Fergie feels like she has to work out because she "loves to eat".
The 39-year-old singer is enjoying getting back into shape after having her 18-month-old son Axl but feels as though she has to exercise harder because of her love of fried sandwiches.
Issuing advice to those who want to get fit, she said: "Find your local gym and get into different classes. That makes it exciting [and] you're doing new moves. You don't even realise you're working out it because you're focusing on 'How do I get this right?' But you're having to control muscles so it's making you sweat.
"Keep it interesting... I have [to do] treadmill, elliptical, bike and dance. I do the bands - I do it all. I have to work out because I love to eat - I had two Double-Doubles last weekend!"
The former Black Eyed Peas star - who is married to Josh Duhamel - took her post-baby exercise "slowly but surely" to ensure she could meet the needs of her little boy first and foremost.
She told E! News: "I just slowly but surely got back into it. I wanted to make sure that Axl came first, and figuring that out came first.
"And you know I have it all figured out now, so that's done."