Jenny McCarthy thinks her breasts resemble a ''sack of potatoes''.

The actress - who recently stripped naked in the pages of Playboy again to mark her 40th birthday - realised she had to boost her sexual skills once the ageing process started to impact on her body.

Discussing looking up former lovers when she joined Facebook, she told online magazine Splash: ''I had thoughts of wanting to show an old flame how good I got in the sack.

''When I was young I just laid there like a sack of potatoes. As soon as my boobs started to resemble a sack of potatoes I knew I had to learn actual techniques to distract any guys from seeing my own ageing sack of potatoes. So, showing off new moves was definitely part of the fantasy.''

Jenny - who has a 10-year-old son, Evan, with ex-husband John Mallory Asher - was named Playboy Playmate of the Year in 1994 and has bared all in Hugh Hefner's magazine several times.

The 'Scary Movie 3' star recently insisted she didn't mind turning 40 in November because she doesn't feel or act like a mature person.

She said: ''I sadly have the same thought that my parents say every birthday which is, 'I don't feel that old.' So, I have decided to make my mindset 40 is the new 15. OK, fine - the new 22.''