The ‘Lipid Overflow-Ectopic Fat Model’ of Metabolic Disorders!
Introduction
Fat around the belly (especially surrounding organs) is more of a concern as opposed to fat under the skin. Whereas, subcutaneous fat (fat under the skin) affords disease protection, preferential deposition of fat over the belly can be a problem!
Accumulation of excess visceral fat (fat in the abdominal cavity surrounding the viscera – the organs) is a marker of a dysfunctional adipose tissue, which is unable to appropriately store energy excess. How visceral fat causes metabolic derangement and therefore, disorders, is explained by researchers using the ‘lipid-overflow-ectopic fat model of metabolic disorders.
Lipid-Overflow-Ectopic Fat Model of Metabolic Disorders
According to this model, the body’s ability to cope with:
- surplus calories, resulting from excess caloric consumption,
- surplus calories resulting from a sedentary lifestyle or, as is often the case,
- acombination of both above factors, combined with a genetic predisposition to accumulate fat around the belly (Asian Indians), and
- presence of an ‘obesogenic’ environment (more about this is an upcoming post – article)
- Might, ultimately, determine the individual’s susceptibility to developing metabolic syndrome
Genetic Influence
There is evidence suggesting that:
- If the extra energy is channelled into insulin-sensitive subcutaneous (under the skin) adipose tissue, the individual, although in positive energy balance, will be PROTECTED against the development of the metabolic syndrome (See left column in the picture above). This is usually the case in most Caucasian populations (white folks).
- In cases where adipose tissue is absent, deficient or insulin-resistant with a limited ability to store the energy excess, the fat surplus will be deposited at ectopic sites (sites which don’t normally store fat such as the liver, the heart, the skeletal muscle and in visceral adipose tissue) — this is called ectopic fat deposition. This is what precisely happens in Indians.
Factors associated with a preferential accumulation of visceral fat and with features of insulin resistance include, among others:
- Smoking,
- Genetic susceptibility to visceral obesity (such as in Indians)
- A neuroendocrine profile related to a maladaptive response to stress
Take Home Message
The resulting metabolic consequences of this ‘defect’ in energy partitioning include visceral obesity, insulin resistance, an atherogenic (atheroma-forming) dyslipidaemia and a pro-thrombotic, inflammatory profile; these are all characteristic features of metabolic syndrome.
PS: Although definitions and diagnostic criteria vary, the simplest clinical criterion for diagnosing metabolic syndrome is the simultaneous presence of: increased waist girth, and raised fasting triacylglycerol levels, which together, have been termed the ‘hypertriglyceridaemic waist’.
So although, as an Indian, you may feel proud that our a typical Indian ‘square meal’ makes our nutrition one of the healthiest in the world and protects us from diseases and disorders, I wouldn’t be so sure. If you want to stay free of diabetes or heart disease (and other metabolic disorders), there’s more to it than just having the so-called ‘home-made, healthy, square meals’.
References:
- Jean-Pierre Després and Isabelle Lemieux. Abdominal obesity and metabolic syndrome. NATURE |Vol 444 | 14 December 2006
- Lemieux, I. et al. Hypertriglyceridemic waist. A marker of the atherogenic metabolic triad (hyperinsulinemia, hyperapolipoprotein B, small, dense LDL) in men? Circulation 102, 179–184 (2000).
About The Author
Dr. Deepak specialises in Sports & Exercise Medicine. He has previously worked in the UK (with top athletes, as well as reputed personalities from the entertainment industry..
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