Well here's what I've been considering Justin...ever notice how much easier it is to lift weights or do cardio all amped up on caffeine and ephedrine? And alot of that comes from the neurological priming that stimulants provide...they allow the nervous impulses to travel much more efficiently from brain to muscle and back, your whole nervous system is revved...you have a higher firing rate of the signal and you recruit more motor units when the signal reaches the muscle. These things are all pretty much related to there being more "charge" in your wiring. It would seem to me that lifting weights or taking steps would be much more calorically efficient if your electrical sytem was hyper-responsive...I guess what you're gotta look at is at what point the ATP is used to generate the contractions...more ATP production would come from more calories being broken down, no? If there's alot of help to get a stronger contraction through stimulant use, wouldn't it be reasonable to assume that it would require fewer calories to perform the same amount of work? Forget about how much actual "fat" is metabolized, I'm just saying you might actually burn more calories doing the same workload off stimulants than on. The thing is that when you are "on" stimulants you normally do more of a workload...go faster, longer, or lift more, for more reps. Etc...
I don't see how the calories would change. A calorie is just a measure of the amount of heat it takes to raise 1g of water 1 degree celcius. A Calorie with a capital C, is 1kg of water 1 degree celcius.
I can't imagine that the contractions involved in any given workload would require an appreciable change in calorie consumption.
The amount energy required to move X amount of workload is going to be the same for that X amount no matter the circumstances. The methods of contraction (Na/K pump) is extremely efficient. I would imagine that as a necessity of survival, it would be effecient.
There's going to be MUCH greater variance in the storage capacity of the body. A glycogen depleted body may have as much as a 4,000 excess calorie consumption variance.....assuming 1,000g of glycogen storage potential.
I would argue that stimulation of the 'fight or flight' mechanisms in the body would have a greater caloric impact. The body is going to be less interested in anabolism in a state of nervous system stimulation....the caloric amount that could be varied by that (how much muscle won't be built due to the decreased emphasis on anabolism, how much glycogen won't be stored due to the decreased glycogenesis in a state of nervous system stimulation) is going to be much more than any potential decrease/increase in neural effeciency.
And...in the end, it won't matter.
The person that stays on their diet and remains focused is going to progress the best. One cheat, mishap, splurge...one skipped session of cardio, one bite of candy, etc., is going to cause more of a caloric change than the above could ever cause.