Abstract
Overweight and obesity are significant public health concerns that are linked to numerous negative health consequences. Physical activity is an important lifestyle behavior that contributes to body weight regulation.
Physical activity is inversely associated with weight gain and the incidence of obesity. Physical activity also contributes to additional weight loss when coupled with dietary modification, and it can result in modest weight loss when not coupled with dietary modification. Moreover, physical activity is associated with improved long-term weight loss and prevention of weight gain following initial weight loss. Current evidence supports that physical activity should be moderate to vigorous in intensity to influence body weight regulation. There is also a growing body of evidence that physical activity can be accumulated throughout the day in shorter periods of time rather than being performed during a structured and longer period, and that physical activity performed in this manner can be important for body weight regulation.
The literature supports the inclusion of physical activity as an important lifestyle behavior for regulating body weight. There are multiple intervention approaches that may be effective for enhancing physical activity engagement within the context of weight control.
The age-adjusted prevalence of overweight [body mass index (BMI) ≥ 25 kg/m2] and obesity (BMI ≥ 30 kg/m2) in adults at least 20 years of age in the US is estimated to be approximately 69.5% and 36.4%, respectively (1). The prevalence of overweight is estimated to be higher in men than in women, with the prevalence of obesity estimated to be higher in women than in men (38.1% vs 34.5%) (1). The prevalence of overweight and obesity is 76.3% and 48.0% in non-Hispanic blacks and African-Americans, 77.5% and 42.6% in Hispanics and Latinos, 69.6% and 34.6% in non-Hispanic whites, and 40.0% and 11.8% in non-Hispanic Asians, respectively (1). Of particular public health concern may also be the increase in the prevalence of severe obesity (BMI ≥ 35 kg/m2), with current prevalence rates estimated to be 15.7% in adults at least 20 years of age (1).
Excessive body weight that results in overweight or obesity has been shown to be associated with numerous health-related conditions, including cardiovascular disease, diabetes, some forms of cancer, musculoskeletal disorders, and others (2, 3). Thus, overweight and obesity are significant public health concerns in the US and other countries throughout the world (4). Physical activity has been identified as an important lifestyle behavior that can impact body weight and body composition, and it can therefore influence both the prevention and treatment of overweight and obesity. This review addresses key areas related to the influence of physical activity on body weight, which include prevention of weight gain, weight loss, and weight loss maintenance. Moreover, this review addresses potential pathways in which physical activity influences outcomes in adults who are overweight or obese, and areas for future research.
Weight Gain Prevention
While the prevalence of overweight and obesity suggests the need for effective treatments, it is also important to implement strategies to prevent weight gain that may lower the incidence of overweight and obesity. Cross-sectional evidence demonstrates an inverse association between measures of adiposity and physical activity. For example, cross-sectional baseline data from the Look AHEAD trial, a study of 5145 adults with type 2 diabetes who are also overweight or obese, highlight the inverse relationship between measures of adiposity and moderate-to-vigorous intensity physical activity (MVPA) (5). These cross-sectional data show that weekly MVPA accumulated in bouts of ≥10 min was lower at higher levels of body mass index (BMI). The pattern of how MVPA was accumulated was examined from the accelerometry data, which showed that both the number of bouts per day and the duration of each bout of MVPA were inversely associated with BMI. The Look AHEAD trial also examined vigorous-intensity physical activity [≥6 metabolic equivalent tasks (METs)] measured by accelerometry and again showed an inverse relationship between level of physical activity and BMI.
Data from the National Health and Nutrition Examination Survey also support that there is an inverse relationship between MVPA and BMI (6). Physical activity of lower intensity, however, does not appear to be associated with BMI. Combined with the data presented above from the Look AHEAD trial, these cross-sectional findings suggest that physical activity needs to be at least moderate in intensity to influence body weight and levels of adiposity.
