Katherine Heigl used to ''pray and fast'' for bigger boobs.

The 36-year-old actress pleaded with God to give her larger breasts during her teenage years because she was getting bullied for being ''super-flat chested'', but the star's mother now thinks he got revenge on her for being ''shallow'' by making her assets too big.

She said: ''I was a real doormat in those years and I was a very late bloomer so by like 14 and 15 I was super-flat chested and the boys made a lot of fun of me.

''My favourite was, 'Hey Katie, would you wear shoes if you didn't have feet?' to which you reply, 'No, of course not ...' and they reply, 'Then why are you wearing a bra?' It was pretty terrible!

''I spent the next however many months and years praying and praying and praying to get big boobs, like that's all I wanted.

''I prayed. I fasted for big boobs. I grew up Mormon and once a month you have a fast and testimony meeting and you're supposed to skip two meals and fast for things that matter. Good health. Safety of the family. World peace. That sort of thing. I fasted for big boobs.

''I cut photos from the Victoria's Secret catalogue of the body I liked and put the head I liked on top of it.

''The problem is, no one warns you that, well, this is a lot of information, but with real larger size breasts come issues the Victoria Secret models don't have like gravity and bigger butts and bigger thighs.

''So I've had to spend the rest of my life with big boobs trying to make sure everything stays tight and where it is supposed to.''

When asked on talk show 'Conan' if she thinks that's God's revenge, she replied: ''I do. Right, he's like, 'You're that shallow, try this.' ''

Katherine's breasts naturally increased while she was away from school shooting 1995 action film 'Under Siege 2' but when she went back she was still ridiculed because her bullies made up a rumour that she had been to Los Angeles to get a boob job aged 15.

She added: ''I thought that was hilarious, [but] I guess it is not that out of the ordinary. In my town in my day that was not something people did.

''So I would just wear the tightest shirts I could and flaunt it as much as I could. And get my revenge.''

Catch 'Conan' Monday-Thursday at 11pm on truTV in the UK, freeview channel 68.