iTNT Blog

Which is more important for weight loss, exercise or diet? — Martha Hagman, Conn.

This is a complicated question and one that I can’t completely answer because it hasn’t been completely answered by science. A satisfactory explanation for how best to lose weight and why it is so easy to gain weight has yet to be determined. I’ve discussed many possible contributing factors in this column: Genetics, hormones, biological viruses, social viruses, stress, your romantic partner — even air conditioning. All are suspected of playing a role in how and why the body stores fat.

It’s easiest to point a finger straight at calories because it makes sense that if you take in more energy than you burn off, you will hold on to what’s left as excess body weight. So let’s talk about whether eating fewer of them or burning more of them is the better weight loss strategy.

A number of studies have concluded that restricting calories is a better way to drop a pants size than spending more time in the gym. For example, one University of Pennsylvania trial found that men and women who exercised — but didn’t bother to control what they ate — lost 0.3 percent of their initial body weight compared to those who dieted but did not exercise and lost 8.4 percent of their weight.

Don’t cancel your gym membership just yet. This study, like many others looking at the problem, did not compare diet and exercise on equal footing. The women in the diet-only group cut 945 calories per day, and the men cut 1,705 calories. Meanwhile, the exercise-only groups walked or jogged for 30 minutes, five times a week, expending an average of 255 and 190 calories per session for men and women, respectively.

This is sort of like comparing apples to really big apples. In a research study cited by the American College of Sports Medicine to support their daily exercise recommendations, researchers compared people who ate 500 fewer calories per day with those who burned an extra 500 calories by walking and both groups lost about the same amount of weight. This seems to be the general finding with more recent studies, as well.

Of course, you’d have to run about six miles to burn off a Milky Way Bar that takes less than a minute to eat (speaking only for myself, of course). That’s why once you step outside the laboratory, dieting probably plays a bigger role in weight loss than exercise.

Still, it’s clear that combining diet and exercise achieves better results than doing either separately. In a review of more than a dozen studies lasting up to a year, the National Institutes of Health found that groups who did aerobic exercise and cut calories lost an average of 4.2 pounds more than groups who just dieted. Groups that added weight training to the mix were rewarded with losing two additional pounds on average.

Putting all this aside for the moment, the better question seems to me, “What is the best way to prevent yourself from gaining weight in the first place?” or perhaps more applicable to most of us, “What’s the best way to keep it off once you’ve lost it?” Here, the evidence is becoming crystal clear: Exercise is the key factor. The Center for Disease Control (CDC) estimates that over 70 percent of people who succeed in keeping their weight down over a five year period exercise regularly as part of a lifestyle change, compared to only 20 percent of people who have regained their weight. The National Weight Control Registry puts the percentage of successful losers who exercise closer to 80.

I’ve often said on this blog, and I’ll say it again, that the formula for losing weight is as simple as moving more and eating less. I think as we continue to unravel the mysteries of body weight we will find this to be fundamentally true still but with many factors tossed into the mix which complicate how your body stores and sheds calories. For now, the best pieces of ammunition you have to fight extra pounds are to get your fanny in gear and use a smaller fork.

You can check out Dr. Oz’s 10 Commandments for Weight Loss and see what fellow That’s Fit blogger Jonny Bowden has to say about fiber and weight loss.

Now it’s your turn. Have you tried to lose weight by either cutting back on desserts, trudging it out on the treadmill or some combination thereof? Have you been happy with the results? Or have you found some other secret to weight loss that you’d like to share with the rest of us? Post it here or tweet me @lizzyfit.

Liz Neporent is a diet and fitness expert and co-author of “The Fat-Free Truth.” She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider.