Let's first talk about insulin. Insulin is the central hormone that regulates carbohydrate and fat metabolism in the body. Our body ultimately processes all starch (and proteins, if needed) into glucose (read: blood sugar, which is dangerous when excessive). Glucose is the chief source for energy and growth for most cells, but in order for the cells to utilize glucose, the pancreas must secrete insulin. Cell membranes have special receptors that insulin can bind to, sending a chemical signal that opens glucose channels and allows glucose to enter the cell. Think of a cell membrane as a door, and insulin as the key that unlocks it for glucose.
[*In the case of type I diabetes, the cells that produce insulin in the pancreas are destroyed via autoimmunity beginning at birth (through no fault of the individual), and therefore insulin injection is required to regulate glucose in the blood. Type II diabetes results when glucose "wears out its welcome" in the cells, i.e. chronic carbohydrate intake and the resultant binding of insulin cause the cells resist opening their channels, or "change the locks." Even in the presence of insulin, glucose remains in the blood stream, which can cause numerous complications, including death.]
The problem with insulin is when it binds to cells, it completely shuts down the fat metabolism in those cells. Cells can either produce ATP (energy's "currency") from glucose (glycolysis) or from fatty acids (lipolysis). Lipolysis results in more energy (~9 kCal/g opposed to ~4 kCal/g) but also requires more time, so the cells prefer glucose if present (especially during exercise, when energy is needed faster). When a person consumes excess carbohydrates, some of the glucose that is not needed for energy (when ATP yield is greater than energy requirement) is stored in muscle and liver cells as glycogen, which can be re-converted to glucose in a future energy crisis. When glycogen storage units are full, the liver cells convert glycogen into FATTY ACIDS (via a process called lipogenesis). Meanwhile, lypolysis is halted. Oh, and I almost forgot, the persons current fat cells let the glucose in too, but they are can't use it for energy, and it only makes them bigger – so you can gain fat without eating any! Finally, when all the glucose has been absorbed and/or stored, the pancreas stops secreting insulin and the cells can begin using fatty acids from the liver and stored adipose tissue for its fuel.
So what happens when someone goes on a diet featuring few to zero carbs? First, the body will utilize the glycogen it has stored in the muscle and liver cells. When the body has no free carbohydrates available, one of two (or both) processes must occur in order for the body to produce energy:
1.) Lypolysis – The breakdown of fatty acids requires several steps, but yields a lot of energy. Low-carbers prefer this to occur. And it does, often, when at rest and at low intensity exercise.
2.) Gluconeogenesis – A complex process in the liver that produces glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids (ingested protein or stored muscle. YIKES!). This becomes the body’s fueling mechanism when it needs to make energy quickly (moderate-high entensity exercise). Because this process ultimately results in glucose metabolism, it also stimulates insulin, shutting down lipolysis.
By this logic, shedding fat is as simple as sitting there and not eating! But that’s not really the case. First of all, your muscles are continually breaking down and rebuilding even at rest, so you need to eat some of that “muscle-building” protein (not THAT simple, be on the lookout for a future protein interest piece: A Day in the Life of an Amino Acid). Secondly, lipolysis requires energy of it’s own, hence you need to “eat fat to burn fat.” Lastly, without ingested calories and/or periods of higher-energy requirement (exercise), your body will enter “starvation” mode, in which cells become stringent with their energy use (lipolysis occurs at slowest possible rate and you feel like dog shit).
By now you’re probably freaking out. “You’re saying if I eat carbs, I will get fat, but if I don’t, I will lose muscle even if I work out?!” That's what I'm saying today. Of course, it's entirely false, but you’ll have to wait until Monday to see why. This weekend you’re on your own. I’m about to go eat some carbs. PAYSH.
WOD: Slow-pitch softball. 7 innings!
Song of the Day and Adam Perlo Workout of the Day are the same today:
(Sweatshop Union - Hit The Wall)
QOD: "Besides, we both know that I'm training to be a cage fighter." - Kip Dynamite, and a million and a half other wannabes.
Boom.
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