Lack of Willpower May Not Be the Cause of Weight Gain

Posted February 13, 2008 at 01:30 PM by Denise Musumeci

Section: In The News, His Health, Physical Health, Lifestyle Health, His Nutrition, Healthy Eating, Diets

Hundreds of diets ad exercise techniques have been tried over the last few decades. Even though they work sometimes, there is still an overwhelming problem with obesity. Fad diets come and go, but still don’t work for most people.

What can we do to help people who suffer from obesity? What is the cause of this epidemic? The New York Times recently interviewed Dr. Barry Levin, a neurologist at New Jersey Medical School who has studied the brain’s role in obesity for 20 years. His research suggests that exercise early in life may help in the prevention of obesity.

People often gain weight from overeating, but are not sure why they overeat. According to Dr. Levin, balancing energy expenditure and food intake is a process involving two parts of the brain, a need-based system and a reward-based system. The need-based system involves metabolism. Changing levels of glucose and the hormones insulin and leptin trigger your body to feel full, and this stop eating.

However, those who are genetically prone to obesity are less sensitive to these hormones and do not feel full unless these hormone levels are much higher. Dr. Levins says that the body’s metabolism strives to stay at a constant weight. If you increase your caloric intake over a long span of time and gain pounds, your body will adjust to a higher weight and your metabolism will slow down to support the extra weight.

As for the reward-based system, which responds to your desire to eat certain foods, works differently. Certain smells, tastes and textures, such as those of your favorite foods, will stimulate your desire to eat those foods and trigger hunger, even if your body does not need energy. This may explain cravings for certain foods and why we may go on an eating binge.

Dr. Levin did a study about reward-based systems and obesity in rats. He fed rats a chocolate liquid supplement. Those who liked the supplement consumed it with no inhibitions and almost their entire calorie intake came from it. When the liquid was taken away and they went back to eating the original diet, food intake decreased by almost fifty percent and in a few weeks, they lost the weight gained from the supplement.

After a while, Dr. Levin reintroduced the liquid, and once again, the animals binged on the chocolate supplement and regained the weight they just lost. In conclusion, the reward system overrides the need system and causes people to overeat, even if they are not hungry.

People often blame their weight on genetics. For almost 70 percent of cases, genetics are to blame, making it difficult to lose weight. It is not necessarily a lack of willpower to stop over indulging, but a genetic link that makes people more sensitive to the smell or taste of their favorite foods.

Dieting often does not help because the amount of energy you expend at rest goes down. This is part of the need-based system. When you fast for even a short period of time, leptin levels go way down and trigger your body to be hungry again. By eating, the leptin levels go back up and trigger the body to be full again.

Obesity-prone people are not as sensitive to high levels of leptin, so they do not get the message to stop until they are higher than normal. Initially, fad diets may work because people are not eating as much, but going long periods of time without their favorite foods causes them to have uncontrollable cravings that make them over indulge and give up the diet.

Although exercise is a big factor for weight loss, it may not work on its own for most people. However, Dr. Levin’s experiments have shown that exercise at an early age, between ages 2 and 8, may help prevent obesity in the future, even if they are genetically prone to gaining weight. Dr. Levin’s gave obesity-prone baby rats access to a running wheel. Even after the wheel was taken away, the rats managed to stay thin. The results showed that increased exercise during the developmental stage of life has made obesity-prone individuals more sensitive to leptin hormones. There is not enough evidence to suggest that it is a permanent change, but it is certainly long-term.

Why do we not have effective weight loss drugs? The problem with weight loss drugs is that our energy levels are linked to many areas of the brain. When the weight loss drugs act on these receptors, they are also altering other aspects of the brain, such as signals for mood swings, depression, and anxiety. Since the weight-control receptors are linked to other areas of the brain, there has not been a drug on the market yet that acts only on weight loss without affecting other areas too. Until we develop a drug that only focuses on weight loss, the best way to stop obesity is by preventing it in early age.

Research sources and for more information: [NY Times]; [picture]