Erik Willis

Ph.D., M.P.H.

National Cancer Institute

Cancer Prevention Fellow

IDATA (Learn more about this study)

IDATA-18

Oct 31, 2017

Association between total energy expenditure, physical activity, and sedentary time in older adults

It is well established that being obese increases the risk for many chronic diseases, such as heart disease, hypertension, diabetes, and is rapidly overtaking tobacco as the leading preventable cause of cancer. Current obesity prevention and treatment strategies promote increasing physical activity, assuming that increased activity will additively lead to subsequent increase in total energy expenditure. While exercise alone has been demonstrated to produce clinically significant weight loss (≥ -4%) without energy restriction, typically a large volume of exercise energy expenditure (≥ 2,000 kcal/week) is necessary and there is considerable inter-individual variability in the magnitude and direction of weight change. Furthermore, several reports have shown that the accumulated negative energy balance created by an exercise intervention alone is less than theoretically projected. The concept of behavioral (energy intake and non-exercise energy expenditure) compensation in response to exercise has been a proposed mechanism for the reduced magnitude of weight loss in response to exercise, however evidence of long term behavioral compensation is inconclusive and conflicting.

The “Constrained energy expenditure model” offers an alternate explanation for why exercise interventions often result in minimal weight loss. The model suggests that energy expenditure linearly increases with exercise at low doses but plateaus at higher doses as the body adjusts to maintain an equilibrium of total energy expenditure through metabolic adaptations such as changes in somatic functions. However, limited data is available exploring the Constrained energy expenditure framework. To date, only one cross-sectional study in a pooled sample of adults living in five populations of African descent (Ghana, South Africa, Seychelles, Jamaica, and United States) has assessed the association of between physical activity and total energy expenditure. In addition, studies have not assessed the role of energy balance status (negative, stable, positive) in the relationship between physical activity and total energy expenditure. It has been proposed that these limits on energy expenditure may only function under conditions of negative energy balance. Data from the Interactive Diet and Activity Tracking in AARP (iDATA) study affords a unique opportunity to examine the relationship between physical activity, total energy expenditure, energy balance status (negative, stable, positive) and sedentary behavior in a large sample of free-living older adult men and women.