Losing Weight: Less Food or More Exercise?

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Weight Management Specialist and Cardiologist Dr. Luiza Petre Offers Tips on What Really Works for Weight Loss

Dr. Luiza Petre

We've known for some time that it's easier to lose weight by modifying diet than by increasing activity.

October 2015 – More than one-third of American adults are obese1. Obesity is a serious health issue. It is associated with the leading causes of death, including heart disease, stroke, type 2 diabetes, and some cancers, as well as poor mental health and quality of life. The causes of obesity are complex, involving individual factors like genetics, behavior and medications, and societal factors like education and how food is marketed.

Dr. Luiza Petre, medical director of three Medi-Weightloss® clinics, a physician-supervised weight loss program, believes it is imperative to address the overall health implications of obesity and has extended her cardiology practice to emphasize weight management as a key factor in disease prevention and wellness. "Americans have been following each iteration of 'eat-this-not-that' advice just as they follow changes in fashions," she says. "They've also driven the growth of the multi-billion dollar fitness industry, in the hope that they can eat whatever they want if only they exercise more. What they need is a basic understanding of how food and exercise affect weight and well-being and how to find the balance that will work for them."
Gaining and losing weight is a matter of calories consumed and calories expended. A calorie is a unit of energy. The energy a body needs to survive is provided in the form of calories derived from food. Calories are used by the body as fuel for everything we do: It takes energy just to stay alive, to digest food and absorb its nutrients, to go about our daily routines, to fidget, to run marathons, and even to sleep. Calories not expended are stored as potential energy in the form of fat. If we consume approximately the same number of calories we expend, we are in caloric balance and our weight remains stable. If we consume more calories than we expend, we gain weight. If we consume fewer calories than we expend, we lose weight. To put real numbers on it, we gain one pound if we consume 3,500 calories more than we expend and we lose one pound if we burn 3,500 calories more than we take in.

By increasing physical activity, we increase the number of calories we burn, so shouldn't we be able to lose weight without changing our diets? Dr. Petre says that's true only in theory. “Theoretically, we should be able to lose one pound by creating a 3,500-calorie deficit, either by exercising more or by eating less. But in fact, it is almost impossible to lose weight simply by increasing exercise. For example, you could burn 300-350 calories by jogging at a pace of 9 miles per hour for thirty minutes, at which rate it would take 5-6 hours to achieve a 3,500-calorie deficit and lose one pound. Or you could achieve the same 350-calorie deficit by eliminating two 16-ounce soft drinks a day.”

Tracking studies have shown that most people do not maintain a regimen of thirty minutes of even moderately strenuous exercise day in and day out. Most manage a few days a week at best and most overestimate the number of calories they burn through exercise and underestimate the number of calories they consume. Also, many increase their caloric intake in response to the increased appetite stimulated by exercise.

“We've known for some time that it's easier to lose weight by modifying diet than by increasing activity,” says Dr. Petre, “and that many who start an exercise program lose little or no weight. One reason is that as hard as it is to stick to a reduced calorie diet, it is even harder to maintain a regimen of regular exercise.” Another reason is that human metabolism slows as we lose weight. And it is a myth that exercise will rev up the metabolism or prevent it from dropping. A slower metabolic rate means that we're burning calories more slowly and will therefore lose little or no weight as a result of exercise.

“Controlling weight is critical for good health,” says Dr. Petre. “Even a loss of just 10% of body weight is important to improving health outcomes. And while the best way to achieve sustainable weight loss is by reducing caloric intake, this should not be taken to dismiss the value of exercise,” says Dr. Petre. “It is well established that regular physical activity reduces the risks and severity of cardiovascular disease, diabetes, pulmonary disease, various chronic diseases and the effects of aging. Both weight management and exercise must be components of every effort to improve health and well-being. But if weight loss is the primary goal, what happens in the kitchen is more important than what happens in the gym.”

1. CL Ogden, et al. Prevalence of Childhood and Adult Obesity in the United States, 2011-2012, JAMA. 2014;311(8):806-814.

Luiza Petre, M.D. is board certified in cardiovascular diseases, internal medicine, echocardiography, nuclear cardiology, and vascular ultrasound. She is an assistant clinical professor of medicine at Mount Sinai School of Medicine and cardiology clinical instructor at NYU Langone Medical Center. As medical director of three Medi-Weightloss® Clinics, she has expanded her work beyond her cardiology practice to emphasize the need for preventive healthcare, especially as it relates to weight management.

Medi-Weightloss Clinics offer individualized, physician-supervised programs that balance education, appetite management and activity to support weight loss goals and long-term weight management.

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Melissa Chefec
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