From a 45 year vegetarian: with a balanced diet enhanced by an awareness of bodily needs (craving broccoli for instance) it can be done-I have a resting heart rate of 55, BMI of 22.5% can walk @ 3.2MPH.. (76 this year) What I don't like is all the hormones and antibiotics used to fatten up cattle-the growth hormones seem to have reduced the age of of moon cycle of girls and the antibiotics have made some bacteria drug resistant.. Strict organic standards met, I might even eat a burger!!