Quote:
Originally Posted by Valtor
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I will add that not only is it impossible to grow fat by overeating fat, it's impossible to grow fat by eating anything in the absence of carbohydrate, with the exception of certain causal agents such as drugs and the like.
Mathematics to the rescue.
Let's establish how much carbohydrate it takes to grow fat over time. 86g per day for twenty years should do it. This is the toxic threshold for diabetes type 2. Since diabetes type 2 and obesity are tightly associated, it's reasonable to assume that the toxic threshold for diabetes type 2 also applies to obesity. So it takes 86g per day for twenty years to grow obese. How much protein, or fat, would we need to ingest in order to reach that amount of carbohydrate by converting the protein and the fat?
Protein can be converted to glucose at the rate of about 55%. I don't know exactly how much glycerol, the substrate from which we can get carbohydrate, fat contains but I'm positively certain that it's no more than 10% at best. So I'll use this figure for now. It is said that only excess protein is converted into glucose. Let's say a normal human male needs about 1.5g per kilo of protein to maintain lean tissue mass. Whatever is in excess of this will be converted to glucose. A 100kg human male would need 150g of protein. If he ate 200g of protein, he would convert the excess, about 50g, but only 55% of this will end up as glucose, so about 25g. That's still not yet to the toxic level of 86g. That's not all, we haven't yet established how much food we would need in order to obtain that much protein. Let's use plain old beef for this. Beef contains about 20% protein by weight, or about 25% when cooked. To ingest 200g of protein from beef, we need to eat 1kg of meat. Less if it's cooked. So, from one (actually the first kilo of beef we eat) kilo of beef, we can extract only 25g of glucose. In order to reach the toxic level of 86g, we need to eat an additional amount of meat that would give us the equivalent of about 60g of glucose to make up the difference. That's another 600g of meat. So, to get to 86g of glucose, we need to eat a total of about 1.6 kilo of meat. Whom do we know, besides myself and a few others, eat that much meat (never mind that it's lean meat in this example) in a day, let alone every day for 20 years? And whom do we know, from that group, who grew fat from it?
I discounted the amount of glycogen that may be stored in muscle cells of the meat we eat because first, it's not much more than 1% by weight, and second, it's entirely possible that the cells used it up once the animal was dead and thus unable to supply the oxygen needed to use fat as fuel, and consequently the cells would use the glycogen anaerobically until it ran out. Even if there is still some glycogen in there, it's only going to add no more than 10g per kilo of meat, or in our example above 16g total. That's still way off the toxic threshold.
The problem with the hypothesis above is that it's impossible to eat only protein since it's catabolic and toxic. In other words, not only can't we use protein as fuel for the purpose of converting protein because in order to be used as fuel it must first be converted into glucose, it makes us sick. Nevertheless, the math shows that it's extremely difficult to reach the toxic obesogenic level of 86g per day of glucose just by eating protein, if it were even possible to do so.
Now for fat. Only 10% percent of it (maybe less, somebody correct me), the glycerol substrate, can be converted to glucose. The math is simpler here. We would need to eat at least 860g of fat to get 86g of glucose. In terms of calories, that's 7740.
Just think about that for moment.