Six diet myths busted

Do quick-fixes that offer instant weight-loss  actually work?

1. Will chewing foods like sugar-free gum and celery help me burn kilojoules?

It might, but hardly enough to trigger weight loss. Gum and certain veggies are often called “negative-kilojoule” foods because they supposedly take more energy for your body to chew or digest than they contain.

This was tested when researchers asked people to chew sugar-free gum at a rate of 100 bites per minute. After calculating the energy expended (about 46kJ per hour), they concluded that a person who chomped on a piece every waking hour of the day for a month would lose less than 420g. Crunching celery burns less energy than the 25kJ stalk contains. The bottom line: If you really want to lose weight, give your jaw a rest and start moving your body.

2. Can coffee really rev up my metabolism?

It’s true. Java can stoke your energy-burning furnace, provided that you drink it black. A study in the journal Metabolism found that the caffeine in two cups of coffee may cause a 65kg woman to expend up to 200kJ over the next four hours. “Caffeine stimulates your nervous system, signaling the body to release a small amount of energy from its fat stores,” says lead researcher and exercise scientist Professor Paul Arciero. “But stirring in milk, cream, or sugar can cause your insulin levels to rise, which diminishes that metabolic effect.”

Don’t try to accelerate the weight-loss process by sipping black coffee all day, though. Prof Arciero recommends not exceeding three cups a day, as too much caffeine can cause anxiety, nausea, and headaches.

3. Will blotting my pizza cut down on kilojoules?

It won’t soak up all the fat in your lunch, but it can definitely make a dent. “If you’re eating a medium slice of cheese pizza, blotting it first can remove up to 190kJ and five grams of fat,” says Farrell. But all the mopping in the world won’t help if you’re ordering the wrong kind of pizza. Stuffed-crust and meat-lovers’ varieties, which can clock in at up to 3 350kJ per slice, contain more than a day’s worth of fat and sodium.

To boost the nutritional value of your pizza, skip the meat toppings, ask for half the cheese, and opt for extra veggies like mushrooms, spinach, or broccoli — and make sure it’s on a thin crust.

4. Will eating after 8pm make me gain weight?

Contrary to popular belief, the snack you have before bedtime won’t automatically be stored as fat. “The most important factor affecting your weight is how many kilojoules you consume in total each day, not what the clock reads when you eat them,” says nutritionist Suzanne Farrell. That said, skimping on meals during the day may set you up to overeat at night, which can pack on kilos. A recent study in the Journal of Nutrition found that the less food people ate for breakfast and lunch, the more they ate after sundown — and the higher their total kilojoule intake for the day.

“Our brain’s satiation mechanism — its way of telling us we’re ready to stop eating — tends to become weaker as the day progresses,” says professor of psychology John de Castro. “That means you may have to eat more in the evening in order to feel full.” His research suggests that having a larger breakfast, a moderately-sized lunch and a smaller dinner can help you consume fewer kilojoules and reduce the temptation to nosh at night.

5. Would eating carbs, fat, and protein separately help me lose weight?

No. While the concept of “food combining,” or eating certain nutrients at specific times (and excluding others), has fallen in and out of fashion for decades, there are no proven benefits. The theory is that different food types (proteins, fats, starches, sugars, and acidic foods) require their own digestive enzymes in order to be metabolised properly. Some claim that mixing these groups or eating them at the wrong times could cause digestive issues or weight gain. For advocates of this eating style, having orange juice and scrambled eggs at a sitting, or even a turkey sandwich, is forbidden.

To determine if a food-combining diet could confer any health or weight-loss benefits, researchers in Switzerland put two sets of obese patients on low-kj diets for six weeks. The first group followed a food-combining plan (eating carbohydrates at one meal and fats and protein at another), while the second ate meals that contained all three nutrients. While both groups took in the same amount of kilojoules, those on the balanced diet actually lost about 1.5kg more than the food-combining group — and lowered their blood pressure to boot.

6. Does exercising on an empty stomach burn more fat?

Yes, but you might not be able to work out as hard as you would if you’d eaten first. Canadian researchers asked two groups to hit the treadmill in the morning until they’d blasted 1670kJ. The joggers who skipped breakfast burnt 58 percent more fat than those who had a meal before their run. Pre-workout fasting won’t necessarily translate into weight loss. “People incorrectly assume that if you’re using fat for fuel, it equates to losing body fat,” says sports nutritionist Nancy Clark. “What affects weight-loss most is how many kilojoules you’ve depleted during your workout and if you’ve sustained a deficit by the day’s end.”

It may sound counterintuitive, but a 600–800kJ snack at least 30 minutes before you train could help you slim in the long run. And eating a banana or a granola bar before lacing up your trainers can give you the energy you need to crank up the intensity during your workout.