I've been working out for at least 30 years and always found it funny that some guys spent hours in the gym. In high school I worked out for an hour at a time max. Today, I work out for 1/2 hour cardio 1 to 2 times per week and lift 1/2 hour 45 minutes 2 to 3 times per week if I'm lucky. The last 2 years I've changed my eating by decreasing my caloric intake and I have lost 10-15 pounds. I have always done a very high impact cardio work out like hitting the heavy bag or kickboxing. This works all the super fast muscle fibers and gets your heart rate up quickly. Start out slow and work your way up to 30 minutes.