Cameron Diaz keeps fit by making sure she remains ''active'' wherever she is.

The 41-year-old actress - who has penned the health and lifestyle guide 'The Body Book' - insists every little bit of exercise helps, and urges people to make a conscious effort to do physical tasks even if they can't make it to the gym.

She told HELLO! magazine: ''Just be active. When I'm in California I run in the hills, but for me, I love living in New York and being able to walk everywhere. But even if you're at home watching TV, get up off the couch and do some jumping jacks.

''Whenever it is, makes a difference - and people don't realise that. They think 'I'm not going to be physical because I can't get to the gym.' If you want to be healthy and happy and well, it has to be a priority.''

However, Cameron insists the mind is the ''most important'' part of us since it decides whether you want to do something or not.

She said: ''That was really important to me. As I say in the book, it's the most powerful part of us. It determines whether you do or don't. The body's instinct is to survive and be strong - the body is never saying no. It's the mind that does. The mind is what shuts you down from being able to do things.''