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Someone (bodybuilder) made the comment today.

"I don't eat fat. Fats will make you gain weight not just sugar. It breaks down in the body and fats turn into sugars after. Not just sugar spikes your blood sugar."

Fat does not get turned into sugar! Only if insulin is present because you had a high carb meal, does the excess fat get stored, but it doesn't convert into sugar. Am I wrong here?

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Well...As back-asswards as his final conclusion is, I suppose he isn't completely wrong since fat can convert into glycogen in the liver as I understand it, and that can provide glucose for the brain. But yeah, he's not helping anyone with that advice as far as I'm concerned. – Happy Now Jan 20 2012 at 8:49
Masterjohn has proposed some evidence that there is indeed a pathwway for acetyl-CoA from fat to convert to pyruvate and later glucose, but it is highly unlikely that it is utilized to any measurable degree in gluconeogenesis. – Travis Culp Jan 20 2012 at 22:27

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Fat does not break down into sugar. It is either stored (in fat as fat) or it is oxidized (burned).

Many people do not realize that fat does get stored even if your in fat burning mode and even when your not eating carbs. If someone in ketosis sat down and ate or drank 200 grams of fat in one meal, (1800 cals) that fat will go into storage, but it will come out as needed for fuel.

You are also right, that in a mixed meal of course, fat gets stored then too. The difference is in a mixed meal with carbs, fat burning is turned down low in the presence of insulin. This allows the glucose to be burned off for a time period directly related to how much glucose is present.

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Well, yes, both protein and carbs can trigger insulin, and when they do, all nutrients are pushed to be storage, this is why we can get away with eating some fats during a fast and still remain in ketosis, and not shut down fat burning. – raydawg Jan 20 2012 at 11:23
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Fat burning doesn't get turned off, it just gets eclipsed by fat storage for a short time. – Matt Jan 20 2012 at 12:26
@raydawg: Any fat in excess of immediate needs can and should go to the fat tissue for storage. It will be released as needed. ASP can take care of that with or without an insulin spike. – Evelyn aka CarbSane Jan 20 2012 at 23:43
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Don't let it make you mad.

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The human body is pretty amazing, it can basically convert any form of food into any other. According to Chris Masterjohn, it is possible to convert fat to glucose.

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Yes, but it takes about 200 grams of fat to be burned to make about 20 grams of carbs and it makes a mess in the kitchen. – Bill1102inf Jan 20 2012 at 3:50
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At a high level, in terms of the bodybuilding diet with high carb+protein, he's correct. You eat that high carb/protein + high fat and the fat gets stored.

In detail however, he's not correct. Yeah, fat can get converted to some glucose, but it's a fairly negligible level and as needed, not all the time. It's not a major threat. You eat low carb/high fat and the majority doesn't get stored, it gets used, etc.

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