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What is obesity, morbid obesity, and what does it mean for a person’s health….?

What is obesity, morbid obesity, and what does it mean for a person’s health….?


Quite simply obesity is the presence of excessive adipose tissue (fat) in the body. Morbid obesity means the person has disease or diseases (morbidities) which are associated with the storage of excessive fat. WHO classifies morbid obesity as a BMI (body mass index) of 30 or more. There are further subclassifications including class 1, class 2, class 3 morbid obesity, and super morbid obesity. These will be discussed in further detail in subsequent articles but for now I will elaborate upon obesity in general terms.


I should first note that the BMI, whilst the current gold standard measurement, does indeed have limitations. BMI is calculated by dividing your weight (kg) by your height (m) squared. A normal or healthy BMI is in the range 19-25. The overweight range is BMI 26-29 and a person is considered obese if their BMI is greater than 30 as previously mentioned. Limitations of the BMI are due to the formula not taking in to account different body types and also ethnic differences. For example the BMI overcalls obesity in Pacific Islanders as they have, in general, larger muscle mass and bone mass and similarly under calls obesity in Asian populations who again, in general, have lower bone density. What does this mean? It means a person of Asian ethnicity may have an apparently “normal” BMI but be subject to significant metabolic ill health. Similarly a Pacific Islander may have a BMI of 29 or even 31 but be in good health.  This is not to say however that a Pacific Islander who is overweight or obese by BMI criteria will not have metabolic consequences, just that the BMI should be viewed in the context of a number of factors, including ethnicity.


Another very telling anthropometric measurement is the AWC (abdominal waist circumference). A measurement in males of more than 92 cm indicates an increased risk, and more than 102 cm a greatly increased risk, for chronic disease including diabetes, hypertension, obstructive sleep apnoea, cardiovascular disease and numerous cancers, amongst others. For females the measurements are 80 cm and 88 cm respectively. This is because the AWC reflects fairly well the burden of visceral fat in the abdominal cavity. This is fat in (infiltrating) and around the abdominal viscera (organs). Most notably the liver and pancreas when subject to this burden of fatty deposits develop into disease states such as fatty liver disease and diabetes. These disease states will be further discussed in later posts. The way in which fat is deposited in males is particularly bad for the health of the individual and is known as truncal obesity. I see this frequently when operating on males. The classic “beer gut” seen in truncal obesity often correlates with a very thin (attenuated) abdominal wall musculature and a gross burden of visceral fat. The view in the male peritoneal cavity in this context is often a sea of yellow fat. The liver is large, distended and non compliant and nutmeg brown, rather than a healthy, compliant, deep purple. This is due to infiltration of fat into the liver tissue. The consequence of this yellow fatty deposition is to turn the liver nutmeg brown. There are often severe metabolic consequences associated with fatty liver disease. Conversely typical female pattern fatty deposition is predominantly corporeal fat, seen in the abdominal wall, hips, thighs and breasts. There is often significantly less visceral fat in the female with a BMI of 40 as compared to the male BMI 40. This is of course a generalisation and a spectrum of fat deposition patterns exists. Either way the impact on a person’s metabolic health is significant. Conversely, and fortunately, reducing the burden of fat similarly reduces the burden of obesity related disease and improves a person’s metabolic health. The typically correlates with an improved quality of life and increased longevity.  Put simply…a healthier, happier and longer life.