You Don't Have To Run Marathons to Benefit From Physical Activity

Sure, we all know that it's important to be physically active to help achieve and maintain a healthy body weight and perhaps diminish the risk of heart disease, some cancers and overall mortality. But how much is enough? Does one really have to exercise 5 days per week, 30 minutes at a clip to accrue health benefits, and does that exercise have to be vigorous or will a brisk walk suffice? The World Health Organization recommends:

• Adults aged 18–64 should do at least 150 minutes of moderate-intensity aerobic physical activity throughout the week or do at least 75 minutes of vigorous-intensity aerobic physical activity throughout the week or an equivalent combination of moderate- and vigorous-intensity activity.

However, a study in JAMA Internal Medicine suggests that you might need less than that to get health benefits.

Senior author Dr. Mark Hamer from Loughborough University, Loughborough, England and colleagues combined data on physical activity from iterations of the Heath Survey for England and the Scottish Health Survey which were obtained between 1994 and 2012. The data in the present study came from 63,500 participants who were aged 40 or more, 46 percent of whom were male. On the basis of their self-reported physical activity, they were assigned to one of 4 groups:

1. Inactive at baseline — 63 percent
2. Insufficiently active — 22 percent
3. Weekend warriors — 4 percent (about half took part in one and half in two exercise sessions weekly)
4. Regularly active — 11 percent.

The investigators analyzed the relationship between the level of physical activity and death from any cause, from cardiovascular disease (CVD), or from cancer during the follow up period. They adjusted their analyses for factors such as smoking which could also affect the outcomes, and then compared the risk of death from these causes for the active groups compared to that of the inactive group.

Individuals in the inactive group tended to be older and were more likely to be smokers, to be in unskilled occupations, and to report long-standing illnesses. Compared to these individuals, the risk of death was lower in the 3 more active groups:

The investigators noted:

"The present study suggests that less frequent bouts of activity, which might be more easily fit into a busy lifestyle, offer considerable health benefits, even in the obese and those with major risk factors. A particularly encouraging finding was that a physical activity frequency as low as 1 or 2 ses- sions per week was associated with lower mortality risks, even in the insufficiently active. "

They also pointed out some limitations to their results — the fact that most participants were Caucasian means one cannot automatically assume these results are similar for other groups. In addition, physical activity levels were only assessed once at the start of the individual surveys, and thus any subsequent changes would not be included in their analyses. There is also the possibility of reverse causation — i.e. that those with underlying health issues might be less likely to be active — although this was somewhat controlled for by eliminating data from those who died during the first 2 years of the study.

Even taking such caveats into account, the study should still be encouraging for those who want to be active, but aren't likely to train for marathons. The take home message is that even moderate amounts of physical activity can have significant health benefits.