Sitting around all the time is a sure recipe for obesity. Everybody knows that. But what if it’s the other way around? What if being obese is the cause of too much sitting around? Someone wanted to get to the bottom of this mystery, and used information gleaned from 3,864 mother-offspring pairs to help figure out what is really going on. The project required technology of course, so monitoring devices would play a very important role.
An article published in 2020 explains the background. First of all…
[…] it is important to understand whether early-life obesity drives sedentary behavior in adulthood, as this further highlights the importance of controlling childhood obesity for preventing poor behaviors that are likely to impact health outcomes in later life.
The researchers wondered if a basic tenet of causality has been too easily accepted. It seemed important to establish that weight causes immobility, as much as immobility causes weight. In fact, it looked to them as if “the association more strongly operates in the direction from obesity to sedentary behavior/moderate-vigorous intensity physical activity (MVPA) rather than inactivity causing obesity.”
In other words, obesity leads sometimes to sloth, except for the times when it leads to moderate and even intense activity (and in some cases, TV contracts). At the same time, no one denies that sedentary behavior can and does contribute to obesity. So, there is a lot going on here.
Stage one
The first round of information was lifted from the 1970 British Cohort Study when, at ages 31 and 10, respectively, the height and weight of each mother-offspring pair had been recorded, along with other information. In 2016 the researchers returned to take a second look, when the younger generation of subjects had reached the age of 46 or 47.
Information was collected by a motion-detecting device called activPAL fastened around each participant’s thigh to report on the person’s level of activity. The activPAL device had started being used in 2001, so it was well-established by that time. The accuracy of the information was undoubtedly higher than in the first round, when activity levels had been determined by self-reporting. According to the study results,
Intergenerational data on mother-offspring pairs were utilized in an instrumental variable analysis to examine the longitudinal association between BMI and sedentary behavior.
A causal pathway was found, leading from high BMI in early life to greater device-measured sitting behavior in adulthood. The study authors concluded that “There is strong evidence for a causal pathway linking childhood obesity to greater sedentary behavior.”
The report said that the study “aimed to assess causal associations between obesity in childhood and sitting behavior in middle age,” which has an unintentional ring of satire. It also refers to a number of observational studies “that have suggested adiposity to be a stronger predictor of future sedentary behavior and lower MVPA rather than the reverse (i.e., activity predicting obesity).”
Pinning down this relationship is said to be vital because, if we can keep kids from getting obese, they won’t sit around so much in later life. According to the study authors,
Our findings suggest that obesity in early life may be causally related to adverse sitting and physical activity behaviors in adulthood, potentially further amplifying the risks of obesity and other cardiometabolic conditions. Policies to promote physical activity should focus on preventing childhood obesity and weight gain.
Your responses and feedback are welcome!
Source: “Childhood Obesity and Device-Measured Sedentary Behavior: An Instrumental Variable Analysis of 3,864 Mother–Offspring Pairs,” Wiley.com, 11/01/20
Image by Katy Warner/CC BY-SA 2.0
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