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The Science Of Food Addiction

Responding to the urgent need for a remedy, scientists are exploring the chemistry of weight gain. Their research begins with an effort to ascertain whether certain foods are addictive or not.
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It' a grim fact that only a minority of Americans―one adult in three―enjoys a normal weight.

It's not as if the majority of us aren't trying to slim down. We spent an estimated $40 billion on diet-related products in 2009, yet the only thing we thinned was our wallets.

So if fad diets, weight-loss products and the latest exercise craze aren't the solution, can researchers help us find the answer?

Responding to the urgent need for a remedy, scientists are exploring the chemistry and mechanisms of weight gain. Their research begins with an effort to answer key questions. For example, since so many of us are overweight, is it possible that certain foods are addictive? Are we programmed to overeat?

The notion that certain foods, like narcotics, are addictive and that this addiction explains the compulsion to overeat is gaining traction. Recent findings based on research with rats reported in Science News (November 21, 2009) provide support for this idea.

Rats fed a diet rich in junk food (processed cakes, sausage, bacon, cheesecake, etc.) quickly adopted the habits of drug addicts. They wanted more and more junk food and needed more and more to feel satisfied; they refused to eat regular food once they were hooked on the rich, sweet food, even if rejecting normal food meant starving; they continued to eat junk food even when consuming it triggered an electric shock to their feet; and once they went back to nutritious rat chow, their bodies took a long time to recover. In fact, some never did return to normal eating habits.

Tests on the rats' brains and intestines during and after the rats consumed junk food showed biochemical changes. Researchers concluded that the rats' brains and digestive systems had become captive of the chemical changes resulting from eating junk food--the very definition of addiction. And like drug addiction, junk food addiction can produce changes that are difficult to unwire.

If the experiment with rats is predictive of human behavior, then the chemical changes in the rats' bodies and the rats' addictive habits could explain the growing problem of obesity in the United States. As we consume more and more rich, sugary food, we want more and more, and we gain more and more weight.

That brings us to the next question: If overeating is inevitable, can we somehow avoid storing the surplus calories as fat?

Breakthroughs is a publication of the UC Berkeley College of Natural Resources featuring scientific advances with far-reaching implications. The lead article in the fall 2009 issue, titled "Burn, Baby, Burn: Key Enzyme Tunes Fat Metabolism," explains the findings of Hei Sook Sul, professor of nutritional sciences and toxicology, a scientist with a lifelong passion for understanding metabolism.

When explaining the mechanism of obesity, Dr. Sul's research on one particular enzyme confirms what we all have observed: that some of us can eat whatever we want and stay lean while others of us eat very little and gain weight.

Dr. Sul, the principal investigator on the research team, reports, "We have discovered a new enzyme within fat cells that is a key regulator of fat metabolism and body weight, making it a promising target in the search for a treatment of human obesity."

In their experiments, the investigators gave two groups of mice an appetizing buffet of tasty, high-fat mouse food. One group had the gene that expressed the enzyme; the other group did not. The presence of the enzyme did not affect appetite: both groups ate the same amount of food. But as the mice grew older, the group without the enzyme gained weight while the other group stayed lean.

Photo courtesy of Sul Laboratory

If Dr. Sul and her investigators could work with drug companies to patent and market an inhibitor of this enzyme in a pill that I and others could take without side effects, we could eat whatever we wanted without fear of gaining weight.

My first question to Dr. Sul was, "How long will it be before this or an equivalent enzyme is available in prescription form?" Her answer was more prudent than I would have preferred: "We are far down the road from translating research on this enzyme in mice into an application for humans for the management of obesity. What works with mice doesn't always work with humans." Dr. Sul added that researchers across the nation are exploring different approaches to understanding the chemistry of obesity, and her research is only one piece of this larger effort.

My second question involved the difference between the metabolism rates of the mice that stayed lean compared to those that gained weight. Here, Dr. Sul's insight was more hopeful: "The range is tiny." But, she explained, the results are cumulative. Over time, even a small amount of excess calorie consumption will eventually result in excess fat. Conversely, because the range is tiny, we can underconsume a small amount each day and trigger a cumulative weight loss.

The dialogue with Dr. Sul was enlightening, even though her answers were not what I might have hoped for. Given her brilliant background as a leading researcher in metabolism, I shouldn't be surprised that she confirmed the hard truth: there are no magic pills when it comes to fitness and weight loss--at least not yet.

I am, however, reassured that she and other researchers are exploring the mysteries of metabolism and obesity. Their efforts reminded me of a passage from T. S. Eliot that was quoted by another scientist to explain his passion for research:

We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time.

For those of us pursuing fitness and trying to maintain a reasonable weight, the place where we started and now return to (at least for the foreseeable future) is the same: exercise regularly and eat healthfully.

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