Go Back   Catalyst Athletics Forums > Nutrition > Weight Gain, Weight Loss, Body Composition

Reply
 
Thread Tools Display Modes
Old 10-14-2010, 06:34 AM   #1
Darryl Shaw
Senior Member
 
Join Date: Apr 2008
Posts: 706
Default Dietary Carbohydrate Deprivation Increases 24-Hour Nitrogen Excretion.

Quote:
Dietary Carbohydrate Deprivation Increases 24-Hour Nitrogen Excretion without Affecting Postabsorptive Hepatic or Whole Body Protein Metabolism in Healthy Men.

ABSTRACT


Because insulin is an important regulator of protein metabolism, we hypothesized that physiological modulation of insulin secretion, by means of extreme variations in dietary carbohydrate content, affects postabsorptive protein metabolism. Therefore, we studied the effects of three isocaloric diets with identical protein content and low-carbohydrate/high-fat (2% and 83% of total energy, respectively), intermediate-carbohydrate/intermediate-fat (44% and 41% of total energy, respectively), and high-carbohydrate/low-fat (85% and 0% of total energy, respectively) content in six healthy men. Whole body protein metabolism was assessed by 24-h urinary nitrogen excretion, postabsorptive leucine kinetics, and fibrinogen and albumin synthesis by infusion of [1-13C]leucine and [1-13C]valine.

The low-carbohydrate/high-fat diet resulted in lower absorptive and postabsorptive plasma insulin concentrations, and higher rates of nitrogen excretion compared with the other two diets: 15.3 ± 0.9 vs. 12.1 ± 1.1 (P = 0.03) and 10.8 ± 0.5 g/24 h (P = 0.005), respectively. Postabsorptive rates of appearance of leucine and of leucine oxidation were not different among the three diets. In addition, dietary carbohydrate content did not affect the synthesis rates of fibrinogen and albumin.

In conclusion, eucaloric carbohydrate deprivation increases 24-h nitrogen loss but does not affect postabsorptive protein metabolism at the hepatic and whole body level. By deduction, dietary carbohydrate is required for an optimal regulation of absorptive, rather than postabsorptive, protein metabolism.
http://jcem.endojournals.org/cgi/content/full/88/8/3801
Darryl Shaw is offline   Reply With Quote
Old 10-14-2010, 07:37 AM   #2
Samuel Hughes
Senior Member
 
Join Date: May 2010
Posts: 400
Default

A couple of thoughts:

-Very small sample size (n=6), though the error bars are remarkably small for having 2 subjects per condition

- They were limited to daily activity... i.e. no physical stimulus for growth. May or may not have an effect on protein absorption. This would definitely be interesting to play with.


Their results say that if you are not exercising and eat low carb, you don't absorb as much protein. Seems pretty intuitive. I don't think they prove that insulin is a necessary mediator of protein absorption, but repeating in diabetics/mouse model could do so.
__________________
S. Emile Hughes

Workout Log

Current Lifts (December 2010): BW 166lbs; 285lb Bench Press; 315lb Squat; 175lb Overhead Press; 405lb Deadlift; 205lb Power Clean
Samuel Hughes is offline   Reply With Quote
Old 10-15-2010, 06:13 AM   #3
Darryl Shaw
Senior Member
 
Join Date: Apr 2008
Posts: 706
Default

I agree, the sample size was too small to draw any firm conclusions so it would be interesting to see further studies performed on a larger group of more active/athletic subjects. I doubt that the results would be all that different though because of the well documented protein sparing effect of carbohydrates.

Edit: I'm forgetting that energy balance plays an important role in maintaining nitrogen balance and that carbohdrates and fats have a simlar protein sparing effect in hypercaloric diets. Carbohydrates do however have a greater protein sparing effect than fats in eucaloric and hypocaloric diets so any further studies would need to take energy balance into account.
Darryl Shaw is offline   Reply With Quote
Old 10-15-2010, 07:19 AM   #4
Steven Low
Super Moderator
 
Join Date: Mar 2007
Posts: 3,091
Default

Who is going to try to cut off fat with just diet though? People that often rebound back up?

Strength training is the most protein sparing thing when cutting weight....

Macronutrient partition matters very little at that point, and higher fat diets are proven to drop more fat mass quicker.
__________________
Posts NOT intended as professional medical, training or nutrition advice.
Site // Bodyweight Strength Training Article // Overcoming Gravity Bodyweight Book
Steven Low is offline   Reply With Quote
Old 10-15-2010, 08:58 AM   #5
Darryl Shaw
Senior Member
 
Join Date: Apr 2008
Posts: 706
Default

Quote:
Originally Posted by Steven Low View Post
Who is going to try to cut off fat with just diet though? People that often rebound back up?
According to the findings of the US National Weight Control Registry the majority of people who were successful in losing 30lbs and maintaining that weight loss over a three year period reported that they followed a low-energy and low-fat diet (link) with only 10.8% of participants reporting losing weight after following a low-carbohydrate diet (link). Most of the participants in the study who regained weight reported an increase in the percentage of total calories coming from fat (link).

Quote:
Strength training is the most protein sparing thing when cutting weight....
Agreed.

Quote:
Macronutrient partition matters very little at that point, and higher fat diets are proven to drop more fat mass quicker.
While high-fat diets have been shown to result in greater weight loss than low-fat diets in the short term the differences between hypocaloric diets with different macronutrient intakes even out over time so that in the long term the extent and duration of the calorie deficit ultimately determines how much weight is lost.
Darryl Shaw is offline   Reply With Quote
Old 10-15-2010, 05:22 PM   #6
Jarod Barker
Senior Member
 
Join Date: Jul 2008
Posts: 320
Default

I could be completely wrong, but I would imagine that exercise, though it breaks down our protein, likely stimulates some mechanism that would then enhance our bodies' ability to digest, absorb, and process protein. If there's a post workout window for carbs, I figure there's probably a post workout window for protein too, and maybe it lasts much longer than the carb window? Just a guess.

In any case, I know when I eat truly keto, my urine smells like ammonia, so I'm not surprised that not eating carbs increases nitrogen excretion. You're probably eating even more protein than you normally would as well.
Jarod Barker is offline   Reply With Quote
Old 10-23-2010, 03:35 PM   #7
Derek Weaver
Senior Member
 
Join Date: Nov 2007
Posts: 2,642
Default

Chad,
The post workout window for carbs is important primarily for endurance athletes, and/or athletes who have got more than one workout in a set time period.

For protein, it's largely the same. Glycogen re synthesis, and protein synthesis is an ongoing process. I think Darryl had a post showing glycogen re synthesis can take up to 21 hours.

Lyle McDonald goes into this fairly often at his forum and in several of his articles.
__________________
Quote:
And if you don't think kettleball squat cleans are difficult, I say, step up to the med-ball
- CJ Kim
Derek Weaver is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump




All times are GMT -7. The time now is 06:05 PM.

Powered by vBulletin® Version 3.8.9 Beta 3
Copyright ©2000 - 2014, vBulletin Solutions, Inc.