Louis Theroux on getting close to the people (and dogs) he interviews, and what Jimmy Savile told him

You have a beard today, but in your new series, LA Stories, you are clean-shaven. Do people not trust a man with facial hair?

I've heard that anecdotally. Actually my wife thinks I look better with a beard and maybe I think that too, but I've been doing these shows for more than 16 years and I feel as though there needs to be a uniformity. There were ructions round the turn of the millennium when I changed my glasses and that was bad enough.

You often spend a lot of time with the people you interview – in these three shows, dog owners, terminally ill patients and sex offenders. Do you ever consider them friends?

There is a little element of ambiguity in the sense that you get to inhabit quite an intimate space with someone – especially in the film about people who have life-threatening conditions – and it's a very personal and human story. At the same time I think it's understood that you're there to do a job. But it can be a little tricky. In that programme, three people we filmed with ended up dying in the course of filming. I went to the funeral of one of them – not for filming but to show our respects – but there was always a conversation in the office about what was the appropriate thing to do.

Have previous subjects ever felt betrayed by your films?

I remember Max Clifford was very unhappy with the film we made and said something along those lines.

Did that concern you at all?

In a basic human way, I was disappointed. I'd rather he'd said: "Oh well, it's a wonderful warts-and-all portrait of me and how I operate and I appreciate the chance to see an unvarnished version of how I am." But he didn't say that and it didn't overly worry me.

LA Stories starts tonight with a show on dangerous and abandoned dogs in south Los Angeles. Were you more scared of the dogs or the owners?

Growing up I was quite nervous around dogs, but I feel more comfortable having made that programme, oddly enough. Was I afraid of the humans? If I'm honest, no I wasn't. We went in with a guy called Dog Man in a van covered with pictures of dogs and I think it was quite clear that we weren't trying to set up shop dealing drugs on someone's corner.

Doesn't one man who has his dog taken by the authorities say to you: "Take your bitch-ass back to London"?

Yes. That was slightly different. I was nervous all through that encounter because there's a big difference between dealing with someone who's involved in a criminal lifestyle and someone who's mentally ill, as that guy was. But I was safely behind the fence at that point and his dog had been taken away from him.

You've lived in LA for more than a year now. Is that a personal choice or did you go there because the access and the subjects were better than the UK?

It was a personal choice. We went over there as a family: my wife grew up abroad and was sick of the British winters and I did feel as though I'd spent a bit too long in the same house in the same part of London. When you're in your 40s you become more conscious of life being of limited duration and that you need to create memories and go on little adventures from time to time.

One of the sex offenders asks you how many pull-ups you can do and you tell him five. Do you stand by that?

I think I could do five. I could definitely do five, five years ago, maybe I couldn't now. It's a shame we don't have a pull-up bar here. [To the press officer…] Could that be arranged, Suzie?

One of your most famous interviews was with Jimmy Savile in 2000. There's a retrospectively uncomfortable moment where he says: "It's easier for me, as a single man, to say 'I don't like children' because that puts a lot of salacious tabloid people off the hunt."

We could easily have not put that bit in. It's not the strongest moment in the film and it was almost a throwaway remark in the car going back to his penthouse in Leeds. So it was driven by him but in hindsight clearly I'm sort of pleased that we had that in there and that we were able to get as far as we did with revealing the strangeness of his private side. I'm still proud of the programme.

Were there warning signs with Savile that everyone missed?

At that point all I'd heard were rumours and the rumours were very inconsistent and some of them were beyond outlandish, to do with dead bodies and things. So based on what I heard it didn't seem to be a priority in terms of the journalistic journey we went on. His MO was to tantalise and hint that he had secrets, but one never knew whether the secret might turn out to be rather banal.

You recently put a call out on Twitter for Scientologists for a new documentary. What was the response?

Good, in the sense of a lot of people responding, but it doesn't seem as though I'm getting a big response from active, paid-up Scientologists. It was mainly people saying, "Be careful, those guys are scary."

You once wrote that your professional interests were sex, crime, religious strangeness and mental illness, but you couldn't work out if those were personal tastes or intrinsic to us all. Have you resolved that?

I guess when we stop getting commissioned that will answer the question. But so far I've still got people tuning in and I think I'm making good programmes. So based on that, I assume other people are interested too.