The real benefits of exercise
By David Dunaief, M.D.
With holiday dinners right around the corner, what would be a better topic than exercise? To quell our guilt about Thanksgiving dinner indiscretions, many of us will resolve to exercise to burn off the calories from this seismic meal and the smaller, calorically dense aftershock meals, whether with a vigorous family football game or with a more modest walk.
Unfortunately, exercise without dietary changes may not actually help many people lose weight, no matter what the intensity or the duration (1). If it does help, it may only modestly reduce fat mass and weight for the majority of people. However, it may be helpful with weight maintenance. Therefore, it may be more important to think about what you are eating than to succumb to the rationalization that you can eat with abandon during the holidays and work it off later.
Don’t give up on exercise just yet, though. There is very good news: Exercise does have beneficial effects on a wide range of conditions, including chronic kidney disease, cognitive decline, diabetes, cardiovascular disease, osteoporosis, fatigue, insomnia and depression.
Let’s look at the evidence.
Weight loss attenuated
The well-known weight-loss paradigm in medicine is that when more calories are burned than consumed, we will tip the scale in favor of weight loss. The greater the negative balance with exercise, the greater the loss. However, the results of a study say otherwise. They show that in premenopausal women there was neither weight nor fat loss from exercise (2). This involved 81 women over a short duration, 12 weeks. All of the women were overweight to obese, although there was great variability in weight.
However, more than two-thirds of the women (55) gained a mean of 1 kilogram, or 2.2 pounds, of fat mass by the end of the study. There were a few who gained 10 pounds of predominantly fat. Significant variability was seen among the participants, ranging from significant weight loss to substantial weight gain. These women were told to exercise at the American College of Sports Medicine’s optimal level of intensity (3). This is to walk 30 minutes on a treadmill three times a week at 70 percent VO2max — maximum oxygen consumption during exercise — or, in other words, a moderately intense pace.
The good news is that the women were in better aerobic shape by the end of the study and that women who had lost weight at the four-week mark were more likely to continue to do so by the end of the study. This was a preliminary study, so no definitive conclusions can be made.
Other studies have shown modest weight loss. For instance, in a meta-analysis involving 14 randomized controlled trials — the gold standard of studies — results showed that there was a disappointing amount of weight loss with exercise alone (4). In six months, patients lost a mean of 1.6 kilograms, or 3.5 pounds, and at 12 months, participants lost 1.7 kilograms, or about 3.75 pounds.
However, exercise may be valuable in weight maintenance, according to observational studies. Premenopausal women who exercised at least 30 minutes a day were significantly less likely to regain lost weight (5). When exercise was added to diet, women were able to maintain 30 percent more weight loss than with diet alone after a year in a prospective study (6).
Chronic kidney disease
As just one example of exercise’s impact on disease, let’s look at chronic kidney disease (CKD), which affects 14 percent of adults in the United States, according to the Centers for Disease Control and Prevention (7). The U.S. Preventive Services Task Force has indicated that there is insufficient evidence to treat asymptomatic CKD. In fact, the American College of Physicians has said that asymptomatic CKD, which includes stages 3a and 3b, or moderate disease levels, should not be screened for, since the treatment risks outweigh the benefits, and lead to false positive results and unnecessary treatments (8).
However, in a trial, results showed that walking regularly could reduce the risk of kidney replacement therapy and death in patients who have moderate to severe CKD, stages 3-5 (9). Yes, this includes stage 3, which most likely is asymptomatic. There was a 21 percent reduction in the risk of kidney replacement therapy and a 33 percent reduction in the risk of death when walkers were compared to nonwalkers.
Walking had an impressive impact; results were based on a dose-response curve. In other words, the more frequently patients walked in the week, the better the probability of preventing complications. Those who walked between one and two times per week had 17 and 19 percent reductions in death and kidney replacement therapy, respectively, while those who walked at least seven times per week saw 44 and 59 percent reductions in death and kidney replacement. These are substantial results. The authors concluded that the effectiveness of walking on CKD was independent of kidney function, age or other diseases.
Therefore, while it is important to enjoy the holidays, it is food choices, not exercise, that will have the greatest impact on our weight and body composition. However, exercise is extremely beneficial for preventing progression of chronic disorders, such as CKD.
So, by all means, exercise during the holidays, but also focus on more nutrient-dense foods. At a minimum, strike a balance rather than eating purely calorically dense foods. You won’t be able to exercise them away.
(1) uptodate.com. (2) J Strength Cond Res. Online Oct. 28, 2014. (3) ACSM.org. (4) Am J Med. 2011;124(8):747. (5) Obesity (Silver Spring). 2010;18(1):167. (6) Int J Obes Relat Metab Disord. 1997;21(10):941. (7) cdc.gov. (8) Ann Intern Med. online October 21, 2013. (9) Clin J Am Soc Nephrol. 2014 Jul;9(7):1183-1189.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, visit www.medicalcompassmd.com or consult your personal physician.