Starvation Study #1 - July 2005

With this device in my hand and a package of ketone urine test sticks (Ketostix) I embarked on a personal "scientific study" of starvation. The whole idea of this long-term project is to record blood glucose levels when starving under different circumstances; e.g. autumn/winter/spring/summer simulated survival weekends, semi-starvation (living on meager rations for at least several days), etc.

Starving is a piece of cake

Once the hunger has been conquered the next obstacle will follow - migraine headache - mainly caused by lack of serotonin (a neurotransmitter, or "chemical filter substance") in the brain. Serotonin is synthesized from Tryptophan, an essential amino acid which we get from a wide variety of foods (nuts, bananas, fish, meat, milk, etc.). The medical literature I've read doesn't seem to know exactly what causes "starvation headache", but one thing is clear - not everyone starving seem to suffer from it and low levels of serotonin has a lot to do with headaches in general. After about a day the headache ought to be gone and at this point the body has adapted to the new condition - starvation - in which the body will (continue) resorting to breaking down fat reserves into energy. You eventually smell a slightly fruity, acetone-like smell in your breath. This is due to build-up of so-called ketone bodies (or rather beta-hydroxybutyrate, acetoacetate and acetone, the latter is expelled via the lungs) in your body. Although I have not gone without food for more than about 48 hours, I have on several occasions experienced that when the headache is gone everything starts to feel really good - read all about it under Digging deeper below.

The experiment

Working and starving was a perfect match, no problem walking fast through the city despite of that I hadn't eaten since Friday evening (rest is really all you need after air & water and I got plenty that night). I took 1 blood sample test every 2 hours.

Back home I drank water, took a Ketostix test, put on my backpack and went out for a short walk. On my way back I hiked a little faster - I really felt that I was going slightly above the bar, I literally felt my blood glucose level sink, which the glucose test later on proved.

Later, at 19:15, I ate a biscuit chocolate bar and an "almond bun" (mandelkubb in swedish). I immediatly started to take 1 sample each 10 minutes in order to record what happened and the result was very interesting. It took approximately 10-15 minutes for the blood glucose value to start to change, certainly due to digestion of sugar. I didn't eat anything more until about 24:00, which is when the blood glucose had got back to it's preprandial levels (the levels before meal).

The result

Detailed curve when eating snacks

The Ketostix result was obviously approximate and may have been completely different if tested with proper equipment. Below you'll find a few pictures of the tests conducted. Click on an image for a larger version.

LifeScan's OneTouch Ultra and Ketostix from Ames	A little tricky with only one hand (the other operating the camera)	Blood glucose levels during 24 hours starvation followed by food intake
A detailed plot of blood glucose levels after eating	Ketostix showing pink	Two of my favorite snacks :)

Digging deeper...

Ketone bodies are created when the mitochondria of a liver cell receives too much acetyl-CoA as a result of breakdown of fatty acids. The excessive acetyl-CoA is converted to acetoacetate, beta-hydroxybutyrate and acetone (all 3 commonly called ketone bodies). Ketone bodies can be used as fuel by the cells in the brain (up to 50-60% after about 2 weeks of starvation, some areas of the brain still require glucose so it can't shift to ketones completely), the heart and other tissues. In these cells the ketone bodies - except acetone - are converted back into acetyl-CoA and used as energy. However, the red blood cells are completely dependent on glucose and in addition, the brain still need about 50% glucose to function. After about 12 hours of starvation all glucose stores are basically empty (the liver and, to a lesser extent, the muscles store glucose in the form of glycogen). Since many organs are dependent on glucose it has to be re-generated in some way. This process is called gluconeogenesis.

In an attempt not to create too much confusion: A cell's mitochondria (the body's power plants) has something called the TriCarboxylic Acid cycle (TCA cycle) AKA citric acid cycle or Kreb's cycle which is responsible for both anabolism (build-up, storage) and catabolism (breakdown). When glucose is plentiful it will be converted to pyruvate, then converted to acetyl-CoA which enters the TCA cycle via oxaloacetate and eventually produces ATP - Adenosine TriPhosphate - a substance able to store and transport energy within cells. ATP is crucial for us to live so the TCA cycle and ATP production never stops, but slows down during rest or starvation.

Gluconeogenesis

Since oxaloacetate is being used for gluconeogenesis, it's quite "busy" and doesn't have enough time to deal with all the massive amounts of acetyl-CoA released from breakdown of fatty acids. When there's not enough oxaloacetate to deal with the acetyl-CoA of fatty acids it's commonly called incomplete fat breakdown. The acetyl-CoA won't wait, but will instead be converted into ketone bodies, namely acetoacetate, beta-hydroxybutyrate and acetone. Various muscles (most importantly the heart) and the central nervous system can use these ketone bodies as fuel during long-time starvation - all part of the body's impressive survival system designed to use fat and reduce the usage of important glucose. A healthy person (non-diabetic) will be in a state called ketosis (not harmful) for many weeks before eventually dying of heart failure (the last protein source in the body that is used for gluconeogenesis). A diabetic will get ketoacidosis and eventually die from that (whenever the ketone level in the blood goes passed 10 mmol/L).