Is Assortative Mating an Obesity Villain?

In 2007, the Rowett Research Institute and the University of Aberdeen wrote about how people tend to become romantically involved with others who have similar characteristics:

For instance, tall people tend to marry other tall people, and we tend to marry within our own social class, within our own educational class, and within our own race.

A doubter might object that, if this were so, the commercial services that report on genetic ancestry would have little reason to exist. At any rate, this is the doctrine of assortative mating. The point of the referenced article was that people also tend to choose partners with “similar body fatness,” and that this might contribute to the obesity epidemic. Their children inherit whatever genes might be responsible for inappropriate weight gain, as well as a collection of attitudes, beliefs, and customs connected with food.

That assortative mating applies to body fat had already been established through BMI measurements, but now it was confirmed with “a sophisticated technique called dual-energy X-ray absorptiometry,” much more accurate and reliable.

But unlike many other factors suggested as obesity villains, assortative mating has increased rapidly and recently. One of the researchers, Professor John Speakman, theorized that people used to marry younger, when it was too soon to tell if a wife or husband would eventually expand.

But now, people go ahead and manifest their body fat destiny much earlier in life. Not only that, but they marry later, when their true obesity status is more likely to have already been revealed, so it is easier to find a prospective mate in the same obesity bracket. Although the idea seems rather tenuous, there may be something to it.

As we discussed previously, a school of thought then arose, holding that…

[…] common environmental influences may play a more significant role in the resemblance of spousal behaviors than assortative mating.

It was also found that using a method other than BMI to measure body fat gave more accurate results on which to base speculations about assortative mating. But a decade later, The Obesity Society publicized a study that used BMI measurement to establish the degree of overweight experienced by almost 900 multinational participants, who were then asked to rate the attractiveness of potential partners by looking at their photos.

The study authors took a long-winded route to explain that the reactions were, figuratively, all over the map, which struck rather a blow to the assortative mating paradigm. The lead author, Professor John Speakman said,

What is new here is that with a large international sample, we can pretty much eliminate the mutual attraction idea as an explanation. Despite the overall patterns, some people prefer individuals of intermediate adiposity and others prefer partners that have obesity over individuals that are lean. However, these preferences were not related to the rater’s own BMI.

Your responses and feedback are welcome!

Source: “Love At First Sight Of Your Body Fat,”, 08/13/07
Source: “Entry into Romantic Partnership is Associated with Obesity,”, 04/09/09
Source: “Does Mutual Attraction Explain Assortative Mating for Obesity?,”, 02/21/18
Image by Stuart Richards/CC BY-ND 2.0

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About Dr. Robert A. Pretlow

Dr. Robert A. Pretlow is a pediatrician and childhood obesity specialist. He has been researching and spreading awareness on the childhood obesity epidemic in the US for more than a decade.
You can contact Dr. Pretlow at:


Dr. Pretlow’s invited presentation at the American Society of Animal Science 2020 Conference
What’s Causing Obesity in Companion Animals and What Can We Do About It

Dr. Pretlow’s invited presentation at the World Obesity Federation 2019 Conference:
Food/Eating Addiction and the Displacement Mechanism

Dr. Pretlow’s Multi-Center Clinical Trial Kick-off Speech 2018:
Obesity: Tackling the Root Cause

Dr. Pretlow’s 2017 Workshop on
Treatment of Obesity Using the Addiction Model

Dr. Pretlow’s invited presentation for
TEC and UNC 2016

Dr. Pretlow’s invited presentation at the 2015 Obesity Summit in London, UK.

Dr. Pretlow’s invited keynote at the 2014 European Childhood Obesity Group Congress in Salzburg, Austria.

Dr. Pretlow’s presentation at the 2013 European Congress on Obesity in Liverpool, UK.

Dr. Pretlow’s presentation at the 2011 International Conference on Childhood Obesity in Lisbon, Portugal.

Dr. Pretlow’s presentation at the 2010 Uniting Against Childhood Obesity Conference in Houston, TX.

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