Aging Men Can Curse Estrogen, Too Researchers find that sinking estrogen levels to blame for expanding waists By Kate Seamons, Newser Staff Posted Sep 12, 2013 7:32 AM CDT 6 comments Comments Why don't aging men's waistlines look like this? Estrogen plays a part. (©) (Newser) – It turns out both sexes have a reason to curse estrogen. A new study has found that what the New York Times dubs one of men's "familiar physical complaints of midlife"—that ballooning waistline—is not, as long believed, due to dipping testosterone levels. While those levels do produce other "complaints," such as dwindling muscle tone, the researchers found that estrogen is the hormone that causes body fat to accumulate, and it, in union with testosterone, affects sex drive. "A lot of things we think are due to testosterone deficiency are actually related to the estrogen deficiency that accompanies it," the study's leader tells the AP. First, a one-sentence science lesson from the Los Angeles Times: Estrogen is actually converted from testosterone in both sexes (males produce a form of estrogen called estradiol). Researchers found that men have at least two times the amount of estrogen that postmenopausal women do; once testosterone drops from a youthful average of about 550 nanograms per deciliter of blood serum to the 300- to 350-nanogram range, estrogen drops to a point where weight is affected. It's a big realization, but not an actionable one just yet. And the AP notes that doctors don't typically prescribe estrogen to men, as high doses can cause things like enlarged breasts; the way to remedy low estrogen is to give them testosterone and let the body convert it.