Carbohydrates are just like they sound – compounds made of carbon, hydrogen, and oxygen. The diversity of carbohydrates all comes down to the ratio and linking of these chemical structures. They can be classified in the following ways:
Monosaccharides: These are carbohydrates in their simple sugar form. Classic examples are glucose, fructose, and galactose. Each example contains a slight variation of the sugar carbon ring.
Disaccharides: Disaccharides are composed of two monosaccharides. Classic examples include sucrose (combination of glucose and fructose, aka table sugar), lactose (combination of glucose and galactose), and maltose (combination of 2 glucose sugars).
Polysaccharides: These sugars are typically long, complex chains of sugars that have a large number of sugar molecules bonded together. These include starches, cellulose, or glycogen.
Since the human body metabolizes or processes different energy sources through different avenues to break down the food, part of understanding the keto diet is first understanding how the body metabolizes these sugars.
To avoid getting too technical, carbohydrates are metabolized through a chain of events to be broken down to glucose, which is broken down to pyruvic acid, to acetyl CoA which enters the Citric Acid Cycle (aka Krebs Cycle). Lastly, the output of the Citric Acid Cycle goes through another series of conversions to release the bulk of ATP or energy. Cumulatively, carbohydrate metabolism is meant to produce glucose for energy in an efficient way.
Depending on your carbohydrate structure, it may take more or less time to digest and metabolize a food. Typically, the more complex a carbohydrate, the more effort to metabolize, which is why starches don’t often give a sugar rush but supply energy at a steady rate.
As glucose enters the bloodstream, the pancreas secretes the hormone insulin to stimulate cells to take up the glucose. When blood sugar runs low, the pancreas conversely secretes glucagon to stimulate the liver to release glucose back into the blood. All of this helps achieve a level of normality, or homeostasis.