The way it is currently measured obesity greatly underestimates the actual number of obese women, suggests a new study.
Almost half of women who currently are not considered obese by virtue of their body mass index (BMI) were found to be obese when measured by a newer method that focuses on body fat percentage by weight, the researchers found.
The researchers, Dr. Eric Braverman, president of the Path Foundation in New York City, Dr. Nirav Shah and the current state health commissioner of New York, indicate that an accurate measure of obesity should include the body fat percentage and the proportion between height and weight known as BMI.
?Observing body fat based on body mass index is something that almost can not be trusted at all,? said Braverman.
According to the BMI alone, ?about 30 percent of Americans are obese, but when using other methods, the figure is closer to 60 percent,? he said. ?We believe that BMI is not reliable,? he said Braverman.
?We?re fatter than we think. What makes one obese is the percentage of body fat, not BMI,? he said.
The problem is seen mostly in women, because ?As women age, they tend to lose bone mass and muscle to replace fat,? said Braverman.
The study is published online April 2 issue of the journal PLoS ONE.
Braverman and Shah found that when women received a special scanner known as dual X-ray absorptiometry (DEXA, for its acronym in English), which measures body fat, muscle mass and bone density, BMI underestimated obesity alone.
The more than 1,300 people who submitted to DEXA in the study, almost half of women (48 percent) were misclassified as not obese by BMI, but were found to be obese by body fat percentage found with DEXA.
In contrast, 25 percent of the men were misclassified as obese by BMI, but in fact were not obese according to the percentage of body fat.
In fact, the researchers, all participants in the study that found that obese DEXA were women.
Braverman said the DEXA is expensive, so would not be practical for routine screening. However, a simple blood test that measures levels of leptin may serve the same purpose, he said. Leptin is a hormone involved in regulating appetite and metabolism.
In the study, leptin levels correlated with body fat. The researchers noted that leptin levels can be used in conjunction with BMI as a more accurate measure of obesity.
?Leptin is a better marker of obesity in women,? he said Braverman, adding that successful weight loss depends on the reduction of leptin levels. But he said that women can develop resistance to leptin, a metabolic disorder that is seen with increased frequency after menopause, making dieting ineffective.
People who have leptin levels below 5 monograms per milliliter (ng / mL) are considered thin, and levels of up to 10 weights are considered normal. Leptin levels 10 to 30 ng / mL can be corrected through diet and exercise, Braverman said, but the extremely high levels are difficult to correct.
The effect of leptin is not as strong in men, he said. But men with low leptin levels are very fit, he added.
Braverman believes that eventually the evidence will become part of leptin regular physical examination, and that people with high levels will be treated with various medications and diets designed to reduce leptin levels.
?Everyone will get [a reading] leptin levels, as happens today with [reading levels] cholesterol,? he said.
Commenting on the study, Dr. William O?Neill, a professor of cardiology and executive dean for clinical affairs at the Miller School of Medicine, University of Miami, said, ?is a bit alarming.?
?Traditionally, we used BMI. But this study shows that BMI is relatively accurate in men, but women really underestimated how many are obese,? he lamented.
There is not much data on the health benefits of reducing leptin, O?Neill said. ?We still have to see if elevated levels of leptin are a cause of a bad outcome. Has not been done,? he said.
?I certainly sensitized to find out the possibility that leptin levels in women could be obese might be worthwhile,? added O?Neill.
But it is not known if only to reduce leptin levels reduce obesity. ?We do not know whether leptin can be a primary objective, may only be a marker of body fat,? he suggested.
But people with high levels of leptin should lose weight, O?Neill said.
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