When you're happy with your weight and have never dieted, you rely on your body to tell you when to eat and (crucially) when to stop

But when you diet, this simple process goes very wrong. My clients often say: "As soon as I decide to go on a diet, I get this desperate urge to eat!" And, whilst they are "good" for a while and stick to the diet, if they ever break the diet and start eating, then they REALLY eat, wolfing down their food like young Labrador retrievers.

The ice cream experiment

Psychologists have looked at how dieting affects the amount we eat, by doing an experiment with dieting and non dieting students. The students were invited to eat as much ice cream as they liked after being given one of three different "pre loads": one milk shake, two milk shakes or nothing at all.

As you would expect, the non-dieters ate less ice cream after they'd had one milk shake than when they'd had none, and even less ice cream if they had been given two milk shakes first. But the dieters actually ate the most ice cream when they'd had the two-milk-shake, super-sized "pre load"! According to the psychologists, the effect of the milk shake pre-load was to undermine the dieters' resolve. After the excessive consumption of milk shake, the dieters decided that since the diet had been blown out of the water anyway, they may as well make the most of the situation and have lots of ice cream! Hunger and fullness had nothing to do with it!

This is a feeling which all dieters recognise. After succumbing to a biscuit you think: "Oh sod it, I may as well eat the cheese cake as well, and start the diet again tomorrow!"

The scary film experiment

By denying themselves the food they really want, dieters also make food much more important and give it a significance that it does not have for non-dieters. For instance, dieters are more likely than non-dieters to eat in order to suppress bad feelings.

In a study carried out in London, female volunteers were divided into three groups: the first were put on a strict diet, the second undertook a rigorous exercise programme and the third neither dieted nor exercised. After five weeks, the researchers got the women to watch a stressful film, and measured the women's food intake while they watched it. Bowls of food such as sweets and nuts were left beside the women and they were told to eat as much as they liked. Even though none of the women were hungry, those in the diet group ate far more than the women in the two other groups.

Choosing the best slimming foods as part of your diet is an easy way to help you lose weight without having to do a lot of calculations. The best slimming foods are those that fill you up without a lot of calories.

10 of the Most Effective Slimming Foods

1. Green vegetables - Mom was right when she told you to eat your vegetables. Vegetables have lots of fiber, so they fill you up. They are also very low in calories, so you can eat until you're full. Finally, green vegetables like broccoli, spinach, green beans and asparagus are loaded with vitamins.

2. Fruit - Fruit also contains lots of vitamins and fiber. It has plenty of vitamins and contains natural sugar, which can help satisfy a sweet tooth.

3. Lean protein - Lean protein like meat, eggs and low fat cheese are great for keeping you full and providing fuel for muscles. Protein keeps you feeling full for a long time, helping to ensure that you don't overeat.

4. Low fat dairy - Low fat milk and other dairy products contain calcium. Studies have shown that dieters who consume an adequate amount of calcium lose more weight than those who don't.

5. Green tea - Green tea contains EGCG an anti-oxidant that speeds up the metabolism. A few cups of green tea each day can help ensure that you burn more calories, so you lose weight faster.

6. Whole grains - Whole wheat bread, brown rice and oatmeal are all among the best slimming foods. These provide good carbohydrates and lots of fiber, which is good for all of us.

7. Nuts - Nuts are filling and full of vitamins. However what makes them one of the best slimming foods is the fact that they're packed with "good fats" - the kind our bodies need. The fats from nuts are nutritious and help you feel full. Nuts are high in calories, however, so you do have to watch portions.

8. Hot peppers - Hot peppers contains capsaicin, which speeds up your metabolism. So, in addition to having vitamins and fiber like all vegetables, eating hot peppers may really provide a boon to your weight loss efforts.

9. Beans - Beans are a great source of complex carbohydrate and protein. They are very nutritious, have lots of fiber and keep you feeling full for a long time. In addition, they are inexpensive and can be prepared many different ways.

10. Fish - Fish, especially oily fish like salmon and tuna, are not only good lean proteins, but they also contain Omega 3 fatty acids. These acids are not only good for your heart, but may speed up your metabolism, too.