What is the probability of an obese 23 year old having a heart attack?

Very: Rare. But now is the time to start reducing the risk factors that you can modify to prevent it in the future. Focus on diabetes management, weight control , BP control, cholesterol lowering and smoking abstinence. The only thing you can't change it the genetic card you were dealt.

Very low!: Congenital, anomalies can happen aortic root, aortic valvular disease aberrant coronary anomalous coronary origin but as another has noted: Cocaine and other drugs of abuse are more likely in your age group. If you are smoking, hypercholesterolemic, diabetic you have increased risk work on the risk factirs youbave, .