Comments on: Nutrient Metabolism Overview

By: lylemcd

lylemcd — Wed, 15 Sep 2010 15:01:53 +0000

All nutrients have to be converted to ATP for fuel use as ATP is the only fuel that can be burned directly for energy by any cell. Fatty acids are burned through mitochondrial oxidation in various cells; they don’t have to be converted to glucose first (in fact, fatty acids can’t be converted to glucose in the first place).

Ketones are produced when an excess of acetyl-coa is produced in the liver and the liver forms them into ketones (which can be used to generate ATP as well in various cells).

By: Gaurav

Gaurav — Tue, 14 Sep 2010 13:07:17 +0000

You said “After a day or so, most cells in the body, with a few exceptions, are using fatty acids for fuel.”

But I wonder how these fatty acids could directly used as energy OR be converted to ATP, without being converted to Glucose first..!!

and if we believe above theory, why there would be a need for ketosis then ?

Simply put, Please explain me the difference in these two processes ;-
a. Fat burning in liver through Ketosis ?
b. Fatty acids used directly in cells as energy ?

By: lylemcd

lylemcd — Tue, 16 Feb 2010 15:52:59 +0000

When you reach 5% bodyfat, you might get there. And no you can’t do permanent damage. Things always recover when weight/fat is regained. Even moving calories back to maintenance will undo some of the adaptive change (for example, the post-obese at weight maintenance often still show a 5% reduction in metabolic rate for their weight).

Unfortunately, most of the reduction (in the Minnesota study case, 25%) is due simply to weighing less. That never goes away unless you regain the weight. A smaller body simply burns fewer calories.

By: Eric D. Nath

Eric D. Nath — Tue, 16 Feb 2010 15:48:46 +0000

I have another quick question from an interview.

“In one of the all-time classic studies (the Minnesota semi-starvation study), men were put on 50% of their maintenance calories for 6 months. It measured the largest reduction in metabolic rate I’ve ever seen, something like 40% below baseline. Yet at no point did the men stop losing fat until they hit 5% body fat at the end of the study.”

Is it possible to permanently alter your metabolism in a negative way? Also, by 40% below baseline did you mean 40% below regular BMR? For instance, I weigh 350 lbs so my BMR would be roughly 3500 calories. 40% reduction would leave me at 2100. I know you can’t be exact, but how long would you guess I’d have to be dieting using your Rapid Fat Loss Diet to reach that metabolic deficit?

Thank you very much for answering my questions.

By: lylemcd

lylemcd — Tue, 16 Feb 2010 15:40:56 +0000

Eric: The process is simply very rate limited. On average, the body will make ~10% of total fat broken down in a day into glucose from glycerol. So if you broke down a whopping 180 grams of fat in a day, you could get at most 18 grams of glucose. And you’ll usually get less than that. So other substrates are required.

By: Eric D. Nath

Eric D. Nath — Tue, 16 Feb 2010 10:26:02 +0000

“When necessary, the body can make glucose out of a number of other substances including glycerol (which comes from fat metabolism), lactate and pyruvate (which comes from carbohydrate metabolism), and certain amino acids (from protein).”

I was wondering why the body can’t simply use glycerol to maintain its requirement of glucose in lieu of carbohydrates. Why is protein necessary? Is it simply the fact that the body can’t produce the remaining 25% needed fast enough with glycerol? Do the amino acids and glycerol combine in some fundamental way? Both questions refer to that particular context.

Thanks!

By: Bob

Bob — Thu, 14 Jan 2010 00:51:24 +0000

Very interesting thanks!

I must admit though that I am trying to figure where Cortisol comes into it. This is an understanding and research thing because I have Addisons..

Cheers!