Taking Steps to Be Healthier
Abstract & Commentary
By Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington. Dr. Phillips is a consultant for Cephalon, and serves on the speakers bureau for Resmed and Respironics.
Synopsis: Simply increasing the number of steps taken daily reduces obesity and improves insulin sensitivity in middle-aged adults.
Source: Dwyer T, et al. Association of change in daily step count over five years with insulin sensitivity and adiposity: Population based cohort study. BMJ 2011;342:c7249; doi: 10.1136/bmj.c7249.
These Australian investigators set out to see if change in objectively measured physical activity affected risk factors for diabetes in middle-aged Australians. They worked with a subset of the AusDiab study cohort,1 which was designed to estimate the national prevalence of diabetes and its risk factors. The population presented in this analysis included 592 participants who were evaluated in 2000 and 2005. At enrollment in 2000, these people were about 50 years old, and a high proportion of participants were overweight or obese; the mean body mass index was 27.1 kg/m2 for men and 26.0 kg/m2 for women. In addition to the usual anthropomorphic measures, data collected included a questionnaire to report the frequency and duration of physical activity in the previous week, pedometer reading over a 2-day period, smoking status, educational level, food frequency questionnaire, alcohol use, and homeostatic assessment of insulin sensitivity (HOMA insulin sensitivity). At baseline in 2000, average daily step count correlated with self report of walking/moderate activity and with self reported vigorous activity.
Over the 5 years of follow-up, most people gained weight; the men gained an average of 1.3 kg and the women gained an average of 1.6 kg. (Coincidentally, the number of smokers fell from 14.% to 11.2% for men, and from 11.2 to 10.6% for women what do the Australians know that we don't?) A majority of people also reduced the number and the intensity of steps over the 5-year period. On average, men fell from 10,172 to 9108 steps daily, and women from 10,969 to 8700 steps daily. (For reference, there are about 2000 steps in a mile, and 10,000 steps is close to 5 miles2). Despite this overall fall in steps/day for the group as a whole, more than a third had more daily steps by 2005.
Both higher daily steps in 2000 and higher daily steps in 2005 than in 2000 were associated with a lower body mass index, a lower waist-to-hip ratio, and greater insulin sensitivity in 2005. Self-reported physical activity time was also generally associated with improved outcomes for BMI and insulin sensitivity.
Based on the data, the investigators calculated that if a relatively inactive person increased his or her daily steps by 10,000 a day, this would result in a decrease in body mass index of 0.83 units and a 13.85-unit improvement in insulin sensitivity. By increasing the number of daily steps by 2000, the resultant changes would be a decrease of 0.16 units for body mass index and an improvement of 2.76 units for insulin sensitivity. Further calculation demonstrated that the effect of higher step activity on improved insulin sensitivity resulted mostly from reduced adiposity.
Commentary
Previous studies have demonstrated that increased physical activity reduces weight and improves insulin resistance.3-5 What is new about the current study is that this population was not selected or randomized, that physical activity was objectively monitored (with a pedometer), and that the study was long term (5 years).
Addressing obesity is a daily challenge for many clinicians. This report reminds us that a person doesn't have to join a gym or go on an extreme diet to have improvement in weight or insulin sensitivity. Practical information about ways to increase the number of steps taken is available on the internet,2 as are inexpensive pedometers.
And the benefits of physical activity (especially walking) appear to extend far beyond control of weight and glucose metabolism. Regular, moderate physical activity is associated with a reduction in mortality, reduced risk of coronary heart disease, improved lipid profile, lowered blood pressure, and reduced risk of stroke.6,7 Further, reduced risk of breast and colon cancer, increased bone density, and reduced risk of dementia have also been reported in those who continue moderate physical activity as they age.7 We need to remind and encourage our patients to get a move on!
References
1. Dunstan DW, et al. The Australian Diabetes, Obesity and Lifestyle Study (AusDiab) methods and response rates. Diabetes Res Clin Pract 2002;57:119-129.
2. The Walking Site. Available at: www.thewalkingsite.com/10000steps.html. Accessed Jan. 17, 2011.
3. Pan XR, et al. Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance: The Da Qing IGT and Diabetes Study. Diabetes Care 1997;20:537-544.
4. Tuomilehto J, et al. Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med 2001;344: 1343-1350.
5. Knowler WC, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002;346:393-403.
6. Lee IM, Buchner DM. The importance of walking to public health. Med Sci Sports Exerc 2008;40 (7 Suppl):S512-518.
7. Vogel T, et al. Health benefits of physical activity in older patients: A review. Int J Clin Pract 2009;63:303-320.
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