Tipping the scales at just over six stones, 41-year-old Elizabeth Young thinks she's found the elixir to eternal youth: an extremely disciplined diet. She exists on a radical diet of Brazil nuts, rice, garlic and not much else. In the feeding clinic, Dr Christian Jessen, begs to differ and has the challenge of persuading her that her lack of eating is doing the exact opposite; it's prematurely ageing her. Dr Jessen's prescription is a short, sharp shock, a week of eating the food of 34 stone 9lbs supersized milkman Stefan Ginesi, the fattest contributor of the series. The Northern Irish 'carb junkie' lives on potatoes and Irish stew and is keen to lose weight to start dating and get involved in a relationship. Into the fourth week of her diet, journalist Anna Richardson goes nil by mouth when she swaps food for diet pills. On the way she meets Denise Townsend, whose prescription pills left an unsightly and permanent residue in her pants… and her toilet. And more alarmingly she encounters two young pill poppers whose cocktail of diet pills is potentially seriously damaging their health. Corporal Gillian McKeith gives a posse of Portsmouth girls their marching orders as they attempt to reduce their rears with the help of Masai technology, a trainer designed to get the wearer to copy the tribe's long-distance walking technique. And do the high-rollers at the dogs know a high calorie takeaway when they see one? With pizza, a burger and an Indian on offer which one is odds on favourite for a feast? Gillian McKeith reveals how to indulge and avoid the bulge.

At just 6 stone 10lbs, 19-year-old Tatiana Moxey is extremely underweight and desperate for people to stop asking her if she's got an eating disorder. Weighing in at 23½ stone, jazz singer Sandra Andrew is a late-night food lover, enjoying home-cooked West Indian food through the day before feasting on junk food all night long. In the feeding clinic, under the supervision of Dr Christian Jessen, Tatiana and Sandra take part in an extreme diet swap to fatten up skinny Tatiana and slim down overweight Sandra. Meanwhile, size 14 journalist Anna Richardson immerses herself into the world of serial dieters and attempts to drop a dress size or two by following their faddy diets and lifestyle regimes. This week she looks behind the glamorous façade of modelling and exposes the body-abusing methods some models use to stay skinny as she embarks on an extreme apple-only 'model' diet. And it's no wonder we're obsessed with the size of our bottoms: Britain has the biggest bums in Europe; so Gillian McKeith is on a nationwide campaign to reduce the size of our rears. And with the help of 101 women, the latest treatments, hi-tech gadgets and machinery that claim to achieve a perfect rear are put through their paces. This week a group of Nottinghamshire lasses are lassoed to horse-riding simulators to gee up their chances of success. And if you wise up to calorie content you can still indulge without the bulge. Gillian McKeith heads to Billingsgate Market to find out if the fishmongers of London know a high-calorie breakfast when they see one.

Pizza delivery driver Thomas Barnes weighs 27 stone 10 lbs, largely due to his weakness for pizza. Glamourous granny Linda Chik loves fruit and veg, but doesn't eat enough for her busy-bee lifestyle, so weighs in at only seven stone. Before they swap diets, Dr Christian prescribes a supersized wake up call for Thomas - sending him to visit 35 stone Robin Jones from Missouri. Robin is registered disabled and suffers from a host of health problems due to her obesity. And Emma Woolf concludes her investigation into eating disorders with a meeting with 21-year-old Aria Valzano who developed anorexia aged 14.

This week Dr Christian Jessen tackles the eating habits of Amy-Jo, a superskinny undereater, who is due to spend five days in the 'feeding clinic' with 38½-stone Andy. The participants' attitudes towards food couldn't be more different, but they are both putting their health in danger. Amy-Jo may look perfect on the outside but her extreme exercise regime and diet, which restricts carbs, could lead to her body crumbling inside. To shock her into a new way of eating, she must gorge on the gigantic meals and colossal snacks of the biggest supersize of the series. Meanwhile Andy must learn to survive on the limited calorie intake of Amy-Jo. The aim is for them both to learn how they are affecting their bodies Journalist Anna Richardson tries another extreme diet, taking the star-studded route to dropping a dress size: living on tiny jars of baby food. She also meets former Liberty X star Michelle Scott-Lee, who spills the beans on the pressures for celebrities to be thin. Gillian McKeith has a shock in store for a team of large-bummed female rugby players from York as she continues her quest to reduce the nation's rears. Gillian also tests the knowledge of a bunch of London taxi drivers. With cheesy jackets, ploughman's and scampi and fries on the canteen menu, can they recognise a high calorie option when they see one?

Dr Christian Jessen faces a bumpy ride this week in the feeding clinic as superskinny size zero Louise Sapsford, who clocks in at 6 stone 2lb, faces up to supersize 28 stone 13 pounder Desroy Gordon's challenging diet of non-stop take-aways. Louise comes to terms with the fact that size zero is not a good look and changes her eating habits for good. Stuffing herself with Desroy's gigantic meals and a relentless run of take-away dinners teaches Louise she can eat more than the tiny meals she never normally finishes. Journalist Anna Richardson nips across the pond to New York City where she discovers the very latest fat-busting techniques, including cheerleader aerobics! Gillian McKeith has a powerful arse-busting technique in store for some London lasses as she continues her quest to reduce the nation's rears. For this week's Extra Helpings Gillian finds out if a bunch of jive dancers know their calories as well as their moves as she offers them a variety of romantic dinners for two. Can they tell which dishes they can dine out on without building up their love handles?

Long and lanky, 22-year-old Alex Law from Stockport hits the scales at just over ten stone because he barely eats a meal. Tired and exhausted he lives on a diet of caffeine pills supplemented by stodgy cakes and snacks despite holding down the physically demanding job of a plasterer. Dr Christian Jessen decides to hit him where it will hurt most with a stiff warning about his manhood. His diet swap partner Tracy Morgan from Wales has a mouth that's constantly on the move. If she's not talking at the call centre where she works she's snacking, just like Alex, but the trouble is she's snacking before, after and in between her already substantial daily meals which has caused her weight to soar to nearly 20 stone. Deprived of the meals and forced to eat just Alex's snacks she soon realises where she's going wrong. Journalist Anna Richardson meets Isabelle Caro, the actress who unwittingly found herself a worldwide celebrity as the star of a media campaign to highlight the shocking affects of anorexia. And for the first time in her life Gillian McKeith pigs out as she gets a group of ladies from Basingstoke to reduce their rears with a workout at a pig farm followed by trying out the bum-shrinking effects of mud-packs. Does mum know best when it comes to counting calories? The nation's favourite family meals are checked out by supermarket check-out girls for their highest calorie content as Gillian dishes up spaghetti Bolognese, good old-fashioned sausage, mash and gravy, and a traditional roast beef meal.

Fussy eaters put up a food fight in the feeding clinic as Superskinny Yasmin Smith is forced to swallow a gargantuan diet of snack foods and diet drinks, while Supersize Darryl Weston weighing in at a whopping 33 stone and one pound suffers on Yasmin's lactose, wheat, sugar and fat free diet. Dr Christian Jessen referees the match. Journalist Anna Richardson takes the nip and tuck route to slimming by investigating the world of cosmetic treatments, but she meets with unforeseen complications during the procedure. Gillian McKeith is sent to Coventry as part of her nationwide campaign to turn bountiful bottoms into bums of steel. This week can the personal services of a gym bunny reduce their rears? And there's no need to battle the bulge if you know the calories of your favourite foods. With Cornish pasties, chicken salad and ham rolls on offer, do the market traders of St Albans know a high calorie lunch when they see one?

