One of the ways obesity affects the cardiovascular system is that fat (cholesterol) builds up inside of the veins and arteries and clogs them, it can build up so much that it restricts blood flow and can even block blood flow. When you hear about someone getting stints put in or a bypass it is generally because of clogged arteries. Also fat can build up inside and outside of your heart, making it work harder to pump blood through the body. It can build up inside the abdominal cavity and crowd organs, cause insulin resistance which in turn can cause stroke, heart disease, and even some types of cancer.
Obesity affects the cardiovascular system and lymph system in that it leads to the accumulation of fats in the blood vessels. The disposal of fats alters metabolic profile which can affect the heart through its influence on risks like hypertension and glucose intolerance. Obesity and being overweight can also lead to other associated complications like heart failure, coronary heart diseases and sadden deaths.