Diet advice: what you need to know about cutting calories

You've heard it before: calories are the key to weight-loss success (or failure). Consume less than you burn, and the pounds will vanish like last night's cheeseburger. Simple, right? Actually, no. Calorie cutting works — but not as well as you might think.

Will I lose weight if I eat less?

Cutting calories does leads to short-term weight loss, but the results won't last forever if that's all you do.

• Weight loss is a notoriously difficult feat to pull off, and overwhelming research shows that most people who try, fail. According to a review of studies, the word on dieting is downright dismal: an average of 41 percent of people gain back more weight than they lost within a year after starting to diet.
• That said, cutting calories does work in the short term, though it's necessary to cut more calories than most people realize (3,500, to be exact) in order to lose .45 kg (1 lb).
• According to a review of studies, going on a low-calorie diet (1,400 to 2,000 calories a day, depending on your current size) can help people lose eight percent of their body weight over three to 12 months.

Why do so many diets fail?

There are lots of reasons.

• First, people are human, and diets are hard to stick with.
• Second, our bodies work against us: after you've lost some weight, your metabolism slows down so that you have to eat less and less just to maintain that weight loss. It's your body's way of making sure you don't starve.
• A third problem: people who are overly anxious to drop pounds sometimes cut too many calories. In the beginning, this can cause intense food cravings, although they eventually wear off. (In fact, in the long run, low-calorie diets have actually been shown to curb hunger.)
• Finally, if you don't exercise while dieting, you're likely to lose muscle mass, which slows your metabolism even more.

Does it matter where your calories come from?

Calories are not created equal. Those from fat or refined carbohydrates are more likely to end up on your thighs.If a cream-filled doughnut and a chicken breast sandwich have the same number of calories, does that mean you can have the doughnut for lunch instead of the sandwich and come out even? Nutritionally, not a chance. But even weight-wise, you're worse off with the doughnut.

• First, there's the thermic effect of food. It means that some foods take more energy to chew, digest, metabolize and store than others.
• Unfortunately, the body is very efficient at processing fat and expends very few calories doing so. The body is quite good at processing carbohydrates, too. Protein, on the other hand, has to be converted into carbohydrates before it can become fat. That takes a lot of work, burning up as much as 30 percent of the calories in the food you're eating.
• Then there's the effect of food on blood sugar. Refined carbohydrates (think white bread, cookies and fruit drinks) tend to raise blood sugar levels rather dramatically, which encourages fat storage, weight gain and hunger.
• On the other hand, fibrous foods like apples, as well as protein foods, not only take more energy to digest but also raise blood sugar less, making them friendlier to your waistline.
• Finally, foods that contain a lot of water, such as vegetables and soup, tend to fill the belly on fewer calories, so you'll stop eating them way before you stop eating the Timbits.

Cutting calories can be an effective way to lose weight. Just remember to check with your doctor before getting started.