where does the fat go? - Weight Loss Message Board

jlbroome · 05-06-2003, 03:21 AM

When you lose weight, where does it go? Am I going to converting too much fat to muscle by doing weight training before I lose the desired weight?

CobaltBlue · 05-06-2003, 05:28 AM

Hi JL,

Used up as energy, E=mc2

? Seriously, though, the usage of fat and formation/increase of muscle mass are two independent systems. When one says "converting fat to muscle" what is really meant is that loss of fat through exercise and increase in muscle mass through, presumably, but not exclusively a different kind of exercise.

First, lets talk about fat and its metabolism. You ingest carbs, proteins, fats, the extra dietary fat is converted into free fatty acids (FFAs) and deposited nicely around your body in the fatty tissue. Now, when you exercise... Lets say you do some wind sprints, 40 yard dashes, and do just a couple. Burn much fat? Not really--fast movements, or short burst types of exercise tend to rely on the carbohydrates you have available already. The carbos are stored as glycogen in muscle tissue and glucose in your blood. These are relied upon first, including say, when I start off my morning run.

After a few minutes of sustained exercise, your body starts needing to draw upon its reserves to keep the muscles going. This is where you get into fat metabolism. You will see some posts where DonutsnCoffee mentions the targeted or best fat burning zone, and for most people, this occurs between 68% and 85% of their calculated max heart rate. (The actual experiments were done in VO2, but its easier for us to rely on our heart rates). This is why you will see those posts in here that support a low intensity sustained exercise (like running) with heart rates in these ranges.

Anyway, I should get back to the question you asked, and finish up the "fat" part. In extreme cases, when carbos and fats are severely depleted, yes, protein can be drawn upon for energy by the body. However, the body's least preferred pathway for energy is the breakdown of proteins into its constituent amino acids. The proteins are mainly used for increased muscle size (as bodybuilders well know) and the repair of muscle tissue.

Anyway, what I tried to do here was explain (hopefully it made sense?) the fat burning part, and that its separate from the muscle building process.

jlbroome · 05-06-2003, 07:13 AM

Thank you so much....I have been hesitant to step on the scales because I was afraid that I had gained due to the increase in muscle mass. I am alternating cardio and strength training six times a week...so hopefully.....I am crossing my fingers...Thanks again for the info...

andreaphilip3 · 05-06-2003, 09:06 AM

the fat goes "out"

DonutsNCoffee · 05-06-2003, 10:04 AM

jlbroome,

As was said above, fat does not convert directly to muscle. The stored fat you have is glucose that wasn't needed and moved into fat cells. Muscle is composed of protein which is made up of amino acids so there's no direct conversion between fat and muscle (there is a mechanism the body has to create amino acids from glucose, but I won't get into the biochemistry of it all). When you exercise and you reach the point where your body will want to use fat, the glucose is moved out of the fat cells causing the fat cells to shrink. The glucose is moved into the bloodstream so your muscles and organs can burn it. Of course, this depends on your blood glucose already being low. If it's too high, then insulin will come along and put it back in storage. But the glucose that came from fat cells is treated just like any other glucose. The muscles burn it and the byproducts of that process are flushed out of your body causing your overall mass to decrease.

Keep in mind that gaining muscle isn't easy. People who are new to weight training see gains in the beginning, but eventually they hit a plateau. So if you're weight training now, you may not see much change in your weight since you're both losing fat and gaining muscle. Eventually, you'll see the weight decrease as the fat loss continues but the muscle gain has slowed.