DIET REVIEW There's nothing magical to losing weight. The average 150-pound person burns about 1,800 calories a day just in the act of living. Add any kind of activity to that, and your body will need more fuel to maintain that weight. If you increase your activity but keep your calorie intake the same, you will eventually lose weight.

The bottom line: if you consume more calories than you burn, you will gain weight. And it doesn't take long. For every 3,500 excess calories consumed, you will gain a pound. You can do that every two months or so by eating one cookie a day. Or you could burn off that cookie by running a little under a kilometre. Low-carb, low-fat, high-carb, high-fat - to your body, a calorie is a calorie - and if you take in more of them than you need, you will gain weight.

Still, diets are a multibilliondollar industry (some estimates suggest $20 - $30 billion annually). Much research has been conducted to try to determine which plans work - here's a brief look at some of the more popular ones.

Atkins

The 70’s low-carb diet that has been rekindled but has once again fizzled out! Dr. Robert Atkins argued that traditional low-fat calorie counting diets all include some degree of deprivation. You rarely feel satisfied. Low-fat, high-carb foods are digested quickly. They lead to blood-sugar spikes, which lead to blood-sugar nosedives, which lead to more hunger. On a controlled-carbohydrate eating plan, which allows you to fill up on satiating proteins and fats and select the carbohydrates that don't send your blood sugar soaring, the theory goes, you shouldn't feel hungry. The two main stages of the diet are weight loss and weight maintenance. After you reach your goal weight, you switch to a maintenance program during which some carbohydrates are reintroduced to the diet. The diet does stress that some foods should always be avoided - like sweets. The diet also says that once on maintenance, you can enjoy the occasional potato. Although the most recent version of this diet was titled “New Diet Revolution” it’s basically a low-carb regime that tends to work for a while then becomes restrictive. Some research suggests this diet is hard on the kidneys.

South Beach

Devised by a Miami cardiologist for his patients in the 1990s, this diet shares several features with the Atkins diet. But the diet's creator, Dr. Arthur Agatston, stresses that South Beach is not a low-carb diet. He focuses on a healthy balance between "good" carbs and fats. Highly processed foods, like baked goods and soft drinks are banished on the South Beach Diet. Agatston argues that by decreasing these kinds of carbs, your body will metabolize what you eat better and will also improve insulin resistance, leading to weight loss. In the first phase of the diet - which lasts two weeks - you cut all fruit, bread, rice, potatoes, pasta, sugar, alcohol and baked goods. In the second phase, you begin to reintroduce some of the banished foods, and in the third, you bring back some more. But you have to be choosy - and are advised not to fall back to your old eating patterns. This low-carb diet relies on the participant’s ability to only re-introduce “good” carbs – it’s more healthy than Atkins, but still doesn’t necessarily promote “healthy” eating.

Deal a Meal

Devised by exercise and weight-loss guru Richard Simmons in the 1980s, Deal a Meal is more a product than a diet. The program relied on three basic premises: teaching good eating habits, emphasizing the importance of exercise and promoting a positive mental attitude. Through a series of colour-coded index cards, people who bought the diet were taught proper food combinations. Dieting became more of a card game: once you consumed the proper combinations as dictated by your cards, you were finished eating for the day. This program, although generally promoting good eating was gimmicky and faded as Richard Simmon’s popularity waned.

Weight Watchers

One of the most successful diet support groups, it was founded in the early 1960s by Jean Nidetch. She began inviting friends into her Queens, N.Y., home once a week, to discuss how best to lose weight. Weight Watchers says it's more about giving people information on making the lifestyle choices that are right for them. Diet consists of a points program. Foods are assigned points and you are allowed a certain number in your individual program. Weight Watchers is generally viewed as one of the healthiest “diets” currently available – it’s only drawback might be that it primarily rewards weight-loss which is measured by regular “weigh-ins”. Although the plan promotes physical activity it does not account for the fact that gaining weight in the form of lean tissue is a positive result of activity – as success is generally only measured by the amount of weight loss.

Pritikin Program for Diet & Exercise

It's a low-fat, high-fibre diet that includes a moderate exercise program. His objective was to help other people with similar medical problems restore their health. The diet is almost completely vegetarian, and encourages the consumption of large amounts of whole grains and vegetables. It is high in fibre, low in cholesterol, and extremely low in saturated fat and total fat, containing less than 10 per cent of total daily calories from fat. Processed foods such as pasta and white bread are banned, as are most animal proteins. Diet was revised to include limited amounts of "healthy" fats high in omega-3 fatty acids. The diet is restrictive, and many people who are active comment that it is sometimes difficult to consume enough total calories on this program.

The Beverly Hills Diet

Promises weight loss of up to 15 pounds over five weeks. Relies heavily on fruit. It recommends eating fruit by itself and never eating protein with carbohydrates, in order for food to be properly digested and not stored as fat. The diet begins with a 35-day plan that specifies items to be eaten at each meal, without counting calories or fat grams. In the first 10 days, you can only eat fruit. On day 11, carbohydrates and butter are added and on day 19, protein is added. Fatty treats are permitted. It gained popularity when word spread that several Hollywood stars were on it. Like other “fad” diets it doesn’t promote learning how to select food and is very restrictive. Not a great program.

Grapefruit diet

Another very low calorie diet. The premise is to consume only 800 calories a day through eating lots of "fat-burning" grapefruits to kick-start your metabolism. The 21-day program calls for mostly grapefruits, some protein (mainly boiled eggs), and some vegetables. As much coffee as you like. This is likely one of the most famous fad diets that has been around for many years – although it is truly not an intelligent eating plan.

The Zone

Another diet that preaches the evils of refined carbohydrates like pasta, white bread and bagels. You are in The Zone if you eat five times a day, if the protein you consume is the size of the palm of your hand and carbs are the size of your fist. Relies heavily on the glycemic index, a ranking of carbohydrates based on their immediate effect on blood glucose (blood sugar) levels. The theory (as in other low carb diets) is that diets relying on foods with a low glycemic index make it easier to lose weight. This diet fails to recognize the fact that the glycemic index is, when used properly, an individualized index – that is, foods react differently when eaten by different people…so a food that might cause one person to increase blood sugar levels may not have the same effect on another person. The diet suggests that high glycemic index foods are not necessarily good for you – which contradicts what sport nutritionists say about people participating on endurance types of activities.

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