At any given moment in time, tens of millions of Americans are dieting, in an effort to both look and feel better. Success rates, however, are dismal. Very few dieters actually lose weight– even fewer manage to keep it off. Anyone who has attempted to lose weight knows that there are no easy answers to this troubling condition. The effort to lose weight and keep it off involves a complex interplay between appetite regulation (eating) and energy metabolism (exercise). These two components are regulated by genetics and biochemistry, as well as environmental, psychological and social factors. Frustrating attempts at longterm weight control have led many to believe that they are genetically programmed to be fat– that somewhere hidden in the spiraling helix of their DNA lurks a “fat gene.”
Recent and ongoing genetic research is confirming this suspicion. Numerous studies of twins who were reared apart but still maintained similar body weights seem to validate the role of genetics in obesity. Recent scientific inquiry is attempting to isolate the exact genes that play a role in obesity and figure out what they do.
Dr. Claude Bouchard of the University of Laval in Canada has reviewed the possible geneticc influences on body weight. He points out that approximately 20 genes have been identified that appear to influence body weight. Furthermore, increasingly sophisticated obesity research is creating an atmosphere of “imminent breakthrough” in the discovery of additional genetic factors.
Much media fanfare recently surrounded the discovery of a gene that might cause obesity. Numerous articles went so far as to say that scientists could now possibly create a drug that might repair the gene or mimic its malfunction, thus preventing obesity. Sound too good to be true? Read on.
Genetic researchers at Rockefellar University reported that they found a gene (dubbed the ob-gene) which, when defective, causes obesity in mice. Further research confirmed a similar gene in humans. In mice, the gene operates in the fat cells and secretes a hormone-like protein that signals the brain that the body has enough fat in storage and should adjust food intake and energy expenditure. The defective gene either does not produce the appetite-regulating protein or produces too little of it to have an effect. The result is that the brain does not get the “stop eating” satiety signal from the fat cells. The mice overeat and become obese. Could a new drug mimic the satiety signal protein and cause people to stop eating?> Maybe, but first scientists must prove that the gene indeed works the way they think it does. Then, they need to discover a safe and effective way to use it to cause weight loss.
Following up on the question of how the ob-gen works, researchers at Thomas Jefferson University found that the genetic makeup of the “obesity gene” is the same in thin and fat people. They believe that in humans the gene is secreting its protein as it should, but in some obese people, the brain might not be getting the signal to stop eating. This could be due to defective brain receptors or something that happens to protein on its way to the brain. This team is trying to figure out why the satiety signal is not being picked up.
These two studies clearly project the complexity of obesity research. While each new discovery raises several new questions, some long-held theories of weight control in humans might possibly be confirmed by genetic research.
Weight control scientists have been talking about “set point theory” for almost two decades. Most weight control experts present set point theory as fact rather than speculation. Ths is because the theory explains much of the frustrating difficulty dieters experience in both losing and maintaining weight loss. They say that the set point is determined by a genetically programmed amount of body fat. Or, put another way, it is programmed to minimize the discrepancy between your programmed weight and yoru actual weight.
The control mechanism in this theory, often called an adipostat because it controls adiposty, or fat, seems to receive information from the fat cell and signals the brain to control your hunger level, thereby controlling both your eating and phyical activity habits. In effect, it functions to adjust your behavior and your metabolism to maintain a preprogrammed degree of fatnes or weight. Unfortunately this degree of fatness may produce a weight drastically different from what you or your doctor thinks you should weight.
Has the discovery of the ob-gene confirmed the set point theory? The answer for now is “maybe.” The protein emitted by the ob-gene may be the way adipostat communicates between the fat cells and the brain. When the 0b-gene malfunctions, it sends signals that result in uncontrollable hunger and overeating, resulting in obesity.
All of this science can be extremely confusing and frustrating to the person who needs to lose those unhealthy extra pounds. Recent reports may leave a person feeling doomed to a life of being overweight. On the other hand, everyone knows someone who has lost a lot of weight and kept it off.
Genetic and weight loss experts caution that obesity in humans is much more complicated than most of us suspect. The rapidly increasing rate of obesity in America cannot be explained by genetics. The gene pool does not alter in two or three generations. The simple truth is that many Americans are eating more and exerting themselves less.
Most experts agree that how we choose to live our lives continues to play an important role in obeisty. In fact, Dr. Xavier Pi-Sungyn, director of Obesity Research Center at St. Luke’s/ Roosevelt Hospital, believes that “only a fraction of human obesity is due to genetic predipositions.” The discovery of the gene, he adds, ” leaves diet and exercise right where they have always been central– in preventing obesity.”
In summary genetic influences determine whether a person can become obese, with behavioral and environmental influences determining whether and to what extent a person becomes obese. Obesity is not an inherited and unatlerable trait like eye color, but a tendency that can be controlled by behavioral change. Those people who are predisposed to being overweight will find weight control more challenging but not impossible.
Daryl Conant, M.Ed.