Thursday November 22 2007
10,000 steps burn 500 calories
“Looking for a simple way to improve your health? Consider the lowly pedometer”, suggests the New York Times today. Other, mainly US papers, report that the step-counting gadget, worn at the waist, is a surprisingly effective encouragement for people to be more active.
The research these news stories are based on provides reliable support to the idea that pedometers promote physical activity. However, the studies looked only at pedometer use over a relatively short time (18 weeks) and longer-term studies are needed to see how long this sort of motivational tool will work for.
A pedometer gives the user the ability to measure how much they have done and a goal to aspire to. Walking the recommended 10,000 steps in a day will burn 500 calories, and doing that five days a week will burn 3,500 calories – enough to lose 500g (1lb) of body fat. Watch the video: "I took the 10,000 steps a day challenge" to see what this involves.
Where did the story come from?
Doctor Dena Bravata from the Center for Primary Care and Outcomes Research, at Stanford University, California, carried out the research. The study was supported by a grant from the National Institute on Aging and the National Science Foundation. The study was published in the (peer-reviewed) medical journal, The Journal of the American Medical Association (JAMA)
What kind of scientific study was this?
This was a systematic review with meta-analysis of both observational and randomised studies.
The researchers searched seven databases to find primary research that looked at the link between pedometer use and activity in adult outpatients. The research had to be carried out on more than five people and report a change in number of steps per day.
Two investigators worked independently to read the papers and record the data described in them, and assessed the studies against quality criteria.
What were the results of the study?
There were 26 studies that met their pre-determined criteria with a total of 2,767 participants, mostly women. The average age of the participants was 49 years.
The researchers divided the studies into Randomised Controlled Trials (RCT), which compared the increase in steps of pedometer users against a randomly selected control group, and observational studies which compared the increase in steps in each individual pedometer users against their own number of steps before their uptake of the pedometer. The different study designs were analysed separately.
In the RCTs, the pedometer users significantly increased physical activity by an average of 2,491 steps per day more than those in the control group. In the observational studies, the pedometer users significantly increased their physical activity by 2,183 steps per day. Overall, the researchers calculated that the pedometer users increased their physical activity by 26.9% compared to what they were doing before they started using a pedometer.
When the researchers looked at whether having a goal increased the amount of physical activity undertaken, they found that a goal such as 10,000 steps per day, was significantly associated with more steps taken. Other findings from the studies were that pedometer users, especially the older ones and those with a goal, significantly decreased their body mass index by 0.38. The participants also significantly decreased their systolic blood pressure by 3.8 mmHg. This was especially evident in those with high blood pressure to start with and those who managed the greatest change in number of steps.
What interpretations did the researchers draw from these results?
The researchers suggest that “the use of a pedometer is associated with significant increases in physical activity and significant decreases in body mass index and blood pressure. Whether these changes are durable over the long term is undetermined”. They estimate that an increase in 2,000 steps is equivalent to walking about a mile further each day, but also make the point that this is associated with important and relevant improvements in weight and blood pressure.
Setting goals appeared to be important, though the researchers acknowledge that it is unclear what that goal should be. Pedometer users who began with low levels of activity rarely reached the goal of 10,000 steps a day.
What does the NHS Knowledge Service make of this study?
The results from this well-conducted review are dependent on the quality of the studies that were included, and the authors acknowledge several features of these that made them cautious about making their conclusions too broad:
- The number of participants in each individual study was. often small and they were only followed for short periods of time, and this places a limitation on the interpretation of the results.
- In some studies, the researchers were unable to evaluate more than one outcome which often did not describe their participants in detail, and this reduces knowledge about who the results apply to.
- Only a few studies included participants over 60 and few included men, so it may not be possible to draw conclusions about the older man from these results.
- Some studies investigated other motivational interventions such as diaries and direct counselling, this may make it difficult to find out how much of the effect was due to the use of pedometers alone.
Overall this systematic review provides evidence for the effectiveness of pedometers as one of the few interventions proven as a motivational tool to improve activity levels.