Sedentary Behavior, Exercise, Obesity and Health

 

June 2011 

 

 

Sedentary Behavior, Exercise, Obesity and Health

Does Physical Exercise Hold the Key?

 

Data from the most recent (2007-2008) NHANES survey shows that the prevalence of obesity (BMI ≥ 30) among adult men was 32.6% and for adult women, it was 36.2%. The prevalence of severe obesity (obesity class III) was 4.3% and 7.6% respectively. Add to this the number of people who are in the overweight range (BMI > 25) and we now have 73.7% of adults age 20 and over who are overweight and/or obese.1

 

As the rate and severity of obesity rises so do the numbers of Americans at risk for obesity-related diseases and health conditions.2 Increased physical activity (with or without associated weight loss) has been shown to reduce abdominal fat deposits (visceral adiposity) and waist circumference which, independent of weight, is related to improved health risk.3 Health-related quality of life, which includes mobility, is another important consideration as it is well-documented that quality of life deteriorates as weight increases and improves with weight loss.4 In addition, one long-term study suggests that weight loss may not be the only factor involved in quality of life improvements. Blissmer and colleagues found that 24 months following a behavioral weight loss intervention, health-related quality of life remained improved irrespective of the weight loss that was maintained.5

 

Despite our knowledge of the relationships among physical activity and improved health, quality of life and weight, we have yet to establish clear-cut guidelines for physical activity in obese populations. The majority of public health recommendations are directed towards maintaining a healthy weight and/or maintaining health in non-overweight populations. In other words, they are not directed towards three quarters of Americans. The US Surgeon General’s Report6 of 2001 recommended that people aim for 30 minutes of moderate intensity exercise most days of the week to maintain health. Building on this recommendation, Shape up America! translated this into what we now commonly see touted as the desired activity goal of 10,000 steps daily.7 More recently, the Department of Health and Human Services (HHS) published the 2008 Physical Activity Guidelines for Americans,8 which recommend 2.5 hours (150 minutes) per week of moderate intensity physical activity (e.g., brisk walking, bicycling, gardening, vacuuming) or 75 minutes vigorous intensity activity (e.g., running, aerobics, heavy yard work) per week, plus increasing „baseline activity throughout the day. However, for those who are overweight, this may not be enough. Data from clinical trials suggest that it may be necessary to work towards as much as 70-80 minutes per day of moderate activity or 35 minutes per day of vigorous activity in order to maintain weight loss over the longer-term.9, 10, 11 Reports derived from The National Weight Control Registry, a self-selected registry of very successful weight loss maintainers, which was founded over 15 years ago by researchers at the University of Colorado and Brown University, have provided additional evidence in support of this notion. Currently, the website for the registry reports that more than 5,000 members have lost an average of 66 lbs and kept it off for 5.5 years and that 90% report exercising at least 60 minutes per day. Furthermore, approximately 35% report burning, on average 3000 kcal per week (430 k/cal per day) or roughly the equivalent of walking over 4 miles per day.12,13 In a recent 18-month, prospective study by Obesity Society members at the University of Pittsburgh, 3 levels of exercise prescription: (1) Moderate Physical Activity (PA), (2) High PA or (3) a Self-Help PA intervention were considered in relation to weight loss over a period of 18 months in an overweight sample. Moderate PA participated in a behavioral intervention to promote eventual maintenance of 150 min/week of structured PA; High PA got about the same intervention, but asked to progress to 300 min/week; Self-Help PA received self-help manual and only attended assessment visits with no additional intervention. The mean change in body weight based on 150–300 min/week of moderate-intensity PA with no reduction in energy intake was reported as < 2 kg. However, further analyses examining a subset of participants who had lost > 3 kg (weight-losing subset) indicated that these subjects had both better compliance with maintaining higher PA (at least 161 min/week) and they reported concomitant self-directed reductions in caloric consumption suggesting the need to combine these factors is necessary in order to achieve weight loss.14

 

Quantity of sedentary behavior (physical inactivity) is also receiving considerable attention of late. Research has suggested that the quantity of time spent in sedentary behavior in and of itself may be related to poor health and increased mortality, even in regular exercisers. In a recent study, researchers at the Pennington Biomedical Research Center in Baton Rouge Louisiana considered more than 17,000 men and women longitudinally (13 years) and found a 54% increase in cardiac mortality in the sedentary participants.15 The emerging body of evidence suggests the need to target increasing planned physical activity, while at the same time engendering overall reductions in sedentary behavior if we are to improve health outcomes for our overweight and obese patients. “The role of sedentary behavior in weight and health is a fascinating and timely topic. The concept that sitting is inherently bad for you seems to really catch peoples attention,” states Obesity 2011 Program Chair Timothy Church MD, of the Pennington Biomedical Research Center. “This is clearly an area in need of much more research. At this years annual meeting we have a symposium focused on sedentary behavior being presented by some of leading experts in the field.”

 

References

1. Ogden CL, Carroll MD. Prevalence of overweight, obesity, and extreme obesity among adults: United States, trends 1976-1980 through 2007-2008. Hyattsville, MD: National Center for Health Statistics, 2010 http://www.cdc.gov/NCHS/data/hestat/obesity_adult_07_08/obesity_adult_07_08.pdf.

2. U.S. Department of Health and Human Services. Healthy People 2010. 2nd ed. With Understanding and Improving Health and Objectives for Improving Health. 2 vols. Washington, DC: U.S. Government Printing Office, November 2000.

3. Janiszewski PM, Ross R. Physical activity in the treatment of obesity: beyond body weight reduction. Appl. Physiol. Nutr. Metab. 2007; 32: 512-522.

4. Kolotkin RL, Meter K, Williams GR, Quality of life and obesity. Obesity Reviews 2001Nov;2(4):219-29.

5. Blissmer B, Riebe D, Dye G, Ruggiero L, Greene G, Caldwell M. Health-related quality of life following a clinical weight loss intervention among overweight and obese adults: intervention and 24 month follow-up effects. Health Qual Life Outcomes. 2006; 4:43.

6. US Dept of Health and Human Services. The Surgeon General's Call to Action to Prevent and Decrease Overweight and Obesity. Rockville, MD: US Dept

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