Okay. I took an anatomy/physiology class a while back. One of the topics covered was how weight is lost.

Keep in mind that it's been a long while so my scientific terminology is way, way, WAY off. :P

Let's say you start a fast (I don't agree with fasting and I personally would never fast for long periods of time, but just for the sake of discussion). So you're fasting. I read that first, if there are any carbs lurking around in your system from the food you ate just before starting the fast, your body will use up those carbs first.

When all of that carb is used, your body will then take stored glucose from your liver. I think it was liver. Remember, it's been a while.

When THAT supply runs out, your body then takes in stored fat for energy. And I believe stored fat is actually all the glucose that we didn't burn off/use up and so it became stored fat, to be used when our body goes through fasting/famine, etc.

Finally, I read, the last thing to go was muscle tissue. When the stored carbs/fat is used up, protein is used up.

Now here's my question. In so many forums (not just this one), books, articles, etc, people say that if you fast or starve yourself, the first thing to go is muscle tissue, while your body holds on to the fat.

What's correct?

I hope my rambling made sense.

I would like clarification on this, too!

hmm I really don't know. I would like to know too though Sorry I'm no help.

I don't know much about the order of those things but I know a couple of interesting bits.
Muscle atrophies (shrinks) very quickly. Anyone who has ever been in a cast will tell ya. Your body is not eating it but it's shrinking and can't use calories.
And you do use blood sugars first .... after that I'm not sure. But I thought it always went after easy first ... so fat would be easiest????

What I've heard is our body will only let so much of our fat go before it starts going for muscle, since muscle is metabolically active. I've heard that the reason you should aim for 2 lb/week loss (for those that aren't morbidly obese) is because after 2 lbs, your body will start tearing down muscle. It makes sense to me that your body would start burning both its stored fat but then also try to get rid of your muscle because muscle burns fat. If your body isn't getting any energy to keep your body running, why would it want to waste its time on trying to sustain muscle that it may not necessarily need?

So I'm wondering from your text, if it is has any reference to what happens over time or if it is looking at a small window of time and what happens during that small window.

You've asked the number one question in the weight loss world! There have been numerous studies on this subject and everyone has their own interpretation of the "facts." There are an equal amount of studies on each side of this subject. IMHO, I don't think anybody really knows for sure. I'd love to see somebody do a major study on weight loss that is not subsidized by some company or organization that will profit from 'favorable' results! I was taught the same thing as you were in my Anatomy and Physiology courses. And, if you research starvation and the effects on the human body, the sequence is the same as you describe....available carbs, then stored glucose, then ketones from fat...and finally, muscle mass and organs.

In the past, I've fasted many times for spiritual reasons...one fast lasted for 30 days. These were total fasts with water intake only. After the first 2-3 days, I felt absolutely fine. As a matter of fact, I often felt incredible! And, I did lose some weight, however, it was gained back rapidly once I started eating again.

On 3FC, you will find many friends who strongly believe that eating too few calories is detrimental to your health. You will find an equal amount of friends who can only lose the weight by lowering their calorie intake drastically. For me, I hate tracking calories. One day, my weight loss may stop and I may have to start tracking. For now, I prefer to follow my Southbeach program and eat protein with each meal and get aerobic exercise daily. So far, this works (When I stay on-plan!)

Interesting article:

http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

Very interesting.

One other thing I was thinking about....if losing too fast means you're losing muscle and not fat...then how come some of our friends are still standing after losing so quickly? And, looking fit, toned and feeling so good? Shouldnt they be flabby and too weak to lift themselves out of bed each day? Hmmm.....definitely something to think about.

Losing quickly and fasting aren't really the same thing. If you are fueling your body, then you will lose less muscle than if you are fasting. Although, when you lose weight you are usually losing a mix of fat and muscle, hopefully more fat than muscle. When I was near my heighest weight, I did a variety of body fat tests which said my lean mass was at about 178 lbs. Lean mass being everything but fat so it is your organs, muscle, bone and water. More recent tests have put me at 160 lbs of lean mass. So in losing 100 lbs, I have supposedly lost 82 lbs of fat and 18 lbs of "other". How much is water? How much is muscle? I really don't know but I really consider that a good ratio.

One thing I believe strongly in doing is lifting weights because that helps retain your muscle mass.

So you can lose fairly quickly, especially when you start from a high weight but you can minimize your muscle loss. When you are fasting though, your body is really in a survival "where is the food?" mode.

I agree with Nelie.

Our bodies need protein every day to survive. It's what builds and repairs our bodies. If we don't feed it adequate protein, a body is forced to get protein from itself. Where is protein stored in our bodies? In our muscles and organs.

So in the absence of adequate dietary protein, our bodies cannabalize themselves. They burn precious muscle and even will start to digest organs such as the heart (this happens to anorexia sufferers). This is bad news because muscle is what burns fat in our bodies. The more muscle you have, the higher your metabolism is - a good thing!

So maintaining my muscle mass was my highest priority as I lost fat.

After a year of weight loss, I actually gained seven pounds of muscle and lost 129 pounds of fat, for a net loss of 122 pounds. I did it by lifting weights (as heavy as possbile ) five days a week and by eating high protein (between 120 - 150 grams a day, or about 45% of my calories). Eating high protein spared the protein stored in my muscles and organs from being used as fuel. And lifting weights built new muscle to replace any that was lost through dieting.

I guess that's why I'm still standing, even after losing fairly quickly. I deliberately worked hard on maintaining my muscle mass. It was very, very different from fasting.

Yup, I'm still standing as well. In fact I'm not only standing, I'm MOVING. Way better then I ever have in my entire life. I have more energy then I did when I was a teenager, at least from what I remember. I was 135 lbs. then, but didn't exercise or eat properly. Now my diet is completely nutritious and full of protein and I exercise 7 days a week. Like Meg, I have also gained a fair amount of muscle in the process. At 177 lbs my body fat % is 27%. Meaning I am 129 lbs of lean mass. It really, really angers me when people say that losing more then 2 lbs a week is too quickly. If done wrong then yes, it is too quickly. But when done properly, well it can't be quick enough. IMO.

Robin,
That 2 lb/week number is really not based on those that are morbidly obese. I think the studies done were on those that had well under 100 lbs to lose. So I've always heard that 2 lb/week is "safe" but if you are morbidly obese, then the number is a bit more flexible. How flexible? Who knows.

I agree with you 150%. That's why when people say that, about losing more then 2 lbs per week, it's really a very general thing. For the morbidly obese, all bets are off. It's a whole other matter. My goals were NEVER to lose a certain number of pounds per week. I never even considered that. My main goals were to eat highly nutritous foods and to add exercise and movement to my life and to add muscle to my body. I knew if I did those things the weight would come off in as safe a manner as humanly possible.

I don't think many studies have ever been done on those of us losing more than 100 pounds without surgery. We're the orphans of the medical and research communities. So we're doing the research here ourselves ... and if the researchers are smart, someday they'll come to US for answers!