Kimberley Walsh gains weight on her bum first.

The Girls Aloud singer has expressed her frustration at her body, revealing that when she packs on the pounds, she always notices that her pert derriere - which was the envy of all her former bandmates - becomes more sizeable than the rest of her body.

She said: ''If I put weight on, the first thing that expands is my bum. It creeps out slightly, while my belly still stays flat.

''My stomach has always been good; it's my best body part. It pretty much stays flat whatever.''

The 31-year-old star has also given up ''fad diets'' and insists that years of watching what she eats hasn't helped her gain a svelte figure.

She explained in an interview with Closer magazine: ''I'm just bored of fad diets. I've spent years trying to figure out what works best for me, but the real answer is exercise and being happy. I do have to work out so I can enjoy a normal diet but I'd rather spend loads of time in the gym than starve myself.

''Because I exercise, I can eat whatever I want. I don't want to count calories or feel faint because I've not had any sugar. I've done Atkins and a few others, and they were rubbish quick fixes.''