You step on the scale and groan at the number peeking between your toes. "I'll go on a diet today!" you think. Not so fast. Unless you are mentally ready to lose weight, any diet you try is likely doomed to failure.

In a widely accepted model of behavioral change, there are five stages of motivational readiness. If you're stuck in an early stage, your diet won't work, says registered dietician Karen Collins. Studies suggest that people may feel ready to lose weight, but if they are unprepared to alter their behavior, they'll fail, reports the American Institute for Cancer Research in Washington, D.C. in a column titled "Nutrition Notes."

The five stages of motivational readiness that can be applied to dieting, exercise, or just about anything in your life:
Stage One: Precontemplation
A person has no intention of changing.

Stage Two: Contemplation
A person intends to change--later.

Stage Three: Preparation
A person is ready to change within the next month.

Stage Four: Action
This stage is reached when a person has recently changed a behavior.

Stage Five: Maintenance
This final level occurs only when a person has carried out the new behavior for at least six months to two years.

When we get stuck in one of the first three stages, the difficulties we perceive with the change outnumber any advantages. In addition, Collins says we lack confidence in our ability to successfully make changes.

"If you want to move forward in living a healthy lifestyle, the 'pros' have to outweigh the 'cons' in your mind," says Collins. "Find ways to get around barriers that you think are inconvenient, expensive, boring, or difficult. Be specific about what you are trying to overcome and creative about possible solutions. Research shows that the balance of pros and cons relates to each small behavioral change, not just to the goal, like losing weight."

She explains that someone who is trying to lose weight may see many more benefits to shedding the pounds than remaining overweight, but if all the person can envision are barriers--instead of benefits--to decreasing food portion sizes and exercising regularly, then change is unlikely. "However, if you are ready to change some behaviors, make at least these changes," Collins advises. "Small successes can build your confidence in making more changes."