The fat burning zone is a term developed from research to improve the performance of endurance athletes. It's unfortunately construed by the non-informed as something to do with weight loss. I'm constantly running into this misconception with friends and acquaintances and it's difficult to convince them otherwise.

Weight loss is simply the difference in calories burned vs the calories consumed.

Walking burns more calories per mile than jogging, but jogging burns more calories per minute. You take your choice depending whether you take the time or the make effort IF weight loss is your only goal.

Both Spark and Younger Next Year which deal with reducing age related decay, recommend spending some time each week at the high heart rates or in the very high carb, low fat burning zone. They both recommend using heart rate monitors. The reason is the amount and types of chemicals released into the bloodstream.

Higher levels of fitness accomplished by activity at high heart rates (> 80% (?) of measured max) reduces mortality rates over sedentary folks by a factor of 5. Lesser fitness, then higher mortality rate. That's from Physical Activity and Health (p150), Cooper institute data from 25, 341 men .

In other words, if you are at the top of your fitness level, your risk of dying from all causes at any instant is 1/5 that of a sedentary person.

I personally make sure I spend time above 85%. Sometimes if I feel really into it or when riding with a fast friend, I'll spend almost a whole ride above 80. Two weeks ago I spent 1 hour 21 minutes above 80 and 21 minutes above 85. That was on a 19 mile single track with a total ride time around 1 hour 43 minutes. Post ride and the next day you seem to have extra high energy.

Al