I'm a 37-year-old man who is recently divorced and just getting back into the swing of things with the dating scene. I'm also starting to have sex again for the first time in a long time, since my wife and I stopped having sex more than two years before we separated, and I never cheated. Recently on a date a woman asked me if I was circumcised (I am). She went on about how circumcised men are missing out, because they lack sensation. Is this true? Is there research on this subject?
Circumcision is one of those topics everyone has an opinion on and most people are perfectly happy to give you theirs, whether you asked for it or not. It seems like kind of an intense topic for a first date, but I suppose that depends on the date, and the people. So maybe it made perfect sense. At any rate, she's not all wrong, but she's not all right either.
The short answer to your question is that yes there is research. There is research on circumcision and sensitivity, circumcision and sexual pleasure, and how circumcision changes sexual behavior. Some of it indicates that being circumcised has an effect on how stimulation feels and even possibly on the kind of sex people have. But there are plenty of problems with that research and a longer answer is needed.
That answer has to include thinking about the difference between sexual feelings, sexual sensation, and sexual pleasure. It also calls for you (and your date) to take into account the many factors that go into how much we enjoy sex. Everyone will have their own experience, but if I were to make a generalization based on speaking with thousands of people about their sex lives, I'd have to say that the presence of absence of a foreskin is rarely going to be the most significant factor in terms of sexual desire or the ability to give or receive sexual pleasure.
If you're feeling out of the look and want to read up, you can find information and references to the research here. But I would also take some time to think about why someone would feel it necessary to tell you that you aren't able to feel as much pleasure as the next guy? It sounds like an argument with a motive that has nothing to do with you or your penis.
