Monday, May 19, 2008

New Math

I found an interesting post by Lyle McDonald on his forum and I wanted to post it here for future reference.

Originally Posted by patriots
So this again becomes an issue with lower caloric expenditure from decreased NEAT, offsetting the low cal and higher activity?

Originally Posted by lylemcd

again, I think that may be part of what's going on, yeah

this has been discussed before although usually in a different context when people try to claim that thermodynamcis doesn't apply because the math doesn't work. the problem is usually that they are treating the system as unvarying on the output end

so for input we have food

on the output end we have
BMR: marginally variable for people at the same weight, can adjust slightly to changes in food intake (up or down). will generally adjust downwards to some small degree with food restriction/fat loss

thermic effect of food: fairly consistent although insulin resistant people show half the response of insulin sensitive. clearly this goes down as you eat less food

thermic effect of activity: this is formal exericse. there might be changes in efficiency/caloric expenditure during dieting, Im tryign to remember what I'e seen in the liteature and none of it comes to mine

NEAT/SPA: the big crapshoot. as the bugg users are finding out, non-exercise activity expenditure plays a MUCH larger role than any non-excessive exercise bout. simply moving from sitting to standing for many hours burns considerably more calorie and this will tend to adjust itself downwards with dieting.

so at least part of this is that you have a situation where, say at maintenance, your total energy expenditure is 3000 calorie. that includes everything above

now you reduce to 2500 calories per day. BMR may come down a bit in a while (depending on such things as deficit, iniial bodyfat percentage, etc), TEA may go down, TEF goes down (only about 50 calories), NEAT/SPA may come down.

suddenly your lovely 500 cal/day deficit has been offset coming out of the starting gate and the math stops adding up. what should have been a 1 lb/week fat loss is now 0.5 lbs/week becuase of the output adjustments. and 2 pounds per week can easily be masked by a touch of water retention

suddenly, nothing is making sense anymore and the 'math doesn't work'. except that

a. yes it does
b. water doesn't have calories

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