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Fat burning vs. sugar burning stumper?(5 posts)

Fat burning vs. sugar burning stumper?rpicayo
Aug 26, 2001 8:57 PM
I heard/read that 60-85% of your max heart rate is your "target" heart rate zone. If you exercise at 60% then your body burns a higher percentage of fat than when you body is at 85% of the max heart rate. At 85% your body cannot get energy fast enough from your fat stores so it taps into the sugar supply (glycogen I believe) in the liver. OK, now the question.

When you stop exercising where does the energy to replace the sugar in your liver come from? From the fat stores? From the next meal you eat (thus taking calories that could be stored as fat)? Either case it seems not to matter whether you exercised at 60 or at 85% because in the latter case the glycogen would eventually have to be replaced right and that would come at the expense of fat, right? Or is there another way?

What's the deal? Is it hype?

Aug 27, 2001 6:12 AM
at lower intesities you do burn a higher percetage of fat, but at higher levels you burn a higher # of calories--some of which are fat calories and often this means you burn MORE fat. Still you shouldn't assume that you should ALWAYS train at high intensities. Training at all levels--and especially endurance (lower) levels allows your body to adapt to using fat as a primary fuel over the long haul. If all you do is intense exercise your body will only use the most available fuel which is glycogen or simple sugars. Not really that simple but this is the basic theory.
Glycogen replenished in first hour after ride, and fat...PdxMark
Aug 27, 2001 8:32 AM
From what I've read, you can best replenish depleted glycogen by eating complex carbs during the first hour after a workout. The theory is that during that first hour, your body is still "thinks" its in a workout (ok, that's not the technical way of putting it), and will efficiently convert complex carbs to glycogen. Apparently, after that first hour, your glycogen stores are replenished much more slowly in the "normal" way, whatever that is... Also, you'll want protein post-workout too for rebuilding muscles.

As for the amounts of fat burned at different heart rates, books talk about lower hear-rate levels being "fat burning zones, but if you look at the detailed tables, it seems that the same amount of fat is burned at all heart-rate levels. It's just that as calories burned go way up at higher heart rates, the numbers of calories from carbs (glycogen) shoot up. My sense of the "fat burning zones" ias that they refer to the PROPORTION of calories burned (much higher proportion of calories from fat at lower levels), but the total fat calories burned are almost constant at all workout levels.
they slightly dropcyclopathic
Aug 27, 2001 8:54 AM
from what I read slow twitching fibers are the fat burners and fast consume glycogen. At certain point shift occurs and slow fibers produce slightly less, less oxygen more competition from fast fiber.
re: what's the question?cyclopathic
Aug 27, 2001 8:47 AM
sugars come from what you eat. Assuming you eat as much as usual it would come up at the fat expense.

The reality is that you'll also eat more (more insulin production) and you'd gain more fat.

What is your primary objective? Do you wanna loose fat? then you'd better off riding Zone 2 centuries. If your objective is to train for crits and short 1-2-3hr events then aerobic training is not gonna make you much faster (with the exception of lost weight effect).

Usually training programs address both aspects (aerobic and anaerobic) with aerobic going first (it takes longer time to build it and it lasts longer) then anaerobic to prepare for specific events (effects of anaerobic training last about 6-8weeks). Doing intervals without proper aerobic base is waste of time IMHO