martes, 17 de diciembre de 2019

Why is Visceral Fat Dangerous?

Download PDF Copy

By Sara Ryding, B.Sc.Reviewed by Dr. Jennifer Logan, MD, MPH

Visceral fat is fatty tissue that surrounds the organs and is different from the subcutaneous fat that is often more visible around the arms or legs. Visceral fat tissue has been linked to metabolic and chronic inflammatory disorders, thereby earning it the reputation of being dangerous.

Image Credit: Sebastian Kaulitzki / Shutterstock.com

Visceral fat’s role

Healthy visceral fat is white adipose tissue that is stored in the abdominal cavity. However, increased visceral fat deposits associated with obesity are linked to metabolic disorders and inflammation, where changes in visceral fat can increase the chances of developing metabolic syndromes.

Visceral fat and health disorders

Obesity and health complications can have a clear link, but this can differ depending on the distribution of fat tissue. Diseases related to obesity can have varying severity depending on this distribution, with high visceral fat associated with severe disorders such as glucose intolerance, hyperlipidemia, and insulin resistance.

Links have also been reported between visceral fat tissue accumulation and high blood pressure in women. Similarly, monitoring of hypertensive people revealed that visceral fat reduction, but not subcutaneous fat reduction, was strongly correlated with blood pressure reduction.

One aspect that has not been investigated to the same extent is the relationship between visceral fat tissue and adipose tissue. Some evidence shows that with higher levels of visceral fat accumulation, plasma levels of adiponectin are reduced. The mechanism is unknown, but evidence suggests inhibiting factors for adiponectin synthesis are secreted by visceral adipose tissue.

Interestingly, some evidence suggests the decreased levels of plasma adiponectin may be partly responsible for the insulin resistance often associated with visceral fat accumulation.

Although links between obesity and cardiovascular disorders may seem more intuitive, evidence also suggests visceral fat obesity can affect the brain’s neurology and atrophy, which is the loss of neurons and neuronal connections. The effect occurs through the detrimental cardiovascular effects visceral fat obesity can have, particularly targeting grey matter.

However, it should be noted that such studies included subjects with histories of other factors known to affect the cardiovascular system, such as smokers or frequent alcohol consumption, or even cardiovascular disorders, such as hypertension, which may confound the results of the study.

Detection and treatment

Visceral fat tissue can be difficult to diagnose due to its internal distribution. Some methods use CT scanning, where the area of visceral fat tissue is determined and treatment strategies are developed based on the area the fat covers. In Japan, visceral fat tissue over 100 cm2 is treated.

More basic measurements, such as those of BMI and waist to hip ratio, have also been used. BMI is considered indicative of peripherally stored fat, whereas waist to hip ratio is believed to indicate visceral fat deposits. For men, central obesity is indicated by a waist to hip ratio greater than 0.9, whereas central obesity is diagnosed for women with a ratio of greater than 0.8.

As highly multifaceted disorders, metabolic disorders are difficult to treat through just one avenue. Treatment methods vary, with lifestyle changes typically being the first method of intervention. However, as visceral fat accumulation can be just one aspect of a larger problem, lifestyle changes can be less effective, and drug treatment may be necessary.

For some disorders, it can be difficult to know what is the cause and what is the effect. For example, while obesity has been linked to reduced grey matter brain volume, it is unknown whether obesity drives brain atrophy or whether damage induced by atrophy drives obesogenic behaviors such as appetite and satiety regulation. Therefore, treatment becomes difficult as it is hard to ascertain cause and effect.

References

Matsuzawa Y., et al. (2011). The concept of metabolic syndrome: contribution of visceral fat accumulation and its molecular mechanism. Journal of Atherosclerosis and Thrombosis. https://doi.org/10.5551/jat.7922
Hamer, M., and Batty G.D. (2019). Association of body mass index and waist to hip ratio with brain structure. Neurology. https://doi.org/10.1212/WNL.0000000000006879
Batra A. and Siegmund B. (2012) The role of visceral fat. Digestive Diseases. https://doi.org/10.1159/000335722