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When it comes to weight loss, how much does diet matter?



Ever since American waistlines started rapidly expanding approximately 40 years ago, the question has been, "What's the best way to lose weight? Diet or exercise?"   Health experts always say "diet and exercise." But in spite of hearing this advice over and over again, we live in a world that wants black-and-white answers. And in the case of weight loss specifically, science does seem to have given us a simple answer: diet is the way to lose weight.

  "It's easier to eat 500 calories less a day than exercise enough to burn up 500 calories," says Dr. Tim Church, professor of Preventative Medicine at LSU's Pennington Biomedical Research Center.

  Numerous studies back up that finding and reputable health organizations now state it, including Mayo Clinic, which says on its website, "Cutting calories through dietary changes seems to promote weight loss more effectively than does exercise and physical activity."

  Why is that? Most of the calories we expend each day are what we use to stay alive. That energy is known as our "resting energy expenditure," or REE. Mackie Shilstone, a New Orleans fitness expert and sports performance manager who has worked with everyone from Peyton Manning and Serena Williams to non-athletes, says REE accounts for 65 percent of the calories we burn in a day. He also says metabolic rates don't differ as much between less active and more active people as was once thought. That is what leads Church to say, "Ninety-nine percent of the benefits of exercise are not related to weight. We get weight-obsessed."

  But if it's really just a matter of eating less, and if people find it easier to eat less than exercise, why are 69 percent of Americans overweight and/or obese?

  Because it's not quite that simple. Church says people need to look at weight from three perspectives:

Prevention of weight gain. "If you are a normal weight, you need to keep exercising throughout your life to maintain that weight."

Weight loss. "Here's where diet rules the day."

Weight loss maintenance. "After you lose the weight, exercising will keep it off."

  Shilstone takes the question of weight even further.

  "If you look at diet alone, you can lose weight," Shilstone said, "But depending on your age and your situation, what are we defining as weight? What five pounds did you lose? Fat? Water? Muscle?"

  Citing post-menopausal women, who traditionally have problems with sudden weight gain, Shilstone says, "I have seen women who have been dieting for years — and training their body for storing fat. They would even be losing weight, but still storing fat and losing muscle."

  Over the years, those observations and questions led Shilstone to use a "DEXA scan." This dual X-ray technology is traditionally used to measure bone density, but Shilstone uses it to look at bone, muscle and fat mass to better understand people's body compositions and from there, their REE. The information Shilstone gets from the DEXA scan helps him determine the best diet and exercise regimen to help clients lose weight, maximize potential and be healthy.

  When it comes to diet and exercise, people should keep a few other things in mind. Americans didn't get fat overnight because of a sud- den attack of gluttony. For most of human history, food has been difficult to obtain, and we are designed to store fat to last us through lean times. When there aren't any lean times, we just keep adding on. We're also more sedentary, so people have to make the effort to do the 150 minutes of moderate activity a week that the Centers for Disease Control and Prevention (CDC) recommends to stay healthy, which amounts to about 7,000 or 8,000 steps a day. (Shooting for the popular "10,000 steps" is even better.)

  Be aware that broad forces are working against us. Poor agricultural policies and junk food engineered to be addictive are only some of the systemic issues we now face. Shilstone says the low-fat craze didn't help.

  "We replaced fat with sodium and sugar and that catapulted us into the major problems we have now," he says. Portion sizes too have ballooned over the last few decades.

  Finally, there are the mind games we play with ourselves. "We are absolutely horrible at estimating calories [we eat]," Church says. "And we tend to overestimate how many calories we burn."

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