Dr Christian visits McAllen's mortuary, which is having to be supersized to cope with wider doorways and autopsy tables. In the feeding clinic, LJ Marley, a takeaway addict who tips the scales at 24 stone, with a 59 inch waist, swaps diets with Katie Reeve, whose childlike portions see her weigh in at a paltry 6st 11lb. LJ visits the US for some shock therapy, being forced to face up to the damage his eating habits could be doing to his body. And Emma Woolf reveals how she developed anorexia and lost half her body weight after a break-up while a student at Oxford.

Dr Christian Jessen comes face to face with twenty-six-year-old Kevin Calladine from Brighton who hasn't had a decent meal since he left home. Short on time and money, his weight has plummeted to just 8 stone 5lbs, two and a half stone underweight, which is no great surprise because Kev lives on a diet of coffee and cigarettes for breakfast, pre-packed sandwiches for lunch and a liquid dinner of orange juices. Meanwhile, supersized super-eater Julie Mead from Essex weighs in at 26 stone 6lbs. Julie hopes some motherly love will help fatten Kev up while she learns to curb her excessive food consumption. Journalist Anna Richardson continues her weight-loss crusade, hoping that hypnosis will help her drop a dress size. Surfer girl Gillian McKeith dons her wetsuit to get some Welsh rare-butts to reduce their rears. And how to have your cake and eat it: with three posh puddings on offer – Pavlova, Belgian chocolate cake and apple tart – can the horsey set guess a high-calorie pudding when they see one? Gillian offers some low-calorie alternatives.

Twenty-stone comfort eater Julie Henry swaps diets with coffee addict Dougie Reid. Emma Woolf explores the importance of the early diagnosis of eating disorders. And in America, Dr Christian takes a ride on a bus that's helping Texans battle the bulge.

It's all out war as round-the-clock snacker Emma Cain goes head to head with Robert Musgrove, who can't be bothered to eat. Dr Christian shows lager-guzzling Emma just what her favourite tipple is doing to her body. In America's fattest town he visits an after-school scheme that aims to help combat childhood obesity. And Emma Woolf travels to Holland to investigate online therapy in the treatment of eating disorders.

In the feeding clinic this week with Dr Christian Jessen are two women at opposite ends of the weight spectrum but with one thing in common: they both want to look wonderful in their wedding dresses. Wafer-thin Jenette Nolan from Lancashire refuses to marry her husband until she can fill her wedding dress but she's got a long way to go. Weighing just 6 stone 8lbs, she's two stone underweight. Meanwhile Rosemarie Palmer, who lives on the Isle of Man, is hoping that a week's food swap will kick start her weight-loss plan to get from over 21 stone to a size 14 in time for her wedding this summer. Meanwhile, journalist Anna Richardson looks into the dark world of extreme dieting. She meets Lisa Bond who became partially blind by taking the radical decision to stop taking insulin in order to lose weight. Anna also talks to ex-Big Brother housemate Nikki Graham about the extremes she has gone to in order to stay thin. And when it comes to reducing the size of the nation's rears, Gillian McKeith is cleaning up the act of a group of Brummie bottoms with a device that promises to vacuum away the fat. And after dealing with the ladies of Birmingham Gillian's off to test some ten-pin bowlers on what they know about the calories in some typical party food.

Facing off in the Feeding Clinic is 24-stone takeaway addict Craig Nellies and superskinny cola addict Simon Tacaks, who's just too lazy to bother to eat. Dr Christian shows skeletal Simon how concentrated amounts of the chemicals found in cola can cause extreme damage to teeth. In America's fattest town, where levels of obesity-related diabetes have hit epidemic proportions, Dr Christian visits a patient suffering chronic wounds and organ damage. Plus, former anorexia sufferer Emma Woolf investigates anorexia during pregnancy.

