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Parental beliefs about portion size predict child’s BMI

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April 20, 2017

Parents who select larger “ideal” and “maximum tolerated” food portions for their children are more likely to have a child with obesity than are parents who identify smaller portions, according to published findings.

“To date, the relationship between children’s tolerance of (and willingness to accept) large portions and child BMI has not been explored,” Christina Potter, BSc, of the School of Experimental Psychology at the University of Bristol, United Kingdom, and colleagues wrote in the study background. “Parents tend to select their child’s portions at mealtimes and often encourage their children to consume all of food that they are served. However, it has been suggested that parents lack an understanding of age-appropriate portions for their children. Perhaps, for this reason, portion size plays an important role in determining energy intake in children.”

Potter and colleagues analyzed data from 217 parent–child dyads recruited from a randomized controlled trial (n = 69) and an interactive science center (n = 148). Children were aged 5 to 11 years (mean age, 8 years); the mean child BMI percentile was 73.1%; mean parental BMI was 28 kg/m². For a range of seven main meals viewed on a laptop screen, parents estimated their “ideal” and “maximum tolerated” portions while viewing the question: “Imagine you are going to eat this food for dinner and no other food is available. What would be your perfect amount for dinner?” Portion sizes could be increased or decreased using arrows on a keyboard. Parents then performed the same task estimating portion sizes for their children; children then completed the same tasks. All participants also completed a rating scale regarding the likeability of foods shown.

Researchers observed an association between parents’ beliefs about their child’s ideal (beta = 0.34; P < .001) and maximum tolerated (beta = 0.3; P < .001) portions, and their child’s BMI. Children’s self-reported ideal (beta = 0.02; P = .718) and maximum tolerated (beta = –0.09; P = .214) portions did not predict their BMI. Results persisted after adjusting for children’s liking of the meals, parental BMI and parental ideal portion size.

With increasing child BMI, parents’ estimations aligned more closely with their child’s self-selected portions, according to researchers. To highlight the differences, researchers stratified the sample by BMI percentile quintiles.

“Parents of lean children (quintile 1) believed their children would select smaller portions for themselves than their children actually selected,” the researchers wrote. “In other words, the parents of especially lean children tended to underestimate their children’s own portion size selections. With increasing child BMI quintile, parents’ portion-size estimations tended to align more closely with their child’s self-selected portions.”

Researchers also found that parents’ estimates of their child’s ideal portion were not associated with their own ideal portion size (r = 0.06).

The researchers noted that the study did not asses several modifiable predictors of child BMI, such as child’s level of energy expenditure and other parental feeding practices.

“However, as beliefs about portion size are modifiable, our findings may help to inform targeted public health obesity intervention programs aimed at reducing obesity in children,” the researchers wrote. – by Regina Schaffer

Disclosure: The researchers report no relevant financial disclosures.