Gluttony, lust and the other ‘deadly sins’ are seen as immoral, but are we hardwired to commit them? | Guy Leschziner

Scientists are increasingly finding that behaviours once seen as depraved often have a direct physical cause

The first thing that strikes me when I visit Alex in her supported accommodation is the huge lock on the kitchen door. The accessible rooms are devoid of any food or drink, the exception being two dispensers of sugar-free squash in the living room. Even the food-waste bin outside the back door is padlocked. Packages delivered to the home’s residents are opened in front of staff and searched for surreptitiously ordered food. These extraordinary efforts are crucial to prevent the housemates from eating too much.

For Alex and her fellow residents, their perpetual and insatiable hunger is not a matter of gluttony. It is not a marker of immorality, or depravity of the soul. It is a function of their biology. All those living in that house have a rare genetic disorder, Prader-Willi syndrome, which affects the region of the brain that controls appetite and hunger. For them, the signal to stop eating never materialises. People with this condition are destined never to feel full, sometimes even eating non-food items in the search for satiety. So extreme is their hunger that occasionally they will overeat to the point that they die of a perforated stomach, or choke on regurgitated food.

Guy Leschziner is a consultant neurologist at Guy’s and St Thomas’ hospital trust. He is the author of Seven Deadly Sins: The Biology of Being Human