Results from an exciting new analysis were released today and highlight the important advances that are being made in understanding how energy expenditure relates to cancer. The results, from the American Cancer Society’s Cancer Prevention Study show that individuals who report more time spent sitting (6 hours/day or more) have a higher risk of mortality than those who report little sitting (less than 3 hours/day). Importantly, this effect is independent of the amount of time the individuals reported engaging in physical activity. As we’ve previously reported, physical activity also predicts obesity, chronic diseases and mortality.
I spent last week at an exciting workshop at NIH addressing how we measure physical activity and sedentary behaviors. While objective devices like pedometers and accelerometers help us get information on certain physical activities and can help estimate energy expenditure, they don’t tell us about the context or type of behaviors. This is really important when thinking about sedentary behaviors, which are increasingly being shown to have an important role in obesity and chronic disease. Some sedentary behaviors are modifiable, such as TV watching. While others, like time spent driving to work, may be largely unchangeable. Great work is being done in the US, UK, and Australia to improve our understanding of how people spend their sedentary time so that interventions can better target behavior change and measure effectiveness of interventions.
To understand the ACS results a bit better, think about a couple examples. Most of us on the CNiC team spends our days sitting at a desk, writing papers, and analyzing data. We all try to get at least 30 minutes of moderate intensity activity a day, but if we spent more of the day moving about, we’d be better off. In fact, standing during some of those long meetings we have burns more calories and may help improve health. In contrast, plenty of people are on their feet all day (which brings back bad memories of my days in the retail and service sectors, which left me exhausted!), but may never be active enough at a pace to increase their heart rate enough to qualify as “moderate intensity” activity. As a result, in many research studies, these people would be considered “sedentary”. What today’s study from Alpa Patel and colleagues suggests is that these busy-on-their-feet people, even though they may not meet the physical activity guidelines, are doing better than those folks who are in an office and don’t get any physical activity. Of course, that doesn’t mean those who are busy on their feet couldn’t do better by adding in some moderate intensity activity each day!
The current recommendations are to get at least 30 minutes of activity of at least moderate intensity each day. This means walking, gardening, dancing, cycling, or easy running – really, anything you enjoy that gets you moving and your heart rate up. For an extra, and increasingly important, boost, do something each day that cuts down on the amount of time sitting. Stand at a counter and work on your computer for a while; choose to stand on the bus rather than sit; or take the occasional stand-and-stretch break at school, home, or work. They may all seem like little things but add them all up, and they can have an important impact on your health.