Exercise is known to prevent or treat metabolic syndrome, which is a group of health conditions that raise the risk of heart problems and type 2 diabetes. Now, a new study suggests that less than 1 hour per week of resistance training, even without aerobic exercise, can be of benefit.
Lead author Esmée Bakker, of Radboud University Medical Center in Nijmegen in the Netherlands, and colleagues report their findings in the journal Mayo Clinic Proceedings.
To be diagnosed with metabolic syndrome, a person must have at least three of the risk factors, which include: a large waistline, high levels of triglycerides (a type of blood fat), low levels of high-density lipoprotein ("good" cholesterol), high blood pressure, and high blood sugar.
Today, metabolic syndrome affects more than 1 in 3 adults in the United States, up from 1 in 4 in the 1990s. It is thought that this rate is likely to continue rising as the U.S. population ages.
Exercise prevents metabolic syndrome
In their study paper, Bakker and colleagues explain that increasing exercise is a "cornerstone for preventing and treating" metabolic syndrome, and they cite several studies that show the benefits of aerobic exercise - such as running and cycling - in reducing metabolic risk factors.
Some studies have also found that higher levels of resistance exercise are tied to lower risk of type 2 diabetes in men and women.
However, the authors note that while there is evidence that higher levels of resistance exercise or weight training are linked to lower incidence of metabolic syndrome, this has largely come from cross-sectional studies and not from following large groups over a period of time to see how exercise habits link to the emergence of a condition.
Therefore, they decided to explore the relationship between resistance training - separate from, and together with, aerobic exercise - and the development of metabolic syndrome.
For their analysis, the team used data from the Aerobics Center Longitudinal Study on more than 7,000 adults. The average age of the participants was 46 years and 19 percent were women.
The participants underwent extensive medical exams between 1987 and 2006 and completed questionnaires about frequency and intensity of resistance and aerobic exercise. All were free of metabolic syndrome when they enrolled.
Aerobic plus resistance is best
Of the 7,418 participants that the researchers included in the analysis, 1,147 (15 percent) of them developed metabolic syndrome during their follow-up. While the maximum follow-up was 19 years, the median follow-up was 4 years.
The researchers found that any amount of resistance training that met the 2008 U.S. guidelines for physical activity was linked to a 17 percent lower risk of developing metabolic syndrome, compared with not doing any at all.
The U.S. guidelines suggest that adults, "Do muscle-strengthening activities (such as lifting weights or using resistance bands) that are moderate or high intensity and involve all major muscle groups on 2 or more days a week."
The analysis also showed that doing up to an hour each week of resistance training was linked to a 29 percent lower risk of developing metabolic syndrome, even after adjusting for other potential influencers such as smoking status and endurance training.
More intensive resistance training appeared to show no additional benefits in relation to metabolic risk. Also, whether participants did their resistance exercise in one or two sessions at the weekend or spread it over the week appeared to make no difference to the results.
However, the greatest benefits - in terms of preventing metabolic syndrome - appeared to come from combining resistance training with aerobic exercise, note the researchers.
"Our results indicate that a modest amount of resistance exercise, such as two 30-minute sessions per week, has the most beneficial effect. These findings should be included in the standard medical recommendations for preventing metabolic syndrome and future cardiovascular disease."