For the past 15 years, Jacara says she's tried every diet out there, but she can't quite reach her ideal weight. "I find that I get to a certain point where I'm close to my goal weight, and I sabotage myself," she admits. When she's in "the zone," Jacara says she exercises up to eight times a week, but still doesn't seem to lose weight.

Currently, Jacara weighs 162 pounds and she says she'd like to be 135. What more can she do?

First, Bob says, Jacara and millions of dieters should get rid of the "all or nothing" attitude. The key isn't about how often you exercise—it's about how consistent you are.

The one thing every dieter has to remember is that exercise is not negotiable. "Decide what's right for you—how much you are willing to do," he says. "Whether it's just 10 minutes or 20 minutes, and don't negotiate that."

Also, don't make the mistake of adjusting your diet before determining how often you're going to exercise. "You need to establish how active of a human being you're going to be, and then move on," Bob suggests. "Then your food has to adjust. If you exercise more, you're going to have the liberty to eat more."