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Hello everyone,

It is often said 3500 kcals are needed to lose 1 lb of body fat and 2500 kcals are required to gain 1 lb of LBM.

I know how the 3500 kcal value is arrived at but does anyone know how the 2500 kcal value can be explained physiologically?

Many thanks..

It is really a lot more complicated then that. That may be how it is on paper. In practice there are so many variables. It is just like the pound of feathers and the pound of rocks falling. In theory they should fall at the same rate. However it only works in a vaccum. In tests the feathers get slowed down by air. The raw calories in and out don't take all the other variables into account.

So an extra 2500 calories a week may or may not be the right ammount to gain a pound of muscle over the week. A raw calorie deficit of 3500 can yeild any ammount of weight less. It depends on so many things.

Want proof? try this. Eat 2500 calories a day in doughnuts and do 300 calories a day in cardio. See what happens after a week. Then try eating eating 2500 calories a day of chicken and broccoli and doing 300 calories of HIIT. See what happens after a week.

Then you will understand the number=number math doesn't work and the real equation is probably a mile long.

^true

Fat = 9 calories/gram, protein = 4 calories/gram. Fat deposits are going to be more calorie dense per unit weight than muscle deposits.

I think the 3500 kcal is a guideline for long term fat loss. Obviously in the short term, there are more complex systems interchanging calories but over time, 3500kcal will result in fat loss. The assumptions are, whatever you are doing right now, you arent gaining weight and you are gradually creating the 3500 kcal deficit over a week to 2 weeks so that you dont shock your system. Also, you should maintain a weightlifting protocol so that you do not lose too much muscle.

I think if you do all of the above things, then over the course of 6 months 3500kcal*4weeks*6 months really woudl result in near 24 lbs. of fat loss. I think this also assumes you do not have super low bodyfat to start with. Certainly, you cant drop below 4% and as you get near 4% it is going to be harder and harder to drop fat because your body will want to grab it more so the complex short term exchange of calories becomes more important and strict eating becomes important.

As far as the 2500kcal for 1 lb of muscle, I have never heard of that.

Thanks for your comments. I appreciate your time.

Most of the sources who cite the 3500 kcal for body fat reduction, including respected authors Katch, Katch & McArdle for example, include an explanation as to how this figure is arrived at.

However, when they cite the 2500 kcal for muscle gain, not a single one of them provides a similar explanation.

I was just curious as to how the figure is arrived at, irrespective of its 'real-life' application, so to speak.

Thanks again..