What (Not) to Eat on a Date, According to Evolutionary Theory
Women who are primed to think about mating choose less fattening foods, whereas men want to pig out.
Human bodies evolved over endless epochs of want, designed by natural selection to convert occasional calorie-rich foods into adipose reservoirs of energy for those times of scarcity. Now we have at our pudgy little fingertips Twinkies, Ding Dongs, and Pop Tarts (basically, the entire American section of the International Foods aisle here in New Zealand). Faced with such a corn-syrupy bounty, with no effort required other than a casual stroll or mobility-cart ride down the grocery-store aisle, it’s unsurprising that those handy little pockets of vroom have sadly morphed into troughs of crippling obesity. The public health costs are staggering.
I’ve abstained from Twinkies since, I think, the mid-1990s (but for the grace of God, one day at a time). Still, speaking as a middle-aged Type-I diabetic with an unfortunate sweet tooth and the love handles to match, I know all too well how such ubiquitous food abundance is both a blessing and a curse. Unless you’re like my elderly dad and have the metabolism of a hummingbird, most of us will wage that battle of the bulge at some point in our lives. But according to Mengyan Yang and Jinlong Su, psychologists from Nanjing Normal University, the genetic stakes of this war are never higher (er, heavier) than at our sexual primes.
It’s young women, argue Yang and Su in a recent study published in Archives of Sexual Behavior, who are especially attuned to dietary mating tactics—not (entirely) because of pressure from society and cultural norms, but because they’re keenly aware that male psychology innately favors reproductive partners with a low body mass index (BMI).
Cross-culturally, BMI accounts for 80% of the variance in judgments of female body attractiveness, with a score of about 19 (the low side of underweight) seen as being ideal. We can’t credit most men with having any greater wisdom here than a puerile inner voice saying, “that’s hot.” But from an evolutionary perspective, the male preference for female slimness—especially when it comes to long-term relationships and paternal investment—makes sense, given that women with high BMIs are more likely to suffer from menstrual disfunction (and possible anovulation and infertility) and to have poorer maternal and fetal health outcomes. Infant pathophysiology and even neurocognitive problems have been linked to high maternal BMI. “High-fat sweet food might play a special role in human evolution,” contend Yang and Su. “Despite its advantages in energy provision, high-fat sweet food has the potential to cause a negative effect on female body attractiveness. It was likely that a trade-off existed.”
Flabby, pear-shaped male physiques aren’t usually mating assets either, of course, but that’s a different set of evolutionary problems. Here, the focus was mostly on female bodies.
In two experiments with Chinese undergrads, the researchers investigated whether “inducing a mating state” influenced participants’ reproductive body-shaping decisions through their food choices. In Study 1, sixty online participants (30 males, 30 females, all straight and with an average age of 22) were randomly assigned to one of two conditions: either the mating prime condition or the control condition. For the former, participants read a short vignette in which they spent a romantic day with a highly desirable person of the opposite sex, flirting, chatting it up, and topping it off with a steamy dinner date. The other half—the control group—instead read about spending a pleasant day with an old childhood friend of the same sex. Following this, all participants were presented with a series of food images from the Leeds Food Preference Questionnaire and asked to judge how much they wanted the food shown, on a scale of 1 (“do not want at all”) to 5 (“strongly want”). There were four categories of food: high-fat/savory; high-fat/sweet; low-fat/savory; low-fat/sweet. Each category had ten images, and the forty pictures were randomly presented.
The results from the study were clear. Compared to their peers in the control condition, female participants from the mate-priming condition chose significantly less high-fat food, especially when it came to the sweet stuff. By contrast, being horny apparently made the males more likely to say they wanted the high-fat foods. “It is possible that the mental state of mating might contribute to the desire of muscle mass gain for males,” suggest the authors. Another trap, of course. Sure, muscles got the girls, and our male ancestors needed calories for bulk, but they weren’t hunting wild cinnamon rolls and tracking lemon meringue pies.
In Study 2, Yang and Su changed things up a bit. This time, the researchers used film clips to elicit mating motive, and they also added a measure of physical self-esteem to see if that might be moderating food choices. In this study, which had only female participants, half were randomly assigned to the “mating group” and watched a clip from A Moment to Remember (2004), “in which the leading actor and the leading actress developed a romantic relationship and had a sweet and happy time.” Those in the control group instead watched a scene from Winnie the Pooh (2011), presumably one without, ahem, any sexual overtures. As in Study 1, women in the mating group chose significantly fewer high-fat foods; they were also more likely to say that they wanted the low-fat foods, an effect missing from the earlier experiment. “Compared with word priming,” argue the authors, “video priming elicited more intense mating motive.” The women’s physical self-esteem played no role at all, it seems.
Did the romantic primes in the study merely activate some cultural Barbie-like script among the (Chinese) female participants, or did they indeed tap into some evolved body-shaping female mating strategy, as the authors contend? Personally, I don’t think we can disentangle that from these data alone, but neither do I think these are mutually exclusive interpretations.
Still, Yang and Su’s work fits within a broader array of experiments testing aspects of sexual selection theory. Human reproductive strategies are sex-specific, meaning that—all else being equal—the things that men find attractive in women are not the same things that women find attractive in men. All else is never really equal, of course. But when we view our species’ mating behaviors through the broad, mindless, mechanistic lens of evolutionary theory, adaptive decision-making is rather predictable. Other studies have found that mate priming leads male participants, for instance, to take more risks and to exaggerate their resources (i.e., spending more money on luxury goods), whereas women get cattier with other women (i.e., socially excluding competitors) and choose more revealing clothes. “Under the pressure of sexual selection,” write Yang and Su, “we might have evolved a mating psychology: a series of psychological adaptations for attending to mating cues, encoding mating-related information in memory, and driving us to respond to mating-related information.”
The flipside here is what food choices may signal to prospective partners, or at least what we read into them. Do men think that if their date orders a chocolate mud cake for dessert, that it’s a sign of her disinterest in him? Or if a man orders a watercress salad for his main course and pushes the croutons to the side, does he lose some sex appeal? But that’s another study.
Also, as far as I know, evolutionary theorists have yet to explore Ozempic and other modern weight-management drugs. Surely, that’s just the newest curveball in this age-old story.
Yang, M., & Su, J. (2024). Love matters: The effect of mating motive on female food choice. Archives of Sexual Behavior, 53(3), 969–979. https://doi.org/10.1007/s10508-023-02768-3
Questions? Concerns? Ideas? Email the corresponding author directly: Jinlong Su jlsu@njnu.edu.cn
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