Matthew Mcconaughey still hasn't lost all the weight he gained for 'Gold'.

The 49-year-old actor piled on the pounds to play prospector Kenny Wells in the 2016 movie and though he worked hard to get back in shape for his role in new movie 'Serenity', he's still got ''a couple of things'' he thought he'd have shifted by now.

He said: ''It's been a while. I needed to get in shape. I wanted to. I was 220lbs in 'Gold', of which I still have a couple of things back here [on my back].

''I thought these guys were renting but they seem like they've moved in.

''I had a trainer on 'Serenity' and he became the trainer for all the rest of the actors on set.''

However, Matthew - who has children Levi, 10, Vida, nine, and Livingston, six, with wife Camila Alves - refused to work out on the days he was filming because he values his sleep too much.

He said to Red magazine: ''I won't work out on days I work. I'm not getting up at 4am to work out before a 6am call. No. I need my sleep more than that. I love healthy eating.''

And over the years, the 'Failure to Launch' actor has changed his eating habits to keep his weight in check.

He explained: ''I eat for energy. Last night we had a great Italian, pastas and steaks. But I didn't work today.

''When I work, I eat smaller amounts four or five times a day to keep energy throughout the day. Little tricks I've learnt are things like don't eat your main meal after 6.30pm.

''You can actually eat what you want if you don't eat after 6.30pm, because you're burning a lot.

''If you have that meal when it tastes best, which is about 9pm .... Some good bread or pasta at 9pm and go right to sleep on it?

''I love doing that but you would look at me and go, 'Oh I can tell you love doing that, Matthew!' You know what I mean? So yes, I am conscious.

''My diet is mainly for energy but it's also about maintaining a certain look.''