Being physically active is a primary way to lose or manage weight—right? And sedentary behavior is largely to blame for current rates of obesity? Well, let's slow down. Findings from a study conducted at Loyola University Chicago challenge both those statements.
Published in PeerJ (2017; doi: 10.7717/peerj.2902/supp–1), the 3–year study included 1,944 men and women aged 25—40 from Ghana, South Africa, Jamaica, the Seychelles islands and the United States. At baseline, the researchers measured participants' weight, height and body fat, and the men and women were asked to return for follow–up measurements 1 year and 2 years later. Accelerometers were used to determine activity levels. (Many previous studies have relied on self–reports, but evidence has shown that people tend to overestimate their own activity levels.)
Upon reviewing the data, the researchers were unable to link activity with weight changes. Surprisingly, subjects who met physical activity guidelines at baseline had higher yearly weight gains than those who did not meet the guidelines. And the scientists found no significant association between sedentary time noted at the initial visit and subsequent weight changes. These results led the researchers to believe that other factors, such as the food environment, may have had a more pivotal role in weight increases.
"Recent evidence from the United States—based Coronary Artery Risk Development in Young Adults (CARDIA) cohort using 20 years of BMI follow–up data, found significant effects for neighborhood fast food restaurants, such that BMI increases were associated with a higher consumption of an obesogenic fast food–type diet," wrote the study authors. "This was after controlling for effects of socioeconomic status and physical activity."
Despite this, they said that physical activity remains necessary for a wide range of health improvements: "Importantly, this is not to say that physical activity per se is not important for overall achievement of health, such as the prevention or delay of diabetes and cardiovascular disease, which is undisputed, but that its role in the prevention of population level weight gain may be overstated."