Weight loss occurs when you burn more energy than you consume. A deficit of 500 calories per day leads to a one pound per week loss, but that deficit can come from cutting calories from your diet, burning them off through exercise, or a combination of both. Strictly in terms of weight loss, which could mean a combination of fat, muscle and water weight, diet modifications seem to be more effective. To specifically lose fat, whether or not the number on the scale changes, exercise is key.
Exercise Alone
Only one percent of the members of the National Weight Control Registry were able to achieve and maintain significant weight loss through exercise alone. This is because moderate exercise generally doesn't burn enough calories to stimulate weight loss, and it can actually stimulate your appetite so you take in more calories. Exercise helps you build more lean muscle mass, which burns more calories than fat, and a 2007 study in the "International Journal of Obesity" found that the more aerobic exercise you do, the more visceral fat you'll lose. Losing the fat will lower your weight, but the muscle gain will increase it. So you'll get thinner, but not necessarily lighter.
Diet Alone
Ten percent of the National Weight Loss Registry had success using only a restricted diet. The progress may be slower, because cutting 500 calories per day can be very difficult. For some, it may leave them below starvation level, which will force your body to hold on to fat rather than burn it. Weight lost through diet restriction alone can be from muscle mass and water weight, not just fat. The more muscle mass you lose, the more your metabolism slows and the more difficult it is for you to lose weight. A dieter is not likely to change her body composition, just her weight. She won't be firm or toned, just lighter.
Diet and Exercise
The vast majority -- 89 percent -- of the National Weight Loss Registry used a combination of diet and exercise. This allows you to eat sensibly without feeling deprived because the majority of the calorie deficit comes from your workout, and the workouts help you preserve lean muscle mass that aids in fat burning. A 2006 study in "The International Journal of Behavioral Nutrition and Physical Activity" found that people who formulated a weight loss plan that included both diet and exercise have better success than those without a plan.
Beyond Weight Loss
Exercise should be a part of everyone's life, whether or not it is part of a weight loss plan. It boosts your mood, helps keep your heart healthy, builds strong bones, and helps you stay flexible, even into old age. Even if you manage to reach your weight loss goal without exercise, it may be vital to keeping the weight off. The American Council on Exercise claims that only about five percent of dieters are able to maintain their weight loss, and those who do exercise an average of an hour per day.
References
- American Council on Exercise: Weight Loss: Diet vs. Exercise
- Nature Clinical Practice - Endocrinology and Metabolism; "The Role of Physical Activity in Producing and Maintaining Weight Loss"; Catenacci VA, et al, July 2007
- The International Journal of Behavioral Nutrition and Physical Activity; " The Relationship Between Prevalence and Duration of Weight Loss Strategies and Weight Loss Among Overweight Managed Care Organization Members Enrolled in a Weight Loss Trial; Jennifer A Linde, et al, February 17, 2006
- International Journal of Obesity; "A Dose-Response Relation Between Aerobic Exercise and Visceral Fat Reduction: A Systemic Review of Clinical Trials"; Ohkawara K, et al, December 2007
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