Tuesday, November 4, 2014

Prevent Obesity w/ More exercise - less fast food

Morales, Gordon-Larson and Guilkey (2014) conducted a simulation experiment where they statistically modeled several factors that are related to the probability of a person being obese in the future.  The model tested their assumptions by predicting who would become obese. You can read the study here .- Several statistical equations were used to simulate decisions about smoking, physical activity, starting a family, and fast food consumption.  In addition, the researchers added a neighborhood level factor.

The data used were real - information came from the National Study of Adolescent Health (USA) which contains several years of information following people from high school through young adult hood.  During those years, people in the study usually transition from a home environment chosen by their parents, to one they chose themselves.  The choice of environment is based on some unknown personal preferences or necessities of the person.  Since many researchers speculate that where a person lives has a direct impact on whether or not that person becomes obese, these researchers felt it important to capture neighborhood choice in their model predicting obesity.  In fact, Morales, et al knew exactly where the participants lived at all times and added the number of parks, complete streets and fast food restaurants in each persons neighborhood to their simulation model.

The results of the study are interesting and give public health advocates, researchers, policy makers and the general public some things to consider.  The researchers tracked people over time in their simulation model, too, so they carried forward things about the person that had been learned at the previous time point.  They found that the best or most powerful predictor of whether or not a person would be obese at time 2 or 3 or 4 was whether or not they were obese the time before that.  In fact, the researchers assert that the most important thing to do is prevent obesity in the first place, because a reversal just isn't seen.  In other words, if a person was obese at any of the previous times it is very unlikely that they will be normal weight at any point in the future.  I agree that prevention is the key.

Other findings that seemed important to me, include; the more fast foods a person consumed the more likely they were to be obese; and physical activity reduced the probability of obesity, but in a nuanced way.  The researchers found that at least 30 minutes of physical activity 5 days a week were needed to keep a person from becoming obese and that the greatest impact on weight - or the best chance of not being obese - came from maintaining that level of physical activity from adolescence (i.e., high school) throughout adulthood.

Neighborhood characteristics, a main focus of this study, did have an impact on the probability of being obese, but the magnitude of the effect was much smaller than physical activity and fast food consumption.

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