It has been revealed that the speed in which people eat their food is the key to the obesity crisis. Eating too quickly can double a person's risk of becoming overweight, as it may interfere with a signalling system which tells your brain to stop eating because your stomach is swelling, a Japanese study has uncovered.

"The old wives' tale about chewing everything 20 times might be true - if you did take a bit more time eating, it could have an impact" concluded Professor Ian McDonald of Nottingham University. But which apparent diet foods may do you harm no matter how slowly you eat them?

The artificial sweeteners in soft drinks (especially the diet ones) tell the brain that you're about to consume a lot of calories but when this doesn't happen you eat more to compensate for the loss.