6 Big Mistakes People Make When They Try to Lose Weight

Why it's wrong: "The trends in your life–Do you always snack at night? Eat out more than you think you do? Or really get as much activity as you thought?–should inform the changes you make to lose weight," says Holly Lofton, MD, an assistant professor of medicine and surgery and director of the medical weight management program at NYU Langone Medical Center.

What to do instead: Before starting a weight-loss plan, try this at-home version of what Lofton has her patients do. Keep a food diary for three to five days (include at least one weekend day) and wear an activity tracker to see how much you're moving. Then look for places where you can make changes–for example, if you see that you eat a tiny lunch then overeat at dinner, a bigger lunch is a good place to start.

Continuing to track your diet and activity can also help you identify reasons why your weight loss might have stalled, says Scott Cunneen, MD, a co-director at the Weight Loss Center at Cedars-Sinai in Los Angeles. (Cunneen always has patients do a food and activity diary when they regain weight, if they haven't already been keeping track.) "You can look at the food diary and see that maybe you're eating the right foods but eating too much of them, or you weren't exercising as much as you were a month ago when you were losing weight."