Low-fat diets make women more masculine?

Here and in various comment sections, I've bemoaned the masculinization of our female sex symbols, referring to the 1960s as the last time when they oozed estrogen, a transition sometime during the 1970s, and a falling off the cliff throughout the 1980s to the present.

These days, they seem much more lantern-jawed, long-faced, and strong-browed. Look at the girls in the music videos for "Girls on Film" (NSFW) from 1983, and "I Wanna Fuck You" from 2006. Or compare The Ronettes from the early 1960s, The Go-Gos from 1981, and The Pussycat Dolls from within the past few years. Ignore attractiveness -- I'm talking only about how girly or manly their faces look. Even as recently as the early 1980s, they still looked fairly feminine.

I've always thought that this was a change in what the elite allowed us to see, and that it was probably a result of the Second Wave of hysterical feminism that erupted in the mid-1970s. But maybe the change is more general -- that not only our sex symbols are more masculine-looking, but perhaps ordinary women are too. I wasn't alive before 1980, but I've seen pictures and movies of ordinary people from before then, and my vague impression is that they looked more feminine. That seems like a better place to start: assume that the sex symbols are just part of a bigger picture. What could have caused this recent shift toward more masculine looks in women?

Americans started to cut fat out of their diet, replacing it with higher carbohydrates, sometime in the mid-to-late 1970s, when the current obesity epidemic had also just begun. (It didn't become widespread until later in the 1980s.) Boosting our routine carbohydrate consumption will raise our insulin levels chronically, and this will be even more pronounced if these are refined and easily digestible carbs like sugars and starches. So does insulin affect how much testosterone or other androgens are circulating in women?

I don't pretend to know much endocrinology, but I just read a review by Poretsky et al. (1999), "The Insulin-Related Ovarian Regulatory System in Health and Disease" (Endocrine Reviews). Free full text here. Here is part of their summary of how insulin itself affects the production of sex hormones within the ovaries:

At this time there is no convincing direct in vivo evidence that hyperinsulinemia acutely stimulates ovarian steroid production, but there is direct in vitro evidence and indirect in vivo evidence for a stimulatory effect of insulin on ovarian steroidogenesis. The in vitro evidence suggests that the stimulatory effect of insulin on steroidogenesis is mainly mediated by the insulin receptor and may involve the inositolglycan pathway. The in vivo evidence is largely derived from experiments in which a reduction in circulating insulin levels produces a decline of circulating androgens and from clinical observations in women with both insulin deficiency and insulin excess.

If you give women a boost of insulin, their testosterone levels don't appear to change, but this is only during the short-term. When women with high insulin are given insulin-lowering drugs and followed up over the long-term, their testosterone levels decline. That's the indirect evidence the authors refer to. And here is their diagram of insulin-regulated ovarian function:


Just as one example of how higher insulin could masculinze a woman's appearance, insulin secretion leads to down-regulating sex hormone binding globulin (SHBG). Having low SHBG allows more testosterone to be converted to dihydrotestosterone, and high levels of this are associated with male pattern baldness. In an extreme case, women with polycystic ovary syndrome have hyperinsulemia, as well as a tendency toward more body hair and male pattern baldness.

A similar mechanism could affect the shape of their skulls -- we know what women with high androgen levels look like in the face.

So, maybe the feminist movement of the mid-1970s had nothing to do with masculinizing our sex symbols -- maybe this reflected a larger shift toward more manly looking women, due to a profoundly higher consumption of carbs (especially the refined ones) that would chronically elevate insulin levels.

Before I suggested the role of dietary differences in accounting for differences in attractiveness between the French, Spanish, and Italians vs. the English and Americans, focusing on high-carb diets driving glycation-related aging of the skin. Here we see that it's likely that French, Spanish, and Italian women just have a more feminine appearance in general, as they consume fairly low-carb, high-fat diets. Probably more womanly in demeanor too, for the same reason.

Femininity -- another casualty of the high-carb crusade.