The Man of Steel actor bulks up and undergoes intense training to become Superman, but does not keep up the regime when he is not working.
Cavill admits the iconic role does earn him more attention from the ladies, but he is worried they will not be so keen once he takes off his clothes.
He tells Britain's The Guardian newspaper, "There's a blessing in being Superman. You get more attention. But there's also a curse, which is that you'd better f**king look like Superman any time you need to get your kit off...
"I'm very self-critical and I use that to motivate myself. If I look in the mirror, I might say, 'You're looking good!' Other days, like today, because I'm off-season and haven't been training, I'll say, 'Look at you, you fat f**k... I tell myself, 'Mate, you're a mess. If you were to meet a bird (woman) out in a bar and bring her home, she's expecting Superman. This is not Superman and she's going to be mega-disappointed.'"