Inflammation Molecule May Determine Fat Levels
Link only seen in normal-weight women, suggesting it protects against obesity
WEDNESDAY, March 24, 2010 (HealthDay News) -- Swedish scientists have discovered that a well-known marker of inflammation may help determine how much fat tissue people carry around.
But the relationship was not present in obese individuals, according to the research, which appears in a letter to the editor in the March 25 issue of the New England Journal of Medicine.
"There seems to be a certain feedback in patients with normal weight that's not there with patients who have obesity," said Dr. Jacob Warman, chief of endocrinology at The Brooklyn Hospital Center in New York City. "This tells us that [this inflammatory marker] seems to be protective."
"The real question people have been asking is why is heavy bad? Elephants are large and don't die of heart disease. They're meant to be big," said Dr. Mitchell Roslin, chief of bariatric surgery at Lenox Hill Hospital in New York City and Northern Westchester Hospital in Mt. Kisco, N.Y. "Being big doesn't make you ill or sick, so the question is why does this go on?"
Obesity, which contributes to a range of health ills, has emerged as one of the most pressing public health problems in the world today, although researchers are still trying to untangle exactly why obesity and disease go hand-in-hand.
"For years, we thought of fat as a dormant storer of energy, and now we realize that the fat cells are much more dynamic. They're much more active and much more involved in many processes," Roslin said. "Essentially obesity is an inflammatory state. Obesity activates the immune system and makes [people's bodies] behave as if they're inflamed."
And that leads to the various complications of obesity, such as heart disease.
These authors, from the renowned Karolinska Institute in Stockholm, Sweden, did a test-tube experiment of fat tissue taken from 23 lean, premenopausal women aged 26 to 49.
The investigators found that levels of tumor necrosis factor-alpha (TNF-a) were heightened in these normal-sized women. The women also had fewer but larger fat cells, as opposed to many more small fat cells.
But when looking at 26 obese healthy women of roughly the same age, the researchers found no relationship between TNF-a and body fat or body mass index (a measurement that is based on height and weight).
Tumor necrosis factor is a cytokine that contributes to inflammation. It has been implicated in a number of diseases, including rheumatoid arthritis.
According to the authors, TNF-a changes how fat tissue works and contributes to some of the metabolic problems associated with diabetes.
Still, there are a number of questions not answered by the study.
One is whether the relationship or lack thereof would hold true in older individuals.
Also, the authors only looked at surface fat, not the visceral fat deeper inside the body that is more closely associated with heart disease, Warman said.
"That would have meant putting a needle in the belly and taking out the fat tissue. That's really more invasive," Warman said.
The U.S. Centers for Disease Control and Prevention has more on obesity.