Celebrity follower
Brook Shields

The theory
Grapefruit contains enzymes that speed up the way our body burns fat, resulting in quick and easy weight loss.

The plan
Although there are quite a few different versions of this plan, all require that you eat half a grapefruit before every meal, to reap the benefits of the fat-burning enzymes. Calories are typically limited to less than 800 per day, although some versions require that you 'eat until you are stuffed'.

Pros
If you love grapefruit, this plan may be for you. Grapefruit has no fat, is low in calories and sodium, is packed with vitamin C, and the pink variety contains beta-carotene. You don't have to count calories, and the plan causes rapid weight loss, primarily due to loss of body fluids.

Cons
The lack of calories and the amount of caffeinated beverages one has to drink make this diet dangerous, as this can lead to dehydration. In addition, the diet is deficient in protein, fibre and several important vitamins and minerals. Any diet that relies this much on a single food is too restrictive.

Duration
One to three weeks.

Checklist
Restaurants: Difficult.
Alcohol: Not allowed.
Caffeine: Strongly encouraged.
Need to buy special foods: Yes —grapefruit!

OK for vegetarians: Yes.

The pros say
What a load of old tosh! There is absolutely no scientific proof that grapefruit contains fat-burning enzymes. There is no good reason to follow this meal plan. It could even be dangerous for people who are food obsessive, have eating disorders or are prone to yo-yo dieting.