Is BMI alone a good Indicator of Disease Risks across Ethnic Groups?? Other Recommendations for Black Women

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                                               Understanding BMI:


Body Mass Index (BMI) is a measure of an individual's weight in kilograms (or pounds) divided by the square of the individual's height in meters (or feet).  "Body Mass Index (BMI) is now the most widely used measure of adiposity" globally (Heymsfield, 2016).  Research has shown that chronic disease risks such as the risks for developing diabetes, heart disease and other weight related health risks increase with increasing BMI.  However, findings suggest even from the earliest studies that, at a given BMI, health risks are not evenly distributed across ethnic groups (Shai et al, 2006).  In addition, as an index, BMI is not without its predictive challenges.  For instance, individuals who are very muscular with a low percentage of body fat may also have a body mass index (BMI) that fits within the range for overweight individuals.

BMI differences across Ethnic Groups:

Research findings have shown that particularly with diabetes risks, at the same BMI category, Asians demonstrate twice the risk of developing diabetes as whites, and this is followed in degree of risk by Hispanics and blacks. Some studies have also found that at a given BMI category, Asians demonstrate higher risks of hypertension and cardiovascular disease than white Europeans (Wen et al, 2009).
 


The Catch?
In analyzing these ethnic differences, some studies have postulated that body fat is a significant influence.  Earlier studies have demonstrated that Asians have a three to five percent higher total body fat compared to white Europeans of the same BMI category (Deurenberg et al, 2002).  This observation was markedly notable in South Asians (Mistra et al, 2009). Conversely, some earlier studies have also demonstrated that for the same BMI category, blacks have a lower body fat content and higher lean muscle mass than whites of the same BMI (Rush et al, 2007).  Based on this theory, the suggestion is that at a given BMI, blacks should indeed be at a lower risk of acquiring diseases for which obesity related factors were central.
As we are here in 2023, the reality of non-Hispanic blacks bearing the burden of higher rates of obesity in the United States of America speaks to other social issues starting with the social determinants of health and including environmental factors such as living in food deserts, economic justice factors including wages and access to healthcare.  It is imperative that these social, economic, and environmental factors along with cultural factors including standards of beauty and body shape be acknowledged and addressed appropriately prior to making decisions for ethnic groups regarding appropriate BMI cutoff points for overweight and obesity.  This is particularly necessary prior to leveraging these indices in efforts aimed at health promotion and disease prevention among certain ethnic groups.



Important Considerations:
 Caleyachetty et al (2021) pointed out that findings from their more recent study have been consistent with findings from earlier studies which suggest that recommendations from the World Health Organization (WHO) and other health related organizations such as National Institute for Health and Care Excellence (NICE) regarding BMI cut off points for non-white populations should be lowered in an effort to be proactive about chronic disease prevention.

It was interesting to note that in their article, Caleyachetty et al (2021) reiterated that the underlying factors for suggesting lower BMI cutoff points for non-white populations remain unclear. It is speculated that contributing factors may be a combination of    "differences in body composition, biochemical characteristics, lifestyle factors (eg, physical activity and diet), the genetic architecture of type 2 diabetes, or life-style-gene interaction."   Amazingly, none of the social, economic, and cultural factors were addressed as a part of the conversation.

Considerations for Black Women:

In addition to monitoring your BMI status, important indicators that predict chronic disease risks include body composition measures such as waist circumference, waist to hip ratio and total body fat.  
As indicated by Heymsfield (2016), waist circumference is used as a measure of total body fat, visceral fat and as a marker of metabolic risk."   A waist circumference of greater than or equal to 35 inches in women is associated with elevated health risks.  Assessing body shape (pear shape versus apple shape) is also important. This is usually an indicator of fat deposition with the apple shape indicating abdominal obesity and presence of visceral fat.