The 2008 US Department of Health and Human Services Physical Activity Guidelines for Americans aged 18–64 (7, 8) recommend that physical activity be accumulated in bouts of at least 10 min in duration; however, this recommendation is not based on data examining the relationship between physical activity and measures of overweight or obesity. Data are available from cross-sectional studies that examined whether physical activity needed to be accumulated in bouts of at least 10 min might be associated with measures of overweight or obesity. White et al. (9) reported that a lower incidence of obesity was associated with physical activity accumulated in bouts of at least 10 min; however, the incidence of obesity was not associated with physical activity accumulated in bouts that were <10 min in duration. There is additional evidence that physical activity accumulated in bouts of at least 10 min in duration is inversely associated with BMI (10–12) and measures of body fatness (13). Contrary to the above data, there is evidence to support that physical activity accumulated in bouts of <10 min in duration is also inversely associated with BMI (6, 14, 15) and measures of body fatness (10–12, 14, 15). Taken together, these data suggest that total volume, regardless of the duration of physical activity bouts, may have a favorable influence on measures of body weight and adiposity.
In addition to cross-sectional evidence, prospective data also demonstrate that physical activity may be an important lifestyle behavior that prevents weight gain. Some of the earliest prospective evidence of this relationship comes from the National Health and Nutrition Examination Survey I Epidemiology Follow-Up Study (16). The data showed that the odds of weight gain were higher in adults who remained at a low activity level throughout a 10-year follow-up period than those who became more active or remained at a high activity level. The Aerobics Center Longitudinal Study, which examined data from 2,501 men who were 20–55 years of age, reported that weight gain across an average observation period of 5 years was inversely related to physical activity (17). Data from the Women's Health Study (18), a prospective study of more than 34000 healthy women (mean age = 54.2 years), and the Harvard Alumni Study (19), which examined prospective data from 5973 men (mean age = 60.0 years), also showed an inverse relationship between engagement in 60 min of physical activity per day and prevention of weight gain during a 3-year and 5-year period, respectively.
There is also evidence of an association between physical activity and maintaining a healthy body weight. For example, Brown et al. (20) report that the odds of maintaining a healthy body weight, defined as a BMI of 18.5–25 kg/m2, significantly increased with engagement in >500 MET-min per week (approximately 167 min per week assuming a 3 MET intensity). Rosenberg et al. (21) reported that engagement in vigorous-intensity physical activity of at least 1 h per week was associated with a significant decrease in the incidence of obesity, and the odds were reduced in a dose–response manner relative to level of physical activity.
The literature review conducted for the 2009 American College of Sports Medicine Position Stand also supported that physical activity may result in prevention of weight gain (22). The evidence reported in this position paper supports that between 150 and 250 min per week of physical activity, which is estimated to be an approximate energy expenditure of 1200–2000 kcal per week, will results in prevention of weight gain >3% in adults.
Physical Activity and Weight Loss
There is a high rate of obesity in the US (4). Thus, in addition to approaches to prevent further weight gain, there is also a need to implement effective strategies for weight loss. Physical activity has been shown to be an important lifestyle behavior for both weight loss and prevention of weight gain following successful weight loss.
PHYSICAL ACTIVITY COMBINED WITH DIETARY MODIFICATION
Recent clinical guidelines for the treatment of overweight and obesity recommend a comprehensive approach that includes behavior modification strategies that focus on facilitating dietary changes that result in reduced calorie intake and increased physical activity (2). This is supported by consistent evidence that the combination of physical activity with dietary modification results in greater weight loss than what is achieved with dietary modification alone. A systematic review by Washburn et al. (23) examined studies that were at least 12 months in duration. On the basis of this systematic review, it was concluded that physical activity combined with dietary modification resulted in greater weight loss than dietary modification alone (median weight loss of 8.8% of initial body weight vs 6.9% of initial body weight). This was also supported in an earlier review that reported a 20% greater weight loss with the combination of physical activity and dietary modification than with dietary modification alone (24). There is also evidence that this magnitude of difference between physical activity combined with dietary modification compared to dietary modification alone is present with even shorter intervention periods that range from 12–24 weeks in duration (25, 26).
