The portal hypothesis describes a possible mechanism for some of the health effects of

obesity Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...

, particularly the

metabolic syndrome Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Metabolic syndro ...

. It says that obesity (especially visceral obesity) results in increased circulation of

free fatty acids In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...

and thus, via Randle's effect, in

insulin resistance Insulin resistance (IR) is a pathological response in which cells in insulin-sensitive tissues in the body fail to respond normally to the hormone insulin or downregulate insulin receptors in response to hyperinsulinemia. Insulin is a horm ...

. The word "portal" refers to the hepatic portal circulation from the digestive system to the liver. The portal-visceral hypothesis is a replacement for the earlier "portal hypothesis", which said that visceral obesity leads to an increase in fatty acid levels specifically in the portal vein. Later research did not favor the portal hypothesis. It was determined that liver fat accumulation, as opposed to total visceral fat, was correlated with reduced insulin sensitivity and increased VLDL. Additionally, most of the free fatty acids reaching the liver via the portal vein do not originate in visceral fat, rather they are generated largely by abdominal subcutaneous fat. The later adipose tissue expandability hypothesis hypothesizes that the cause of type 2 diabetes is not obesity, but reaching the limit of what an individual's adipose tissue is able to store. This capacity limit varies between individuals and can be very low for people with

lipodystrophy Lipodystrophy syndromes are a group of genetic or acquired disorders in which the body is unable to produce and maintain healthy fat tissue. The medical condition is characterized by abnormal or degenerative conditions of the body's adipose tissu ...

References

Diabetes Medical conditions related to obesity {{endocrine-disease-stub