Bogalusa Heart Study - a 40 year study investigating the early natural history of coronary artery disease and essential hypertension. This type of long term cohort study was pioneered by the Framingham Heart Study which began in1948 and is now on its third generation of participants. Such studies have generated literally thousands of papers and have helped to unravel and quantify the contribution of various risk factors to heart disease.
In class Claudia mentioned BMI (online calculator here). Someone mentioned how broad the categories were (for my height even the normal category covers a 50lb range from 144 to 194lb). Which is a very good point - putting people into three categories: normal, overweight and obese is about the crudest measure we could use. However it is a simple measure that is easy to calculate.
There are other more complicated measures of health that use more information and express the outcome as risk rather than just 'good' and 'bad'. For example one of the classic outcomes of the Framingham heart study has been the development of the Framingham risk score - which expresses your 10-year risk of developing cardiovascular disease. This number can then be compared to the mean for people you age. Your values will all be very low because you are young. If I put my values in I get 2%, which is slightly alarming until you compare it to the average for men 40-49 which is 11%. Yikes.
Other risk score calculations are available at the Framingham Heart Study website.