A more recent study of a 6-month, comprehensive behavioral weight loss intervention that examined data from 424 adults [median age = 30.9 years (25th, 75th percentile: 27.8, 33.7); median BMI = 31.2 kg/m2 (25th, 75th percentile: 27.4, 34.3)] used objective assessment of physical activity and sedentary behavior (27). This study demonstrated that weight loss achieved at 6 months was associated with change in both MVPA performed in bouts ≥10 min in duration and total light-intensity physical activity. However, changes in total MVPA or changes in sedentary behavior were not associated with magnitude of weight loss at 6 months. These results provide insight into the potential pattern and intensity of physical activity that should be targeted within comprehensive weight loss interventions that also include behavior and diet modification strategies.
A major public health concern is the increasing prevalence of severe obesity (BMI ≥35 kg/m2) (4). There is evidence that lifestyle interventions can be effective for inducing weight loss in adults with severe obesity and that physical activity added to dietary modification further enhances the magnitude of weight loss achieved. For example, in a study of 130 adults (BMI approximately 44 kg/m2) randomized to either receive dietary modification plus MVPA or dietary modification alone, weight loss at 6 months was 10.9 kg and 8.2 kg, respectively (28). Thus, the addition of MVPA to dietary modification resulted in an additional 2.7 kg of weight loss compared to what was achieved with dietary modification alone.
While physical activity can add to the weight loss that is attained through dietary modification alone, it also appears that the effectiveness of physical activity in contributing to additional weight loss is dependent on the degree of dietary modification that is undertaken and the magnitude of caloric intake. A review of the literature conducted by Donnelly et al. (22) suggested that the effect of physical activity on weight loss in minimized when dietary restriction is severe (energy intake less than what is needed to meet resting energy expenditure needs). For example, studies of very-low calorie diets (≤800 kcal per day) have shown that weight loss or fat loss is not enhanced with the addition of endurance or resistance exercise (29, 30) compared to what is achieved with severe dietary restriction alone. However, there are improvements in cardiorespiratory and musculoskeletal fitness in response to either endurance or resistance training, respectively, even when coupled with severe dietary restriction (22).
PHYSICAL ACTIVITY IN THE ABSENCE OF PRESCRIBED DIETARY RESTRICTION
While a comprehensive approach that includes behavior modification strategies, dietary modification, and physical activity is recommended as the most effective lifestyle intervention for inducing weight loss (2), not all interventions include all of these aspects. Specifically, some individuals elect to enhance physical activity as their primary modality for inducing weight loss. However, a number of systematic reviews have concluded that the mean weight loss with physical activity alone typically does not exceed 3 kg (7, 22, 23, 31–33), whereas the combination of dietary restriction and physical activity elicits weight loss of approximately 8–10 kg (equivalent to approximately 9% weight loss) (23). However, there is also evidence from the Midwest Exercise Trial (34) and the STRIDDE Study (35) that there is a dose–response relationship between physical activity and weight loss. This is consistent with the literature review conducted by Donnelly et al. for the 2009 American College of Sports Medicine Position Stand, which also concluded that a greater dose of physical activity results in greater weight loss (22). When studies have compared dietary modification to physical activity and the same energy deficit was achieved with both approaches, the magnitude of weight loss achieved has been shown to be comparable (36). Moreover, even in the absence of weight loss, physical activity has been shown to reduce abdominal adiposity (37), which is of importance because abdominal adiposity has been shown to be associated with cardiometabolic risk independent of body weight (38).
