grapefruit weight loss

Photo: joannatkaczuk/istockphoto

4 of 6
Mistake #4: Trying to Travel Back to Your 20s

Why it's wrong: "If you use the same diet you did before and expect to get the same result, you'll be disappointed," says Lofton, who notes that this is the biggest mistake she sees in her practice. Your body wants to stay at the weight it's at, and actively fights against weight loss (see the research about what happens to The Biggest Loser contestants after the show). It also learns from what happened in the past. Plus, if you've regained the weight you originally lost, odds are the diet you were on wasn't sustainable, and not something you should be trying again anyway.

What to do instead: Talk to your doctor about a weight-loss plan that you can stick with long term, and explain what you've tried in the past so you know what to avoid.