We hear people talking about "crash diets" without really knowing what they mean.

All health experts agree that a crash diet is the last thing you should do if you want to lose weight. And yet, thousands of people every year embark on a sudden, quick weight loss programme which can often do them more harm than good.

The first six months of the year often see the heaviest reliance on crash diets. This is from people who are trying to lose weight after Christmas, or embarking on a slimming programme so that they look good in the summer. What they fail to realise is that if they try to lose weight in this way, they could end up losing more than body fat, and ultimately gaining the weight back, and possibly becoming heavier than they were before.

The problem with weaning people off diets like these is that they often produce the desired results in the very short term. People do lose weight. This is, however, because they have restricted themselves to a very limited range of foods, and have reduced their calorie intake dramatically. This will result in weight loss, because the body isn’t getting its usual amount of calories and so starts to use up its own stores of carbohydrate to increase energy. This type of diet isn’t sustainable in the long term though, because limiting your range of foods also limit’s the intake of certain vital nutrients and, in the long run, this will cause more harm than good.

On this type of diet, you will also be losing more than the body fat you were aiming for; you will be losing muscle mass as well, and this isn’t desirable because it’s a lot harder to replace. Indeed, if your weight loss is through body fat and muscle mass on these types of diets, and then return to your original weight, it is likely that the weight gain will be all body fat and no muscle.