Long-Term Weight Loss and Prevention of Weight Regain
While behavioral interventions that focus on dietary modification combined with physical activity have been shown to be effective for weight loss, physical activity may be particularly important for enhanced long-term weight loss and prevention of weight regain. Moreover, it appears that physical activity between 200 and 300 min per week that is at least of moderate intensity may be necessary to enhance long-term weight loss and minimize weight regain following weight loss (22). Evidence for this magnitude of MVPA to enhance long-term weight loss and to minimize weight regain following weight loss is supported by a variety of studies. These include the National Weight Control Registry (39–41), studies that have used prospective designs (42), secondary analyses from several clinical trials (43–49), and findings from randomized trials (50).
An important development in recent years has been the inclusion of objective physical activity measurement, rather than relying on self-report, when examining the relationship between physical activity and long-term weight loss. This has allowed for data to be examined by patterns of physical activity and a broader spectrum of physical activity intensity (light and MVPA) when examining these relationships. For example, Jakicic et al. (45) reported that MVPA accumulated in bouts that were ≥10 min in duration was predictive of both 18 months weight loss and the ability to maintain ≥10% weight loss from 6 to 18 months (Fig. 1); whereas MVPA accumulated in bouts <10 min in duration was not predictive of either of these weight loss outcomes (Fig. 2). This study also demonstrated that light-intensity physical activity (1.5–3.0 METs) was predictive of these same outcomes (Fig. 3). These findings provide important insights regarding how physical activity should be accumulated and the intensity of physical activity that may be most promising for enhancing long-term weight loss and weight loss maintenance.
Change in moderate-to-vigorous intensity physical activity (bouts ≥10 min in duration) by weight loss achieved at 18 months.
Data from Jakicic et al. (45).
Change in moderate-to-vigorous intensity physical activity (bouts ≤10 min in duration) by weight loss achieved at 18 mo.
Data from Jakicic et al. (45).
Change in light-intensity physical activity by weight loss achieved at 18 months.
Data from Jakicic et al. (45).
Sedentary Behavior and Weight Control
In recent years there has been an increased focus on sedentary behavior as a key lifestyle factor that is associated with negative health outcomes, and there is some evidence that this may be independent of physical activity engagement (51). This has resulted in some studies examining whether targeting sedentary behavior, rather than or in addition to physical activity, should be a focus of weight management efforts.
Data from prospective studies have shown mixed results regarding whether sedentary behavior is associated with weight gain in adults, with some studies reporting that sedentary behavior was associated with weight gain and others not showing an association. Healy et al. (52) reported that a lower BMI was not associated with the transition from sitting to standing, but was associated with a transition from sitting to ambulating or from standing to ambulating. This may be because there is only a modest increase in energy expenditure when one transitions from sitting to standing (53, 54). Moreover, change in objectively measured sedentary behavior has not been shown to be predictive of weight loss within the context of a comprehensive behavioral weight loss intervention (27). Thus, while it may be appropriate to encourage a reduction in sedentary behavior to enhance a variety of health-related outcomes, for the purpose of prevention of weight gain or to enhance weight loss, solely targeting sedentary behavior without also increasing engagement in physical activity may not be sufficient.
Effects of Exercise on Energy Balance
There are various potential pathways by which physical activity may influence energy balance (the balance between energy intake and energy expenditure) and therefore impact body weight regulation. One common pathway is the increase in total energy expenditure that may accompany an increase in physical activity that elicits an energy deficit and subsequently impacts body weight regulation. However, as described in a review by Blundell et al. (55), the process of energy balance is dynamic and complicated, with physical activity influencing a variety of factors in addition to energy expenditure. These other factors may include signaling pathways that influence energy intake, with some signals stimulating an increase in energy intake and others stimulating a decrease in energy intake. In addition, physical activity can stimulate responses in both adipose tissue and muscle tissue that also may influence overall energy balance and therefore body weight regulation.
