Connections
Eating Disorders
Why is it important to understand the mechanisms that control hunger and eating behavior? Today, we know that many medical conditions are aggravated by obesity. Excess body weight increases the risk of hypertension, coronary ar-tery disease, diabetes, gallbladder disease, sleep apnea, gout, arthritis, and certain types of cancer. We also know that preventing the body from digesting adequate food can cause physiological distress, even to the point of death.
Obesity
| Obesity also takes a tremendous personal toll on many people's lives, interfering with their social relationships and occupational success, and often leading to depression. Obesity is highly stigmatized in society, as shown in a study in which college students were asked who they would be least inclined to marry: An obese person was rated one of the least desirable, following an embezzler, a cocaine user, an ex-mental patient, a shoplifter, a sexually promiscuous person, a Communist, a blind person, an atheist, and a marijuana user (Venes, Krupka, & Gerard, 1982). People who believe that obese individuals are responsible for their own condition are thus embracing "weightism" as one of the last remaining acceptable forms of prejudice and discrimination. |
|
Dieting
Dieters spend billions of dollars each year on commercial weightloss programs, yet their weight loss is usually temporary. This is because a substantial weight loss leads to a significant slowing of body metabolism and a reduction in energy requirements. The body now burns less energy, and so it becomes harder and harder to continue losing weight without going on a star vation diet.
There is yet another complicating factor to consider: Our genes may have a profound effect on our food consumption, energy metabolism, and body weight. Some people's bodies seem designed to store more fat than others; people with this genetic tendency find it almost impossible to lose weight.
Genetic Factors
For years research pointed to a genetic predisposition toward obesity: Twin studies showed that genetic programming can overcome learned eating habits and lead to obesity. Only recently have researchers been able to examine the genetic structure and hypothesize about the processes in action. Jeffrey Friedman and Stephen Burley (1995) have identified an obesity gene (ob) by studying overweight mice. This gene carries the instructions to make leptin, the protein that signals us to stop eating. When the ob gene is defective, as it was in their obese mice, either leptin is not synthesized in the fat cells or the hypothalamus is missing leptin receptors. Either way, leptin cannot transmit its signal, and the organism continues eating. Obese mice injected with leptin reduced their food consumption and increased their energy expenditure-and they lost 30 percent of their body weight in 2 weeks without side effects. Normal mice receiving the leptin injections lost 12 percent of their body weight.Further studies conducted by Friedman and Margherita Maffei (1995; see Web site) found that in humans there is a high correlation between leptin levels and the amount of fat stored in the body. They believe that leptin signals the hypothalamus, which coordinates eating behavior, sending messages to stop eating. Reduced sensitivity to leptin would explain the higher levels of leptin found in obese people; the body would make leptin at a greater rate to compensate for a faulty signaling process or action. They also found that leptin levels decreased with dieting. This reduced level of leptin means that less is available to trigger the hypothalamus; this may contribute to increased hunger and slower metabolism and, therefore, to a tendency to regain the weight.
Other Eating Disorders
| Obesity is certainly a concern, but some young people become obsessed with their weight. They go to extreme lengths to reduce their body weight by starving themselves, often to the point that their bodies resemble those of concentration-camp inmates. This condition, called anorexia nervosa, occurs more often in women, perhaps because society places more pressure on women to be thin and attractive. A related disorder, bulimia nervosa, is also more common in women. Bulimics are obsessed with thinness but periodically go on eating binges, following which they try to reduce the absorption of the food by self induced vomiting or by taking laxatives. |  |