NavigationHazard wrote:ranger wrote: (snip) If you burn 6000 calories a day, you can still eat 2500 calories and lose a pound of fat.
(snip)
No you can't. Even at moderate, so-called "fat burning" exercise intensities, a good deal of the necessary energy is going to come from carbohydrates. Here's a graph from a 2001 study of intensity's relation to energy source:
Plasma FFA in the graph refers to "free fatty acids," i.e. fat bound with blood-plasma protein albumin.
At a steady-state 55% of maximum workload these subjects were deriving maybe half of the necessary energy from fat burning and half from carbohydrates. I
think there's evidence out there suggesting that the percentage derived from fat maxes out at about 60% at around 65% of maximum workload. Even this leaves ~40% coming from carbohydrates.
At a 60/40 fat/carbohydrate ratio, to burn the 3500 calories that is the equivalent of 1 pound of fat will require a net exercise expenditure of 5833 calories. At 50/50 it's a whopping 7000 calories.
Well, you might add my basal metabolism in there, too, which would be about 1600 calories.
So, let's say I burned 4000 calories, 60% being fat, in my exercise, which makes 2400 calories from fat, and then a similar proportion of fat in my basal metabolism, which would add 960 calories. The total would be 3360 fat calories burned, pretty close to a pound. I am also active in other ways; I don't just sit around all day. These expenditures would also have to be added to the sum, making the total well over a pound of fat burned each day, if I watch what I eat and avoid fats almost entirely. For instance, I have just been out shoveling snow for an hour. Yesterday, I walked several miles all over campus getting tasks done in preparation for next semester.
The remaining 40% of the calories comes out to be almost exactly 2500, as I claimed, and I eat these back largely with carbohydrates.
Anyway, the proof is in the pudding, not the calculations, which are entirely hypothetical and unconstrained by fact.
Truth is: Doing what I am doing, eating as I am eating, I lose about a pound of fat a day.
I'll post a shot of my Tanita scale with my weight at 160 lbs. early next week.
ranger
Rich Cureton M 72 5'11" 165 lbs. 2K pbs: 6:27.5 (hwt), 6:28 (lwt)