I came across something interesting in the Tissues chapter of my Anatomy & Physiology textbook (Introduction to the Human Body by Tortora & Derrickson). In a section about adipose tissue, commonly known as fat, it has this to say about why obese people frequently have high blood pressure:
As the amount of adipose tissue increases with weight gain, new blood vessels form. Thus, an obese person has many more blood vessels than does a lean person, a situation that can cause high blood pressure, since the heart has to work harder.
So, fat cells are a type of tissue that is capable of “growing” more blood vessels as they increase.
I have to admit that this wasn’t something I’d given much thought to before. I’d assumed that high blood pressure was generally due to the strain on the heart from carrying more weight in general!