Overweight based on BMI or Body Fat %??

EvgeniZyntx

MakePeasNotWar wrote: »

EvgeniZyntx wrote: »

Rocknut53 wrote: »

Packerjohn wrote: »

Rocknut53 wrote: »

Packerjohn wrote: »

Rocknut53 wrote: »

My problem with BMI is that it doesn't factor in your level of fitness, it's just height & weight. Pretty arbitrary. You look great in your pic, I wouldn't worry much.

BMI works for 80% or so of the population reliably. If someone has been doing resistance training or a manual labor job they may be overweight by bmi but an acceptable level of bodyfat. Otherwise moat likely not.

I'm not doubting your statistics, I'm just curious as to where you got the information.

Here is a sample:
http://www.sciencedirect.com/science/article/pii/S221133551500073X

Highlights

o The accuracy of age adjusted BMI for passing or failing body fat standards was 83%.
o The correlation between BMI and % body fat as determined by DEXA was 0.86
o An equation was derived to estimate % body fat: % body fat = 1.3974(BMI) − 19.166.
o Soldiers with a BMI of 27.5 < 30 had 10 kg more fat mass than Soldiers with a BMI < 25.
o Soldiers with a BMI of ≥ 30 had 17 kg more fat mass than Soldiers with a BMI < 25.

Thank you for a good science based article. Appreciate the info.

That's really best case scenario though. In women and adolescents there is a lot of evidence that the specificity of BMI to identify obesity is very low.

http://ajcn.nutrition.org/content/80/3/597.full
http://www.nature.com/ijo/journal/v32/n1s/full/ijo200887a.html

This study was done on a much larger sample (~12k ) with varying age groups and both genders and found about a .8 correlation for women. Body fat was determined by DEXA.

http://m.ajcn.nutrition.org/content/89/2/500.full

RESULTS

Basic descriptive information about the analytic sample is shown in Table 1. Differences in mean values between men and women were tested by using a 2-sample t test for complex survey data (14). Pearson correlations between percentage fat, BMI, WC, and WSR are shown in Table 2 by sex and age group. Correlations by race-ethnicity group within sex and age groups were similar to those seen overall (data not shown). All correlations were significantly greater than zero (P < 0.0001). For men, the correlations between percentage fat and BMI ranged from 0.789 (20–39 y of age) to 0.716 (≥80 y of age). The corresponding values for women were 0.839 and 0.724. For comparisons between pairs of correlations, statistical significance was based on a P value of 0.00045, which was equivalent to a P value of < 0.05 after Bonferroni correction.

Which corresponds with the first study posted.

MakePeasNotWar

Unfortunately, I can't see a link to the original study, but assuming this description is accurate (and the numbers seem to agree with what I've seen elsewhere), it's rare to find a person who is overweight by BMI standards but in the normal range of body fat percentage. Most of the misclassification is due to normal weight obesity.

This article gives 5% as the proportion of overweight subjects who were lean, but it is for both genders and I have seen (and am trying to find the reference) a 3% estimate for women.

http://blogs.plos.org/obesitypanacea/2015/04/30/30-of-people-with-a-healthy-bmi-are-actually-obese/

DebSozo

macchiatto wrote: »

You look great in your pic! I don't think there's any way you're overweight. I'm guessing your body fat percentage is a bit lower than the 30%.

I think her actual body fat is lower also. I look a lot "thicker" than OP and have the same body fat %.