Energy Expenditure and Compliance with Physical Activity Recommendations: What should we believe?

L.M. Mudd, J.M. Pivarnik, FACSM, J.J. Ode, A.P. Rafferty, M.J. Reeves

Departments of Kinesiology and Epidemiology, Michigan State University; East Lansing, MI, Michigan Department of Community Health

ABSTRACT: Both the American College of Sports Medicine and the Centers of Disease Control and Prevention (ACSM/CDC) recommend that adults perform 30 min of moderate physical activity (PA), five days per week, or 20 min of vigorous PA, three days per week. In contrast, the Institute of Medicine (IOM) recommends 60 min of moderate PA daily, for the purpose of balancing energy expenditure (EE) with intake to prevent weight gain. PURPOSE: To determine whether individuals who meet ACSM/CDC recommendations also perform sufficient PA to meet or exceed weekly EE values coincident with IOM guidelines. METHODS: National data from the 2000 Behavioral Risk Factor Survey were analyzed. Respondents were asked to describe the mode, frequency, and duration of two (at most) leisure-time physical activities performed during the previous month. Participants were classified into three groups based on the intensity of their activities: moderate (MOD: 1-2 activities, 3-6 METS), vigorous (VIG: 1-2 activities, >6 METS), or mixed (MIX: 1 MOD activity and 1 VIG activity). Within each group, the proportion of those meeting ACSM/CDC and/or IOM guidelines based on frequency and duration was determined. Total leisure-time EE (kcal/kg/wk) was calculated for each group based on the MET level, frequency, and duration of reported activities. The estimated EE range for meeting IOM guidelines was calculated as 21-42 kcal/kg/wk, based on 3-6 METS, performed for 60 min per day. RESULTS: Of the 113,154 respondents who reported leisure-time PA, 34.2% met ACSM/CDC guidelines but only 6.7% met IOM guidelines. Among those who met ACSM/CDC guidelines, 23% of MOD, 8.5% of VIG, and 17.9% of MIX also met IOM recommendations for frequency and duration of PA. The average EE for those meeting ACSM/CDC guidelines was 37.1 kcal/kg/wk for MOD, 61.6 kcal/kg/wk for VIG, 43.6 kcal/kg/wk for MIX, and 41.2 kcal/kg/wk for all 3 groups combined. Based on the EE data, 65.6% of MOD, 73.8% of VIG, and 81.3% of MIX exceeded minimal EE requirements coincident with IOM recommendations ( > 21kcal/kg/wk). CONCLUSION: Compliance with PA recommendations differs when PA is considered in terms of overall EE rather than frequency, duration, and mode. While 34% of US adults meet ACSM/CDC recommendations for weekly PA, only a fraction of these perform 60 min of activity daily. However, the majority of individuals meeting ACSM/CDC guidelines achieve weekly EE criteria for meeting IOM recommendations, regardless of the intensity level of their PA. Thus, when evaluating PA, long-term weight control, and chronic disease risk, researchers should consider the interaction of overall EE with the frequency, duration, and intensity of activities performed.