Evidence for What Works in Obesity Prevention

“This childhood obesity prevention program works best,” says the headline from Futurity. It’s a catchy headline with a catch. The catch is that there’s absolutely no evidence in the research this story highlights regarding the effectiveness of programs for actually preventing obesity. None. Works in this context apparently means that the obesity prevention program runs smoothly. Does it actually prevent any obesity? Seemingly irrelevant. Whenever we ask such questions, we draw blank stares in response.

All too often, on the subject of obesity prevention, the bar is so low for defining success that actual health outcomes are not part of the evaluation. Most often, the toughest question is whether a program changes behavior.

This logic works only if one presumes obesity is a problem of bad behavior. But the scientific understanding of obesity is making it clear that such a biased mental model does not reflect the reality of obesity. Obesity is more often a problem of physiology and through excessive hunger, physiology drives eating behaviors linked to obesity.

A Randomized Controlled Trial, Neither Rancomized nor Controlled

The low bar for evidence of what works in obesity prevention unfortunately finds its way into scientific literature.

Take, for example, a recent study in the Journal of Healthcare for the Poor and Underserved. The authors studied the usefulness of home gardening for improving food security and health. Their abstract tells us:

“One hundred participants were randomized into the control and intervention group of which the intervention group received training in home gardening. Results showed that the percentage of participants with normal body mass index decreased from 24.4% to 20% in the control group whereas it remained unchanged in the intervention group.”

There’s just one problem. Randomization did not occur. So there’s not a comparison of an intervention and a control group here. Just a comparison of people who signed up for a gardening program and others who did not. A group of scholars from the Indiana School of Public Health at Bloomington point out this and other problems in a letter to the editor:

“We read with interest the article by Tumwebaze et al. on the impact of home gardening on household food security, BMI, waist-to-hip ratio, and blood pressure. However, we have concerns about the description of the study as randomized, the use of within-group comparisons to draw conclusions, and numerical inconsistencies.

“Tumwebaze et al.’s misreporting of randomizing participants in the abstract and incorrect use of within-group comparisons do not permit valid conclusions to be drawn from the analyses.”

We Need Prevention That Works

Our point is that obesity prevention is important. So we need programs that actually work to reverse the trends of increasing prevalence and severity of obesity. Merely educating, nudging, or taxing people to change behaviors is not good enough – not if it has no measurable effect on health and obesity outcomes.

Click here for the article in Futurity and here for the study it was based upon. For the study by Tumwebaze et al and the letter to the editor about it, click here and here. We note that the journal has now published an errata here, acknowledging the errors in the original manuscript.

Allegory of Science, painting by Sebastiano Conca / WikiArt

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February 21, 2023