Dear colleague, in fact, there is no "reference" for the percentage of fat mass in any population that clearly identify excess of body fat (BF) in a subject, as the term "obesity" really implies. WHO defines obesity as the excess of body fat in such that extent that may impair health (biological definition). What is common to see in some papers is that by using a representative (or not representative) sample from a country, researchers develop a sex and age-reference data for %BF, and consider the highest percentiles (95 per., usually) as the cutoff point for establishing excess of body fat (statistical definition). Different technics or methods are used for the estimation of BF. In the epidemiological context, anthropometry, bioimpedance analysis or DEXA, are commonly employed. In the other hand, some works have aimed to identify relationships between %BF and other surrogate indicators of obesity, such as body mass index (BMI), waist circumference (WC) or subcutaneous skinfold thickness (SFT). I attach some papers related with this issue (there are many more). Hope, these information had been useful for you.

Cheers.

Alberto Mendoza

Dear N. Marrero-Gordillo, the following publication shows reference values to classify according to values of percentages of body fat: Bray G, Bouchard C, James WPT. Definitions and proposed current classifications of obesity. En: Bray G, Bouchard C, James WPT, ed. Handbook of obesity. New York: Marcek Dekker, 1998;31-40.

Thank you very much to both of you, Marta and Alberto. I will take a look to those papers and book that you recomend me, sure they're gonna help. Hug.

NM 

I know that BMI is closely correlated to body fat percentage. If a person is obese with BMI 30, their body fat is probably very close to that.

I attach two recent publications including a letter to the editor about correlation of BMI-SDS and %BF by DEXA. we review some of the literature as well. I hope that this will be helpful.

Respectfully

Thanks Chrystyne for your comment, and thanks Christoph for your link. I can see this web really works, thanks a lot to all of you guys. Greeting. 

Have a look at

http://de.wikipedia.org/wiki/K%C3%B6rperfettanteil#Normal-_und_Grenzwerte

these data come from

http://ajcn.nutrition.org/content/72/3/694.full

Ref. David Nieman (1995). Fitness and Sports Medicine- A Health related approach, 3rd Edition, pp 134

Alberto:

I have been interested in this issue for decades. In 1999 my letter to the editor was published in the New England Journal of Medicine:

http://www.nejm.org/doi/full/10.1056/NEJM199912303412715

Although obesity has traditionally defined as "excessive body fat" and incorrectly measured by BMI, the pathology is more than just about fat. Some people with excessive body fat are metabolically healthy and some people with minimal excess fat are metabolic disasters. To tease out these issues we need to look at inflammatory markers, insulin levels, homocysteine levels and other relevant parameters.

As a clinician I need a concept of obesity that has relevance to a patient's health and quality of life. We now believe that the metabolic affects of excessive body fat are also somehow tied to common brain disorders (see attached). Yes, it is complex but the good news is that one variable seems to be driving all the pathology--the long term consumption of highly processed food.

Thank you very much Mr. Wilson for your consideration answering my question, and for your comment. No doubt about the so important role of fat in our body, but, I got another question for you, if you don't mind. Is the muscle mass a risk factor for health?. I work with big guys, wrestlers, to be precise, with canarian wrestlers, an special style of wrestling, and all of them are pretty heavy guys, with lot of fat (average of 28% of weight, but more), and also with large muscle masses (specially in the extremities, but also at the torso). I can imagine their heart pumping blood against those "tons of tissues". What do you think about this?. Thanks in advance for your answer.

NM

The problem with the http://ajcn.nutrition.org/content/72/3/694.full article is that the authors are categorizing %BF according to BMI.  You might as well just use BMI.  What we need are studies that link %BF categories with disease risk, lipid levels, blood pressure, insulin resistance etc.  I work with children and therefore am aware of Laurson's work. In the first article I posted below %BF is set up as percentiles according to national data as in a growth curve.  The second article uses Metabolic syndrome as the criterion to establish %BF cut offs in 12-18 year olds.

Thanks a lot for your comments Mr Schweitzer, I appreciate your time, thanks.

N. Marrero-Gordillo--The group you are describing seems to be far from the norm. How are they getting so big? Are they abusing anabolic steroids? If so this would throw things off. 

Also if someone is big and still has percent body fat of 28%, that is not good. If someone gets big in a healthy way doing strength training, their percent body fat typically will be quite low. If someone gets big by eating a ton of highly processed food, their percent body fat will be high. It really isn't about size or BMI.

It's interesting to note that sumo wresters are not the cream of the crop when it comes to health and longevity. They seem to get big by eating a lot of starchy food:

http://www.livestrong.com/article/485454-sumo-wrestlers-compared-to-bodybuilders/

Dr Wilson they are big but free of steroids, trust me, I belong to the "antidoping brigade" . Their training plans are tough and they fight every week (league competition). Now we started to control their weight in term of % of fat. You can take a look to this recently publication (http://cdeporte.rediris.es/revista/revista57/artaproximacion539e.pdf) to understand better how this wrestling modality is.

And yes, they are not normal guys, we familiarly call them "trained obeses". They got a goal: to be as big as they can because weight is an important balance factor for their style of wrestling. The looser is one who touch the mat first. That's why.

Thanks a lot for your comments.

http://cdeporte.rediris.es/revista/revista57/artaproximacion539e.pdf