References


Caleyachetty R., et al (2021). Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in England: a population-based cohort study.  Lancet Diabetes Endocrinology. 9(7): 419-426

Deurenberg P, Deurenberg-Yap M, Guricci S.(2002). Asians are different from Caucasians and from          each other in their body mass index/body fat percent relationship. Obes Rev. 3:141-6.

Heymsfield et al (2016). Why are there race/ethnic differences in adult body mass index-adiposity relationships?  Obesity Review. 17(3):262-275.

 Misra A, Khurana L. (2009). The metabolic syndrome in South Asians: epidemiology, determinants, and prevention. Metab Syndr Relat Disord. 2009;7:497-514.

Rush EC, Goedecke JH, Jennings C, et al.(2007). BMI, fat and muscle differences in urban women of five ethnicities from two countries. Int J Obes (Lond). 31:1232-9.

Shai I, Jiang R, Manson JE, et al.(2006). Ethnicity, obesity, and risk of type 2 diabetes in women: a 20-year follow-up study. Diabetes Care. 29:1585-90.

Wen CP, David Cheng TY, Tsai SP, et al. (2009). Are Asians at greater mortality risks for being  overweight than Caucasians? Redefining obesity for Asians. Public Health Nutr. 12:497-506.




Lorna C. Hylledig Ed.D, MSPH, R.D, L.D

Comments

  1. Ashley ArcherApril 4, 2023 at 4:52 PM

    What a thought-provoking post! Thank you for starting a discussion on the flaws of the BMI metric! I personally think that the metric isn’t the best indicator of health, especially for individuals who have a muscular build or a lot of lean mass. Muscle mass is denser than fat mass and thus, weight gain is expected from lean muscle gains. So, in this context, individuals may have BMIs in the overweight or even obese ranges, yet have an excellent health status. However, I still think that BMI is a valuable tool for accessing the health status of individuals who have unhealthy lifestyles. Also, I loved your discussion of the social determinants of health! As a current med student, I have noticed that race continues to be medicalized in the medical field. I often see “blank disease occurs disproportionately in African Americans” on my lecture slides without an explanation of why. Access, systemic racism, and political systems don’t only relate to our social mobility, but they also may be important determinants of our health.

    ReplyDelete
    Replies
    1. Dr. Lorna HylledigApril 4, 2023 at 5:13 PM

      Ashley, thank you for your detailed comment and assessment of the topic!

      Delete
  2. EJApril 7, 2023 at 9:25 AM

    What I find interesting is that since race is a social construct, in theory, health outcomes associated with BMI should be fairly consistent across races for the same BMI category. As stated, it truly is these social and economic issues attached to each race that drive the trends in health outcomes and they highlight the major flaws in how we often measure healthiness. What's interesting on a personal level is, due to my muscular build, I have technically been in the "obese" range for my height for a while. It's often hard not to take the numbers at face value, but to understand what may be contributing to the numbers. Like many others, I've gotten caught up with strictly looking at these numbers and drawing conclusions from there, but there are so many other underlying factors contributing to what is considered healthy.

    ReplyDelete
    Replies
    1. AnonymousApril 7, 2023 at 7:21 PM

      EJ, thank you for your comment! Your example truly demonstrates the limitations of using BMI as an indicator. For persons who know you, we all know that you are not obese. You also do not appear to be overweight. However, your very muscular build does place you in that category. As I indicated in the additional recommendations for women, body fat content, fat deposition, and waist circumference should also be taken into consideration for predicting chronic disease risks. For men, a waist circumference of 40 inches and above is highly associated with risks for diabetes and other chronic disease risks. A rounded apple shape is also indicative of visceral obesity.

      Delete
  3. AnonymousJuly 2, 2023 at 4:41 AM

    Discussion presents a more realistic approach to utilizing the BMI to assess weight related chronic health conditions. Heredity and body type are also important considerations.

    ReplyDelete
    Replies
    1. Dr. Lorna HylledigJuly 28, 2023 at 9:33 AM

      Thank you for your comment! Yes, you are correct regarding the importance of heredity and body type.

      Delete

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