Sérgio
Fontinhas. Carbohydrate disposal – a priority. Science Driven Nutrition. Vol 2. December 2015
Abstract
The oxidative hierarchy refers to the relative
order in which fuels (alcohol, carbohydrates, protein and fat) are selected for
oxidative disposal after ingestion. Giving the relative storage capacity for
these different substrates, each fuel assumes different priorities within
metabolic pathways. These physiologic alterations serve to channel energy to
and from the appropriate storage compartments under all circumstances that may
challenge the organism.
The hierarchy is dominated by alcohol, followed
by carbohydrate and protein, and fat at the bottom. Alcohol, carbohydrate and
protein elicit powerful auto-regulatory mechanisms - they promote their own
oxidation – while fat does not.
Glycogen stores can maximally accommodate
800-900g of carbohydrate and perhaps as much as 1000-1.100g in trained
athletes. When glycogen stores are saturated, massive intakes of carbohydrate
are disposed of by high carbohydrate-oxidation rates. Along with a progressive
carbohydrate oxidation, basal metabolic rate and total energy expenditure also
increases.
Another pathway to dispose of carbohydrates is
de novo lipogenesis, however this process is quantitatively small in humans.
Key words: Carbohydrate, glycogen, fuel
selection, lipogenesis, oxidation
1. Fuel storage capacity
1.1 Alchool
1.2 Carbohydrate
1.3 Protein
1.4 Fat
2. Substrate flux and hierarchy of fuel
selection
3. Carbohydrate
disposal
4.
Lipogenesis
