Diet 1: Raw food
(such as the Caveman Diet and Hallelujah Diet)

Hook: If you return to the Garden of Eden and eat like our ancestors, you'll feel healthy, decrease your risk of illness and lose weight.

Diet: Most raw-food diets suggest eating at least 75 per cent of your food raw; strict versions insist on a 100 per cent no-cooking regime. The diet consists of fresh raw fruits, vegetables, sprouted seeds, nuts, grains and legumes. Advocates suggest that cooking destroys certain enzymes; without these enzymes, they say, digestion is more difficult. Subcategories of raw-food dieters include fruitarians, who eat mostly fruits; sproutarians, who eat mostly sprouts; and juicearians, who consume mostly fresh juice. None of the groups eats dairy products, eggs or meat.

Pros: You get all your nutrition from fruits, vegetables, nuts and seeds. They're rich in vitamins, minerals, fibre and antioxidants.

Cons:
• The diets are low in calcium, vitamins B12 and D, zinc and possibly protein.
• They're difficult to follow on a long-term basis.
• Preparation of raw foods can take a lot of time, and the diets prohibit eating prepared foods.
• Raw isn't always best. Certain foods, such as tomatoes, are more nutritious when cooked.

Bottom line: These are fad diets. They're very difficult to follow and are not supported by any scientific evidence.

Diet 2: Glycemic index
(such as Rick Gallop's GI Diet)

Hook: You can eat lots of healthy carbohydrates, as long as they're the right ones, and still lose weight.

Diet: These diets work on the principles of the glycemic index (GI), which shows how different carbohydrates affect blood sugar once eaten and digested. Low-GI foods, such as brown rice, rye bread, oatmeal, eggplant, apples, grapefruit and yogurt, cause a more gradual rise in blood sugar and take longer to digest; they release energy more slowly, leading to more-consistent energy levels. Rick Gallop's GI Diet suggests that low-GI foods are better for blood-sugar control in those with diabetes and may help with weight loss because they leave you feeling fuller for longer. High-GI foods, such as white bread, potatoes and watermelon, are more quickly absorbed, so you don't stay full for as long. The diets suggest you eat lots of low-GI foods for meals and snacks.

Pros: You'll eat lots of healthy fruits, vegetables and grains that will provide vitamins, minerals and fibre

Cons:
• GI diets are not as exact as the books make them sound. The total GI of a meal can be altered by the combinations of foods you eat; for example, if you top a potato with cheese or butter, which take longer to digest, you'll lower the combined GI of that meal.
• There's no GI for meat, fish, poultry, eggs or fats, so you have to limit the amounts of these foods to lose weight.

Bottom line: It takes some work, but you can construct a healthy, balanced diet that will leave you satisfied.

More healthy eating tips:
• 28 days to a healthier you
• 101 ways to cut fat from your diet
• Rosie Schwartz's low-cal, low-fat meal ideas
• The skinny on fats
• Healthy snacks on the go
• Top 10 superfoods