October 2014

Diet or Exercise Interventions vs Combined Behavioral Weight Management Programs: A Systematic Review and Meta-Analysis of Direct Comparisons

Overweight and obesity is an increasing issue in the United States and additionally worldwide.  It is estimated that by 2030, over half of the world’s population will be either overweight or obese.  Being overweight or obese increases the risk of developing chronic diseases like cancer and cardiovascular disease, which can contribute to poor quality of life.  Weight loss can help individuals reverse being overweight or obese, and decrease their risk of developing these diseases.  There are many different opinions about which method is most effective for weight loss.  Some view diet as most effective, while others emphasize physical activity.  However, it is unclear whether these methods are more successful individually or combined.  Results in past research studies are not definitive due to inconsistencies across studies.  If a conclusive result for the most effective weight loss method is identified, then this can be used by health practitioners to decrease the prevalence of overweight and obesity, and therefore improve the health of individuals around the world.

The purpose of this article was to review research studies to compare weight management programs that utilized a combination of both diet and physical activity to programs that utilized either diet alone or physical activity alone in order to determine which method is the most effective for weight loss.  A total of eight research articles were included in this meta-analysis.  Only studies with overweight and obese adults were included, equaling a total of 1022 participants, the majority of which were women.  Across the eight studies, the diet component involved some level of kilocalorie restriction.  Some studies involved a 500 kcal/day deficit in total calories, while other studies utilized Very Low Energy Diets and liquid diets where participants consumed anywhere from 400-1200 kcals total per day.  Five of the studies had dietitians deliver nutrition recommendations to participants.  Two of the studies used clinical psychologists, and one study used “Professional interventionists” with a degree in health sciences to deliver the nutrition recommendations.  For the physical activity component, most studies recommended moderate to high intensity exercise for several days a week.  Physical therapists, exercise physiologists, exercise physiology graduate students, and “Professional interventionists” delivered the physical activity component to participants.  Average differences in weight change at 3 to 6 months and 12 to 18 months for combined behavioral weight management programs (BWMPs) vs. diet-only programs and combined BWMPs vs. physical activity-only programs were assessed.

The results of this meta-analysis regarding diet-only programs were that there was no significant difference in weight loss at 3 to 6 months between the combined BWMPs and diet-only programs.  However, at 12 months, greater weight-loss occurred in the combined BWMPs.  Regarding physical activity-only programs, results showed greater weight loss in the combined BWMPs at 3 to 6 months and also at 12 to 18 months.  Therefore, weight loss was similar for diet-only and combined BWMPs in the short-term, but in the long term, greater weight loss occurred when diet and physical activity were combined.  Programs based on physical activity alone were less effective than combined BWMPs in the short term and also the long term.  The overall conclusion from this meta-analysis was that individuals should combine diet and physical activity for increased long-term weight loss.

Johns, D. J., Hartmann-Boyce, J., Jebb, S. A., & Aveyard, P. (2014). Diet or exercise interventions vs combined behavioral weight management programs: A systematic review and meta-analysis of direct comparisons. Journal of the Academy of Nutrition and Dietetics, 114(10), 1557-1568.
http://www.sciencedirect.com.libproxy.lib.ilstu.edu/science/article/pii/S2212267214010557?np=y

Supplemental Article:

Foster-Schubert, K. E., Alfano, C. M., Duggan, C. R., Xiao, L., Campbell, K. L., Kong, A., … McTiernan, A. (2012). Effect of diet and exercise, alone or combined, on weight and body composition in overweight-to-obese postmenopausal women. Obesity, 20(8), 1628-1638. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3406229/