Let me start by saying, I am not a registered dietician or
nutritionist. I do have knowledge of recommended daily allowances (RDA) for the macronutrients necessary to fuel the body at rest, during exercise, and during recovery . The recommendations in this blog are based on USDA and ACE recommendations. The RDA is based on the average healthy American. For specific nutrition recommendations for your body type, health status, and fitness goals I would suggest speaking with a sport specific registered dietician or nutritionist. At the end of this blog entry I will list several sites for reliable information.
The Science behind Carbohydrate Metabolism
… How your body uses Carbohydrates:
What is a Carbohydrate:
Acarbohydrate is Carbon, Hydrogen, and Oxygen [(CH2O)n]. Carbohydrates are classified as mono- , oligo-, and poly-saccharides. Your mono saccharides are the basic unit of a carbohydrate (C6 H12 O6) and include glucose - blood sugar, fructose – fruit sugar or honey, galactose – milk sugar. Oligosaccharides or Disaccharides, when 2 monoscaccharides combine: sucrose (glucose + fructose) most common type of carbohydrate consumed - honey, sugar, beets; Lactose (glucose + galactose) milk sugar; Maltose (glucose + glucose) a malt sugar found in beers and cereal; Polysaccharides ( 3 to thousands) include starch(complex carbohydrate) carbohydrate in plants and fiber (non starch carbohydrate) found in the leaves, stems, roots, seeds, and fruit skins (McArdle et al, 2007, pp 8-12).
Summary: There are a variety of food sources for carbohydrates.
How carbohydrates effect fat metabolism
…Carbohydrates and Fat production and storage:
According to McArdle et al (2007), digestion rates of various carbohydrate may contribute to excess body fat. Dietary fiber slows carbohydrate digestion and minimizes blood glucose spikes. Simple sugars and low fiber processed carbs enter the blood at a rapid rate -> causing an overproduction of insulin by the pancreas -> elevates lipids in the blood -> accelerates fat production and slow fat use as energy.
The average person should consume 40-60% of their calories , or 6-10g of CHO per kg of bodyweight. ACE reccommendations(2003) are a little different at 55-65% of calories, or 4 to 6g of CHO per kg of bodyweight. When a carbohydrate is ingested it is broken down into its respective parts and the glucose portion is either used as energy or it is stored as Glycogen in the body.
Summary: over consumption of simple sugars can result in accelerated fat production and storage
Why you need Carbs:The average person should consume 40-60% of their calories , or 4-10g of CHO. According to McArdle et al (2007), carbohydrates serve 4 major roles in relation to health and fitness.
1.
Carbohydrates serve as the body’s primary energy source during high intensity exercise. According to McArdle et al (2007), the average person stores about 15g of glycogen per kg of body enough glycogen to power a 20 mile run. Glucose (C6 H12 O6) or blood sugar is structurally similar to Fat (C57 H110 O6). When carbohydrate consumption exceeds carbohydrate needs the
excess is stored as glycogen or as
fat (pp 15).
2.
Carbohydrate use prevents damage or use of protein . According to McArdle et al (2007)When CHO or glycogen is depleted the body uses protein in muscles as its energy, which can reduce lean muscle mass (pp 15).
3.
Carbohydrate used promotes fat use. According to McArdle et al (2007), sufficient carbohydrate ingestion allows for proper fat breakdown.
4.
Central Nervous system health. According to McArdle et al (2007), the central nervous system requires uninterrupted use of carbohydrates to function properly.
Symptoms of low blood glucose: weakness, hunger, and dizziness
Summary: CHO are necessary for normal bodily functions but excess simple carbohydrates can be stored as fat.
Carbohydrates and Exercise:Carbohydrates/glycogen are the primary source of energy at the start of exercise . According to McArdle et al (2007), consuming high glycemic carbohydrates (low fiber, simple sugars) prior to exercise raises blood glucose and can
prevent fat use by working muscles, because it makes blood glucose more readily available for use, versus using energy to recruit the glucose from glycogen stores.
During intense exercise, or the first 20 minutes of initial exercise Carbohydrates are the primary source of energy.
During moderately intense exercise, glycogen provides 40 to 50% of bodily energy needs (pp 15).
When an athlete is depleted of glycogen they can not perform at their previous rate.
According to McArdle et al (2005) Athletes require 60 – 70% of their calories from CHO (8-10g per kg). According to ACE(2003) it takes approximately 24hrs to restore muscle glycogen.
Summary: CHO is the primary source of energy for high intensity exercise. Research supports the consumption of lower gylcemic high fiber carbohydrates pre workout. It takes about 24hrs to restore muscle glycogen stores.
So I know that was a lot of information, and a lot of it was pretty technical. Now let’s summarize the main points of today’s blog:
- There are a variety of food sources for CHO
- Research supports the consumption of high fiber carbohydrates(CHO) as part of a balanced diet
- RDA for CHO is 40-60% of their calories , or 4 to 10g CHO per kg of body weight.
- Over consumption of simple sugars can result in accelerated fat production and storage
- CHO are necessary for normal bodily functions
- CHO is the primary source of energy for high intensity exercise. Research supports the consumption of lower gylcemic high fiber carbohydrates pre workout
For more information regarding the most recent national RDA visit:To determine how many servings you need from each food group to loose, gain, or maintain your weight. 2010 GUIDELINES are Coming!!!
http://www.mypyramid.gov/mypyramid/index.aspxGreat database to enter your food logs and track your physical activity.
Allows you to track your progress as well as your calories deficit over time.
http://www.mypyramidtracker.gov/default.htmComprehensive nutrition and physical activity guidelines.
http://www.health.gov/dietaryguidelines/dga2005/document/default.htmHealth and Happiness
-L-
References for this article:Mc Ardle, William D., Katch, Frank I., Katch Victor L. (2007). Carbohydrates, Lipids,
and Proteins.
Exercise Physiology: Energy, Nutrition, and Human Performance. Philadelphia, PA: Lippincott Williams and Wilkins Publishers. (pp 8-19)
American Council on Education (2003).
ACE Personal Trainer Manual: The Ultimate
Resource for Fitness professionals, Third Edition. San Diego, CA: American Council on Exercise.
