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Is obesity a mental health issue?
In the last 20 years, scientists have learned a great deal about weight control. It is an intricate feedback system in which energy expenditure and food intake are balanced. The brain responds to hormonal signals that maintain body weight by telling us when to start and stop eating and how much to consume. One central player is leptin, a hormone produced by fat cells in the stomach, which suppresses appetite and stimulates energy expenditure. Other weight-regulating hormones are ghrelin (an appetite stimulant), insulin, the orexins, and cholecystokinin. The neurotransmitters serotonin, norepinephrine, and dopamine are also involved. When fat stores diminish, hunger increases and metabolic processes slow down to use energy more efficiently.

The system is remarkably accurate, but over a lifetime even a slight imbalance adds up. To gain a pound a year, an adult need eat only an extra 10 or 20 calories a day. How much it takes depends partly on heredity. Weight is as heritable as height, and nearly two dozen genes are known to control the production of weight-regulating hormones. Heavier people do not necessarily eat more than average, and they are not necessarily less active. There is evidence that the obese have congenitally low sensitivity to leptin. Experiments on mice suggest that individual variation in the tendency to gain weight may depend on the action of weight-regulating hormones during early development.

The National Weight Control RegistryThis database, established in 1993 to identify strategies for long-term weight control, contains records of more than 3,000 people who have lost at least 30 pounds and maintained the loss for at least a year. The data hold no surprises and reveal no special solutions. People who lose weight and keep it off join support groups, exercise intensively, restrict the amounts and kinds of food they eat, and carefully monitor their weight and food consumption.

Abundance and frustration

Obesity becomes a serious problem when the human evolutionary heritage expressed in the body’s weight-control system collides with modern social conditions. In the environment in which humans evolved, food supplies were unpredictable, and finding enough to eat could be hard work. We had to store energy beyond our immediate needs. The body’s signals tell us to eat when we can because there may be no food tomorrow. We are especially attracted to the sweet, fatty, and salty tastes and textures that once indicated scarce essential nutrients.

But in modern industrial society, most people don’t need to store fat for an uncertain future. Food is all around us in great quantities and in such variety that we do not become satiated because of monotony. We take little time to prepare our food, and we eat fast, possibly so fast that the body cannot alert us when to stop. Many of us engage in hardly any energy-consuming physical activity. We drive cars instead of walking, and we sit for hours in front of television sets. So the balance of energy intake and expenditure is upset. The average American weighs 7 to 10 pounds more in 2004 than in 1990.

The name of the self-help group Overeaters Anonymous proclaims an analogy between overeating and addiction to alcohol or drugs. Some scientists who investigate food cravings take that idea seriously. Brain scans and animal experiments are suggesting that some of the same brain centers are active in both food addiction and drug addiction. And the same social changes may be involved as well. The industrial revolution that has provided some parts of the world with abundant, highly processed, easy-to-eat food is also loosing a flood of chemically pure injectable drugs of abuse.

Mental health and weight

So a case can be made that blame for the American (and, increasingly, world) weight problem rests entirely on the temptation of fast food and the tyranny of genes. The American Psychiatric Association has never regarded overeating or excess weight as a psychiatric disorder, and most obese people do not qualify for a psychiatric diagnosis. Most studies find no clear association between mental health and weight. In a review of 16 studies, 6 found that obese people were more mentally healthy than average, 7 found them to be less mentally healthy than average, and 3 found no difference. Some studies link depression or behavior problems with obesity in children, but the evidence is incomplete and inconsistent, especially after taking account of their parents’ emotional problems. Overweight children who seek treatment, or whose parents seek treatment for them, may be a group with especially low self-esteem or critical parents.

But even if weight and emotional problems are unrelated in most cases, there is plenty of room for exceptions among the millions who are overweight. Some research suggests that depressed persons are more likely to develop a metabolic syndrome (insulin resistance, high blood pressure, excess abdominal fat, high cholesterol) that often accompanies excess weight, especially when it is deposited around the waist. In a survey of 40,000 Americans, high body weight was associated with symptoms of depression in women, although not in men.

Research in mice and humans suggests that food high in fat, sugar, and calories lowers the body’s response to chronic stress. In animal experiments, weight loss activates the stress response. People may console themselves with "comfort food" because they are anxious, lonely, angry, or suffering from low self-esteem. There is a characteristic type of depression with symptoms that include lethargy and overeating.

Like most mind-body interactions, this one goes both ways. Obesity can lead to ill health, which is linked to depression and anxiety. Overweight people are also more likely to lose the psychological benefits of exercise. If they feel rejected as unattractive or suffer social discrimination, the further emotional strain may cause further weight gain. The problem is worse if they fail to lose weight and are blamed (or blame themselves) for lack of self-control. (Some believe anorexia nervosa — seemingly voluntary self-starvation — is the out-of-control result of an attempt to demonstrate a capacity for self-control.)

