At just seven years old Dzhambulat Khatokhov ('Jambik' for short) is four foot three inches tall and weighs 16 stone - as much as a baby elephant. He dwarfs his older brother who is twice his age and less than half his weight.
Nobody knows why Jambik is so big, or what this means for his long-term health. But Dr Campbell - one of the world's leading experts on obesity - is determined to find out.
Travelling over 2000 miles to the Caucasus Mountains in Southern Russia, Campbell meets the 'biggest boy in the world' to see what, if anything, can be done for him...
click here to see where to watch or .
Ready to Watch Bodyshock, Season 4, Episode 3?