Steve Tyler is terrified of getting too fat to fit into his leather trousers.The Aerosmith frontman is permanently on a diet because he loves being skinny, and is fearful of putting on weight as he gets older.Steve, 59, said in an interview with the Sunday Times magazine: "I have to watch what I eat because I have this ongoing nightmare that I'm going to put on weight and end up looking like some of the other rock stars of a certain age who bounce around the stage."You look at them and think, 'Oh my God, what happened to you? How did you let yourself get like that?'"I always call Joe Perry, my bandmate, and say, 'Do you still weigh 145lbs?'"For God's sake I still want to be able to fit into those pants I wore on the last tour. I just live by the motto that nothing tastes as good as being thin feels."The svelte rock star watches what he eats while on tour and does "250" sit-ups every night before bed.

He said: "I don't eat regularly during the day and in the evening I tend to stick to wild salmon and broccoli.

"Every night before I get into bed, I do 250 sit-ups - religiously."