It is possible that the influence physical activity has on the components of energy balance may vary between individuals, thus accounting for the variability in weight loss that is observed between individuals. For example, in response to an acute bout of exercise, it has been shown that for some individuals physical activity results in an increase in postexercise energy intake and for others physical activity results in a decrease in postexercise energy intake (56), and a similar pattern has been reported by others (57). This variability in energy intake response to exercise may partially explain why for some individuals the same dose of physical activity results in weight loss and for others it results in weight gain (58).
It is also possible that an increase in physical activity may result in alterations in other components of nonexercise energy expenditure that can limit the impact physical activity has on body weight regulation. However, a systematic review conducted by Washburn et al. (59) concluded that there was limited evidence to support that engaging in prescribed exercise resulted in a decrease in nonexercise energy expenditure. However, this review also acknowledged the need for studies specifically designed to address this research question, which also include adequate samples sizes and state-of-the-art assessment to quantify physical activity, sedentary behavior, and energy expenditure.
Seminal research in identical twins conducted by Bouchard et al. (60) also demonstrates that there is variability in biology between individuals that may account for difference in body weight regulation in response to physical activity. These findings suggest that there may be biological and genetic factors that influence the variability of physical activity on body weight regulation. There is also evidence from a cohort of 37051 twin pairs of a potential genetic influence on physical activity traits (61). This has resulted in Rankinen (62) suggesting that physical activity traits may be influenced by genetic factors, and this requires additional investigation to confirm the presence of this phenotype with regard to physical activity engagement.
Importance of Physical Activity in Reducing Cardiometabolic Risk
In addition to the benefits on weight loss and prevention of weight gain, physical activity of sufficient dose and intensity will improve cardiorespiratory fitness in adults who are overweight or obese (37). The improvements in fitness usually occur in a dose–response manner, with greater improvements observed as volume and intensity of physical activity increase (63, 64). The improvement in cardiorespiratory fitness has been shown to be associated with a variety of health-related benefits that include reduced mortality, which may occur independent of the level of BMI (65–68) or body fatness (69, 70). Moreover, cardiorespiratory fitness may also be associated with improvements in a variety of cardiometabolic risk factors, such as blood pressure (71, 72) and glycemic control (72, 73). These findings suggest that physical activity, partially through its impact on cardiorespiratory fitness, may have important health implications beyond the management of body weight in adults who are overweight or obese.
Related to this area is the “obesity paradox,” which suggests that for some health-related conditions there may be a protective effect of obesity rather than a detrimental effect. Recent metaanalyses and systematic reviews have supported this position (74, 75), which may suggest that interventions should focus on enhancing physical activity behavior rather than on weight loss. However, there is debate in the literature on this topic, with some investigators suggesting that there may be confounding bias that results in the presence of the “obesity paradox” (76). Thus, this may indicate the need for additional research specifically targeting whether there are health-related conditions for which excess body weight may have a protective effect, and these studies should consider the influence that physical activity and cardiorespiratory fitness may have on these relationships.
Considerations for Enhancing Physical Activity
As presented here, physical activity appears to be an important lifestyle behavior for the prevention of weight gain, weight loss, and prevention of weight regain. The vast majority of the evidence to support this finding is based on physical activity that is best characterized as ambulatory movement that may contain components of endurance or aerobic forms of exercise. This has important implications because the most common mode of physical activity within the US is walking, supporting that this may be a feasible form of physical activity that can have beneficial effects on body weight. However, there are additional considerations that may be important to enhance engagement in physical activity that can contribute to enhanced body weight regulation.
While numerous studies have been conducted that included center-based supervised physical activity (29, 30, 34, 36, 37, 77), there are also numerous studies that have demonstrated that nonsupervised self-directed physical activity can also have a significant effect on body weight regulation (26–28, 43, 44, 49, 50, 63, 78). A recent short-term study by Creasy et al. also demonstrated that center-based, supervised physical activity and nonsupervised, self-directed physical activity can be equally effective for weight loss (79). This suggests that there are options for the environments in which individuals elect to engage in physical activity, and these can be either supervised or unsupervised settings.
