Many of my overweight patients swear that they eat very little. And yet, basic science would show that they are consuming more calories than their body requires and the excess goes into fat stores. So what is the deal? Do they really not eat that much? Is there some disconnection between perception and reality?

Recent research seems to show that obesity is not as simple as counting calories — there are actually genetic, metabolic and psychological elements to weight.

In a nutshell, the food that we consume is used to provide nutrients and metabolic fuel to our bodies. Some of the excess calories enter fat stores and some leave our body in the form of heat — most of it in the air we exhale during each breath.

On a physical level, weight gain or weight loss is all about how you handle your calories or how efficient you are at burning excess fuel. In this case, less efficient is actually better. Some people are less efficient at diverting excess calories to fat so more calories are burned off as heat. These people seem to have a greater proclivity to eat anything they want. They also tend to be more active, spend less time sitting and move a great deal more.

A recent study in the journal Science identified some unique differences between overweight and lean people. Surprisingly, despite what you might expect, overweight people seem to enjoy food less. Using sophisticated brain imaging studies, a group of scientists from the Oregon Research Institute studied the so-called pleasure center of the brain.

Thin and obese women were shown a picture of a chocolate milkshake or a glass of water. Upon seeing the milkshake, the obese women had far more activity in the pleasure center than the thin women. However, after drinking the shake, activity in the pleasure center was much lower in the obese women.

This research suggests that obese women get less reward from eating high caloric foods and as a consequence are less satisfied. Less satisfaction leads to a particularly vicious cycle, where less satisfaction per bite means increased consumption; this further blunts the sensations of the pleasure center, causing less enjoyment of food, which leads to less satiety, more food intake and weight gain.

In the same study, researchers also showed that overweight people were more likely to have a gene variant called Taq1A1, which not only suppresses the pleasure response but also leads to reductions of the hormone dopamine. Lower levels of dopamine can contribute to increased hunger and a decreased sense of reward from eating well.

This information clearly indicates that genetic and metabolic differences contribute to obesity risk. This sort of insight could one day lead to highly effective therapeutic strategies to alter our metabolism and responses to food intake, which will hopefully make maintaining a normal weight or losing weight easier.

As we learn more about obesity, it is vitally important that we become aware of the many different causes and factors contributing to weight gain. Clearly, the brain plays an important role in maintaining weight. But at the same time, for some overweight people, weight loss is not simply an issue of will or strength. Correcting the problem is extremely difficult and requires a clear commitment to healthy living as well as strong external support.

If you have a friend or loved one battling weight gain, never demean, insult or belittle his struggle. Always be supportive, nonjudgmental and encouraging.

If you are overweight or obese, seek help from an expert if possible and recognize that it is never healthy to "diet." Instead, you must adopt the "don't diet diet," which is balanced, enjoyable and promotes health. Learning to eat healthfully is not about restriction, but rather a process of learning to make healthier choices.

Most importantly, exercise is the key to weight control and longevity. Recent studies have shown that exercise boot camps promote health and reduce weight, as does walking, bicycling, swimming or other activity that causes you to sweat. Not only will you look and feel better but you will live longer and more independently as well.

Dr. David Lipschitz is the author of the book "Breaking the Rules of Aging." To find out more about Dr. David Lipschitz and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate Web page at www.creators.com. More information is available at www.drdavidhealth.com.

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