J Theor Biol. 2005 Mar 7;233(1):1-13. Epub 2004 Dec 8.
A limit on the energy transfer rate from the human fat store in hypophagia.
Alpert SS.
Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131-1156, USA. sialpert1@juno.com
limit on the maximum energy transfer rate from the human fat store in hypophagia is deduced from experimental data of underfed subjects maintaining moderate activity levels and is found to have a value of (290+/-25) kJ/kgd. A dietary restriction which exceeds the limited capability of the fat store to compensate for the energy deficiency results in an immediate decrease in the fat free mass (FFM). In cases of a less severe dietary deficiency, the FFM will not be depleted. The transition between these two dietary regions is developed and a criterion to distinguish the regions is defined. An exact mathematical solution for the decrease of the FFM is derived for the case where the fat mass (FM) is in its limited energy transfer mode. The solution shows a steady-state term which is in agreement with conventional ideas, a term indicating a slow decrease of much of the FFM moderated by the limited energy transferred from the fat store, and a final term showing an unprotected rapid decrease of the remaining part of the FFM. The average resting metabolic rate of subjects undergoing hypophagia is shown to decrease linearly as a function of the FFM with a slope of (249+/-25) kJ/kgd. This value disagrees with the results of other observers who have measured metabolic rates of diverse groups. The disagreement is explained in terms of individual metabolic properties as opposed to those of the larger population.
PMID: 15615615 [PubMed - indexed for MEDLINE]
Et le commentaire de Lyle qui va avec :
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Note that this is a theoretical biology journal. So take it as exactly that, theoretical.
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Ok, so I ground through the PDf last night. Man, a bunch of equations, made my head hurt and I'll have to read it again to get the nuances.
bascially they propose that, by limiting the deficit to what the current fat mass can handle, you should be able to spare fat free mass loss almost entirely. This is interesting, something I"ve had in the back of my mind for a while.
They also make an interesting suggestion that there appears to be an initial dieting period where the body relies prmarily on fat for fuel but as fat mass drops (and how large of a deficit can be sustained also drops), you need to relax your diet by using a smaller deficit. Basically, start with a larger deficit and decrase it as fat mass drops.
They reach a value for fat mass of 290 kj/kg of fat mass which rounds out to
290 kj / 4.2 = 69 kcal/kg / 2.2 = 31 kcal/lb fat mass.
So if you had 30 lbs of fat, you could sustain a deficit of 900 cal/day with no FFM loss.
20 lbs of fat, 600 cal/day.
10 lbs of fat, 300 cal/day.
Translation: fatter people can use larger deficits, leaner need smaller. Which is exactly what I put in the PSMF book but this quantifies it (assuming their numbers are correct).
Like I said, I have to read it again to really get the details, it's a bit dense of a paper.
Lyle