Dr Christian Jessen checks up on diet swappers one year on. Darryl from Derbyshire was a hefty 33 stone, and was keen to lose weight in a bid to be more active with his two young sons. The self-titled 'Blobbie Williams' lived on fry-ups, roast dinners, crisps and kebabs - often all in the same day. Darryl swapped with London mum Yasmin, whose diet was free of wheat, dairy, gluten, lactose and preservatives . Yasmin hoped to gain more curves and boost her energy. London-based jazz singer Sandra was desperate to lose weight to combat her chance of developing diabetes, which runs in her family. She met seven-stone Tatiana in the food clinic. Tatiana, from Brighton, hated her skinny body, but couldn't bring herself to eat anything that wasn't lean and fat-free. How has the last year been for them?

In the feeding clinic this time Joanne Leadley goes head to head with Ross Clarke from Cardiff. Ross is a meal dodger who never finds time to eat, while 41-year-old Joanne is a giant-portion gorger. Their swap is packed with drama, tantrums and tears. Dr Christian shows Ross the damage his diet is doing to his body and sends Jo to Georgia, America, to meet a woman whose life has been destroyed by overeating. Dr Christian visits America's fattest town, where he meets doctors who treat a huge variety of obesity-related illnesses and patients who have lost toes, limbs and even their eyesight. Recovering anorexic and journalist Emma Woolf explores whether anorexia is inherited.

Forty-two- year-old super snacker Julie Menzies swaps diets with 24-year-old fussy eater Zoe Hughes-Blinston in an emotional encounter. Dr Christian discovers how the funeral parlour in America's fattest town copes with bigger and bigger bodies. And journalist Emma Woolf investigates the little known world of male eating disorders.

Checking into the feeding clinic is marathon-running, superskinny Kim Fawke. Following a stressful divorce, her weight has plummeted to just over six stone. In her race to get her relationship with food back on track, she's joined by supersized scoffer and takeaway queen, 23 1/2 stone Trudy Alexander. Meanwhile, Anna and her Flab Fighters club swap gorging on cheddar for a hike in the Cheddar Gorge. And four young women in the grip of the eating disorder anorexia nervosa reveal their extreme eating habits, and are forced to discuss the causes, symptoms and anxieties around their distorted relationship with food.

Weighing in at just 6 stone 8 pounds is superskinny working mum Gillian. The 24-year-old Inverness nurse is so busy caring for others she's forgotten how to look after herself and her weight has plummeted. Her polar opposite is another nurse, 26-stone self-confessed foodie Philippa, whose typical daily supersize menu includes a generous breakfast, followed by burger and fries, Yorkshire pudding and shepherd's pie. Both women get shocking wake-up calls: Gillian discovers the devastating effects her diet has had on her body and Philippa comes face to face with the consequences of a lifetime of overeating when she meets Lisa, a woman about to undergo life-threatening weight-loss surgery. Meanwhile, Anna Richardson travels to LA to investigate the continuing obsession with thinness. Back in the UK, she launches her very own Flab Fighters club and teaches a group of serial failed dieters from Newport how to indulge in their favourite treats and still lose weight.

Featherweight father-of-two Colin Hunt barely tips the scales at nine stone by living on chocolate and little else. Joining him on the five-day diet swap is a supersizer twice his weight, Tracey Hibbert, who binges on bread. Her post-baby weight has rocketed to 18 and a half stone and she is desperate to lose the pounds. Meanwhile, the Flab Fighters weigh in before heading for the hills for a dog-walking session. Will they bank their calories or binge on a barrel of biscuits? And in the home of size zero, Anna Richardson discovers where the overweight go to in LA. At a fat-fighting farm she goes for the burn with an extreme workout and meets the residents of Club Bounce, the dating disco for larger lovelies.

Swapping diets are 18-year-old superskinny Georgetta, who under-eats to look good but at a cost to her model looks. She will be paired with 28-stone supersizer Ameer, who is determined to lose weight so he can find a girlfriend. Anna Richardson's Flab Fighters are four weeks into their battle of the bulge, and this epsiode embark on a calorie-burning rowing trip. But will they choose to have their cake and eat it? There's also an update on the progress of four young women suffering from anorexia nervosa, where a shopping trip reveals the devastating physical affects of their body dysmorphia. Dietician Ursula Philpot then confronts the four young women's food anxieties by getting them to eat a highly calorific sandwich.

