Dennis Quaid developed middle-aged spread to play a jaded professor in his new film Smart People. Jane Miller hears how he was happy to fat suit-up for the sake of his art.

You know you're ageing well if, at 54, you have to don a fat suit and a grey beard to play a slightly dishevelled college professor.

The ever lean and chiselled Dennis Quaid is clearly quite chuffed that he needed help to look middle-aged for his new film Smart People.

"They put a tyre around my middle section because this is a guy who is sleepwalking through life and hasn't paid any attention to taking care of himself, or grooming himself," he says.

Unlike Quaid, who still looks every inch the Hollywood hero.

In fact, with his sunny smile and simple Southern charm, he couldn't be less like a pompous, jaded professor - and he admits the role was a stretch.

"I'll tell you the truth. When they offered me this part I was considering not taking it because I couldn't see myself in it," he says.

"I'm not really the literary sort att first glance... I don't usually get offered things like this and I thought there were some people out there who were more obvious choices who could do such a great job with it."

An hour-long meeting with first-time director Noram Murro changed his mind.

"From then I really wanted to work with Noam and I knew it would be really interesting - and it was," says Quaid.

"It was a small movie, but such a great script. It was a little bit like guerrilla film-making because we shot it in 29 days. I love shooting that way, to tell you the truth. My least favourite part of film-making is sitting in my trailer."

Quaid plays Lawrence Wetherhold, a widower who has lost his passion for teaching. He's also struggling to relate to his teenage children, played by Ellen Page (of Juno fame) and Ashton Holmes.

"He's lost the fire in his belly for what used to make his world go round in a way. He lost his wife ten years back, he has two kids who are now close to adulthood and he just doesn't get it anymore - and he's not even aware he doesn't get it," says Quaid.

The star can relate to that, he says. "I've had phases in my life where I've become jaded or cynical or whatever, but I think it's always important to re-kindle that fire and find that original inspiration that makes your world go round.

"In order to get back there we have to change and I find I have to be dragged kicking and screaming into change. It's called Smart People, but I feel the movie is about emotional numbskulls - something this guy has become."

Wetherhold's world is turned upside by the arrival of his adopted brother Chuck, played by Sideways star Thomas Haden Church, and a chance encounter with Janet - a former student who once had a crush on him, played by Sarah Jessica Parker.

"Sarah was fantastic," says Quaid of the Sex And The City star. "We actually started the film without her role cast, although she looked like she was going to do it.

"She came on in the middle of the movie, which was a daunting task because everybody else was already on board and we had a way of working, and she just jumped right in with both feet."

Quaid has an impressive film career spanning more than three decades, but it hasn't all been plain sailing. In the 70s he appeared in Breaking Away and Our Winning Season, and in the early 80s received acclaim for his performance in The Right Stuff, but he had to wait until 1987 to hit the big time with Innerspace, The Big Easy and Great Balls Of Fire!.

After battling a cocaine addiction, he went clean in 1990 and appeared in Postcards From The Edge, cropping up again in Wyatt Earp in 1994. Although he was always busy, his other roles were far from blockbuster, until, aged 50, he managed to resurrect his star status with The Day After Tomorrow in 2004.

He says he's enjoying riding high again. "I did four films in a row last year. I did Vantage Point, Smart People, and another film called The Horseman, which I call a horror movie with heart, and then another film, The Express, a big studio film which I would liken to a film I did called The Rookie, and it's written by the same guy.

"I must say, at this time in my life, I'm just having more fun now, acting, than I did when I was in my 20s. So I feel very lucky for that. He managed to squeeze in two months off last year and reveals: "Basically, my day Monday through Friday is to take my older son to school, drop him off, and go right to the golf course, get out there with my mates, go pick him up from school, come back and spend some time with my young kids, the twins.

"My handicap's gone up because of work. Right now, it's a seven. I'll tell you the better it gets, the more frustrating it gets as well," he laughs.

Dennis and his third wife Kimberly Buffington had twins Thomas and Zoe in November last year by a surrogate mother, and were caught up in a major news story after it emerged they had been given an accidental drug overdose while in hospital.

They are both now well.

He has a teenage son with his ex-wife Meg Ryan to whom he was m[arried for 10 years. They divorced in 2001.

"Being a celebrity couple is not so easy - it's double the publicity, and it's hard to have a private life," he says.

"I have to tell you that I am happier with my life now than ever."

The actor grew up in Texas and says he turned to drama after being scoffed at for his American Football skills.

"Well, that was one reason," he says, "but I think it's in the family. My great grandfather was a Vaudevillian, my father was a frustrated actor, and my third cousin is Gene Autry. It's kind of in the blood."

Don't take him for a true thespian, though. He's not the kind to dwell on roles, or spend too much time analysing his performance.

"The real satisfaction I get out of my work is when I'm doing it. Afterwards, it's either diluted or I feel a little separated from it," says Quiad.

"Certainly it's nice to be recognised for one's work and if the films do well at the box office you feel downright giddy about it. If they don't, I'm not going to tell a lie, it can be disappointing as well, but that's it."

Whether he'll stay at the top of his game or succumb to another movie blip is anyone's guess - including Quaid's. He says he can't judge if Smart People is a good performance from him or not.

"I'm kind of immune to myself at this point, to a certain extent. I'm not going to be falsely humble; I really do think I'm good at what I do. I've been doing this for a while and I love doing it, but at the same time, I'm really not my best critic."