July 28, 2016
2 min read

Portion-size preference does not determine BMI

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Adults with overweight do not choose larger food portions than their normal-weight peers, according to recent findings.

“Large portions of food are often blamed for rising rates of obesity,” Natalie M. Reily, a researcher in the school of psychology at The University of New South Wales in Australia, and colleagues wrote. “We tested the possibility that people who are heavier may tend to select or prefer larger portions than do people who are lighter.”

The researchers conducted four studies based on four separate online questionnaires. In study 1, 128 women (mean BMI, 25.35 kg/m2) were asked to choose between images of small and large portions of pasta for a hypothetical meal. In study 2, 293 women (mean BMI, 25.47 kg/m2) were asked to choose between images of small and large portions, images of small and large portions with corresponding labels, and “small” and “large” labels. In an effort to provide more portion-size options, 104 women in study 3 (mean BMI, 24.74 kg/m2) were asked to select their preferred portion size in 28 pairs, which consisted of randomized options of eight different portions sizes. Study 4 had the same design as study 1 with 273 male participants (mean, BMI, 26.25 kg/m2).

In all four studies, researchers found that a somewhat greater percentage of participants with overweight than with normal weight chose larger portions, but the difference was not statistically significant. Researchers concluded that participants with a higher BMI did not select larger portions than those with a lower BMI, although in the forced-choice situations there was a slight tendency for heavier female participants to select the larger portion over the smaller one when compared with the lighter female participants.

“If portion size affects food intake to more or less the same degrees across BMI, and if there are no differences in portion-size preference among people who are heavier and people who are lighter (as observed in the present studies), then other factors need to be considered in attempting to explain the connection between portion size and obesity,” researchers wrote. “For example, rather than ordering larger portions, people with higher BMIs might eat more of what they order than do people with lower BMIs.”

Researchers report the hypothetical nature of all of the studies as a limitation, as well as the sole option of pasta. – by Cassie Homer

Disclosure: The researchers report no relevant financial disclosures.