Promotions girl Christine thinks her diet is healthy because she's following the government's advice on eating fruit and veg. At the opposite end of the scale is Martin, who's living on fatty, starchy and salty junk food. Dr Christian Jessen oversees their dietary wake-up call, while Anna Richardson shows the Flab Fighters how to combat their crisp calorie cravings by trimming the maze at Longleat. Anna then heads to LA to prepare dishes for a celebrity meals-on-wheels service and meets the A-lister personal trainer who keeps Hollywood stars red-carpet ready.

Pint-sized Tiffany Patterson had to grow up quickly when her mum left home, leaving her to become the breadwinner and meal-maker. Too busy to eat, the seven stone 25-year-old lives on a daily dose of energy drinks and little else. Joining her for the five-day diet swap is DJ Keith Kelsey, whose out-of-hours eating has caused his weight to balloon to 30 stone. Dr Christian Jessen accompanies him to see 45-year-old Lisa Wheeler as she undergoes life-threatening weight-loss surgery. It's ping pong in exchange for pizza as Anna Richardson takes on the Flab Fighters with a game of table tennis to show them how to have their favourite treats and still lose weight. Plus four young women battling with anorexia nervosa face their food fears in the kitchen of a gourmet curry house, where they have to prepare and eat a highly calorific meal.

Two men confront their lifelong eating problems in the feeding clinic. A former jockey obsessed with keeping his weight down swaps diets with a man whose booze-binging is out of control. In Los Angeles, Anna Richardson discovers that a fascination with celebrity mums lies behind the dangerous trend of extreme post-baby weight-loss regimes. She meets the Hollywood housewife who won't leave her Beverly Hills mansion until she's lost her pregnancy weight, and joins in an exercise class where babies are used as dumb-bells. The Flab Fighters descend on Cardiff's Millennium Stadium for another lesson in how to enjoy their favourite treats and still lose weight. Will they be tempted by a tub of ice cream after a marathon session of step-running?

This week's show features Charlotte, whose dreams of being a pin-up model have fallen flat so far due to her desperate diet. She weighs just six stone and her childlike portions are doing nothing to help her gain the womanly curves she craves. Joining her in the final five-day diet swap is 22-year-old Heather, who's passing on her terrible eating habits to her toddler daughter. The bride-to-be's reliance on ready meals is keeping her at over 20 stone - and no closer to getting into her perfect wedding dress. Three weeks after two thirds of her stomach was cut away in life-threatening surgery, Lisa Wheeler reveals her dramatic weight loss. Ditching diets in favour of a glamorous photo shoot, Anna Richardson discovers the Hollywood cheat's route to a slimmer body, including inch-reducing designer frocks and digital liposuction. And the Flab Fighters' latest calorie-burner takes them to Silverstone for the dirty job of rally car washing in exchange for a celebratory glass of bubbly. While, at the end of their course of therapy, four anorexia sufferers describe their feelings as they visit a spa for a massage and face their biggest challenge of the course.

One year on, Dr Christian Jessen invites diet swappers back to discover how they're getting on with their new healthy lifestyles, and whether they've finally managed to banish their bad eating habits for good. Twenty-six-year-old Kevin from Brighton weighed just 8 stone 5 lbs; he was living on coffee, cigarettes, pre-packed sandwiches and takeaways. He regularly skipped breakfast or lunch - or replaced them with chocolate or crisps. We also catch up with Stefan, a 36-year-old milkman from Northern Ireland. A self-confessed 'carb junkie', Stefan weighed in at 37 stone and was keen to lose weight in a bid to get on the dating scene and boost his confidence. So how are they both faring 12 months later?