Tuesday, November 14, 2017

Early Childhood Physical Activity Does Not Vaccinate Against Obesity

By Pete (originally posted to Flickr as determination_0970) [CC BY-SA 2.0], via Wikimedia Commons
It's not uncommon when I meet parents of children with obesity for them to tell me either that it doesn't make sense because their child is extremely active, or that inactivity is to blame for their child's struggles.

And while my confirmation bias is that weight leads to inactivity in kids rather than inactivity to weight, data is somewhat mixed, with some studies finding total daily energy expenditure in very young children is associated with lesser weight gain, and others, not.

One of the shortcomings of prior studies were that they focused primarily on energy expenditure measured during a child's first year of life, and didn't cover the period known as adiposity rebound whereby BMI typically decreases until the age of 4-7 years before beginning to increase through late childhood.

A recent small study, High energy expenditure is not protective against increased adiposity in chldren, included that time period.

Briefly, 81 subjects who were classified as either at low risk of developing obesity (in that they had lean mothers with an average BMI of 19.5), or at high risk (mothers with an average BMI of 30.3), were recruited, and 53 remained through to the study's conclusion of 8 years. Three measures of adiposity at 8 years were collected - BMI percentile, BMI Z-score, and percent body fat. Total energy expenditure was measured using doubly labelled water at 4 months, 2, 4, 6, and 8 years of age (though only 58% of all total measurements were collected). Body composition was measured by way of bio-impedance analysis at ages 0.25 and 2 years, and by way of DEXA at ages 4 and 6.

What was found was that total daily energy expenditure increased with body size, but,
"there was no evidence supporting the hypothesis that a low habitual TEE for that body size leads to subsequent increase in BMI or % body fat"
Nor was there an association between measures of adiposity at age 8 and total energy expenditure between the ages of 0.25 and 6 years.

The authors overarching conclusion is that when it comes to the genesis of childhood obesity, it's energy in, not energy out.

I can't help but wonder, were that to be the prevailing belief, would parents with concerns about their children's weights be more conscious of their children's diets (especially liquid calories and purchased meals) as energy-in is something that many parents deemphasize during our initial discussions.

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