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Obesity diagnosis

Is BMI the only criteria to determine surgery?

Diagnosis of metabolic syndrome is independent of BMI

Whether BMI is an appropriate measure to determine obesity has been debated for a number of years. In particular, it has been argued that different parameters be taken into consideration for measuring obesity, specifically in the Asian population. Speaking at the recent European Obesity Experts Meeting in Saalfalden, March 2010, Dr Shashank Shah, Hiranandani Hospital, India, said that in Asian patients not only should BMI cut–offs be lowered, but also different factors (such as body fat) should be taken into consideration for measuring obesity. 

“Therefore, today we should not only identify obesity but metabolic markers as well”
Shashank Shah

Shah began his presentation by asking whether BMI is the ‘only’ or ‘primary‘ criteria to determine bariatric/metabolic surgery cut offs and if a patient presents with a BMI35/40 with a co-morbidity, is it ‘clinically meaningful’? “Perhaps in today’s world it is time for a new consensus!” said Shah.


“We have seen a change from bariatric to metabolic surgery, this was brought about by understanding that weight loss was also combined with metabolic restoration,” he added. “Therefore, today we should not only identify obesity but metabolic markers as well.”


He then asked whether morbid obesity and severe obesity were the same and cited the example of two patients: the first was classed as having obesity with 35% body fat and a BMI52; the second patient was classed as having adiposity with 49% body fat and a BMI31. According to Shah, the two cases mentioned above highlight the limitations of using BMI as the only indicator. By definition, metabolic syndrome is a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes. However diagnosis is independent of BMI. 


BMI studies


Moreover, he also stressed that BMI is a poor measure of central obesity, it does not measure body composition, is gender independent and does not take into account genetic ethnic difference. For example, he cited the research by Patel et al (Diabetic Medicine. 1999;16;853-860) who assessed whether four proxy measures of abdominal obesity (waist circumference; waist-to-hip ratio [WHR]; waist-to-height ratio; and C index, a measure of body shape) were uniformly associated with features of the metabolic syndrome (triglycerides, high density lipoprotein (HDL) cholesterol, 2-h glucose) in three ethnic groups.

They collected anthropometric and biochemical data from 629 Europeans (320 men, 309 women), 380 Chinese (183 men, 197 women) and 597 South Asians (275 men, 322 women) aged 25–64 years in Newcastle upon Tyne, UK. Linear regression models were used to determine whether relationships differed between ethnic groups.


A linear regression analysis showed that most proxy measures of abdominal obesity were associated with features of the metabolic syndrome. There were significant interactions between WHR and ethnicity and C index and ethnicity in the relationship with log triglycerides when comparing European and Chinese women. Interactions existed between all proxy measures and ethnicity in the relationship with log triglycerides and HDL cholesterol when comparing European and South Asian women.

In men, interactions between ethnicity and waist circumference, WHR and C index when comparing Europeans and South Asians, and between ethnicity and WHR and C index when comparing South Asian and Chinese for log 2-h glucose were significant (p<0.001). All interactions remained significant when differences in smoking, alcohol and physical activity were taken into account.


Therefore, Patel and colleagues concluded that not all the proxy measures of abdominal obesity were consistently related to features of the metabolic syndrome across the ethnic groups studied. However, waist circumference and waist- to-height ratio were the most consistent and WHR the least when comparing across the ethnic groups.


In February 2009 the Association of Physicians of India (JAPI) published a consensus statement for the diagnosis of obesity, abdominal obesity and the metabolic syndrome for Asian Indians and recommendations for physical activity, medical and surgical management. These differed from those offered by the World health Organization (Table 1).


Table 1: Comparison of definitions of WHO and JAPI

BMI Status World Health Organization Consensus statement: 2009
Normal BMI 18.5 - 24.9 kg/m2 18.0-22.9 kg/m2
Overweight 25.0 - 29.9 kg/m2 23.0-24.9 kg/m2
Obese >30 kg/m2 >25 kg/m2

The consensus also concluded that BMI was gender independent as a result of the different body composition of males and females, particularly different waist circumference and differences in body fat percentages.

“For example, an Indian is likely to have 5% more body fat than a Caucasian, even if they both have a BMI of 22. “Furthermore, 20–22% fat should be considered normal for Indian women, while 7–15% is normal for Indian men. There are clear and significant differences between the sexes and between ethnic groups,” said Shah.


Towards a new consensus – diabetes surgery


“Bariatric surgery has evolved and more procedures are now being performed laparoscopically and there are also new types of surgery or procedures (sleeve gastrectomy, duodenal switch etc),” said Shah. “In addition, the incidence of diseases has increase as well as incidence of obesity and T2DM, leading to a greater understanding of bariatric and metabolic conditions, and populations (diabesogenic). We are now entering the era of ‘diabetes surgery’.”


He added that all surgical studies that have included patients with T2DM and a BMI<35kg/m2 have reported encouraging results, and these were reflected in the American Diabetes Association guidelines (2009):
“Bariatric surgery should be considered for adults with BMI35kg/m2 and T2DM, especially if the diabetes is difficult to control with lifestyle and pharmacologic therapy. 


"In order to treat a patient with T2DM who presents with a BMI>32, more clinical studies required” Shashank Shah

Although small trials have shown glycemic benefit of bariatric surgery in patients with T2DM and BMI30–35kg/m2, there is currently insufficient evidence to generally recommend surgery in patients with BMI35kg/m2 outside of a research protocol. 


"The long-term benefits, cost effectiveness, and risks of bariatric surgery in individuals with T2DM should be studied in well-designed randomized controlled trials with optimal medical and lifestyle therapy as the comparator,” he added,


Conclusion


“So what of the two patients I mentioned early in the presentation? You will remember the first was classed as having obesity with 35% body fat and a BMI of 52; and the second patient was classed as having adiposity with 49% body fat and a BMI31,” he said. “Well, the first patient has uncontrolled diabetes, hypertension and underwent angioplasty a year ago. He continues to suffer from breathlessness and has had repeated ICU admissions. The second patient required no treatment for diabetes or hypertension. and can now can walk few kilometres per day.”


“What do we surmise from this? That in order to treat a patient with T2DM who presents with a BMI>32, more clinical studies required,” he concluded. Shah urged attendess to address and treat this group of unrecognised patients who are grossly under-treated.


For additional information, please see the 'View Point' article in the Febraury 2010 edition of BariMD.

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