Unfortunately Seymore Alpert died from complications of surgery in 2014 so we can’t ask him. I tend to believe the analysis because of those weird facts about the subjects in the data.
These were non-obese subjects (therefore no apparent problem recruiting body fat to use for energy), all men (a gender that has a greater energy demand), religious conscientious objectors (mostly from Mennonite communities with high grain consumption) fed a starchy diet expected to be available in post WW2 europe (therefore more tubers than grains). They were also fat adapted as they had been on an 1560 kCal 2 meal a day intake for 24 weeks and ran 5km a day - they burned 25% of their body weight in fat and lean tissue.
Also it was run by Ancel Keys who was a good collector of data but a slippery weasel when it came to analyzing data.
What Keys did was measure everything while starving them on not enough calories - body weight, immersed body weight (ie: density), internal temperatures, exercise tolerance, mental functioning. The fact that none of this was supporting or refuting his own hypotheses and he had no idea what someone could do with this data 70 years later causes me to not question the data just because it was collected by Ancel Keys.
Remember the question is what is the maximum amount of energy you can draw from the system. There has to be some limit or humans would self-combust when they went for a jog.
What Symore Alpert did was assume that a human body with access to energy stored in body fat, will use that rather than protein to supplement a shortfall in intake energy. That’s probably how I would design the energy system too, burn the chopped wood behind the woodshed first before you have to burn the actual woodshed for energy.
However I suspect that THAT is the area that Alpert’s calculations may turn out to be incorrect, or more likely require a little more nuance.
As for populations who will have different levels of maximal access to energy; I would expect children, women and the elderly to have a lower rate limit. I would expect elevated insulin to also lower the rate, so amount of carbs in an ad-libitum diet would have an effect. For people who are obese hyperinsulinemic diabetics, that could lower to 20% of a normal hpoinsulinaemic man, for ketogenic former diabetics who have lost 100lbs and stalled that could be a much smaller fraction.
The rate limit is “out of adipose”, putting more in such as in a feeding window shouldn’t affect the rate that fat cells can contribute energy but it will decrease the amount they do contribute because they will be taking in some of that energy from the diet - so the net they contribute drops.
Yup. Our plateau when we go ketogenic will be determined by how elevated our insulin remains once we have removed any support from diet.
That makes sense. Your rate of energy access is lower because your energy storing mass is lower, and your body will adjust by dialing down it’s expectations of how fast it can access energy.
Someone with less body fat is trading off a functional advantage for a cosmetic one. Someone with 7% body fat is like an iPhone with half the battery size of someone with 14% body fat, and 1/3 of the size of the battery of someone with 21% BF. Those of us who start out with 50% body fat are like phones duct taped to a couple of extra power bricks.
Nah. That’s just a willful misunderstanding by vegan activists. One of the mechanisms of insulin resistance in muscle cells is the build up of fat droplets - the cells become insulin resistant to decrease the glucose coming in so they draw down the fat. But if insulin is really high they are inhibited from using fat too. The cell stays insulin resistant until insulin levels can be brought down enough to draw down the fatty droplets.
It depends on your total lean mass. If you have 80kgs of lean mass you can probably eat that amount of protein no problems. Humans run into trouble when they go over 3.3g/kg and ammonia builds up which can be quite dangerous.
In a normal human that will be self limiting as the build up of ammonia causes nausea, which can be a misread as satiation, but is likely to be in advance of energy requirements. In other words a protein sparing modified fast if you have normal access to body fat (ie: low enough insulin) is just another way to do a caloric restriction, but it feels like an ad-libitum diet. Not really a good idea if you can’t access adequate energy from body fat (either you don’t have enough or your insulin is high), because then you will run out of the minimal necessary amount of energy and recruit lean tissue for energy resulting in a great amount of ammonia production.
I suspect if the OP goes on a normal ketogenic diet he may find that body fat increases to the point where his body is happy with the size of battery he is carrying.
