The 28-year-old singer revealed she often wears Spanx to help fit into designer dresses because she often gets bored of exercising.
She told Us Weekly: “I almost always wear Spanx.
“I like to say I run on the elliptical for 30 minutes watching CNN, but I don’t do it often enough. So I’m just like, ‘Oh, I guess I’m not fitting into this Lanvin dress for these couple of months.'”
It was recently revealed Katy – whose 14-month marriage to Russell Brand ended last December – is planning to take the next step in her relationship with John Mayer and they have been house-hunting in Los Angeles.
A source said: “John and Katy have decided to give it a proper go and want to find a place in LA to share.
“But lots of people are willing them to fail. They row a bit and have quite a turbulent up-and-down relationship, despite it only being a few months old.
“Many of her friends are certain it will all end in tears.
“But that’s brought them closer in a way. It’s given them an ‘us against the world’ mentality.”
Sources say the couple – who had a brief split in October before getting back together – are smitten with each other and like to spend every moment they can together.
One said: “They are together virtually every day.
“They hang out at John’s place, cooking, watching movies and playing music.
“They take the odd trip away but generally they’re trying to keep it behind closed doors.”