What is the Fat Burning Zone?

You’ve heard it before, but what does it really mean. In simple terms, when you exercise anaerobically (without oxygen present - weight training), you are burning primarily carbohydrates for energy. When exercising aerobically (in the presence of oxygen - walking or light jogging) you are burning primarily fat for energy.
There are 3 zones of training:
Zone 1= aerobic, 65-75% of heart rate max, walking or jogging (Fat Burning Zone)
Zone 2= aerobic/anaerobic, 80-85% heart rate max, group exercise class
Zone 3= anaerobic, 86-90% of heart rate max, sprinting, lifting weights

To figure out your heart rate max : 220-your age. Then times this number by the % of exertion and this is how you determine what zone you are in.
For example, take a 35 year old person.
220-35=185 heart rate max (185 beats per minute)
Zone 1 - 185x.65=120.25 beats per minute
Zone 2 - 185x.80=148 beats per minute
Zone 3 - 185x.90=166.5 beats per minute

The body burns a higher percentage of calories from fat in the ‘fat burning zone’ or at lower intensities. At higher intensities you burn a greater number of overall calories in a shorter period of time. All of the above zones have their place in fitness programs.
The easiest way to infuse intensity into your existing routine is to sneak some intervals into the aerobic workouts you already do. For example: If you walk now, start by warming up for 5 to 10 minutes, then try picking up your pace and running (so your breathing becomes heavy, but you’re not gasping for breath) for 30 seconds, then walk for 3 minutes, and so on. Do this 2 days a week. Before long, the running segments will feel easier, and you’ll be a speedier walker, too, which means more calories burned every time you exercise.