Could an extra slice of cucumber a day make you fat?

Small changes in your daily intake can make a huge difference to your weight. To change your body mass index - your BMI, you would only need to eat an extra seven calories a day more than you burn - the equivalent of half a slice of cucumber. Professor Sadaf Farooqi of the University of Cambridge, explains.

Picture: Cucumber salad
Credit: Barnaby Perkins/BBC