A 16 hours fast is so easily achievable that many probably do it without even knowing. If you stop eating by 8PM, and skip breakfast till lunch at noon. That's

A 16 hours fast is so easily achievable that many probably do it without even knowing. If you stop eating by 8PM, and skip breakfast till lunch at noon. That's a 16 hour fast. I've done that basically my entire adult life without even consciously thinking about it. These days I push it out to anywhere from 18-20 hours, and limit my calorie intake from 2pm-8pm. I've been slim my whole life, 175lbs at 6'1. Never get sick, last time I've been to the doctors was easily 20 years ago as a child. Haven't had an antibiotic since grade school. Cardio exercise daily, hiking mountains, no loss of energy.