Medical ethicist Art Caplan joined Boston Public Radio — a few days later than usual — for his weekly segment, "Ask the Ethicist." Caplan talked about the right age for parents to sign off on a child's gender reassignment surgery, raising the smoking age, and the damage done by marijuana smoke.

Questions below are paraphrased. Caplan's responses are edited where noted [...].

You're encouraging some caution when it comes to performing large numbers of gender reassignment surgeries. Why is that?

CAPLAN: [We need to] set up some metrics, like, Are there fewer suicides after the surgery? [...] You can certainly better survey people before they go through this in a systematic way. [You can take] some sample of [surgeries] and then do a pre- and post-. To me, to continue doing this kind of surgery [...] without any kind of tracking registry, it's unethical.

And you say those metrics have more to do with happiness than with the logistics of the surgery, right?

Are people happier? [...] We don't know much about that. [...] It's all great to argue about your right to do it, and how old [you have to be] to do it. I'd like to know, does it work?

What are the risks of using Caitlyn Jenner's glamorous Vanity Fair photoshoot as the template for all surgeries? Will that create unreasonable expectations?

What does it mean to 'look like a woman?' [...] That beautiful picture appeared of Jenner on the Vanity Fair cover [and] she looked great. [...] It's [important] that the outcome or the way that you look is not set by what you see on the cover of a magazine. [...] I don't want people to think, 'Hey everybody who goes through this ends up looking great, [and then] they're not satisfied. [...] It's kind of our commercial, magazine kind of thing saying, 'Hey, everybody should look like this person.'

How can hospitals provide the best possible service to those who are transitioning, when it comes to — if they should so choose — sex reassignment surgery?

I know that early efforts, way back in the eighties, at John Hopkins, [...] they did it and then they backed away. For a long time you had to go overseas, like to Thailand, to get the surgery. [...] If you're going to do this, and you're going to do it in younger people, then maybe you oughta do it in a couple centers of excellence.

In 2005 the city of Needham, Mass. implemented a minimum smoking age of 21. Since then, smoking rates among students have dropped by nearly half. Are you impressed by the results?

Yeah. We probably never are going to make it illegal to smoke, we probably couldn't really sustain the craziness that a Prohibition-type thing could bring to smoking. [The answer is to] make 'em really expensive. We're gonna restrict where you can smoke — not in restaurants, you gotta go outside to smoke. [...] All of those things I think they make sense, I think they are basically doing something about an expensive, bad habit.

The FDA has made moves to ban all trans fats from US foods. Is this a good idea, or overkill?

In my office there's an entire wall now of Hostess Twinkies and [other treats] I'm storing. [...] They're still in a lot of processed foods, they're still around a lot. [Banning them is] an easy call, and I think it's a good one. There are certain people who are gonna say, 'I don't want the nanny state telling me what to eat' and blah blah blah. [...] This is one where the evidence [indicates] that it's not good for you, and the need to have it is pretty tiny.

So you think trans fats will soon be a thing of the past?

I haven't heard a lot of screaming.

>>Art Caplan is head of the division of medical ethics at NYU's Langone Medical Center, and cohost of the podcast Everyday Ethics. Caplan appears weekly on BPR.