April 2005, Vol. 10, No. 1
47
JEMDSA
To the Editor: It was with favourable interest that I read the recent articles on the treatment and prevention of the insulin resistance syndrome.1,2 I was appreciative of the fact that the authors acknowledged that an increase in voluntary human energy expenditure is essential in the treatment and prevention of the insulin resistance syndrome.
However, the lack of accuracy and clarity of the physical activity guidelines promoted by the authors detracted from the quality of the articles. I fully appreciate the vast scope that they attempted to cover, but regrettably, they relied either on only three studies3,5 or the position statement of a single professional organisation6 specialised in areas other than exercise science and physical activity epidemiology, to provide physical activity guidelines.
In fairness, it must be noted that the American College of Endocrinology position statement,6 although not referring to any authoritative physical activity guidelines, makes a strong case for physical activity and states emphatically in several places that adiposity and physical activity are powerful modulators of insulin action.
The 3.5 hours/week physical activity guideline promoted in the first article1was probably derived from the Framingham study which found a reduction in the incidence of coronary heart disease for those who walked 8 hours/week, exercised moderately for 3.5 hours/week or exercised vigorously for 1.5 hours/week.
Since then physical activity guidelines have advanced substantially and not surprisingly the 3.5 hours/week physical activity guideline falls into a no-man’s land;
above the 150 minutes/week minimum of the American College of Sports Medicine/Centers for Disease Control and Prevention7 and below the minimum IASO guidelines8of 315 and 420 minutes/week. Furthermore, the Framingham guidelines rely on increasing energy expenditure through exercise, while the new- generation guidelines recognise any bodily movement produced by skeletal muscle (occupation, chores, commuting, leisure, exercise, etc.) which raises the metabolic rate sufficiently to be protective.
In conclusion, there are evidenced-based physical activity guidelines7-11and a host of excellent resources from which to draw.12-23 Contributors to JEMDSA are encouraged to draw on the excellence and depth of research in the field of exercise science and physical activity epidemiology, and to promote physical activity
guidelines that are accurate, specific, authoritative, and current.
Ian Cook
Department of Physical Education and Human Nutrition
University of Limpopo PO Box 459
Fauna Park 0787
1. Maritz FJ. Insulin resistance and vascular disease.Journal of the Society for Endocrinology, Metabolism and Diabetes of South Africa2004;9:54-61.
2. Till A, Buys R. Clinical insights into the lifestyle and dietary management of insulin resistance syndrome. Journal of the Society for Endocrinology, Metabolism and Diabetes of South Africa2004;9:64-68.
3. Knowler WC, Barrett-Connor E, Fowler SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med2002;346:393-403.
4. Tuomilehto J, Lindstrom J, Eriksson JG, 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. Higgins M, Kannel W, Garrison R, Pinsky J, Stokes J III. Hazards of obesity – the Framingham experience. Acta Medica Scandinavica1988;723:23-36.
6. Einhorn D, Reaven GM, Cobin RH,et al. American College of Endocrinology position statement on the insulin resistance syndrome. Endocr Pract2003;9:237-252.
7. Pate RR, Pratt M, Blair SN, et al.Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA1995;273:402-407.
8. Saris WH, Blair SN, Van Baak MA, et al.How much physical activity is enough to prevent unhealthy weight gain? Outcome of the IASO 1st Stock Conference and consensus statement. Obes Rev2003;4:101-114.
9. Institute of Medicine of the National Academies. Dietary reference intake for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids.Washington National Academies Press, 2002: 45-72, 697-736.
10. Lambert EV, Bohlmann I, Kolbe-Alexander T. ‘Be active’ – Physical activity for health in South Africa. South African Journal of Clinical Nutrition2001;14:S12-S16.
11. South African Association for the Study of Obesity. Guidelines for the prevention and management of overweight and obesity in South Africa.2003; 13-16.
12. Blair SN, Nichaman MZ. The public health problem of increasing prevalence rates of obesity and what should be done about it.Mayo Clin Proc2002;77:109-113.
13. Erlichman J, Kerbey AL, James WP. Physical activity and its impact on health outcomes. Paper 1: The impact of physical activity on cardiovascular disease and all- cause mortality: an historical perspective. Obes Rev2002;3:257-271.
14. Erlichman J, Kerbey AL, James WP. Physical activity and its impact on health outcomes. Paper 2: Prevention of unhealthy weight gain and obesity by physical activity: an analysis of the evidence.Obes Rev2002;3:273-287.
15. Hawley JA, Houmard JA. Introduction – preventing insulin resistance through exercise: a cellular approach. Med Sci Sports Exerc 2004;36:1187-1190.
16. Hawley JA. Exercise as a therapeutic intervention for the prevention and treatment of insulin resistance. Diabetes Metab Res Rev2004;20:383-393.
17. Booth FW, Gordon SE, Carlson CJ, Hamilton MT. Waging war on modern chronic diseases: primary prevention through exercise biology. J Appl Physiol 2000; 88:774- 787.
18. Eriksson J, Taimela S, Koivisto VA. Exercise and the metabolic syndrome.Diabetologia 1997;40:125-135.
19. Chakravarthy MV, Joyner MJ, Booth FW. An obligation for primary care physicians to prescribe physical activity to sedentary patients to reduce the risk of chronic health conditions.Mayo Clin Proc2002;77:165-173.
20. Stewart KJ. Exercise training and the cardiovascular consequences of type 2 diabetes and hypertension: plausible mechanisms for improving cardiovascular health. JAMA 2002;288:1622-1631.
21. Perez-Martin A, Raynaud E, Mercier J. Insulin resistance and associated metabolic abnormalities in muscle: effects of exercise. Obes Rev2001;2:47-59.
22. Booth FW, Chakravarthy MV, Gordon SE, Spangenburg EE. Waging war on physical inactivity: using modern molecular ammunition against an ancient enemy.J Appl Physiol2002;93:3-30.
23. Blair SN, Connelly JC. How much physical activity should we do? The case for moderate amounts and intensities of physical activity. Res Q Exerc Sport1996;67:
193-205.
Dr Maritz replies: Mr Ian Cook has done me an honour by reading and commenting on my brief review
Treatment and prevention of the insulin resistance syndrome
LETTER
of insulin resistance and vascular disease.1Of course he is correct in all his comments, particularly when he alludes to the vast scope of the topic. No review of the physical activity guidelines nor resume of exercise science and physical activity epidemiology was intended – a lengthy topic in itself. Indeed, the same criticism could be made of the omission of many other guidelines pertaining to the insulin resistance syndrome.
Mr Cook has enhanced the value of my article with his critique and references, for which I am grateful.
Perhaps he would consider writing a South African perspective on the value of an increase in energy expenditure in the management of the insulin resistance syndrome and how this pertains to our diverse ethnic mix, with varied customs and beliefs.
This would undoubtedly have a tremendous impact on how we manage this ever-growing health risk and add to our collective knowledge to a much greater degree than a short, and in itself incomplete, letter to the Editor.
1. Maritz FJ. Insulin resistance and vascular disease. Journal of the Society for Endocrinology Metabolism and Diabetes of South Africa2004;9:54-61.
