Jennifer Aniston admits her toned body takes hard work.

The 44-year-old actress had to bare all for a saucy underwear scene in her new comedy 'We're The Millers' and says she spent hours in the gym doing squats and yoga in order to firm up her buttocks.

Asked how she achieved her buff body at the film's London premiere, Jennifer told Yahoo omg!: ''With a lot of hard work and commitment to a workout regime and your diet! Squats and you know what else is really good for your butt is yoga!

''As is the Bar Method - do you have that over here? Trust me, it just goes in and up!''

The body sculpting technique is an A-list favourite which strengthens the core using dance and physical therapy.

The 'Friends' star is famed for her super healthy diet and hating fast food, but she confessed she has a secret weakness for salty crisps.

She said: ''[I don't crave] doughnut but lots of chips! Not KFC - that's just greasy chicken but potato chips or tortilla chips.''

Jennifer previously revealed she snacked on crisps made out of her favourite leafy vegetable, kale, when she felt peckish on set.

She admitted: ''I did eat that day [of the underwear scenes]. I was on a very like, you know, greens and vegetables and lean proteins and kale.

''When I really wanted to have a cheat day, I had to have a kale chip.''