke swaps with 21-year-old Vicki Smith from Glasgow. It's a highly emotional week in the feeding clinic for 29-year-old Danni Brooke from Lincolnshire. Danni's constant gorging on cakes and snacks has left her a staggering twenty-four stone five. Food-phobic Vicki Smith's picky eating habits have reduced her to a lightweight six stone four. Swapping diets brings extreme emotions to the surface as Danni opens up to Vicki about a foodie secret from her childhood. Dr Christian shocks Vicki with a superskinny gallery designed to highlight the potential dangers of her appalling diet, while Danni breaks down as she gets a wake-up call from America. Eating disorder dietician Ursula Philpot takes the remaining two members of her group to a spa to try and reverse their feelings of low self-esteem.

Second-hand car dealer James Collier goes head to head with uninterested undereater Modasser Zafar in a tense diet swap. Thirty-two-year-old James loves supersized portions of greasy food - sometimes getting through four platefuls in a sitting. James weighs in at over 24 stone six and is terrified that his steady weight gain will end up giving him a heart attack and prevent him seeing his kids grow up. Thirty-one-year-old credit controller Modasser is at the opposite end of the scales at a tiny eight stone three. He skips meals and rarely finishes dinner. James receives a 32 stone wake-up call from America in the form of Mike Eak from Florida. Mike not only lost his job because of his weight but his enormous size has left him incontinent and his lack of mobility has meant he's taken to urinating in cups. Also, the remaining two members of the eating disordered group reach the end of the course and celebrate with a two course meal.