I haven't read the article, but that's never stopped me before.
It seems to have the evidence, that larger women are more likely to have ever had sex, and infer the conclusion, that they are asking for sex and getting it, because no man ever says no. Hey, some of us have standards. Not that I object to larger sizes per se, but the idea that anyone/thing would do is wrong and offensive.
However, I think they have found a correlation that can be explained a different way.
As people get older they often put on weight.
Hence if you line people up according to weight, the low weight end of the line would be a little younger than the higher-weight end of the line.
Likewise, "have ever had sex with a man" is also correlated with age. You've got longer to get lucky.
Hence weight and age are causally connected, and sexual history and age are causally connected, but weight and sexual history are not causally connected, but merely correlated.
And there is a second alternative explanation of the correlation. Women generally gain weight during pregnancy and often stay largeish thereafter. Of course, maternal weight gain selects at nearly 100% for women who have had sex with a man. So there is a second explanation between the correlation between weight and likelihood of having had sex.
Maybe in the study the show that they have allowed for these factors.
But I think Clod may have it right. Skinny women are more likely to have said "no". As a TV show recently pointed out ... "Men are attracted to larger women, because they have larger personalities, and lower standards."