As described above, there is some evidence to support that the accumulation of MVPA can be important for body weight regulation (6, 14, 15) and measures of body fatness (10–12, 14, 15). One strategy that may be effective is to encourage the accumulation of steps, which reflects the accumulation of ambulatory activity. It was recently reported that within the context of a comprehensive behavioral weight loss intervention, physical activity increased to approximately 10000 steps per day when the intervention focused on increasing steps performed at a moderate-to-vigorous intensity (79). This intervention also showed similar weight loss to what was achieved with supervised, center-based physical activity or unsupervised, self-directed physical activity. These findings may suggest that encouraging physical activity in the form of increasing steps accumulated each day can be an effective strategy within the context of a comprehensive behavioral weight loss program.
An additional strategy for increasing physical activity within the context of weight-control interventions has been encouraging structured MVPA performed in multiple daily bouts of at least 10 min in duration rather than in one continuous bout. This strategy in consistent with recommendations that this can be effective for improving a variety of health-related outcomes (7, 8). This strategy has also been applied within the context of weight control interventions, and has been shown to be effective for enhancing engagement in physical activity for at least the initial 6 months of treatment (46, 80).
In recent years the use of wearable devices that measure and provide feedback on physical activity has increased in popularity. However, when applied within the context of a comprehensive weight loss intervention, the addition of these devices has been shown to result in only modest improvements in weight loss (81, 82). When used within the context of an intervention to maintain weight loss, a randomized trial found that the addition of a wearable device resulted in less weight loss achieved at 24 months, and no additional increase in physical activity, when compared to an intervention that did not use a wearable device. This may be explained by the long-term use of these devices not being sustained (83). However, there is some evidence that significant weight loss can be achieved when a wearable device is coupled with a low-touch intervention that involves a brief telephone call with a health coach once per month, comparable to what is achieved with a more intensive, comprehensive behavioral intervention (84, 85).
These findings support that there are numerous approaches to enhancing engagement in physical activity within the context of weight control interventions. This provides a variety of options to healthcare providers and health-fitness professionals to engage adults who are overweight or obese in physical activity, which is a key lifestyle behavior to enhance weight control and to improve a variety of additional health-related outcomes.
Summary and Conclusion
The preponderance of scientific evidence supports physical activity as an important lifestyle behavior for the management of body weight. This includes prevention of weight gain, weight loss, and minimizing weight regain following weight loss. The evidence also supports that physical activity may need to be moderate-to-vigorous in intensity and at a dose of at least 150 min per week to influence body weight regulation. Moreover, there is strong evidence that the dose of MVPA necessary to enhance long-term weight loss and to minimize weight regain is of the magnitude of 200–300 min per week. Thus, it is important to consider strategies that may enhance engagement in physical activity in adults who are overweight or obese. One approach that may be effective is to encourage the accumulation of MVPA throughout the day by increasing steps of ambulatory movement rather than focusing solely on structured periods of more traditional forms of exercise. However, it is also important to acknowledge that physical activity alone will have modest effects on body weight, and therefore it is most effective to couple physical activity with dietary modification to regulate body weight. Conversely, dietary modification in the absence of physical activity will be less effective for both short- and long-term weight control, suggesting that a comprehensive approach that involves both of these key lifestyle components is important to optimize the regulation of body weight. There is also evidence that even in the presence of excess body weight or the lack of weight loss, physical activity may have independent associations with numerous health benefits and therefore should be encourage regardless of body weight or body size.
Author Contributions:All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.
Authors' Disclosures or Potential Conflicts of Interest:Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts of interest:
Employment or Leadership: None declared.
Consultant or Advisory Role: J.M. Jakicic, Weight Watchers International.
Stock Ownership: None declared.
Honoraria: None declared.
Research Funding: NIH.
Expert Testimony: None declared.
Patents: None declared.
References
