The second edition of the Physical Activity Guidelines for Americans was published by the Department of Health and Human Services in 2018 along with the Physical Activity Guidelines Advisory Committee Report. In addition, the American College of Sports Medicine has published a series of manuscript focused on the guidelines and accompanying scientific report in Medicine & Science in Sports and Exercise in June 2019. These guidelines highlight the importance of physical activity across numerous health-related parameters.

One area that was included in the guidelines report is the influence of physical activity on weight gain prevention and prevention of obesity. This is an extremely important consideration given the high prevalence rates of overweight and obesity in the United States. Thus, efforts to minimize or prevent weight gain are of public health importance to curtail the increasing prevalence of overweight and obesity.

It is clear from the scientific evidence that physical activity is an important lifestyle behavior that will prevent weight gain and contribute to the prevention of obesity in adults. This benefit is found for both men and women and appears to be mostly observed in young and middle-aged adults, as this benefit is less consistent with increasing age. However, as highlighted in other aspects of the report and guidelines, there are health benefits of physical activity across the entire age span regardless of the impact on weight gain prevention or body weight status.

An important consideration is that physical activity appears to be most effective for prevention of weight gain and obesity if performed at a moderate-to-vigorous intensity, with less evidence to support that lighter intensity activity will result in this benefit. This suggests that activities that cause a noticeable increase in heart rate and breathing rate, such as brisk walking, are the preferred types of activity to prevent weight gain. Moreover, it appears that the benefit to preventing weight gain and obesity is more likely to occur when the activity accumulates to at least 150 minutes per week.? This does not suggest, however, that less intense or lower amounts of activity are not beneficial. The guidelines highlight the numerous health benefits with the various intensities or amounts of physical activity.

Currently there is also a public health emphasis on decreasing sedentary behavior to improve health. The guidelines report examined the available studies and concluded that there is only limited evidence supporting that the amount of sedentary behavior may be greater in individuals at a higher body weight or level of adiposity. This suggests that focusing solely on reducing sedentary behavior may not be sufficient to reduce weight gain and prevent obesity. Rather, it may be important that any reduction in sedentary behavior results in an increase in moderate-to-vigorous physical activity that accumulates to at least 150 minutes per week to minimize weight gain in adults.

Despite the findings to support the importance of physical activity to reduce weight gain and prevent overweight and obesity, there are additional areas of research that are needed. These include examining the amount of light intensity physical activity that may be required to result in this health benefit, and examining whether the type of activity (e.g., aerobic activity, resistance training, etc.) might be an important factor to consider. It will also be important to study whether the amount or intensity of physical activity to prevent weight gain is influenced by other behaviors such as dietary intake.