There is a substantial body of evidence now that BMI is not the best predictor of CVD risk and esp diabetes risk. One metric that is good across different populations is the ratio of waist to height (WHtR). In metanalysis this was a better predictor of CVD outcomes than either BMI or waist circumference and moreover a value of 0.5 as screening cut off works for all ages and ethnic groups. It also translates to a simple message "keep your waist measurement less than half of your height"

In Asian context, normal BMI range is from 18.5 to 22.9.

There is a substantial body of evidence now that BMI is not the best predictor of CVD risk and esp diabetes risk. One metric that is good across different populations is the ratio of waist to height (WHtR). In metanalysis this was a better predictor of CVD outcomes than either BMI or waist circumference and moreover a value of 0.5 as screening cut off works for all ages and ethnic groups. It also translates to a simple message "keep your waist measurement less than half of your height"

Asians seem to have more body fat at lower BMI levels. They also seem to demonstrate various levels of glucose intolerance and insulin resistance at lower BMI ranges (compared to Whites).

I came across this paper.. it may be of interest to you. http://www.ncbi.nlm.nih.gov/pubmed/12036803

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Thank you Sangeetha

Sigrid,

I agree - regardless of the measure we choose to focus on, the key is translating the evidence into simple advice. Given the evidence to support waist to height ratio over BMI, it does seem many clinicians are moving toward using this measure. There is also ongoing research trying to establish BMI/waist circumference cutoffs based on ethnic group (see below), but it seems there is definitely more evidence needed.

http://www.nice.org.uk/guidance/index.jsp?action=download&o=62266

BMI is a relatively useless, misleading, correlatively derived measure. I know. I was an athlete who swam 10 miles/day, ran in the mountains, weightlifted, etc. I am 5'8" tall and at fittest for my lifestyle, weigh about 190-195. That is very lean and lipid panels are excellent in every way. My BMI is through the roof "morbidly obese" . why? because this is a poorly conceived measure that is used too generally to answer specific questions. Body fat, functional tests, lipid panels, strength, power, aerobic capacity and QOL are better measures for most kinds of feedback and discussion. I suggest using the Therapeutic Assessment model (Steve Finn et al.) to establish a collaborative, individualized approach with each individual.

Hm, I am still left wondering if BMI has any validity as an epidemiological tool.For example, in a long-term study in Africa I am interested in identifying households with both undernourished children and adults (and just one or the other). I use the conventional z-scores for the children and have been using the BMI threshold of 19.5 for adults. Can anyone tell me whether the lower bound of the "normal BMI range" might possess more validity as a cut-off point than the upper bound?

Lilli, I agree that more research is needed on best and simplest index to represent risk, so it is a pity that NICE did not consider waist to height ratio in its recent guidance on thresholds of BMI and waist circumferences for different ethic groups. The beauty of WHtR is that the same cut off (0.5) works to identify body shapes at risk across different populations.

Ashwell M, Gunn P, Gibson S: Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta-analysis. Obes Rev 2012;13:275-286.

BMI cannot be considered as a standard parameter for any medical indications as it has rightly been pointed out as an approximate indicator of tendency towards obesity! There are many other parameters which can be employed but again , whether any one of them is a definite and incriminating one, has to be further researched!

It is best to use WHO BMI cut off points for population corresponding to a particular region. However, BMI may not be a good tool for screening . Rather , waist to height ratio would be a better tool. Pl. refer to the link below for the detailed paper ascertaining this statement.

http://www.ncbi.nlm.nih.gov/pubmed/22106927

BMI is not considered adequate for research purposes. Functional body composition will likely be the standard in the future.

http://www.nature.com/ejcn/journal/v67/n11/full/ejcn2013174a.html

The risks associated with North American or European BMI cut-offs do not reflect the same risks in Asian body types. The Singaporean government came up with their own cut-offs. Research also has been done in China regarding CVD risk and BMI.

BMI is inaccurate period. Should not even be used in this country. Body fat percentage is a much better indicator.

Michael—I agree with you. BMI is essentially a size measure. I can estimate your size by simply looking at you, but it tells me nothing about how much fat is in your body. In my opinion all research using BMI is invalid. Although there is a correlation between BMI and body fatness in large populations, it doesn’t hold up when it comes to individuals. As a clinician I treat individuals, not populations.

In 1999 my letter to the editor was published in the NEJM:

To the Editor:

Willett et al. endorse the use of the body-mass index because published studies demonstrate a fairly strong correlation between body-mass index and the results of hydrodensitometry or dual-energy x-ray absorptiometry. At our primary care clinic, we perform direct measurement of body fat using infrared interactance and bioelectrical impedance. We find that the measured percentage of body fat consistently correlates with body-mass index only in persons with a body-mass index of more than 35. As the body-mass index drops, the correlation becomes much weaker. Many people with a “normal” body-mass index have body-fat readings well into the range for obesity. More important, when interventions are introduced, measured body fat and body-mass index can travel in opposite directions. For example, one of our patients recently lost 20 lb (9 kg) by following a calorie-restricted diet only, but her body fat rose from 35 percent to over 40 percent. Virtually every pound she lost came from lean body mass. We believe that clinicians should use the available technology to measure the component that actually creates the risk — elevated body fat.

William L. Wilson, M.D.
Chisholm Medical Clinic, Chisholm, MN 55719

Harriet, please elaborate on your observational findings. What are the BMI ranges in your country (specifically what country) and what do you propose to be a healthy BMI?

I think BMI is a better indicator of obesity for a population that suffers from over-nutrition then for a population where under-nutrition is prevalent.

Hello Harriet - of course BMI ought be used in various populations - meaning I suppose across continents. BUT one has to realize that BMI is not the be-all, end-all to a highly complex issue involving many things. Energy balance and its component measures come to mind. Nutrition is another issue of huge importance. As a starting point, one might consider the Mayan refugees in Florida and the many studies comparing these to their Mayan counterparts who did not flee Guatamala. In the descriptor above you give a really nice example of some of these other factors in your own country that ought be considered e.g. body shape and genetic makeup when BMI is used as a measure. Using BMI at least enables some comparison with other populations.

Ditch BMI--period. It has no use in modern science. BMI does not measure fatness. Fatness is what is killing us. Duh!!!!

I agree with Snigdha, that waist to hip ratio may be a better indicator of obesity than BMI. Body percent fat can be estimated with calipers on several standard areas of the body (and a conversion chart that includes age and gender).

I think it best to consider BMI a "quick and dirty" assessment of healthy weight. The practitioner needs to be aware of the fact that lean people with higher BMI are not necessarily in need of weight loss. I think most people can tell the difference between a lean person with BMI of >25, and an obese one. Part of the physical exam is to ask questions regarding lifestyle, which can further elucidate the health status of the patient. BMI is a blunt tool, but useful when applied correctly. We do not need to dexa scan obese patients to determine obesity, after all.

If there is anything wrong with the BMI system as it is used in the US, it is that it is too kind. As far as I am concerned, >25 (assuming we are not speaking about an athlete), is obese, not merely overweight. I would begin to call people overweight by BMI of 23 and know that I am uncomfortable in my skin at 22, so I try to maintain 20-21. I was recently discussing BMI with a colleague from Japan and she laughed. She is in her words "a big girl" when she goes home, though she is not overweight by US standards, BMI of 22. She told me that in Japan, >25 is definitely obese and >30 is "super obese"