New York: Standard body mass index (BMI) measurements are an inaccurate way to judge whether college athletes and non-athletes are carrying too much fat, a new study shows.

With all the concerns about obesity these days, the BMI is becoming more familiar as a measure of weight in relation to height. It's derived by dividing weight in kilograms by the square of height in meters.

Conventionally, BMIs of 20-25 are considered normal weight, 25-30 is overweight, and anything over 30 is classified as obesity. However, in their study, Dr. Joshua J. Ode and colleagues from Michigan State University in East Lansing found that BMI overestimated the fatness of male and female athletes and male non-athletes, while under estimating the fatness of female non-athletes.

"BMI should be used cautiously when classifying fatness in college athletes and non-athletes," they conclude in their article in the journal Medicine & Science in Sports & Exercise.

"Our results support the need for different BMI classifications of overweight in these populations." Ode and his team compared BMI measurements to body fat percentages in 226 college athletes and 213 non-athletes.

They defined a body fat percentage of 20 percent or greater as "overfatness" for males, while females were considered "overfat" if fat represented 33 percent or more of their bodyweight.

Two-thirds of the male athletes had a BMI of 25 or greater, the standard definition of overweight but were not overfat, as did one-quarter of male non-athletes, the researchers found.

Among female athletes, about a third had BMIs of 25 or greater but were not overfat. The opposite problem was seen for female non-athletes; while just 7 percent were misclassified as overfat based on their BMI, 44 percent of those with BMIs of 24 or less had body fat percentages of 33 percent or greater.

"Because of a larger muscle mass among the male and female athletes, BMI incorrectly classifies normal-fat athletes as overweight," Ode and his team explain. They call for adjusting BMI thresholds to more accurately reflect the body composition of college-age individuals; based on the current findings, they say, the best BMI cut-off points for overfatness would be 27.9 for male athletes, 26.5 for malenon-athletes, 27.7 for female athletes, and 24 for female non-athletes.

Furthermore, for really big male athletes such as football line men, the BMI cut-off should be even greater, at 34.1, they conclude.