Nineteen-year-old Billy Robbins weighs 60 stone and is reported to be the world's heaviest teenager. He has spent the past three years living in a chair as his mother cooks for, cleans and feeds him. But Billy has made the decision to turn his life around in the hope that one day he may be able to move out of his mother's home. Billy realises that after being fed up to 8,000 calories a day, he has to change his diet not only in order to gain his own independence from his mother, but if he is to live into his twenties. The seriousness of his condition is confirmed by Billy's doctor, Dr Nowzaradan, who tells him that the strain on Billy's heart is now critical. He must begin the slow and torturous route to a target weight of just over 14 stone - undergoing a possible seven operations in the process. This astonishing story also revolves around Billy's relationship with his mother and the co-dependency that seems to exist between them.

Half Ton Mum tells the story of the world's heaviest woman, Renee Williams, a 64-stone, 29-year-old mother of two who, in a desperate bid to lose enough weight to save her life, undergoes life-threatening surgery. Renee, who has realised she wants to be around long enough to see her two daughters grow up, hopes her story will help change the lives of the estimated 2 million Americans who weigh more than 40 stone.

In her home town of Nagpur in India, 16-year-old Jyoti Amge is a normal teenager in many ways: she enjoys going to school and socialising with friends, and dreams of dancing in Bollywood movies. But Jyoti is only one foot and eleven inches tall, and will never grow any taller, crippled by brittle bones. This Bodyshock special meets this extraordinary girl to discover her story and explore what her future holds. When Jyoti's mother, Ranjana, who had four healthy children already, became pregnant, she instinctively knew that something was wrong, and even up until the full nine months, baby Jyoti could not be seen on the medical scans. Doctors were in shock when she was finally delivered at 10 months, weighing just over three pounds. The Amge family, devout Hindus, saw Jyoti's birth and survival as a miracle that deepened their faith. Ranjana, and Jyoti's father, Kishanji, meet with senior orthopaedic surgeon Dr Ram Soni, who believes he can mend her fractured legs and help her walk without pain. He is also keen to be the first to diagnose Jyoti's probable condition for certain as pituitary dwarfism, where the body severely lacks the necessary growth hormones from the pituitary gland. The only solution is a high-risk operation to realign her bones and insert metal rods to hold them in place. Jyoti's parents understand that this could change her life, but are extremely concerned about the shock to her body and how much she would suffer. The family turn to their faith to help battle their fears, taking Jyoti to a highly revered guru and also to a renowned healer, in hope of spiritual guidance and an alternative solution. Torn between the desire to repair Jyoti's legs and also avoid further damage to her, can they move forward with the modern treatment offered by Dr Soni?

As experts consider a review of UK guidelines for treating transgender children, this film follows a number of children in the US who told their parents they were born in the wrong body. In America, children under 16 can be prescribed hormone 'blockers' to prevent the onset of puberty, with a view to then follow with hormone treatment to become their new gender. This film follows the American experience. Eight-year-old Josie was born a boy but has been living as a girl for two years since revealing the full extent of his feelings about his identity to his mother. Kyla is also eight. She was born a boy but loves anything pink and sparkly, has grown his hair, and is preparing to return for school after summer dressed as a girl for the first time. She says: 'If I had to wear boys' clothes and be a boy for the rest of my life, I'd probably die.' They have both been diagnosed with gender dysphoria. Sixteen-year-old Chris, who was born a girl, started testosterone treatment at 14. He now has a deep voice and plentiful body hair, and shaves regularly. These children and their parents reveal what it is like to face life-changing questions, giving a frank insight into a subject most people never have to consider.

Forty-year-old American father of four Kenneth Brumley weighed 73 stone when he was cut free from his house. Even bigger than Half Ton Mum, Renee, from the Bodyshock documentary of that name, Kenneth's last chance was to undergo the same weight-loss surgery that she had. Sadly, it did not work for Renee - would things be more successful for Kenneth? Half Ton Dad is the story of a father, his family and a country which currently has 15 million morbidly obese citizens.