Maximum Fat Metabolism and minimum calories

michellekicks

Okay so someone posted this awesome calorie/diet calculator: http://www.1percentedge.com/ifcalc/

And I've been playing with it. What struck me is the "Maximum Fat Metabolism" and "Minimum Calories" area... now, for me, because I know my weight is 160 lbs and I know my fat-free mass is 120 lbs (from a DEXA) I can plug those numbers in to find out that I have 40 lbs of fat on my body.

So... here's what it says on the site:
"Assuming 1 lb of fat contributes 30 calories per day to metabolism, this is the number of daily calories that your body can supply you with from it's fat stores. Theoretically this is the number of calories you could eat below your TDEE without losing muscle mass, assuming no muscle atrophy takes place."

So my TDEE is calculated at 2400 calories/day (because of my height, weight and exercise of 3-5 times/week moderately). Now, because I have 40 lbs of fat that can contribute 1200 calories/day to my needs, I can eat as low as 1200 calories/day without losing muscle mass according to this calculator.

If someone of my height, weight and age were to be sedentary - all other things being equal - their TDEE would then be 1858 calories per day. BUT because they'd have the same 40 lbs of fat that can contribute up to 1200 calories/day to their energy needs, they can safely diet on 658 calories ingested per day IF they are, in fact, sedentary.

So if you know your TDEE and your BF%, you can figure out just how much of your energy needs can be used from your fat mass (30 calories per pound of fat per day)... obviously as you lose weight this will decrease, but it proves that 1200 doesn't have to be the bottom end for people who want to lose faster while maintaining lean mass.

Any other sources that prove the number of "30 calories per pound of body fat" are able to be contributed to energy needs daily I wonder...

heybales

Okay so someone posted this awesome calorie/diet calculator: http://www.1percentedge.com/ifcalc/

And I've been playing with it. What struck me is the "Maximum Fat Metabolism" and "Minimum Calories" area... now, for me, because I know my weight is 160 lbs and I know my fat-free mass is 120 lbs (from a DEXA) I can plug those numbers in to find out that I have 40 lbs of fat on my body.

So... here's what it says on the site:
"Assuming 1 lb of fat contributes 30 calories per day to metabolism, this is the number of daily calories that your body can supply you with from it's fat stores. Theoretically this is the number of calories you could eat below your TDEE without losing muscle mass, assuming no muscle atrophy takes place."

So my TDEE is calculated at 2400 calories/day (because of my height, weight and exercise of 3-5 times/week moderately). Now, because I have 40 lbs of fat that can contribute 1200 calories/day to my needs, I can eat as low as 1200 calories/day without losing muscle mass according to this calculator.

If someone of my height, weight and age were to be sedentary - all other things being equal - their TDEE would then be 1858 calories per day. BUT because they'd have the same 40 lbs of fat that can contribute up to 1200 calories/day to their energy needs, they can safely diet on 658 calories ingested per day IF they are, in fact, sedentary.

So if you know your TDEE and your BF%, you can figure out just how much of your energy needs can be used from your fat mass (30 calories per pound of fat per day)... obviously as you lose weight this will decrease, but it proves that 1200 doesn't have to be the bottom end for people who want to lose faster while maintaining lean mass.

Any other sources that prove the number of "30 calories per pound of body fat" are able to be contributed to energy needs daily I wonder...

http://www.ncbi.nlm.nih.gov/pubmed/15615615

And, if you have enough fat, in theory according to that, you wouldn't have to eat at all, and would not have to worry about losing LBM. And I think we know that just isn't the case.

The study that came up with that, rather the study that examined other studies that came up with that, had a very specific set of parameters they are looking for and at.

In this post is the study link, and a great comment back from Lyle Mcdonald about 3rd post down.
http://forums.lylemcdonald.com/showthread.php?t=11223

And another site using it. I was thinking of putting it in the spreadsheet, but that fact that in some cases you would not have to eat made it difficult to figure out how to plan that, I guess stop at 1200.

Sadly, this study also flies in the face of many other studies where people did lose LBM with no exercise and with cardio, and according to the 31 cal / lb of fat, should not have. Those studies showed that the lifting was the only retainer of LBM with steep deficits in lab environments under Dr supervision.

Here's another calc that had it too. That IF calc added it lately.

http://www.weightrainer.net/losscalc.html

yarwell

http://www.ncbi.nlm.nih.gov/pubmed/15615615 works with 31.5 cals/day per lb of fat mass, +/- 8.6%, in lean active young men. So 30 cals/day per lb of fat seems a reasonable cap to put on energy deficit.

A 120 lb woman at 20% BF could supply a 720 cal deficit on that basis which might be 40-50% of her BMR (if the equation holds true for women, etc).

It seems a useful number as an upper limit, or to generate a warning - "your calorie deficit may exceed the availability of energy from your reserves", but I'm not convinced there's a direct "no loss of fat free mass" connection as many studies demonstrate loss of FFM at deficits well below the above.

ETA: We shouldn't run scared of FFM loss either - in a different study "All nine subjects lost weight fairly steadily for the 6 weeks, reducing fat stores by 4.4 kg and body water by 1.0 kg on average" and the 1 kg of water would be reported as FFM.