The truth about fat.

Surgeon and writer Gabriel Weston presents a programme about fat - focusing on why some people seem to struggle with their weight. Now that a quarter of the population are estimaged to be clinically obese, she discusses the latest research on obesity in the hope of finding a way to fight the current obesity epidemic. Weston dissects a pig to look at levels of fat in its body, then she meets Dr Carel Le Roux who is researching our body's chemical messengers - in particular hormones which make us feel hungry and those which make us feel full. Le Roux experiments on Weston to prove his point. We meet two identical twins - Elaine and Liz; one is overweight and one is not. Tim Spector describes how his research into twins was changed when he met Elaine and Liz who are known as discordant twins. He has since found other discordant twins and has undertaken genetic studies on each in order to see why some seem to have the fat gene switched on and some don't. He puts this down to genes that are switched on by the environment - epigenetics. However, if the fat gene can be turned on, can it be turned off? Other studies are looking at whether or not a tendency to obesity starts in the wombs of undernourished pregnant women. We see a gastric bypass operation on morbidly obese, Marianne. Dr Le Roux believes that these operations are successful both because of the stomach reduction and also the way they changes people's relationship with food. Le Roux's colleague, Samantha Scholtz, is looking at how gastric bypass surgery changes people's brains by studying MRI scans of brains looking at images of high fat food both before and after surgery. All this new evidence goes to show that it is too simple to merely call obesity a problem of willpower.