South Beach, L.A. Shape, and The Perfect Fit -- the latest diet books are flying off the shelves, but do they really work? We put each to the test to determine which diet will help your waist and which are just a waste.

The South Beach Diet
Bill Clinton, Hillary Clinton and singer Lorna Luft all found success on the popular South Beach Diet. "I'm not going to say it was easy," Lorna told us. "But it did work for me."

The diet is heavy on protein and veggies, low on carbs, and bans fruit for the first two weeks. But doctor Lynne Perry-Bottinger says it's not practical for most people, telling us, "You almost have to have your own chef to organize this diet."

Pros: Cuts out bad carbs
Cons: Expensive menus

The L.A. Shape Diet
"ER" star Yvette Freeman lost more than 100 pounds on a variation of The L.A. Shape Diet. This low-calorie, high-protein diet calls for lots of fresh produce, plenty of exercise and protein shakes -- but drinking calories can be a problem, according to Dr. Perry-Bottinger, because: "It may be difficult to determine exactly when you're full."

Pros: Promotes fresh produce and exercise
Cons: Only calls for 1,100 calories per day and too many liquid calories

The Perfect Fit Diet
The Perfect Fit Diet is the one Dr. Perry-Bottinger says makes the most sense. It's tailor made for each person and dieters keep a food and exercise diary so they're held accountable.

Pros: No gimmicks
Cons: Low calorie count

Finally, no matter which diet you choose, always remember the bottom line: think less about quick fixes and more about long-term lifestyle changes.