fitness · weight stigma

It’s dessert week in nutrition science!

CW: discussion of research related to body weight, BMI, and weight gain.

While the rest of us have been busy baking bread at home, nutrition researchers have been hard at work keeping dessert science going strong. They’ve been thinking and plotting and measuring and parceling out various amounts of dessert items to various sizes of people, then watching them closely to see what happens.

A group of busy-bee food science professionals released their results this week in an article investigating associations between body weight and milkshake liking. No, that’s not me rephrasing it– it’s the actual title of the article (using the word “ob*sity”, which I strongly dislike for scientific and ethical reasons).

First, they the formed their hypothesis:

Milkshake hypothesis: Make milkshakes, they said. Boys will come to your yard, they said.
Milkshake hypothesis: Make milkshakes, they said. Boys will come to your yard, they said.

(side note: if you’re not familiar with the references in this meme, you’re in for a sweet treat! Start here, then go here. Important: this is not to be confused with the “mikshake duck” meme, which I just learned about one minute ago.)

Back to the meme at hand: that’s not their research question (better to leave it to the “directions for future studies” section). Here’s what they wanted to know:

Prevailing models of obesity posit that hedonic signals override homeostatic mechanisms to promote overeating in today’s food environment.,,Here we define hedonic as orosensory pleasure experienced during eating and set out to test whether there is a relationship between adiposity and the perceived pleasure of a palatable and energy-dense milkshake.

non-science-journal version: they want to know if people’s body weights have an effect on how yummy milkshake consumption seems to them. What they are actually looking for is whether larger people report yummier milkshake drinking experiences (which they think might partly explain their larger sizes). That’s what these scientists are really up to.

What’s next? The researchers set up their test group: 110 people with BMI 19.3–51.2. They asked them to arrive neither hungry nor full, and to have not eaten for at least one hour. The participants came, and waited.

Please note that this study took place before pandemic social distancing protocols were instituted. Otherwise, group size would be strictly limited.

Safety first: milkshakes are allowed to bring at most 9 boys to the yard. A meme with Kelis.
Safety first: milkshakes are allowed to bring at most 9 boys to the yard.

Back to the study: I can’t tell you about the exact methods because even with my awesome library access I can’t get the full article yet. But: the researchers measured hunger before milkshake consumption and also recorded how much the participants said they liked and wanted the milkshake (during consumption).

Finally, we get the results! Here’s what the article says:

We identified a significant association between ratings of hunger and milkshake liking and wanting. By contrast, we found no evidence for a relationship between any measure of adiposity and ratings of milkshake liking, wanting, or intensity.

We conclude that adiposity is not associated with the pleasure experienced during consumption of our energy-dense and palatable milkshakes. Our results provide further evidence against the hypothesis that heightened hedonic signals drive weight gain.

Uh oh! The nutrition scientists got a negative result! They found that body weight had no effect at all on how pleasurable people said their milkshakes were. Keanu pretty much sums it up:

What if the boys were already on their way to the yard, and my milkshake had nothing to do with it-- meme with Keanu.
Keanu reports test’s failure to find association between two variables. It happens.

Yes, the study did find a correlation between hunger levels pre-consumption and reported pleasure during consumption. But no one doubted that. And yes, it’s a good thing when scientists get and publish a report on failure to find correlations.

This study gives us a glimpse of something very interesting and a bit worrisome to me, as a fat woman and a health ethics researcher: medical research spends a lot of time and effort searching for causal factors involved in body weight and weight gain that are located in individual persons’ actions, psychological makeups and personal habits. Are fatter people fatter because of something they are doing or feeling or attracted to?

These scientific questions make me uneasy about what may be underlying speculations (or assumptions) by researchers, clinicians and even the general public about what fatter people are doing differently or feeling and acting differently that accounts for their increased fatness. These views are likely yet another source for deep-seated fat-biased beliefs and weight-stigmatizing judgments.

Should we stop doing this kind of research? Even as a public health ethics professional, this is not in my lane, so I can’t say. I think we should remain careful about uptake and reliance on nutrition research, lest it leave a bad taste in our mouths.