By Cedric X. Bryant, Ph.D., F.A.C.S.M., Chief Science Officer, American Council on Exercise
Update: The researchers at Pennington Biomedical Research Center that were quoted in the Time article respond to the author’s inaccuracies in a
follow-up statement.
The cover story of the August 9, 2009, issue of Time magazine featured an article entitled, “Why Exercise Won’t Make You Thin.” In this piece, author John Cloud made several inaccurate and unsubstantiated claims regarding the value of exercise, particularly as it relates to weight loss. What follows is a summary of some of the most misleading assertions made in this highly publicized article, as well as the American Council on Exercise’s response to these assertions:
- First and foremost, the article categorically implies that exercise has no meaningful role in weight loss. Such a conclusion is as false as it is reckless. The author’s “evidence” is the fact that he has “gut fat that hangs over his belt when he sits,” despite maintaining a regular exercise habit. In all likelihood, his unwanted abdominal girth is probably a by-product of genetics and/or consuming more calories than he expends.
- Weight loss and maintenance are a matter of simple accounting that is dependent upon energy balance. In order for weight loss to occur, individuals must burn more calories than they consume. Regrettably, many individuals who regularly exercise are unable to meet their weight-loss goals because they eat too much. In reality, however, their “personal weight situation” and overall health profile would be far worse were it not for the extra calories they expend while exercising.
- An overwhelming body of scientific evidence exists that confirms the positive role that exercise plays in weight loss and maintenance (Hill and Wyatt, 2005; Jakicic and Gallagher, 2003; Jakicic et al., 2001). These findings refute the notion (advanced by the author) that exercise impairs weight-loss efforts by substantially and uncontrollably increasing appetite. Recent research suggests that appetite may be suppressed for 60-90 minutes following vigorous exercise by affecting the release of certain appetite hormones. It also appears that aerobic exercise is more effective at suppressing appetite than non-aerobic forms of exercise (Broom et al., 2009). In general, individuals who participate in moderate exercise tend to eat approximately the same number of calories (or only slightly more) than they would if they did not exercise. Elite-level athletes typically consume high volumes of food after their exercise workouts, but they almost always expend more calories than they consumed (Blundell and King, 1999). It is important to keep in mind, however, that appetite is influenced several factors and is a very complex process making it difficult to generalize the impact of exercise on appetite. The bottom-line is that exercise and diet go hand-in-hand with successful weight management.
- Surprisingly (and disappointingly) the author failed to mention the tremendously important role that exercise plays in the maintenance of weight loss. According to data from the renowned National Weight Control Registry, consistent exercise participation is the single best predictor of long-term weight maintenance. In others words, if individuals want to be successful in getting off the weight-loss rollercoaster (i.e., repeatedly losing weight and regaining it), they need to regularly engage in physical activity.
- Another particularly bothersome portion of the article was the misleading comments regarding children and physical activity. A preponderance of evidence shows that kids are often less active after school, not more active as the article implies. As such, community-based youth fitness programs and high-quality school physical education programs are much needed. The available statistics support the fact that well-designed fitness programs aimed at encouraging children to be more active and maintain a healthy body weight remain a significant priority (HHS, 2008).
Needless to say, readers of this article in Time are likely to conclude that exercise is of little to no benefit to them, which makes its publication in such a high profile and respected magazine so disappointing—and possibly even dangerous. Given the enormous economic costs associated with obesity (approximately $147 billion annually), we should be promoting and advocating scientifically proven healthful behaviors like regular exercise participation whenever and wherever we can. Beyond its weight-control benefits, regular exercise provides a plethora of health benefits, including the treatment and prevention of a wide variety of chronic illnesses (heart disease, hypertension, diabetes, certain types of cancer, to name a few), an enhancement of psychological health and well-being, and an improvement in the overall quality of life throughout the human lifespan.
References
Blundell, J.E. & King, N.A. (1999). Physical activity and regulation of food intake: Current evidence. Medicine & Science in Sports & Exercise, 31, 11 Suppl., S573-S583.
Broom, D.R. et al. (2009). Influence of resistance and aerobic exercise on hunger, circulating levels of acylated ghrelin, peptide YY in healthy males. American Journal of Regulatory, Integrative and Comparative Physiology, 296, 1, R29-35.
Hill, J.O. and Wyatt, H.R. (2005). Role of physical activity in preventing and treating obesity. Journal of Applied Physiology, 99, 765-770.
Jakicic, J.M. & Gallagher, K.I. (2003). Exercise considerations for the sedentary, overweight adult. Exercise and Sport Sciences Reviews, 31, 2, 91-95.
Jakicic, J.M. et al. (2001). ACSM position stand on the appropriate intervention strategies for weight loss and prevention of weight regain for adults. Medicine & Science in Sports & Exercise, 33, 2145-2156.
U.S. Department of Health and Human Services (2008). 2008 Physical Activity Guidelines for Americans. Washington, D.C.: Department of Health and Human Services.