High cholesterol can be a very confusing topic for patients. It is important to discuss your test results with the physician who ordered the test, since he or she will know your history and how best to advise you regarding your specific results.
However, part of what can make cholesterol testing so difficult to decipher is the information that is and is not discussed in the popular media. First, you are absolutely correct that people who are overweight may have altered lipid metabolism. Yet cholesterol does not necessarily correlate with body weight. Certain aspects of our cholesterol levels are genetic--some people will have higher levels at baseline than others and this can put them at higher risk for cardiovascular disease which is why physicians do cholesterol screening tests.
Second, much of our cholesterol levels reflects what we eat. Even if you exercise regularly and maintain a healthy weight, if you eat foods that are high in cholesterol (eggs, meat, cheese, whole-milk products) you will likely develop high cholesterol. this can be particularly difficult for vegetarians since protein in a vegetarian diet often comes from eggs and dairy products.
Finally, there are different kinds of cholesterol in the body that are measured on cholesterol tests. While we would like LDL levels to be low (the so-called 'bad' cholesterol), a different kind of cholesterol called HDL has actually been shown to be beneficial for reducing cardiac risk factors when it is *high.* Exercise helps raise this level, so as a young adult who works out regularly, you may well have high HDL (and this is a good thing).