First it was the Atkins Diet. Then the South Beach Diet. And now the Lemon Detox Diet promotion is on again. What next?

You’d think we’d all be slim by now seeing that we invest over $400 million per year on weight loss gimmicks and fad diets.

But no, the nation’s obesity rate is continuing to climb, with more than 60 per cent of adults now overweight or obese.

Sure you might lose weight in the short-term, but the truth is that fad diets are unsustainable.

Infact research shows that those who go on weight loss diets have a 95% chance of regaining everything they have lost plus more within two years.

So why do we keep going back for more? Is it that we are tricked by the promise of a quick fix, or is it that the mixed messages given by these diets have altered our perceptions of which foods we should be eating? Read on for the skinny on some popular fad diets below.

Low-carb diets

Theory: Cutting out or substantially reducing carbs like grains, breads, fruit and starchy vegetables will stimulate ketosis- the phase where your body burns fat because there are no carbohydrates to burn. These diets are high in protein and fat. Examples include the Atkins Diet and South Beach diet.

Reality: Recent studies on low carbohydrate diets have indicated that they are effective in reducing body weight for up to six months. However, in the longer term there is no real difference between weight loss on these diets and other diets anyway.

Most of the quick weight loss from comes from water loss and the emptying of glycogen (stored carbohydrate in the muscles) not from fat.

This diet is unsustainable in the long term because you need glucose (from carbs) to fuel the brain and to function. So when eventually you do start eating carbohydrates again, you are likely to put on the water weight again anyway.

Also to note is that these diets are often very high in saturated fat, which can increase your risk of heart disease, kidney disease and cancer. By cutting down your whole-grain and fruit intake, you will also be missing out on vital vitamins and minerals.

Cabbage Soup diet

Theory: This 7 day diet involves eating cabbage soup for main meals and mixing in other fruits and vegetables.

For example on day 1 you eat just fruit except bananas and soup, and on day two you eat soup, vegetables (except dry beans, peas and corn), and a baked potato with butter for dinner. No fruit allowed on day 2.

Reality: This is a very restrictive, unbalanced diet. Weight loss of a few kilos might occur from water and glycogen loss (not fat) from the body but this won’t last for long. When you restricting your energy intake so much, your body begins to break down muscle which lowers your metabolism (meaning you will burn less energy).

So when you do return to normal eating, it is much easier for the body to gain fat than it was before going on the diet. As a result, people often diet themselves fatter.

Lemon Detox Diet

Made popular by Beyonce, this diet is just as ridiculous as the Cabbage Soup Diet.

The diet involves drinking six to nine ‘detox drinks’ a day.

This consists of water, tree syrup, lemon juice and cayenne pepper. Again the calorie restriction will send your body into starvation mode, so that you will burn more muscle than fat.

A slower metabolism is just more bad news for weight loss.

Meal Replacements/shakes

Theory: You replace one, two or three meals a day with a shake or soup. Examples: Tony Ferguson, Herbalife.

Reality: A Choice survey of pharmacy diet programs published earlier this year found they were successful at helping people shed kilos in a hurry if followed closely – but they did little to change a person’s lifestyle in the long term.

Many were so nutritionally deficient that dieters had to take vitamin supplements.

Meal replacement diets are also unsustainable.

A John Hopkins University study of commercial weight-loss programs last year found 27 per cent of people dropped out in the first month.

Just 42 per cent were still enrolled at three months and 7 per cent were still following a year on.

If you are morbidly obese and need to lose the weight fast for health reasons, meal replacement diets may be a short-term option to consider but see your doctor before considering.

Busting the dieting myth

Carbohydrates make you fat: FALSE. I hear this all the time but this is completely crap.

Weight gain is a result of eating more calories than what the body needs—no matter if those calories are coming from fat or carbohydrate.

Low carbohydrate diets only work in the short term because they restrict a large source of kilojoules (energy) in the diet.

As do most of the fad diets.