Originally Posted by starthaus
your feet and lower leg do not store fat for the body to use at a later date...
Again you insist on this. Sorry and with all due respect, you're wrong.
Originally Posted by markojp
I would advocate listening to Sierra Jim. Strongly.
There's a long and substantial literature showing that on this particular issue, Jim is telling people to ignore both their own experience and the biomedical consensus. Last time around, I just invoked my own expertise, but Jim obviously isn't budging. OK, this time, I spent an hour digging up a few citations - there are plenty more - that I will annotate:
Chuey et al. J. Magnetic Resonance Imaging. 2013 - A nice MRI validation study of the fat and muscle compartments of the human foot, with interest in fat infiltration of muscle and tendon spaces. So yes, the foot has fat in it, and the amount of fat can change significantly. Changes can be related to age, to body weight, and to pathologies.
Ashizawa et al. 1997 Ann Hum Biol. - BMI (Body Mass Index, a proxy for % body fat) is inversely related to the ratio of foot breadth to foot length in Japanese men and women. Meaning, heavier subjects' feet were significantly wider relative to their length; e.g.,thicker.
Schinkel-Ivy et al. J. Sports Sciences 2014 - Uses anthropometric measurements to estimate fat and lean mass of the lower leg and the foot. The foot contains 2-3 g of fat/kg-1 body weight.
Chiou et al. J. Applied Ergonomics 2015 - Pregnant women increased their foot length by 3.6%, their foot width by 2.9%, and their heel surface area by 11.9%. Body mass increases explained 90% of the total variance in these measurements. Yes, foot length can also increase. The foot is a very dynamic structure.
Domjanic et al. Am J. Phys. Anthrop. 2015 - In adults, foot shape is significantly and independently correlated to BMI and to height. Males have more width relative to their foot length. BMI or total body mass can be predicted by footprint shape.
Rodriquez et al. J Amer. Podiatric Med. Assoc. 2013 - Body mass significantly influences foot posture, particularly degree of pronation and loaded width.
Chen et al. Foot and Ankle Int 2013 - In 1024 middle school children, obese subjects' feet were 25% wider and flatter, and significantly higher in mid-foot. The height was not due to higher arches, since arches were lower in heavier children.
Song et al. Gait and Posture 2015 - Heavier subjects produced significantly greater plantar pressure, which produced greater spreading of the mid-foot at peak load.
Dunn et al. Ortho Audio Symposia 2015 - Pregnancy increased laxity of foot ligaments and likelihood of collapsed arch, and corresponding widening of the foot. Subjects who retained the most weight after delivery had a 15% change in shoe size.
There are plenty more. Take away is pretty simple: 1) Feet and ankles do have both internal compartment and subcutaneous fat that can accumulate or shrink; Jim might try his hand at a dissection and see for himself. 2) Foot structure is not inviolate, but changes according to habitual load, health, and life history. 3) Increased adipose tissue in the feet and ankles is associated with increased interstitial fluid and tissue edema. 4) In sum, feet, as I said above, are pretty dynamic structures, not anything like those nice plastic skeletons. (Although the glow in the dark ones are very cool.)
Now you can support Jim cuz he's a good guy and a great fitter who's cradled a lot of feet in his hands. If so, what say you be the one to call out the next woman here who's gone up a shoe size or two after a couple of kids, or the next heavy guy who's psyched he's lost some weight but his boots don't feel right, and tell them they're wrong about their own bodies. Then duck.