Therapeutic approaches

Treatments for obesity include self-help groups like Overeaters Anonymous and commercial programs like Weight Watchers. A common approach is behavioral therapy, often in groups directed by a dietitian or psychologist. The pillars of the therapy are self-monitoring and stimulus control. Self-monitoring means carefully recording weight, physical activity, and the kinds and amount of food eaten. Stimulus control means avoiding occasions of temptation — staying away from fast-food restaurants and convenience stores, food shopping from a list rather than at whim, not snacking in front of the television set, storing food out of sight, keeping portion sizes small, and learning how to handle high-risk situations like parties and holidays. Exercise is also important, not only to expend energy but, some believe, to set the weight equilibrium point at a lower level. Cognitive therapy may help dieters repel self-defeating thoughts and reject unrealistic goals (they will not likely achieve an "ideal" body weight). Psychotherapy or psychiatric drugs can relieve depression and anxiety and help them live as full a life as possible no matter what their weight.

Most weight-control treatment works for a while, but the body’s drive is not easy to frustrate. It’s believed that more than 80% of people who lose weight through diet, exercise, and behavioral programs gain it all back within five years (although they might have gained even more without treatment). The success rate may be higher with follow-up in person, by telephone, or by e-mail (for a record of some successes, see "The National Weight Control Registry," above).

Weight control for children and adolescents makes many people uneasy. If a 12-year-old wants to go on a diet, the true problem may not be weight at all, and she may be in danger of anorexia. But an increasing number of children are obese and in need of help. The most effective treatments combine group with individual counseling and parent participation in frequent sessions, with gradual weight loss through diet and exercise. Results have been a little more encouraging for children than for adults. One study found that a third of children entering a weight-control program at ages 6–12 lost 20% of their weight or more, and 30% were no longer obese 10 years later.

Drugs for weight lossIf weight gain is a physiological problem, why can’t there be a chemical solution? The trouble is that interfering with the complex mechanisms of weight control brings unwanted consequences. Appetite-suppressing drugs have a long history of failure, and the more seemingly effective they are, the more serious their side effects. Amphetamines are addictive and potentially dangerous for other reasons. A combination of fenfluramine and phentermine (Ionamin and others) was banned because it caused heart-valve defects in some patients; phentermine alone is still widely used. The anticonvulsant drug topiramate (Topamax) has been found effective for the treatment of binge eating in one controlled study, but it comes with adverse effects on memory and concentration. The antidepressants bupropion (Wellbutrin) and fluoxetine (Prozac) cause weight loss in some patients. The only drug officially approved as an appetite suppressant is sibutramine (Meridia), which inhibits the reabsorption of norepinephrine and serotonin. Orlistat (Xenical) represents a different approach to weight control: It acts in the digestive tract, preventing the absorption of fats.Drugs should be used for weight loss only as part of a program that includes behavioral counseling, diet, and exercise. Their effects are modest, and tolerance almost always develops within a few weeks or months. There is no magic pill. Although researchers are looking at drugs that act on receptors for ghrelin and other weight-regulating hormones, no weight-loss medication has been presented to the FDA for approval in the last five years.

Binge eating

There is one potential psychiatric diagnosis that is closely related to obesity, even if it is only "proposed for further study." In the American Psychiatric Association’s Diagnostic Manual, binge eating disorder is tentatively defined as a condition that involves at least three of the following symptoms occurring at least twice a week for six months: eating very fast, eating until uncomfortably full, eating when not hungry, eating alone, and feeling disgusted or guilty after eating. It’s distinguished from bulimia by the absence of fasting, exercise, or vomiting to compensate.

As many as 5% of Americans may be binge eaters at some time in their lives, including nearly half of the people enrolled in commercial weight-loss programs. Like body weight, binge eating disorder is highly heritable; a Norwegian twin study found that 40% of individual differences in susceptibility had a genetic basis. Binge eating is associated with depression and even more strongly with anxiety disorders, including panic disorder, obsessive-compulsive disorder, and post-traumatic stress disorder.

Both cognitive behavioral and interpersonal therapies have been found to be effective treatments. Patients find other ways to cope with situations and feelings that provoke eating binges, and they are helped to reject self-defeating beliefs about body shape. But even successfully treated binge eaters do not necessarily lose a great deal of weight, and some doubt that people with a binge eating problem (or bulimia) should diet at all. They believe dieting is part of the problem, not part of the solution. The body will resist, hunger will return, and more binge eating will be followed by further depression and anxiety.

Looking forward

As long as society and biology conspire to promote weight gain, victory in the battle against obesity will be hard to come by. At the level of basic research, this complex problem will require studies in genetics, physiology, nutrition, and neuroscience. Behavioral research may reveal more about the reasons for food choices and why we start and stop eating. In July of 2004, the statement that "obesity itself cannot be considered an illness" was removed from the Medicare manual, opening the way to insurance coverage of any treatment that is proved to be effective. The change will stimulate research, including studies of behavioral and psychological counseling as well as diet and exercise programs and gastric bypass surgery. In the weight wars, depression, anxiety, and low self-esteem deserve attention even if they represent only a small part of a big problem.

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