Dieting is often doomed to failure, despite most women being able to pass an exam on the differences between Atkins, South Beach and WeightWatchers. The problem is, we don’t follow the rules we learn. No carbs after 6pm? No problem — until we’re out for dinner, on our second glass of wine and scoffing the bread basket. Everyone has a flash point that makes it hard to say no, but ultimately, resisting temptation is the key to successful weight loss.

Now research from leading psychologists has identified the parts of the brain involved in resisting temptation, and how we can use them to stop reaching for gooey chocolate cake. Leading the charge is Professor Walter Mischel, the psychologist who, in the 1960s, developed the “marshmallow test”, which demonstrated that if children were able to delay gratification, they would be more successful in later life. Mischel’s research has shown that to resist temptation, we have to shift activity away from the “hot” parts of our brain to the “cool” parts. “The mind brain has two systems: one is cool, slow and deliberate, and allows for self-control, goal-setting and willpower — the ‘no’ system, if you like. The other is hot, emotional and instinctual, and present from birth — the ‘go’ system,” says Janet Metcalfe, professor of psychology at Columbia University and co-author of a paper on willpower with Mischel.

So when you see a chocolate cake, the “hot” part of your brain reacts to thoughts of the delicious taste, and the sugar rush that you have learnt a slice will give you. Instead of giving in, what you need to do is activate the “cool” part of your brain by thinking about your goals and practising far-sightedness. Imagine the sense of satisfaction you’d get, from fitting into your favourite dress in a couple of weeks’ time, say, or from losing your unsightly tummy bulge before you go sunbathing this summer. It’s a simple strategy, but experiments have shown it is highly effective.

Perception is also important. Feasting your eyes on desirable food activates the hot system in the brain, which explains what we know instinctively: putting biscuits out of sight in a cupboard will mean you eat fewer of them. “The problem with diets is they are also full of pictures of delicious diet food, and all of this is just priming the hot system,” Metcalfe says.

Stress is another key issue. It has been shown to switch on the hot part of the brain and cause us to overeat. Daryl O’Connor, a psychologist at Leeds University, has conducted experiments showing that people under stress tend to go for high-fat, energy-dense food. “The first thing to do is to be aware of how stress changes your behaviour. Then develop an action plan to deal with it. This might involve taking healthy snacks to work or finding ways to cope better with your time and emotions.”

Brain scans have also shown that memory plays a significant role in overeating. If you habitually eat chocolate, for instance, then every time you see it, you remember the high. However, Dr Leigh Gibson at Roehampton University has found that if you give something up, far from your cravings increasing, they will actually decrease, proving that cravings result from habitually giving in to temptation. So the research is clear: if you want to be slim, fit and healthy, it’s time to take control of your mind.

Times recommends

• McDonald’s: the world’s local restaurant
• Help me to be a mum: a foyer to fulfilment
• A life online: God likes a laugh