How did data from Brazil and adolescents for BMI body mass index cutoffs for obesity and overweight happen?
This study measured body fat percentages, using the Tanita body fat monitor scale, which uses foot-to-foot bioelectric impedence technique. The sample population is Brazilian adolescents.
They used body fat percentages, 25% for boys, 30% for girls, as the threshold definition of obesity. ( This is commonly used for adults, but who knows if it’s good for children. )
The article included data of mean body mass index, shown in the graph below for boys and girls.
Unfortunately, the article didn’t show data for Brazilian 85th and 95th percentiles. It did show specificity and sensitivity data comparing Brazilian and USA thresholds, but that is not helpful to the reader, without the actual 85th and 95th percentile BMI values being shown. Thus, I found this article of little help.
If you read the abstract, their conclusion focuses on supposed flaws of USA criteria applied to Brazilian population. However, I think the flaw really is that their body fat thresholds (25% and 30%) are not suitable. (Especially 30% for judging obese girls). These thresholds came from adults.
My conclusion, is that the USA 85th percentile threshold for “overweight” is very slightly too low for boys age 10-14, but OK for older boys. The Girls USA 85th percentile threshold for “overweight” is OK for ages 10-14, but is too high for older girls. For “obese” thresholds, the USA 95th percentile is slightly too high for all (ages 10-18) boys. For Girls, the USA 95th percentile threshold is definately too high. ( For Brazilian adolescents, that is.) Perhaps the body fat definition of obesity at 30% body fat, is the problem. Perhaps it should be higher, like 33%.
Does this page have anything to do with dieting? No. Not now, probably not ever. So you are wondering now, where is the back button. It’s up at the top. But wait. I recognize the page is too short. The good stuff was just the way the above study used percentiles and set thresholds. But if this page is too short, so is the CDC page about childhood obesity.
