As a health reporter I often feel like I am stating the obvious. And stating it over and over again. It usually goes like this: "Today a new study shows …" and the sentence ends with something so blindingly logical and grounded in common sense that it's tempting to ask why someone would do the study in the first place. One of my colleagues jokes about yet another study "from the Journal of Obvious Conclusions."

There's an example in the news this week, about a study in the Journal of Preventative Medicine, which discovered that the further people were forced to drive to work, the less time they spent being physically active. The longer they sat in the car, the heavier and less healthy they were. 

I understand that researchers are just doing their jobs, asking questions, and compiling data. After all, if you are trying to convince an urban planning board why it should force developers to create spaces for bike paths in a new development, or build homes closer to where people work, it's nice to have a pile of science to make the case that it’s a good idea, improving health, lowering health care costs, and all of that.

I have enormous respect for the scientists who sort through all the noise and data to find meaning in the chaos, and then suffer the scrutiny of peer review. And it's true that scientists need to publish to renew their research grants and keep employed while the hundreds of scientific journals rushing to print each week need content.  

It's just that if you feel like you've heard this before, it's because you probably have. At least four studies in the last eight years have come up with the same conclusion. How we choose to get from one place to another affects our health. Or to put it more bluntly, you have a greater risk of getting fat sitting in a car than if you walk, ride a bike or run to catch a bus.

It might seem from the excited headlines this week that this fact has never occurred to us before.

But it sounded so familiar I checked my files and, sure enough, the same journal, the Journal of Preventative Medicine, published a paper in 2004 reporting that each additional hour spent in a car per day was associated with a six per cent increase in the likelihood of obesity. Conversely, each additional kilometer walked per day was associated with a 4.8 per cent reduction in the likelihood of obesity. The authors concluded that city planners could affect population health if they designed cities to increase walking time and decrease driving time.

Then, in 2008 another study reported a similar finding, this time in the Journal of Physical Activity. Looking at "active transportation," (walking, cycling and public transit) and obesity rates, the authors concluded that countries with the highest levels of active transportation, in other words, places where people had to expend physical energy to get to work, generally had the lowest obesity rates.

Two years later, in 2010, I reported the same thing, by the same authors, published in a different journal, the American Journal of Public Health. That study concluded that countries with higher levels of walking and cycling had lower levels of adult obesity, that "travel behaviour could have a major influence on health and longevity" and cities should be designed to encourage people to cycle and walk to work.

Each of those studies made headlines on the day they were published, suggesting that it continues to be news to us that the more we walk, and the less we sit, the healthier we are. I suppose there's some merit in reminding folks that we all need more exercise than we're getting. But it would be counterproductive if people instead just stop listening because they've heard it all before.