Scientists Try to Find Causes for Obesity Besides Overeating

ST. LOUIS _ Doctor after doctor told Neal Luehr that he gained weight because he ate too much.

“They’d tell me about how calories work,” says Luehr, 41, of Murphysboro, Ill. “I said, `I know already. I’ve been dealing with this more than 30 years.’”

He maintained that he ate fewer than 1,200 calories a day. He exercised. Still, at one point, his weight reached 270 pounds.

Additional symptoms told him something else was wrong. His normal body temperature was 95. His cholesterol pushed 300, even though he was eating mainly grilled chicken and vegetables. His skin flaked embarrassingly, and he felt lousy _ no energy, down a lot.

He had lived with the symptoms and doctors’ skepticism since he worked his family’s farm as a boy. Farm work should have burned a lot of calories, he says.

Says Luehr, “It’s like my whole life was on a dimmer switch.”

Luehr is one of thousands of people who believe they gain weight without overeating.

The vast majority of doctors insist that you gain weight by eating too much. But a growing number of researchers believe that overeating sometimes fails to explain why some people are overweight.

Luehr is in the minority. Studies published by the Mayo Clinic say that fewer than 2 percent of obese people can blame their weight on anything other than overeating.

For many in the 2 percent, the culprits are illnesses _ hormonal disorders such as thyroid problems; metabolic disorders, which prevent the body from burning enough calories; conditions brought on by pre-diabetes; and side effects from medications, especially steroids and drugs for mood disorders.

Luehr’s problem, it turned out, was a faulty thyroid gland. After two years of trial and error _ and about $6,000 in expenses and drugs _ doctors found a medicine that cleared up the mysterious weight gain overnight.

“I woke up the next morning feeling different,” he says. “I had energy; my body temperature was 98.5. I will never forget that day, waking up and feeling normal.”

That was about three years ago. Now Luehr weighs 200 pounds, he runs and exercises five days a week, he eats 1,500 to 2,000 calories a day, and his cholesterol is a healthy 160 without medication.

But barring a medical condition, most doctors say, weight gain is caused by more calories going in than coming out.

“There’s just a basic law of physics that is not changeable,” says Dr. Michael Cannon, professor of family medicine at St. Louis University School of Medicine.

Dr. Samuel Klein, professor of medicine and nutritional sciences at Washington University, says statistics show that when people who believe they’re on low-calorie diets continue to gain, “it’s unlikely that they’re eating very little.”

An example: People who gain weight on a 1,000-calorie diet often underestimate their calorie intake by half, he says.

A St. Louis researcher, however, says “calories in, calories out” doesn’t always explain weight gain.

Microbiologist Jeffrey Gordon, director of the Center for Genome Sciences at Washington University School of Medicine, led a research team that determined that some people may take more calories from food than others.

The culprits are two key families of microbes in the digestive system. One family extracts more calories in people who are overweight; the other extracts fewer calories in people who are normal or healthy weights.

“The question is: If you consume a bowl of Cheerios, and someone else consumes the bowl of Cheerios, are you going to harvest the same amount of energy?” Gordon says.

Here’s how it works:

Scientists know that microbes in humans secrete enzymes that help with everything from breaking down food to storing calories in fat cells. In exchange, humans give the good microbes a warm, friendly place to live.

The research found that some microbes may extract 100 calories from those Cheerios while the other family of microbes may extract 50.

Gordon says it’s too early to use this as an explanation for the obesity epidemic. The microbes may have a very small effect on weight loss or gain.

“It’s a clue, but it’s not proof,” he says. “It gives a new facet to the factors that control our energy balance _ that there’s a microbial component that not all bowls of Cheerios may have the same caloric yield for each consumer.”

The effect may be small but cumulative, Gordon says.

He explained that 12 additional calories a day added up to more than a pound a year. So exercise and eating right remain the key to weight loss, he says.

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GAINING ON OBESITY

Gaining on obesity: Most people are overweight because they eat too much, but scientists are trying to learn more about what else might contribute to this problem

Researchers say the following are other factors that can contribute to weight gain or raise the risk of obesity.

_Women who sleep five hours or less a night weigh up to 32 percent more on average than those who sleep seven hours, according to research from Case Western Reserve University. The reason perplexes researchers. More time awake should, mathematically, mean more calories burned. The culprit appears to be stress.

_Dopamine, the brain chemical associated with pleasure and addictive behavior, has been linked by the Mayo Clinic to overeating. If you starve yourself all day, the smell and sight of a favorite food act like a trigger that would send a drug addict on a binge. Then you eat too much. The remedy: Nibble during the day, and don’t starve yourself.

_A family history of obesity increases by 30 percent your chance of being overweight. Researchers are unclear whether this is because of genetics or family eating and exercise habits. No one has found a gene that guarantees you’ll be overweight.

_A mother who is obese while pregnant increases her baby’s chance of being obese by age 7 by as much as 300 percent, Ohio State researchers found. Statistics already show that obese children have a greater chance of becoming obese adults. The risk increases if your mother is black or Hispanic.

_Older adults who see their neighborhoods as unsafe and neglected and avoid going outside face an increased risk of obesity compared with people who live in safe neighborhoods, according to the Johns Hopkins School of Public Health. That’s because people stay home and don’t go outside, walk or otherwise exercise. Also, feeling unsafe produces stress, which has been associated with overeating.

_Poverty increases the risk of weight gain, according to a study at Tufts University. The study didn’t give a reason, but many previous studies say that people with low incomes tend to buy less expensive foods that often contain empty, fatty calories.

_Some drugs trigger increases in water weight or appetite. Steroids and transplant immunosuppressant medications are notorious. Drugs for mood disorders, seizures, migraines, diabetes and even high blood pressure can spur weight gain. Hormone-replacement therapy and oral contraceptives can cause weight to creep up.

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