Exercise and health outcomes

Weight Loss

Learning Disabilities and Juvenile Delinquency

Popular vs. scientific press: Weight loss studies

The popular media often sensationalizes the cautious findings of scientific research, in an effort to catch the casual reader's attention at all costs -- even if the cost is the truth. This can be seen in the CNN piece "Exercise lengthens your life -- even if you're overweight," a title designed to communicate an unequivocally positive message in an America where the majority of the population is overweight or obese. CNN reports the findings of a recent scientific journal article in which researchers suggest that moderate exercise can add years to a person's life, regardless of weight status. Although the CNN article does not directly misstate the findings of the original journal article on which it was based, it neglects to mention some of the caution of the studies' authors regarding an excessive BMI.

The actual findings of the article do suggest that some form of exercise is better than no exercise at all. Specifically, it was found that physical exercise in the form of 75 min/wk was associated with a gain of 1.8 years of a subject's lifespan vs. no exercise at all. However, higher levels of activity were associated with greater gains -- with a gain of 4.5 years for 450+ min/wk (Moore et al. 2012: 1). The positive benefits of exercise were reflected in increased longevity for all participants, regardless of BMI group.

In the CNN piece, one of the senior authors of the study is quoted as saying: "if you are active, the results suggest that you ... have more of a benefit than someone who is not heavy but not active" (Hagan 2010). However, strictly speaking, that is an incomplete summary and was not what the researchers actually discovered. The benefits are potentially greater for someone who is thin and physically active and the title of the CNN article misleadingly suggests that moderate exercise for an overweight person is 'enough' to reap the full health benefits. In the actual text of the article itself, the study notes "we found that obesity (but not overweight) was associated with lower life expectancy in each physical activity group" even though physically active persons lived longer, all other factors being equal (Moore et al. 2012: 5).

Additionally, the benefits of physical activity were not the same for all demographic groups: the association between physical activity and longevity was more "robust" for African-Americans, for persons with a college education, and former smokers (Moore et al. 2012: 4). These associations suggest there may be some correlating lifestyle factors that contribute to longevity beyond that of the physical activity itself. The CNN article makes no mention of this demographic segmentation, likely because it assumes that the fact that overweight people can still be 'healthy' is deemed to be the most interesting aspect of the research to the readership.