Please Scroll Down to See Forums Below 
OXANDRIN
New member
The "theory" is that one utilizes mostly fat cal's by doing cardio in the AM since glycogen stores are at a daily low.
This belief is then extrapolated by some (most?) to "one will lose more fat if cardio is done in the AM as opposed to some other time in the day," Implying that 20minutes on the stair master, if done in the AM, will cause more over-all fat loss than if that same 20 min is done some other time.
I have two problems with this reasoning..
The most obvious, it violates the first law of thermodynamics.. Burning 500 cals on the stairmaster is burning 500 cals on the stairmaster, no matter when it is done.
Here is where most will say "yeah, but more of those cals are coming from fat instead of sugar when cardio is done in the AM.
However, if one really wants to get to the nitty gritty, let's say I do my cardio in the afternoon instead of the evening.. I'll even EXTEND the popular belief and say that 100% of my calories came from carbohydrate stores (obviously, this doesn't happen). Now, I eat my normal balanced carb meal. The carbs ingested will replace the glycogen lost during the cardio. The comparison in this hypothetical situation is the same person who has already done his AM cardio.. His glycogen stores (hypothetically) are rather full.. He is more likely to store some of the carbs as fat than am I since my glycogen stores are lower, albeit I am no further ahead of him since he has already expended a portion of cal's from his AM cardio..
In other words, I'm just restating the first law of thermo... The generalization is, if one eats 3000 cals and expends 4000cals, he WILL LOSE WEIGHT, no matter how the cals enter or leave the system. Physiologically, this isn't entirely accurate, as macronutrient profile (etc) will indeed play a role. However, for this discussion, let's assume we're talking about BBers with reasonable eating habits.
The second argument I have against the idea that "AM cardio is better" is a question on the validity of the "greater % of fat burned when glycogen stores are empty" statement. This goes hand in hand with the belief that "slower cardio=more fat loss."
(the following was adapted from BIOCHEMISTRY, Stryer)
Marathon runners consume about equal amounts of glycogen and fatty acids.. If their fuel came from fatty acids entirely, the 2hr run would take more like 6hrs. However, the glycogen stores in the body are not sufficient to provide energy for the race.. Low blood sugar triggers production of glucose (from amino acids) that is needed for such an event.
This is interesting since the aim of BBers is to lose fat without losing muscle.. This is why many won't do high intensity cardio.. However, when glycogen stores are low (as in the morning) it's reasonable to believe that the body will lose more amino's to gluconeogenesis than when the cardio is done another time.. How significant is it? Not very, in my opinion.. Just as the difference between fat loss from AM cardio compared to cardio any other time of the day is also not significant (also my opinion).
Andy13 posted this a while back
This belief is then extrapolated by some (most?) to "one will lose more fat if cardio is done in the AM as opposed to some other time in the day," Implying that 20minutes on the stair master, if done in the AM, will cause more over-all fat loss than if that same 20 min is done some other time.
I have two problems with this reasoning..
The most obvious, it violates the first law of thermodynamics.. Burning 500 cals on the stairmaster is burning 500 cals on the stairmaster, no matter when it is done.
Here is where most will say "yeah, but more of those cals are coming from fat instead of sugar when cardio is done in the AM.
However, if one really wants to get to the nitty gritty, let's say I do my cardio in the afternoon instead of the evening.. I'll even EXTEND the popular belief and say that 100% of my calories came from carbohydrate stores (obviously, this doesn't happen). Now, I eat my normal balanced carb meal. The carbs ingested will replace the glycogen lost during the cardio. The comparison in this hypothetical situation is the same person who has already done his AM cardio.. His glycogen stores (hypothetically) are rather full.. He is more likely to store some of the carbs as fat than am I since my glycogen stores are lower, albeit I am no further ahead of him since he has already expended a portion of cal's from his AM cardio..
In other words, I'm just restating the first law of thermo... The generalization is, if one eats 3000 cals and expends 4000cals, he WILL LOSE WEIGHT, no matter how the cals enter or leave the system. Physiologically, this isn't entirely accurate, as macronutrient profile (etc) will indeed play a role. However, for this discussion, let's assume we're talking about BBers with reasonable eating habits.
The second argument I have against the idea that "AM cardio is better" is a question on the validity of the "greater % of fat burned when glycogen stores are empty" statement. This goes hand in hand with the belief that "slower cardio=more fat loss."
(the following was adapted from BIOCHEMISTRY, Stryer)
Marathon runners consume about equal amounts of glycogen and fatty acids.. If their fuel came from fatty acids entirely, the 2hr run would take more like 6hrs. However, the glycogen stores in the body are not sufficient to provide energy for the race.. Low blood sugar triggers production of glucose (from amino acids) that is needed for such an event.
This is interesting since the aim of BBers is to lose fat without losing muscle.. This is why many won't do high intensity cardio.. However, when glycogen stores are low (as in the morning) it's reasonable to believe that the body will lose more amino's to gluconeogenesis than when the cardio is done another time.. How significant is it? Not very, in my opinion.. Just as the difference between fat loss from AM cardio compared to cardio any other time of the day is also not significant (also my opinion).
Andy13 posted this a while back
