Posted on Jan 11, 2019, 6 p.m.
Type 2 diabetes and other diseases related to the growing global epidemic of obesity may depend on how the body stores excess energy, according to Mary Jane West-Eberhard evolutionary biologist.
She describes her theory on fat inside the abdominal cavity as the VAT prioritization hypothesis, as published in the Proceeding of the National Academy of Science. According to her theory pathogenic obesity is an advantageous process gone awry; early in life the body decides where to store fat, making sense for poorly nourished fetuses to invest in VAT rather than under the skin as VAT evolved to protect us from infections. This early body choice can lead to disaster later in life with access to too many calories later in life.
Over 300 million are affected by obesity associated diabetes, and heart disease is a leading killer; both involve chronic inflammation. The Smithsonian Tropical Research Institute emeritus scientist chooses to take a wider look at obesity in direction and asks how the body makes decisions about where to deposit fat and why; as she explains “trying to understand obesity without understanding the structures that become obese is like trying to understand circulatory diseases without knowing functions of the heart”.
Visceral fat can be referred to as an abdominal policeman and band-aid; surrounding the small intestine to help defend the body from ingested toxins and pathogens. The omentum hangs off the membrane lining of the abdominal cavity and sticks to wounds, foreign objects, and infection sites like a bandage; surgeons sometimes use pieces of omentum to control severe postoperative infections.
Visceral fat tissue evolved to help fight visceral infections, and provides a causal hypotheses on how high fructose sweeteners and saturated fats contribute to chronic disease, influencing intestinal microbiome, making the intestinal walls more permeable and releasing more toxins into the bloodstream, stimulating the visceral immune system potentially leading to chronic inflammatory disease, explains West-Eberhard.
West-Eberhard proposes in fetuses subject to nutritional stress more energy may be stored as fat around the abdominal organs rather than subcutaneous fat, noting that childhood catch up growth may be a better predictor of obesity associated disease than birth weight, which could be a sign of mistake the body made assigning energy to VAT, producing apple shapes of abdominal obesity rather than pear shaped lower body fat distributed more evenly under the skin around the hips, thighs, and buttocks.
A dangerous feedback loop can develop among overweight populations involving increased VAT leading to increased chronic inflammation, contributing to increased insulin resistance, further leading to increased VAT storage and increased susceptibility to disease; ability to produce insulin is eventually reduced, which may result in need of injections to control type 2 diabetes.
Modern diets available on a global scale combined with early malnutrition is leading to situations that are toxic for individuals in many different cultures. Apple body shape vs pear is based on the way the body allocates fat, according to West-Eberhard.
In the future West-Eberhard would like to see more research revealing fetal cues which turn on VAT storage, role of the omentum, disease resistance in obese individuals, development of the visceral immune system, and the capabilities of population of different geographic and ethnic origins to allocate fat differently.
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