It has been well recognized for a while that an elevated body mass index (BMI) does not necessary mean that a person has too much fat. Men and women with well developed muscles may have an elevated BMI and still have a low percentage of body fat. Look at any NBA game and you can see poster guys for that.
The BMI as an indicator of body fat also can also fail at the lower end. As humans age , often weight may not change but body composition does, with muscle mass decreasing and body fat increasing so that you may not gain weight but have a high percentage of body fat. Sarcopenia, or muscle loss, is a major element of old age fragility and so far the only way shown to mitigate that is resistance exercise.Aerobic exercise does not seem to help mitigate the apparently inexorable loss of the fast twitch muscle fibers whose loss is most marked in the age related decline in strength.
Nomal weight obesity (NWO) is a recently minted term that is meant to refer to the condition in which the BMI is in the generally accepted normal range but by some (perhaps less than widely accepted) standard of percentage of body fat, the person is deemed to have "too much". Hence they suffer (well, we haven't really shown yet that they suffer) from NWO. My term would be too much fat (TMF) because we have used BMI to operationally define obesity (as bad an indicator as it may be) and some may think we have at least the appearance of a contradiction in terms. People with this entity may be the some of the same people we used to call flabby.
Researchers from Mayo Clinic have published an article that correlates this NWO with risk for the metabolic syndrome. (You may remember this entity as something perhaps no longer believed in by endocrinologists but still by cardiologists. See here for comments regarding that schism). So, it appears that NWO or TMF would be a risk factor for a risk factor (metabolic syndrome) which is a risk factor for heart disease and diabetes, just to name two.
Tip of hat to Dr. Michel Accad's blog Alertandoriented for alerting me to this "novel" risk factor. Here is a press release for the May0 Clinic article.
The Mayo clinic researchers recommend that a shift from focusing on BMI and perhaps monitoring percentage of body fat or least waist measurements since the "real" definition of obesity is too much fat.
Data from CDC show that 35% of American are obese (as defined by BMI >= 30. Using NHANES data from 2003-2004 we see that 66% of Americans are either overweight or obese.That leaves 34% with a normal BMI but Mayo docs tell us about half of those are really obese after all leaving something around 17-20% of us who do not have too much fat. We now know that there are fat people that don't even look fat., a secret epidemic of fat people who don't look fat. (OK, some of them probably have a bulging tummy).A nation of reverse Lake Wobegon, where most everyone is worse than average.
There are new risk factors cropping up all the time. Risk and pre-risk and proto-risk abound. The cardiologist Dr. Thomas Giles, remarked that we are all pre-dead. Prompt and massive public health funding is the only answer,maybe as part of the stimulus package.