Physical Activity: Are You Getting Enough?

Health Professional

As far as medical-news headlines go, this was an attention-grabber:
"An hour of daily exercise 'needed to stay slim' " the BBC trumpeted.

"Time to hit the gym Women need to work out for an hour to avoid gaining weight," the New York Daily News proclaimed.

A whole hour? Each day? Surely that's a typo, right?

Nope. Experts are saying it's true. A new study from the Journal of the American Medical Association that followed a huge group of women for more than a decade indeed found that the women who stayed at a normal weight did so with a lot of physical activity. This study has a lot to tell us about the importance of staying physically active, so I'm going to discuss it during this blog post and the next.

As the authors point out, the federal government now recommends that we get at least 150 minutes of moderate-intensity aerobic physical activity each week. According to a major 2008 guideline from the US Department of Health and Human Services, this amount "consistently reduces the risk of many chronic diseases and other adverse health outcomes."

But it may not be enough to ward off the extra weight that people typically gain as they age. In the new study, researchers followed more than 34,000 healthy American women, who were about 54 years old at the start of the study. All were following their usual diet. Over 13 years, they gained an average of 5.7 pounds. That may not sound like much, but a growing body of evidence supports the notion that even that level of weight gain could be enough to negatively affect your health (or perhaps indicate behaviors that may be negatively affecting your health).

However, women who did 420 minutes (which is 7 hours) of physical activity a week gained significantly less weight than women who did less activity. When these women doing less activity were further categorized, those who did 150 to less than 420 minutes of weekly activity gained as much weight as those doing less than 150 minutes!

Another interesting finding was that the researchers only saw the relationship between more physical activity and less weight gain in women who started out at a normal weight. This connection didn't show up in women who were overweight or obese.

The authors' take-home message is that preventing weight gain is important. Once you're already overweight, even an hour of activity a day may not keep you from gaining more.

Yes, the headlines were eye-catching (and everywhere). In this case, those headlines were right: To keep weight off, you have to keep moving. But I don't think it should be shocking that we may need an hour of activity daily. Our bodies are meant to move - not sit in a chair for extended periods like so many of us do in our jobs these days. Our muscles and bones, our brains, our metabolic processes, and the rest of our interconnected parts require us to stay active in order to work properly.

In the next blog, we'll take a look at how you can seamlessly fit more activity into your day so it doesn't feel like a major time commitment. We'll also look at all the other life improvements that 60 minutes of daily activity can bring.

Study: JAMA, Physical activity and weight gain prevention, I-Min Lee, et al, 2010, 303(12)