How long into a moderate/high intensity cardio work out does the body begin to burn fat instead of glucose?

Question

I know with low intensity exercises, it targets fat reserves first. But I'm wondering how long it takes to burn fat during a moderate - high intensity cardio work out? I run on the treadmill a lot, and with my resting BPM probably hit a high intensity range for cardio. If I am running for 30 minutes, will I have targeted some fat cells? Or is it just burning glucose?

Answer 1

I am assuming that you want to lose weight, you need to be concerned with how many calories you burn compared to how many you take in. Once you have used your glucose stores your body will start to use fat.

To answer your question, your high intensity will burn glucose, but, once you get rid of these stores your body will burn the fat. Remember that if you exercise with low intensity and burn your fat stores and leave the glucose , your body will turn the glucose into fat. Exercise hard and watch your caloric intake.

Mike

Answer 2

Never
Never
Maybe
Probably

Here's what I can provide you regarding high intensity cardio-you won't burn any fat.\

Provided you run at a mild conversational pace, your body will burn glycogen for about 30 minutes before it starts to burn fat. If you start and continue a high energy cardio, the body will continue to burn glycogen until it runs out.

The answer to burning fat is LSD. Long Slow Distance. Once you get beyond the half hour, you'll burn fat for the rest of your workout. Remember, though, no 2 runs are exactly the same, and your body is not always in the same condition, so when/if/how soon your body adjusts to burn fat depends on many factors.

Good Luck

Answer 3

This is a difficult question to answer for the layman. This is truly a question for an exercise physiologist. All I can offer is my personal experience. For me, I think it happens around the 4 mile mark. I usually train by running 7.5 to 8 min. miles. I could be "all wet" but my body feels like it is getting energy from another source about the four mile mark. I'm not sure if it is just psychological or physiological. I apologize. That is the best I can offer. Maybe someone more knowledgeable will answer.