LITTLE ROCK — Maureen Michael likes food. Most days, she has three or four meals, and on occasion she eats yet another in the middle of the night. But she rarely worries about her weight, and at 5-foot-8 and 155 pounds, she looks quite trim.
“I eat anything, and I eat a lot,” the 51-year-old District of Columbia resident says.
Just the other day, Michael ate a salad and two large helpings of spaghetti and meatballs for dinner - after having a hearty bowl of ice cream. For breakfast the next morning, she ate two scrambled eggs, half a package of Polish sausage, English muffins and orange juice. For lunch, she consumed a 12-inch seafood submarine sandwich and some chips, and that night’s dinner featured two pork chops, potatoes and broccoli.
That Michael’s weight remains steady even though she eats whatever she wants and does not exercise interests scientists studying obesity. By looking at people who are near their ideal body weight, reseachers at the National Institutes of Health’s Metabolic Clinical Research Unit in Bethesda, Md., hope to figure out what causes so many others to be overweight or uncontrollably fat.
Michael is among the one third of American adults who are at a good weight relative to their height and build. Another third are overweight, and the rest are obese.
For years, people have been told to diet, control their appetites, use a little willpower. But some scientists believe the rise in obesity has been triggered by a combination beyond an individual’s control: genes, and how they interact with an environment of abundant and hard-to-resist food.
UNIQUE GENETIC MAKEUP
Each person’s unique genetic makeup, these experts think, could affect what he craves, how much he craves and how his body uses fat and burns calories.
“We are hard-wired to be a bit more hungry than we need to, because until very recently - in evolutionary terms - the vast majority of our fellow humans had no idea whether the next meal would be available or not,” says Francesco S. Celi, a clinical investigator at the NIH research unit.
Yet for some people, there is a profound imbalance between what they eat and the amount of energy they expend. Most of these people become obese as a result, but some, like Michael, don’t.
“Some are more sensitive” to that imbalance, says Rudolph Leibel, a diabetes researcher at New York’s Columbia University, who has been studying the biochemistry and genetics of obesity for 25 years. “That’s the genetics.”
“There are people in the population who are skinnier or more slender with a different genetic response to the environment,” he says. That is why “just yelling at people and telling them it is sinful or gluttony is not a particularly fruitful way to deal with the problem. It’s not very effective to insinuate that someone has moral failings when a behavior is involved.”
TEMPERATURE
In Bethesda, Celi and another investigator, Kong Chen, are taking a slightly different approach. Since humans spend so much time at rest and since “obesity is an imbalance between energy intake and energy expenditure,” Celi says, he and Chen are testing what happens to a person’s output of energy, stress hormones and thyroid hormone levels when the body gets cold.
Some studies suggest that lower temperatures help stimulate brown fat to burn more calories. Brown fat, which lies along the neck, shoulders and spine in small amounts, is like muscle tissue in that it burns calories and helps keep the body’s internal temperature stable. Only recently have scientists discovered that brown fat persists in humans beyond infancy.
They have also found that lean people tend to have more brown fat than obese people.
If temperatures can influence brown fat so that the body expends more energy, people with a lot of brown fat may findit easier to lose or maintain their weight, Celi and Chen believe.
PRELIMINARY EXPERIMENT
Michael is one of 24 lean recruits in a preliminary experiment run by Celi and Chen. She spent two 12-hour overnights in a special room with precise temperature and airflow controls. During each session inside the chamber, she ate a diet of 50 percent carbohydrates, 30 percent fat and 20 percent protein - just enough, the scientists calculated, for her to maintain her weight - while they held the room temperature at 75 degrees for one session and 68 degrees for the other.
All the while, they measured her oxygen and carbon dioxide output. They used a Bod-Pod to calculate her body composition. She swallowed a pill containing a sensor that traced her internal temperature, while patches placed on her skin gauged her external temperature.
Her heart was constantly assessed, and every 30 minutes small amounts of fluids were collected from fat tissue around her belly to evaluate her metabolism. Blood and urine samples were also taken.
Celi and Chen are optimistic about some early findings in the trial. Participants’ energy expenditures went up when the room temperature was lowered. They plan to conduct a larger study, involving 180 volunteers.
ActiveStyle, Pages 25 on 07/23/2012