People lose weight when they consume fewer calories than they burn. There are no exceptions. Successful weight loss requires many hard choices every day. Obesity is not an illness; it is more like a typical sunburn: Both are conditions caused by personal choices. Obesity is caused by individuals deciding to overeat or to be inactive, often both. Unless you are an Olympic athlete, decision making about food and activity is often unnoticed, but decision making is a skill each person needs, and it is fraught with psychological land mines. If Medicare administrators want to reduce obesity, they must cover treatment of its many psychological causes and promote good decision making.

There are hundreds of reasons people overeat. One is ignorance, of course, but most involve hopelessness, habituation and self-comforting. In my experience, patients often cry when recounting struggles with obesity. As a family nurse practitioner I can teach nutrition and exercise and prescribe medicines for obesity, but I am not qualified to help patients overcome the psychological barriers to the decision making necessary to resolve the problem. Information, medication and even surgery will fail if the patient continues to make bad lifestyle choices. That is why insurers, including Medicare, need to cover long-term counseling and provide incentives for obese patients.

It is a shame that knowledge alone does not always change behavior. If it did, the government could just send out postcards stating that eating fewer calories than you use each day will cure obesity. The obesity problem would melt away as each person learned that fact. But people are complex, and their decisions are not always rational. Each overweight adult has repeatedly made bad decisions about food and activity, even though many desperately want to lose weight. Of course people struggle with low metabolism, bad habits, depression, social pressures, busy schedules, loneliness, boredom, illness, disability and other obstacles. Those obstacles often make burning more calories than you consume difficult, but they do not change the fact that this is how you achieve weight loss. No medical professional will argue with that fact. Most would also agree that people are complex, and many need help overcoming obstacles before they start consistently making good choices.

Among Medicare patients, 37 percent are overweight and 18 percent are obese. Every single one of those people will lose weight if they consume fewer calories than they expend, but few will do that without psychological support.

I hope Medicare covers and encourages counseling, support groups, exercise classes and education. I hope it teaches people that a low-calorie diet can be inexpensive, convenient and tasty. (Much of the world lives on beans and rice, inexpensive, healthy staples.) I truly hope every person can overcome his obstacles, defeat her demons and live well. But having treated many people for obesity, I fear that calling it an illness will encourage a victim mentality. People may overeat because they have been victims of abuse, poor education, poor parenting or other injustices. But adults are responsible for their adult choices; if they claim to be victims of obesity, they must name themselves as their victimizer. Realizing that truth, believing weight loss is possible and then consistently changing behavior is very hard personal work, work that rarely happens alone and cannot be done by your bariatric surgeon.

The writer is a family nurse practitioner in East Grand Rapids, Mich. She will answer questions at noon today on www.washingtonpost.com.