I have a question for all you biology guys out there. Forgive my ignorance if this is a really stupid question but I have been wondering this for a while. We are always told that fat mass isn’t metabolically active therefore when using diets like t-dawg to use your LBM to calculate your calorie needs. But how can this be? Don’t fat cells have to stay alive? I mean of course fat cells would not burn anywhere near the amount of energy as muscle cells but wouldn’t someone who was once really fat(and therefor has many more fat cells then average) need extra energy for those cells to survive? I’m not saying we should all gain 100 lbs of fat and then loose it so we can have a faster metabolism but I would love to find out how significant those cells are in terms of caloric needs. (When they have been deplete of fat) Just seems more cells = more calories burned.
Fat cells are so metabolically inactive (I seem to recall reading that it takes 3kcal daily to maintain a pound of fat) that there’s no point in including fat mass in your calculations. Even if you put on the 100 pounds of fat (without adding any LBM) that you mention, it would increase your daily requirements by only 300 kcal.
Great thanks! just the type of response i was looking for.
Actually
fat cells are metabolically active.
These has extreme importance for dieting and bulking regimes.
Unfortunately, most people are horribly misinformed on this issue
Vain
Also to mention that you can create new fat cells but you can’t lose them. In other words it will make it harder to lose the fat after you gain it. Fat cells only shrink and don’t go away unless you get liposuction.
Interesting, Vain. Mind elaborating?
Yes Vain68 please enighten us. That is the kind of knowledge I am seeking.
Good question, DJS. I’ve been wondering about something similar lately. Specifically, if fat technically is metabolically inactive, then re-figuring cal requirements after having dieted for awhile isn’t really necessary provided that the weight lost was fat (the ideal situation, I know, but the use of andros/pro-hormones makes this more likely than with diet alone).
But if fat is metabolically active, but less so than muscle, it would be nice to be able to assign a percentage to that mass when determining caloric needs.
So in short, also anxiously awaiting Vain’s reply. 
A very poliquinesque response, Vain.
Care to share?
Tyler,
Well I would think that fat(as in goo) is innactive. So as you burn off the goo the same number of cells remain and the cells are alive while that fat isn’t. So if the cells are metabolically active I would think that wouldn’t change regardless of weight loss. They’re smaller but still burning fuel to live. But this is all guesses and we’ll just have to wait for vain68. They could go into hybernation for all I know. 
Interestlingly enough, after about 8-10 years of age you don’t aquire any more fat cells…like was said, they just get bigger.
I’ve always learned it the way Chris stated. Humans have nearly zero brown fat cells which are much more metabolically active. The white tissue requires very little metabolical input that it’s usefulness in counting it as activity is hihgly limited.
Ever see one under a microscope? Not much too them.
Why are fat cells associated with a decreased basal metabolic rate? Berardi’s Winning Formula doesn’t work for obese people because they have a lower BMR. (There was thread about this a couple months ago. “Do the math” or something like that.) Do the fat cells cause the lower BMR, or does the lower BMR cause more fat, or does something else contribute?
Let me get this straight.If someone loses 100lbs of fat, all those fat cells are still there? They’ve just “shrunk”?? Is this really true?
Pauly Bruce: YES…that’s absolutely true! Sad really…but evolutionarily important. Remember we’re nothing more than animals that can build temperature controlled shelters.