As 2015 meta-analysis by Wang and colleagues shows that a vegetarian diet helps reduce cholesterol levels, reducing all types of cholesterol (both good and bad). One interesting finding was that the effect was muted for obese people. From one key section of the discussion:
Studies have shown that a 1-mmol/L reduction in TC and LDL-C levels results in a 26.6% to 29.5% decrease for any cardiovascular disease–related event.40 The average reductions of TC and LDL-C concentrations following a vegetarian diet intervention included in this meta-analysis were 0.36 and 0.34 mmol/L, respectively, which would correspond to a decrease in cardiovascular disease risk of about 9.0% to 10.6%.
Another 2016 "comprehensive meta-analysis reports a significant protective effect of a vegetarian diet versus the incidence and/or mortality from ischemic heart disease (−25%) and incidence from total cancer (−8%). Vegan diet conferred a significant reduced risk (−15%) of incidence from total cancer."