Losing weight can be a battle, but Kardashian sisters Khloé, 25, and Kim, 28, tell Life & Style they've finally achieved their weight-loss goals and gotten their best body in years. "I'd try the Atkins diet, the cabbage-soup diet -- every ridiculous diet ever," Kim says about her habit of gaining, then losing a few pounds. Here's how the stunning siblings feel now that they've uncovered their diet secret and are looking better than ever.

L&S: Was losing those final pounds the most difficult part?

Khloé: It's always been hard to lose weight in general, and I'm still losing weight, but right now, I feel like I've lost all my fat and just want to tone up. It's really because of QuickTrim [a system of supplements customized for various fitness goals]. I've had weight battles my entire teenage and adult life, but this time when I tried losing it, the weight just fell off. It was easy.

Kim: I trained so hard for my fitness DVDs, Fit in Your Jeans by Friday, and I just needed an extra push. QuickTrim completely took it to this level.

L&S: How much weight have you lost?

Khloé: I've lost about 25 pounds, and I know that only because my best friend, who trains me from time to time, weighed me and told me. I was about a size 10; now I'm a 6. It's weird, though: In denim, I'm the same size. It's just my body shape.

Kim: I'd say I've lost a solid 10 pounds in a little more than a year. For me, because my body is so small, that's a big difference. I'm so much more toned.

L&S: How do you feel?

Kim: I feel like I'm in the best shape of my life. I used to be so shy and insecure walking out in a bikini doing shoots and things -- it just really feels good to finally feel like I did it. I'm the skinniest I've ever been. I stepped on the scale, and it said I was 114 pounds. I always weighed 120, 125 -- I was shocked.

L&S: What's the biggest change you've seen in your sister?

Khloé: Her stomach, for sure. She's always been very skinny, but her stomach used to be kind of pudgy -- we called it a baby bump. Her stomach is ridiculous now!

Kim: Her arms are so much skinnier, and her stomach is flat. I saw a healthy transformation, and it just feels good to see your sister confident and sexy. She's a different person!

Check out more photos of Khloé and Kim showing off their slim bods plus find out their diet secrets and fitness tips in the latest issue of Life & Style, on newsstands now!