Some are popular, some are plain bizarre. But do they really work?
The Zone Diet
What it involves:
This diet plan involves consuming 40 per cent carbs, 30 per cent proteins and 30 per cent fats. This balancing act is intended to control metabolism by regulating the body's insulin hormones and ensuring that a certain "zone" is in place. It works on the assumption that when this is fully under control, you'll burn fat more effectively. Portion control is crucial to this and you can still eat your favourite foods as long as it doesn't take you outside of "the zone".
Who follows it:
The Zone Diet has been a popular choice for celebrities, with the likes of Jennifer Aniston, Sarah Jessica Parker, Demi Moore and Sandra Bullock having all being linked to the food plan.
The bad points:
It can be a complicated diet plan to get your head around and you'll need a good understanding to get the most out of it.
Expert view:
Dietitian Sandra Hood says, "This sounds like an Atkins type, low carbohydrate diet which is moderate in fat but higher in protein. The theory behind low-carb diets is that they reduce the insulin response and prevent weight gain and hunger. However, the opposite is often the case. If blood glucose levels drop due to a lack of carbohydrates, this will trigger sensations of hunger. Another problem with the high protein diet is that it is often reliant on animals foods which are naturally low in fibre, phytochemicals and antioxidants which are highly protective dietary components. The more complicated the diet, often the more appealing it is as dieters try to kid themselves that it isn't about the amount they are eating but some wonderful complicated theory behind it. This diet sounds like it is less about metabolism and more about portion control. Dieters are so focused on following this new miracle diet that they frequently end up eating less calories."