Question: when you are fat why does your blood vessels malfunction

Majid Ahmed answered on 15 Mar 2016:

Sorry for the delay in answering your question. It’s a very good question.

We don’t fully understand why blood vessels malfunction when people become obese. Research has shown that adipose tissue (fat) does a lot more than simply store fat. It also release hormones which can affect our bodies in many ways. One of these hormones (leptin) affects the way our brain interprets whether we are hungry and our eating habits. Another hormone affects the way our body uses sugar in our blood and the way we store sugar (it affects insulin signalling which you may or may not have covered in school). Additionally, most blood vessels are surrounded by a special type of fat called ‘perivascular adipose tissue’. Many of the hormones released from this special fat and the ordinary fat located throughout the body can have a direct affect on the cells within the blood vessels. So I hope you can see here that fat is a lot more complicated than we previously thought and it has a pretty substantial effect on blood vessels.

Now when we are healthy, the fat is beneficial because it dilates (opens) our blood vessels keeping our blood pressure low/normal and the fat also stimulates insulin signalling keeping our blood sugar levels regulated. When people are obese, the nature of the fat changes and it becomes what we call ‘pro-inflammatory’. This means it is in a state of inflammation (like when you hurt yourself and the area becomes swollen) where other things will be released which have a negative effect on our bodies and our blood vessels. The amount of the good hormones which dilate our blood vessels and keep our blood sugar levels regulated are reduced and this has a negative effect. So I hope this helps you to understand that when we are healthy the fat is good and helps the blood vessels to deliver blood to all the organs and tissue throughout the body; but when we are obese the fat becomes pro-inflammatory and it begins to have a negative effect on the body and the blood vessels.

I should also say this is not the only way that fat has a bad effect on blood vessels. The endothelium is the layer of cells on the inside of all blood vessels (see my profile for a picture). It has been found that these cells don’t work properly in obese people compared to healthy people. Part of the reason for this is due to the changes in the hormones released from the surrounding fat, but we don’t yet fully understand the vary different effects becoming obese has. My PhD is looking at these cells and how they act in obese people compared to healthy people.