Kelly Clarkson: Weight Loss Was For Love! 'If I'm Going To Be Messing Around, I Gotta Look Good'

"I lost 18 pounds," the Stronger singer reveals. "And I think that happens when you fall in love or date someone. If I'm going to be messing around, I gotta look good."

"There's not a fad diet. I was working with a trainer, and she said, 'You'd be amazed the amount of weight you can drop by halving your portions. I know it sounds crazy, but do it for two weeks and watch what happens.' I just cut back my portions, I stopped eating late at night, and I work out a little more than I used to, and I literally dropped 18 pounds in a month. I think it happens when you get really busy. But when I'm on my off-time – girl, those 18 might come back."

While most stars are willing to go to extremes to stay slim, Clarkson isn't one of them.

"I'm not willing to do that," she maintains about drastic diet and exercise. "I'm willing to work a little bit because I want to be a healthy individual – which I always have been. I've put on weight, but that's just what I'm happy with at that moment."

And the couple that sweats together, stays together!

"Brandon and I both have bikes on the back of the bus, and we both love the outdoors. Once your lifestyle becomes more active, obviously you drop weight."