In 2015, the National Academy of Medicine hosted a 2-day public work- shop in Washington, DC, entitled “Physical Activity: Moving Toward Obesity Solutions.” The event brought together preeminent researchers from around the world to provide an expert summary of the science demonstrating physical activity’s (PA) impact in the prevention and treatment of overweight and obesity, and to highlight innovative strategies for promoting PA across all segments of the population.
This, the first of a two-column series on the event, will focus on the state of the science surrounding PA and obesity, and the clear implications of this science for health and fitness professionals.
State of the Science
DOES PA HAVE A ROLE IN REDUCING OBESITY?
Obesity is sometimes thought to be linked almost exclusively to diet, and as a result, limited research has been con- ducted on the role of PA in prevention and treatment of the disease.
Keynote speaker James Hill, PhD, who has studied physiological psychology and obesity for 30 years, kicked off the event with facts that underscore PA’s critical role in reducing obesity. Cofounder of the National Weight Control Registry and founding executive director of the University of Colorado Anschutz Health and Wellness Center, Hill focused on the following:
- Any action that targets obesity has
to work through the energy-balance system, a complex system affected by both inherited and environmental factors.
- More fat is lost when PA is added to a weight loss program.
- There are two scenarios in which adding PA to a routine does not
lead to weight loss: when the person becomes more sedentary during the rest of the day, or when he or she compensates by eating more calories. In either scenario, the energy-balance system does not actually shift.
- Increases in PA are essential for regulating energy balance to maintain a healthy, sustainable body weight.
- Nutrition and PA should be linked in our thinking and interventions. An individual’s optimum diet depends on the person’s PA level.
PA AND PRIMARY PREVENTION OF OBESITY IN YOUTH
Kathleen Janz, EdD, professor of health and human physiology at the University of Iowa, and Shari Barkin, MD, MSHS, professor in the department of pediat- rics at Vanderbilt University School of Medicine and chief of general pediatrics at Monroe Carrel Jr. Children’s Hospital at Vanderbilt, addressed facts surround- ing PA and obesity prevention in youth. Among the key points:
- Kids who are consistently active—45 minutes per day—are least likely to be affected by obesity by the time they reach age 19.
- PA patterns are established early, so interventions must occur in early childhood.
- Children move differently from adults. They are active sporadically throughout the majority of their waking hours, whereas adults may work out for an hour but be much less active the rest of the day.
- Routine PA for children is greatly influenced by parental activity.
EFFECTS OF PA ON PRIMARY PREVENTION OF ADULT OBESITY
Moderator Loretta DiPietro, PhD, of George Washington University was joined by panelists Ulf Ekelund, PhD, of University of Cambridge, and Robert Ross, PhD, of Queen’s University. Their discussion included these highlights:
- The amount and intensity of PA needed to maintain a healthy body weight throughout adulthood is unknown but is likely substantial.
- Women who were successful in maintaining normal weight over a 13-year study averaged about 60 minutes of moderate-intensity PA per day.
- Treatment programs for those affected by obesity should strive for prevention of weight gain— not weight loss, which may be too aggressive to be an effective and sustainable goal.
- There are not any clear models that help individuals to sustain PA over the long term, but PA is irrefutably and fundamentally important.
- PA preserves fat-free mass for adults and older adults, which is important for maintaining functional capacity
and quality of life.
- Despite the sometimes confusing research findings, increasing PA throughout the population should be one of the most important goals of public health.
PA-RELATED OUTCOMES WHEN OVERWEIGHT OR OBESITY IS PRESENT
Despite science supporting the effective- ness of PA in the prevention of obesity among adults and children, there still remains the question of whether it has a positive effect after the onset of obesity and any associated chronic diseases. I had the opportunity to lead a discussion among panelists Andrea Kriska, PhD, professor in the department of epidemiology at the University of Pittsburgh; Gabriel Shaibi, PhD, Southwest Borderlands Scholar and associate professor at Arizona State University; and John Jakicic, PhD, of the University of Pittsburgh. The discussion elicited these takeaways:
- There is a need to better understand the relationship between increased PA and caloric intake, as this may help to explain why some subjects lose weight during an activity intervention while others gain weight. Improved understanding may also help us to better individualize exercise programming based on the satiety versus hunger response to activity.
- PA is extremely important in weight loss maintenance.
- PA alone, even without significant weight loss, dramatically reduces the incidence of diabetes.
- PA is protective against morbidity and mortality independent of whether one loses weight.
- Targeting the behaviors of PA and good nutrition may be more appropriate than targeting the outcomes of weight loss and obesity prevention. Instead, obesity can be considered alongside blood pressure and glucose levels as interrelated elements of morbidity, while PA should be considered the driver of change.
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