I am curious, basically, if fat is a draw on the cardiovascular system when under load.

Or does fat just "go along for the ride," and it only burdens the system in the sense of being dead weight to carry?

My gut instinct is that muscle would be more vascularized than fat. Even if it isn't, the function of fat is to store energy, while the function of muscle requires using energy, and also requires more oxygen supply to support the use of that energy, so if someone has gained a lot of lean muscle mass while losing fat, without adjusting their nutrient intake, I would think it's possible to develop anemia...especially if their iron intake was just borderline sufficient in the first place (if they had been consuming excess already, it might not matter).

No, adipose tissue is not very vascular.

It is vascularized. During exercise, the blood flow gets shifted. Blood flow goes to the skin to vent off excess heat. It goes to the working muscles and heart. Blood flow tends to really drop for other part of the body like the gut and so on. Fat like the gut, would take up some but very, very little.

According to Wikipedia: "Adipose tissue contains many small blood vessels."

https://en.wikipedia.org/wiki/Adipose_tissue

If it weren't vascularized, it would die. But, being mostly inactive and not requiring lots of oxygen, it's minimal, thus allowing procedures like liposuction to be relatively safe.

Fat is pretty vascular, not as much as muscle, but still there. As mentioned above there is some shunting with exercise, but that mostly is from the internal organs. As you warm up, there will be increased blood supply to the skin, which is lined by fat, so there really is not a tremendous amount of shunting from fat. Depending on how deep the fat is, it can be quite vascular. I have seen some tremendous size vessels supplying the fat stores of some big folks.

I agree that fat has some vascularization, but disagree with conveying that liposuction is relatively safe. Liposuction is extremely risky in the short and long-term, (for so many reasons), and from my understanding, liposuction doesn't make biological sense.

If you are looking for the adverse effects of fat, I think there might be other impacts to consider:

Fat makes it harder for body to cool off and you reach the point quicker when body overheats and shuts down to protect itself.

If it is really a lot of extra fat it becomes very hard to do ~90+ RPM, which is needed to maintain high power for long time.

Sexual organs are made of adipose tissue. Just saying.

Brown fat has mitochondria, so probably more vascular

It's vascularized, of course.

The amazing rule of thumb is that one pound of fat generates SEVEN MILES of new blood vessels. (Amazing facts about your heart health and blood sugar - New York Healthy diet | Examiner.com). While it is true that much of the blood supply is preferentially shunted to working muscle during strenous exercise, this likely does but some burden on the heart to continue to pump blood through these vessels, in addition to increasing the workload (and oxygen demand) of the working muscles just because of the additional weight being moved.

Guess I shouldn't have had that cookie at lunch after all...

Doug
A Douglas Felts, MD, FAAFP

I read a long time ago that a pound of fat has 7 miles of blood vessels.

By "a long time", do you mean 3 hours and 12 minutes ago?