Food for Thought Try the combo in the diet-exercise debate
LESLIE BECK What's the best way to take off unwanted pounds -- eating less, exercising more, or a combination of both? According to many experts, managing what you eat is what matters most. But other experts maintain that exercise builds muscle that helps people lose weight.
It seems the debate is not over. A carefully controlled study published this month in the Journal of Clinical Endocrinology and Metabolism revealed that diet and exercise are equally good at helping shed pounds. What's more, the study debunked the idea that exercise somehow boosts metabolism and helps dieters lose even more weight.
Findings from previous studies pitting diet against exercise suggest that exercise alone is relatively ineffective when it comes to losing weight. Study participants who engage in endurance activities (e.g.
brisk walking, jogging) for 45 to 60 minutes four times weekly for up to one year experience minimal weight loss -- on average two to four pounds.
Yet these conclusions are drawn from studies in which people's calorie intake and calorie expenditure were not rigorously controlled.
And in many of these studies, the calories burned from exercise were not enough to produce substantial weight loss.
If you keep your diet the same, it takes a lot of exercise to generate a calorie deficit large enough to impact the bathroom scale.
Since one pound of body fat stores about 3,500 calories, you'd have to burn an extra 500 calories every day in order to lose one pound a week. If you want to drop two pounds each week you'd need to expend an additional 1,000 calories daily.
That's a lot of exercise. If you weigh 200 pounds, it takes roughly 35 minutes of jogging, 65 minutes of doubles tennis, 75 minutes of brisk walking (with the dog), or 110 minutes of weightlifting to burn 500 calories. And if you weigh less, it will take longer to burn off those extra calories. A 150-pound woman would need to spend 45 minutes jogging every day to lose a pound each week. A daunting task considering that most people don't exercise that much.
Many experts believe a combination of diet and exercise is the best approach to weight loss. Adding exercise to a low-calorie diet is thought to prevent muscle loss associated with dieting only.
And since muscle tissue burns more calories, muscle mass is a key factor in losing weight.
In the current study, diet only and diet plus exercise were equally effective in helping people lose weight and body fat over a six-month period. Researchers assigned 24 healthy, overweight men and women to a calorie-restricted diet or a calorie-restricted diet plus cardiovascular exercise, five days a week.
The diet-only group ate 25 per cent fewer calories than needed to maintain their weight (roughly 700 fewer calories per day). The diet- plus-exercise group reduced calorie intake by 12.5 per cent and exercised enough to expend an additional 12.5 per cent of calories.
The number of calories restricted was precisely matched in both groups and carefully controlled.
Men and women in both groups lost 10 per cent of their initial body weight, 24 per cent of total body fat and 27 per cent of abdominal visceral fat.
(Visceral fat is not visible to the naked eye; it's the deeper underlying fat that surrounds the organs and is linked to heart disease and type 2 diabetes.) Contrary to what the researchers expected, the addition of exercise did not enhance how much body fat dieters lost. It seems that as long as the calorie deficit is the same, body weight and body fat will decrease the same way.
The study also deflated the notion that if you exercise while dieting, you're going to lose less muscle. The researchers noted that dieting alone did not cause people to lose muscle mass along with fat.
Not all controlled studies have turned up similar results. An earlier study conducted by researchers from Queen's University in Kingston demonstrated that obese men who burned 700 calories daily from exercise alone lost more body fat than men who reduced their daily food intake by 700 calories (13 1/2 pounds versus nine pounds).
Both groups lost the same amount of weight.
So where do these recent findings leave us? To lose excess pounds, should we give up the gym and focus only on what we put in our mouth? No doubt it's easier for many people to simply eat less food than it is to burn hundreds of calories on the treadmill.
And it is certainly possible to lose weight by altering only your eating habits; if you cut calories, you'll lose weight without exercise.
In my opinion, however, you're much better tackling weight loss with both diet and exercise if you are physically able to do so.
There are benefits from exercise that you can't get from dieting alone.
For starters, regular exercise -- even without weight loss -- improves aerobic fitness and the body's sensitivity to insulin, two strong predictors of heart health. (Insulin is the hormone that clears sugar from the bloodstream.) The psychological effects of exercise can also make you more likely to succeed at weight loss. Physical activity helps reduce stress, which otherwise might lead to overeating. And regular exercise boosts self-esteem, a positive feeling that's also linked with making healthy food choices.
If exercise is part of your regime, you're more likely to maintain your weight loss. A 2005 review of studies comparing diet and exercise versus diet alone concluded that people who lose weight by working out and eating less do a better job at keeping the pounds off after one year than do those who only diet.