Yes, Exercise Can Help You Lose Weight
Yesterday, over at PolicyMic, Mr. Cameron English wrote an incisive article on obesity, which we linked to here on RealClearScience. In it, he implicated exercise as an ineffectual solution for weight loss.
Citing sources such as Gary Taubes, Dr. John Biffa, and Dr. Stephen Phinney, all of whom have written books touting low-carbohydrate diets as the best thing since sliced bread (though I'm not sure that they would appreciate that analogy), English lays out what seems to be a fairly convincing case as to why we shouldn't count weight loss among the benefits of exercise.
However, I strongly disagree. I believe his arguments do not properly reflect the majority of research that has been conducted on exercise in the past 50 years.
It's True that Exercise Is Not a Silver Bullet. As a certified personal trainer, I absolutely adore exercise, but I'll be the first to admit that, by itself, it is not an incredibly effective solution for serious weight loss. Outside of The Biggest Loser, it's very difficult for an obese individual to shed pounds through exercise alone. It's far easier to eliminate excess calories from your diet (my favorite target is soda) than it is to burn them off by running on a treadmill, plain and simple.
However, Exercise Alone Can Result in Weight Loss. A 1995 meta-analysis published in the European Journal of Clinical Nutrition reviewed 28 different studies published between 1966 and 1993. The reviewers found that aerobic exercise without any dietary restriction among overweight men produced a 3 kilogram weight loss over 30 weeks compared to sedentary controls. Overweight women lost an average of 1.4 kilograms in 12 weeks. What's more, fat-free mass was not significantly effected, which means that there was little, if any, loss in muscle.
Exercise's Effect on Appetite and Energy Intake. English repeated the distorted message that exercise makes you eat more. This is a huge oversimplification and is simply not supported by most research. In reality, exercise, especially of higher intensity, is commonly known to suppress appetite in the short term. Over longer periods, energy intake can rise without conscious regulation of diet due to increased expenditure, but this additional consumption in calories usually doesn't come close to the amount expended.
Physical Activity's Overall Effect on Basal (Resting) Metabolic Rate is Complicated. In his article, English referenced four studies that apparently showed that endurance exercise decreases resting metabolism among overweight individuals. In truth, exercise's effect on metabolism is not that simple.
The short term effects are fairly well understood. Following a bout of strenuous exercise, an effect known as Excess Post-exercise Oxygen Consumption (EPOC) is induced. During this process, the body undergoes hormone balancing, replenishment of fuel stores, cellular repair, and muscle building, among other things. EPOC is also characterized by measurably increased oxygen intake, as its name implies. As a result of this surge in intake, your body's resting metabolism can increase as much as 13% and remain elevated for up to 48 hours post-exercise, though it will gradually taper off over that time.
The long term effects of exercise on resting metabolism are far less
clear, with the results of many studies in conflict. It makes sense that if exercise results in weight loss, resting metabolism may decrease slightly simply because there is less weight to maintain. However, a habitual exercise program featuring resistance training may boost resting
metabolism due to the resulting increase in lean muscle, which requires more
energy to maintain than fat.
Diet & Exercise in Tandem Do Work. Though English believes "eating less and exercising more" is a "blatantly unworkable solution," there exists plenty of evidence to the contrary. A 2005 systematic review published in the International Journal of Obesity sought to examine the efficacy of diet and exercise on long-term weight loss in overweight and obese individuals. Of the 33 applicable trials found, six of them directly compared the effects of diet and exercise versus diet alone. The researchers found that diet and exercise produced 20% greater initial weight loss, and, more importantly, resulted in 20% greater sustained weight loss after one year versus diet alone.
Also, evidence for the effectiveness of eating less and exercising comes from over 10,000 individuals enrolled in the National Weight Control Registry, the largest investigation of successful, long-term weight loss. Participants in the registry have each lost an average of 66 pounds and have kept it off for over 5.5 years! 98% of registry members modified their food intake and 94% increased their physical activity to lose weight.
The Bottom Line. In the end, a lot of different methods are viable in the pursuit of a healthy weight. Exercise can work; so can simply eating less. Even the low-carbohydrate diets English embraces can work. The issue isn't finding what works. We know what works! The key is finding what works for you and sticking to it. Because the only successful strategy for weight loss and healthy living is one that can be happily maintained for life.
(Photo from the U.S. Navy)