Insulin, Glycemic Index and Low Carbing

A few days ago I posted an article on Glycemic Index and Glycemic Load and the question that I'm sure is in both readers' minds is, "Who gives a shit?" In the interest of my own education, I hope this post will tie it all together.

Let's start off with a quick quiz:

1. What is the goal of reducing carbohydrate consumption in a Low Carb diet?
2. What is the state of ketosis?
3. What is the purpose of insulin?

And here are the answers, in short form:

1. Reducing carbohydrate consumption has the goal of regulating insulin production (decreasing or almost completely eliminating).
2. Ketosis occurs when the body no longer is able to use sugars (specifically glucose ingested from food and glycogen, the stored form of glucose) and must resort to burning fats as the main fuel source.
3. Insulin is secreted by the pancreas in response to a spike in blood sugar levels. Insulin's purpose is to regulate blood sugar levels by storing excess glucose (more on this below).

Typical protocol for a Low Carber in an Active Weight Loss phase is to reduce total carbohydrate intake to some threshold amount, typically this is around 20 or 30 grams of carbohydrate per day. The purpose of this is to drive the body into a state of ketosis in which the main fuel source switches from sugar to fat. Most Low Carbers will stay in ketosis for the entirety of their weight-loss phase.

Insulin

Let's look again at the role of insulin in the body. Insulin plays a role in both carbohydrate and lipid (fat) metabolism.

In carbohydrate metabolism, insulin has two main functions:

• Store sugar in muscle and adipose cells,
• Stimulate conversion and storage of glycogen in the liver.

In lipid metabolism, to put it simply, insulin's main function is to spare fat. Insulin makes the body prefer burning sugar to fat as a fuel source and it indirectly stimulates storage of fat in adipose cells.

So, to summarize: For those of us trying to reduce body fat stores, insulin is bad.

The Low Carb Lifestyle

So where does that leave us? Traditional Low Carb diets ask us to cut out all carbohydrates (except fiber - I won't go into that here), however let's re-examine that idea. The goal of LCing is to limit insulin production. We know that Low GI/GL foods also limit insulin production. So do we really have to cut out all carbohydrate?

Thanks to Dr. Dean Ornish and popular-press making fat into the villain, many people interpret "Low Carbohydrate" as being the same thing as "High Protein." Unfortunately that is not the case. There is a condition known as "Rabbit Starvation" in which the body is given too much protein and it is not able to synthesize proper nutrition.

At most, only about 40% of macro nutrition should come from protein. The rest should come from fats and carbohydrates. In my own personal experience, it is very difficult to eat 60% or more of ones' calories from fat.

Connect the Dots

Low Carbing and Low GI/GL are made for each other. I consider the textbook diets of Dr. Atkins, et al. to be much like the "Dummies" guides. For most Americans who have little or no real understanding of what goes in their mouths, off the shelf LC diets are great. People are told what to eat, what to avoid and when to eat in very explicit, definite terms. Unfortunately, most people get tired of the rigidity and never make the final leap to go from "diet" (which is popularly considered a short-term fix for a long term problem) into "nutritional plan" or "way of eating."

From that point of view, I am not a Low Carber anymore. I'm just a person who makes nutritional choices based on what I know works for me.

References:

"Physiologic Effects of Insulin," http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/pancreas/insulin_phys.html

"Rabbit Starvation," http://www.medbio.info/Horn/Time%201-2/vilhjalmur_stefansson1.htm

"Ketogenic Diet" http://en.wikipedia.org/wiki/Ketogenic_diet