This is obvious to anyone who thinks it through.

1. The vast majority of men don't like to sleep with obese women. Feminists say it's because they are socially conditioned, but we'll come to that.
2. Even very ugly women can get sex. It just involves the right mixture of alcohol and candle light.
3. Women can lose weight by eating less, and exercising more. The Nazis proved this in the second world war: there were no fat people in concentration camps. There were people with aprons of skin where the fat used to be, but not actually fat people. Ergo: eating less causes weight loss.

Hence obese women know they can get sex if they eat less. They choose not to, hence they enjoy food more than sex.

Of course this logic becomes circular: the corollary is that obese women don't enjoy sex as much as thin women, and people who don't enjoy sex are not fun to sleep with. And there is no point at all in sleeping with an obese woman because she is unlikely to enjoy it.

This is why obese women get so little sex, unless their weight is exceeded by their IQ.