Trends over 5 Decades in U.S. Occupation-Related Physical Activity and Their Associations with Obesity

BACKGROUND: The true causes of the obesity epidemic are not well understood and there are few longitudinal population-based data published examining this issue. The objective of this analysis was to examine trends in occupational physical activity during the past 5 decades and explore how these trends relate to concurrent changes in body weight in the U.S. METHODOLOGY/PRINCIPAL FINDINGS: Analysis of energy expenditure for occupations in U.S. private industry since 1960 using data from the U.S. Bureau of Labor Statistics. Mean body weight was derived from the U.S. National Health and Nutrition Examination Surveys (NHANES). In the early 1960's almost half the jobs in private industry in the U.S. required at least moderate intensity physical activity whereas now less than 20% demand this level of energy expenditure. Since 1960 the estimated mean daily energy expenditure due to work related physical activity has dropped by more than 100 calories in both women and men. Energy balance model predicted weights based on change in occupation-related daily energy expenditure since 1960 for each NHANES examination period closely matched the actual change in weight for 40-50 year old men and women. For example from 1960-62 to 2003-06 we estimated that the occupation-related daily energy expenditure decreased by 142 calories in men. Given a baseline weight of 76.9 kg in 1960-02, we estimated that a 142 calories reduction would result in an increase in mean weight to 89.7 kg, which closely matched the mean NHANES weight of 91.8 kg in 2003-06. The results were similar for women. CONCLUSION: Over the last 50 years in the U.S. we estimate that daily occupation-related energy expenditure has decreased by more than 100 calories, and this reduction in energy expenditure accounts for a significant portion of the increase in mean U.S. body weights for women and men

A randomized controlled exercise training trial on insulin sensitivity in African American men: The ARTIIS study: Major category: study design, statistical design, study protocols

BACKGROUND: Lack of regular physical activity at prescribed intensity levels is a modifiable risk factor for insulin resistance and the development of diabetes. African American men are at increased risk for developing diabetes and most African American men are not meeting the current recommended levels of physical activity. The primary objective of the Aerobic Plus Resistance Training and Insulin Resistance in African American Men (ARTIIS) study is to determine the effectiveness of an exercise training intervention aimed at reducing diabetes risk factors in African American men at risk for developing diabetes. METHODS: Insufficiently active 35-70 year old African American men with a family history of diabetes were eligible for the study. The 5-month randomized controlled trial assigns 116 men to an exercise training or healthy living control arm. The exercise training arm combines aerobic and resistance training according to the current national physical activity recommendations and is conducted in community (YMCA) facilities. The healthy living arm receives information promoting healthy lifestyle changes. OUTCOMES: Insulin response to an oral glucose load is the primary outcome measure, and changes in physiological parameters, cardiorespiratory fitness, strength, body composition, and psychological well-being comprise the secondary outcomes. CONCLUSIONS: The ARTIIS study is one of the first adequately powered, rigorously designed studies to investigate the effects of an aerobic plus resistance exercise training program and to assess adherence to exercise training in community facilities, in African American men

Effects of Aerobic and Resistance Training on Hemoglobin A1c Levels in Patients With Type 2 Diabetes

CONTEXT: Exercise guidelines for individuals with diabetes include both aerobic and resistance training although few studies have directly examined this exercise combination. OBJECTIVE: To examine the benefits of aerobic training alone, resistance training alone, and a combination of both on hemoglobin A(1c) (HbA(1c)) in individuals with type 2 diabetes. DESIGN, SETTING, AND PARTICIPANTS: A randomized controlled trial in which 262 sedentary men and women in Louisiana with type 2 diabetes and HbA(1c) levels of 6.5% or higher were enrolled in the 9-month exercise program between April 2007 and August 2009. INTERVENTION: Forty-one participants were assigned to the nonexercise control group, 73 to resistance training 3 days a week, 72 to aerobic exercise in which they expended 12 kcal/kg per week; and 76 to combined aerobic and resistance training in which they expended 10 kcal/kg per week and engaged in resistance training twice a week. MAIN OUTCOME: Change in HbA(1c) level. Secondary outcomes included measures of anthropometry and fitness. RESULTS: The study included 63.0% women and 47.3% nonwhite participants who were a mean (SD) age of 55.8 years (8.7 years) with a baseline HbA(1c) level of 7.7% (1.0%). Compared with the control group, the absolute mean change in HbA(1c) in the combination training exercise group was −0.34% (95% confidence interval “CI”, −0.64% to −0.03%; P=.03). The mean changes in HbA(1c) were not statistically significant in either the resistance training (−0.16%; 95% CI, −0.46% to 0.15%; P=.32) or the aerobic (−0.24%; 95% CI, −0.55% to 0.07%; P=.14) groups compared with the control group. Only the combination exercise group improved maximum oxygen consumption (mean, 1.0 mL/kg per min; 95% CI, 0.5-1.5, P<.05) compared with the control group. All exercise groups reduced waist circumference from −1.9 to −2.8 cm compared with the control group. The resistance training group lost a mean of −1.4 kg fat mass (95% CI, −2.0 to −0.7 kg; P<.05) and combination training group lost a mean of −1.7 (−2.3 to −1.1 kg; P<.05) compared with the control group. CONCLUSIONS: Among patients with type 2 diabetes mellitus, a combination of aerobic and resistance training compared with the nonexercise control group improved HbA(1c) levels. This was not achieved by aerobic or resistance training alone

Occupational METs and energy expenditure since 1960.

<p>The upper panel of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0019657#pone-0019657-g003" target="_blank">Figure 3</a> plots the mean occupation-related METs since 1960 and the lower panel presents the mean occupational daily energy expenditure in men and women since 1960.</p

Trends in the prevalence of sedentary, light and moderate intensity occupations from 1960 to 2008.

<p>Trends in the prevalence of sedentary, light and moderate intensity occupations from 1960 to 2008.</p

Estimated median and range of physical activity intensity (METs) as well as the estimated caloric expenditure of each occupation.

<p>Estimated median and range of physical activity intensity (METs) as well as the estimated caloric expenditure of each occupation.</p

Service, goods producing and agriculture jobs in US from 1960 to 2008.

<p>The top panel depicts the prevalence of service occupations, goods producing occupations and agricultural occupations for the US from 1960 to 2008. The middle and lower panels depict the sectors within the good producing (middle panel) and service occupations (lower panel).</p

Predicted weights and NHANES weights.

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0019657#pone-0019657-g004" target="_blank">Figure 4</a> presents the energy balance model predicted mean U.S. body weight based on change in occupation related daily energy expenditure since 1960 compared to mean U.S. weight gain based on the NHANES examination periods for 40–50 year old men (left panel) and women (right panel).</p