Hunger is a biological function. The hunger feeling is a very powerful survival instinct.
The NPY and The CART
In your brain is an area in the hypothalamus called the satiety center. That’s the area where your brain processes the hunger information. There are two different types of players in this area. The eating chemicals driven by NPY (a protein called neuropeptide Y) and the satiety chemicals led by CART (cocaine-amphetamine-regulatory transcript). NPY decreases metabolism and increases appetite. CART stimulates the surrounding hypothalamus to increase metabolism, reduce appetite, and increase insulin to deliver energy to muscle cells rather than be stored as fat. When you are hungry, NPY will slow you down. It will not let you use your energy because it is afraid you will run out of fuel. So it slows your metabolism down. You have an empty stomach, you are starting your workout and somehow you don’t feel like it’s going to be a good workout. You just can’t feel the energy, and you feel weaker than normal. You hear messages in your mind like:
''I don’t know what is going on, I’m doing the same workout as usual, but today is so much harder.''
You then start wanting to eat. Your brain is telling you to slow down because it’s in need of energy. The light of your gas gauge is on—you need fuel. NPY increases your appetite.
The CART is the reverse. When you have enough food in your stomach, these brain chemicals send the brain a signal to increase your metabolism. The body is ordered to increase the level of energy. Your brain then receives a signal that now the stomach is full of energy, so it tells the body to go ahead and spend some energy: ''I’m good to go, I have a full tank!'' Then you can start running and working out with energy, or you can go back to work after a healthy lunch and start to concentrate again, see things clearly, and move with vigor. CART decreases your appetite. You need some good food in order for your brain to receive the signal that it’s okay to start moving again.
Who Gives These Signals To The NPY and The CART?
The grehlin and the leptin. They are both stress hormones, and they work with the NPY and the CART. The grehlin works hand in hand with the NPY. When you have used up your fuel, the grehlin will transmit the signal to the NPY area of the brain. (I call it the gremlin to remind myself which one is which.) The grehlin is the little voice that tells the brain: I’m hungry. Have you ever heard that voice? Of course you have. That's because, as a human, the very first instinct is always to survive. So when you are hungry, you will hear that grehlin tell you every 30 minutes, then every 20 minutes, then every 15, 10 . . . and then soon, if you still don’t feed yourself, eating will be the one sole thing on your mind.
The leptin is the satisfactory hormone. It will stimulate the CART. It will get information from your stomach and notice if it is being fueled. When it notices real food in the stomach, it will give the message to the CART area of the brain to say that it’s okay to move and spend energy again.
An Example in Layman’s Terms
Now, let’s see if we can explain that to you again in our own words. This mechanism only works with real food. Your body is smart. Your brain is smart. Your body notices what you eat. Surprise! You can’t just put a chocolate bar in your mouth and hope that your body will not notice. It will. Let’s say, for example, it’s lunch time. You had breakfast before work, you may even have had a snack; an apple, a rice cake, or something similar around 10:00 a.m. and now you’re ready for lunch. You have not brought your lunch with you, though. So you go to your favorite coffee shop and get a ham and cheese sandwich. It tastes great, and you feel full–but what does your body say? Your gremlin (grehlin) is yelling, asking for food. It sees this sandwich coming in. So it says: Great! I love ham and cheese sandwiches. What’s this? Bread. Cool! Fiber and carbs are coming.
Wait a minute though. Your body doesn’t recognize the refined and processed white bread, so it decides to just put it aside for now and stores it—on your butt, your thighs, your stomach, anywhere it can. The grehlin keeps asking for more food, so what about the ham? That’s protein, right? It’s processed ham, and again your body doesn’t recognize it. It decides to store that too. Next we have some cheese. Great! Dairy and protein together! But it’s processed cheese, and your body doesn’t know what it is. What does it do with it? Stores it! Same with the mayo. So the grehlin keeps asking for more and more food and will not shut up until you actually feed it.
At the end of your lunch, all you’ve really eaten is a slice of tomato and a piece of lettuce! Vegetables. With that though you’re only good for a few minutes. It’s no wonder you are hungry again in an hour. You haven’t actually been fed properly. So what do you do at the end of the meal with that gremlin still yelling for food in your brain? You go get an oatmeal-raisin cookie. A bit of oat will help and a few raisins are good, but all the refined sugar will be stored with the rest of the junk. So, really, lots of garbage just added to the pile of unwanted inches covering your body. It’s just stuffing yourself with “stuff” that is not real.
Does the Workout Get Rid of the Junk?
Now keep your attention on the next lines because we are not done here. Some of you are thinking right now that it’s okay to store some garbage stuff when you work out a lot. You think that the stuff accumulated on your bum at lunch time will magically burn off at 6:00 p.m. when you hit the gym. We're sorry to have to be the one telling you the hard truth. With no proper fuel, when you do your workout, you crash. Your workout does not fix the problems you ate.
As an example, when you are hungry yourself, do you open the refrigerator door or the garbage can to look for food? You want fresh, good energy, right? When your body needs fuel, it looks for good fuel. So it won’t take the fat, or the body's version of garbage, that it did not want in the first place. It stored it once. It will not run to the garbage at the first sign of hunger. If you are not eating it, you are stealing it from your body. If the glycogen store is empty, your body will look for protein for fuel. It might take some energy from your muscles and bones, and then your workout makes you actually weaker than you were before. It will shrink your muscles, making you lose muscle mass, not fat. The garbage will still be there, but the muscles will be shrinking, changing your body composition.
So How Do You Get Rid of Your Garbage?
You need to contract your muscles so they get rid of the accumulated fat. It is really important, therefore, that you feed yourself before your workout. Eat real food. You have to have the energy to squeeze properly. No more fake and processed stuff. Keep it all real so your body can actually have the strength to kick it out on your next exercise session. Happy healthy eating!