More on how much exercise is needed to predictably achieve health benefits
(May 2004)

The metabolic syndrome is a constellation of five factors that are bad for your health - abdominal obesity, high blood sugar, elevated blood pressure, high blood concentrations of triglycerides (neutral fat), and low blood levels of high-density lipoprotein cholesterol (HDL, good cholesterol). If you have three of the five, you are designated as suffering from the metabolic syndrome which increases your risk of heart attack, stroke, and diabetes (those with the metabolic syndrome also are insulin-resistant).

Those who are overweight, particularly those 20 percent or more overweight and especially those who have abdominal obesity (big bellies, waist to hip ratios that exceed 1), are at much increased risk of developing the metabolic syndrome. Some evidence also indicates that physical inactivity is a risk factor for the metabolic syndrome.

Investigators in the United Kingdom examined the role of physical activity in 5,153 men and women, ages 45 to 68 years, who participated in the renowned Whitehall studies. Intensity of physical activity was measured in METs; one MET is the energy expended at rest; 2 METs is double that energy expenditure (slow walking is a 2 MET activity). Walking at a brisk pace, one mile every 20 minutes, is a 3.5 MET intensity (CLICK HERE for table of intensity in METs of various physical activities). Total physical activity is measured in MET-hours per week - the MET intensity of each activity multiplied by the hours per week of that activity, then adding all activities together.

In this study, the definition of a vigorous activity was 5 or more METs. That is identical to the Healthful Life definition. Moderate physical activity was defined as 3 to 4.9 METs per hour. Healthful Life defines 3.0 to 3.4 as moderate and 3.5 to 4.9 as moderately vigorous.

The findings were as follows:

- Vigorous physical activity to a total of more than 12 MET-hours per week reduced risk of the metabolic syndrome by more than one-third. This applied to both men and women. That would translate to 2 and one-half hours a week (about 30 minutes a day, five days a week) of an activity of 5 METs intensity such as walking at a very brisk pace at one mile every 15 minutes, rapid dancing or playing doubles tennis or about two hours a week of a 6 METs activity (such as jogging, bicycling, swimming laps).

- For moderate activity, a total of 24 MET-hours a week (the equivalent of walking briskly - one mile every 20 minutes - for one hour every day) reduced the risk of metabolic syndrome for men, but not for women. The benefits for moderate physical activity were much less than for vigorous activity.

Commentary: The metabolic syndrome is clearly a risk factor for cardiovascular disease and diabetes. Vigorous exercise appears to be definitely beneficial in reducing risk of developing the metabolic syndrome. What about moderate exercise? A big problem is that, as defined in this study, it includes both moderate and moderately vigorous physical activities. Healthful Life believes that, to achieve a predictable benefit, individuals need at least 12 MET-hours per week of at least moderately vigorous activities (that is, 12 MET-hours a week of any combination of the moderately vigorous and vigorous activities shown in the table on MET intensities of physical activities). Physical activities at work, in the home, and at leisure all count. It is almost certain that, if the moderate physical activity in this study had been restricted to at least 3.5 MET intensity activities instead of including any activity of 3 or more METs (that is restricting the category to 3.5 to 4.9 instead of 3.0 to 4.9), more benefit would have been found.



for the health benefits of regular vigorous physical activities



for the health benefits of at least 12 MET-hours a week of physical activities of at least 3.5 METs intensity (moderately vigorous).



for the health benefits of lesser intensity physical activities.

Healthful Life sees no reason to change our physical activity recommendations (see Archives or Human Tune-Up for article on Exercise and Health).

Rennie, K.L., et al. Association of the metabolic syndrome with both vigorous and moderate physical activity. International Journal of Epidemiology. Vol 32 (August) Pgs 600-606. 2003.