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Diet vs Exercise for Weight Loss

Which Is More Important?

By Densie Webb, PhD, RD

For clients and patients wanting to lose weight and keep it off, the ultimate question typically is, “Which is more important—diet or exercise?” The answer is both far simpler and far more complicated that you might think.

Calories Do Count
Clearly, to lose weight, a reduction in calorie intake is needed. It’s the basic rule of weight loss we all know—calories expended must exceed calories consumed for weight loss to occur. But, there’s no magic number of calories that must be expended and consumed that will translate to weight loss success for everyone. The degree of calorie restriction required to lose weight varies greatly among individuals. “Weight loss methods should be individualized, since one method may not work the same for everyone,” says Yasi Ansari, MS, RDN, CSSD, a spokesperson for the Academy of Nutrition and Dietetics. “There are a variety of factors,” she says, “that can influence one’s body weight and ability to lose weight, such as hormonal health, genetics, metabolism, stress level, and current eating patterns—just to name a few.”

Physical Activity
What about exercise? “Regular physical activity not only burns calories, contributing to a calorie deficit; it blunts the metabolic slowdown that occurs with weight loss and helps regulate appetite,” says J. Graham Thomas, PhD, associate center director of the Weight Control and Diabetes Research Center at the Warren Alpert Medical School of Brown University in Providence, Rhode Island. Still, Thomas says, “some amount of dietary change is usually required to produce more weight loss than just the few pounds that are typically achieved via exercise alone.” Research supports this, as studies have shown that diet plus exercise provides significantly greater weight loss—long term or short term—than diet alone.1,2

Despite these findings, less than 5% of adults participate in 30 minutes of physical activity each day; only 1 in 3 adults get the recommended amount of physical activity each week.3 The Physical Activity Guidelines for Americans recommend a minimum of 1 1/4 hours per week of vigorous-intensity aerobic physical activity (eg, jogging, backpacking, bicycling, aerobics, jumping rope) or a minimum of 2 1/2 hours per week of moderate-intensity physical activity (eg, walking, yoga, boxing, dancing, golf).

The Physical Activity Guidelines for Americans are general guidelines, but, as with calorie intake, there’s no one-size-fits-all rule for physical activity that will lead to weight loss. “There is a large amount of individual variability in energy expenditure that can make it difficult to specify the exact amount of physical activity needed daily for each person to continue weight loss,” Ansari says.

Maintaining Weight Loss
While a combination of diet and exercise appears to be essential for successful weight loss, exercise, and plenty of it, seems to be equally important for maintaining weight loss. “On average, individuals in the National Weight Control Registry report exercising the equivalent of about 200 minutes of moderate-intensity activity per week,” Thomas says. The National Weight Control Registry is the largest prospective investigation of long-term successful weight loss management.

In a recent study of people in the Registry who had maintained an average weight loss of 26 lbs or more for at least one year, researchers found that participants took part in significantly more physical activity and burned more calories (180 per day) than normal body weight individuals.4 The study provides further proof that successfully maintaining weight loss relies on the addition of regular physical activity rather than calorie restriction alone to avoid weight regain.

Bottom Line
While the rule of thumb hasn’t changed—cut calories and increase physical activity to lose weight—a single recommendation won’t work for everyone. Because of the tremendous genetic, hormonal, environmental, and socioeconomic variability among clients and patients, diet plans and recommendations for the types and amounts of physical activity also will vary. One thing that should be emphasized when counseling clients and patients who successfully have lost weight: Regular physical activity will—probably more than they think—be required to maintain the weight loss over time.

— Densie Webb, PhD, RD, is a freelance writer, editor, and industry consultant based in Austin, Texas.



1. Wu T, Gao X, Chen M, van Dam RM. Long-term effectiveness of diet-plus-exercise interventions vs. diet-only interventions for weight loss: a meta-analysis. Obes Rev. 2009;10(3):313-323.

2. Johns DJ, Hartmann-Boyce J, Jebb S, Aveyard P; Behavioural Weight Management Review Group. Diet or exercise interventions vs combined behavioral weight management programs: a systematic review and meta-analysis of direct comparisons. J Acad Nutr Diet. 2014;114(10):1557-1568.

3. Ostendorf DM, Caldwell AE, Creasy SA, et al. Physical activity energy expenditure and total daily energy expenditure in successful weight loss maintainers. Obesity (Silver Spring). 2019;27(3):496-504.

4. Health and Human Services, President’s Council on Sports, Fitness & Nutrition. Physical Activity Guidelines for Americans. https://www.hhs.gov/fitness/be-active/physical-activity-guidelines-for-americans/index.html. Updated February 1, 2019. Accessed January 17, 2020.

5. Health and Human Services. President’s Council on Sport, Fitness & Nutrition. Facts & statistics: physical activity. https://www.hhs.gov/fitness/resource-center/facts-and-statistics/index.html. Updated January 26, 2017. Accessed January 17, 2020.