Take the Real Age Test and find out. It's tough but if you're very honest about your answers the result is a thorough analysis of your overall health. It gives easy to follow advice on ways you can improve on your lifestyle and diet. The results are the same if you ask for follow up emails or not, so don't worry about lots of advertising clogging your inbox.
I just found out I'm three years younger than my chronological age and they gave me lots of ways to improve on that. It's encouraging to hear about what you're doing right for once. Now I need to start flossing and eating more vegetables everyday.