is your body starting to "eat" muscle ONLY when all the fat storage has been burned?

Question

some people say if you do cardio work outs you burn muscle tissue too, some others say it is impossible and it will start consuming muscle only when the fat storage has been completely used. Your opinion?

Answer 1

OK here is how this works. Assuming you are a person of healthy body weight and eat regularly your body will have within it a store of a sugary substance called glycogen. This is your immediate reserve of energy that your body calls on when doing exercise. It typically takes about 20 minutes to use up your glycogen stores at which time your body goes looking for other fuel to burn.

Now here's the trick: different parts of your body burn different substances by preference; for instance your brain will only use sugar, it can't use fat or protein. Your heart prefers to burn fat though, which is why cardio exercises help you to burn fat.

Our bodies are pre-programmed to hang on to their precious fat reserves, so they actually will burn muscle in preference to fat, in a famine situation. However, as long as you are not subjecting your body to a famine i.e. by eating properly and you are exercising, to keep building your muscles up, you don't need to worry about your muscle tissue being burned up.

A lot of weight lifters take protein supplements to try to prevent this muscle 'wasting' that cardio is supposed to do; I don't believe that this is a healthy thing to do. Excess protein will just get washed out in your urine and if it is metabolised makes life harder for your kidneys. You don't actually need very much protein to repair your muscles, a lot less than most people actually eat.

Here are some opinions on food and diet:

http://uk.blog.360.yahoo.com/blog-iQ_TenI9dLT74fuxz0hwQxOHovpKsgI-?cq=1

All feedback appreciated.

Answer 2

The two terms that you should be concerned with are catabolism(muscle wasting) and gluconeogenisis(conversion of other macronutrients to glucose).Cardio or any work out can put you in a catabolic state if you don't train,eat and rest properly.The very first thing to be targeted during anaerobic exercise is glycogen(stored carbohydrate).But the body may very quickly move to another source well before your glycogen anfd fat are depleted.Your fat is never going to be completely used so the answer to that part of the question is no.Youdon't say anything at all about what your work outs consist of or what your goals are so all I will add in parting is eating 6-8 small meals a day and consuming protein every 3 hours to retain a positive nitrogen balance are two things that you can do to prevent catabolism.During heavy weight lifting cycles consume 1.5 grams of protein per day per pound of body weight.Not my opinion.100% fact.Wow,I submitted this then saw you did get some really good answers except the part about us getting enough protein in our diets.That applies only to non athletic people and definitely not to weight lifters as shown in clinical evidence.Good for those of you who included science in your answers.GREAT JOB!

Answer 3

Your body will eat muscle (protein) when there is a negative nitrogen balance. Your body needs protein to repair cells so if you don't eat enough protein your body will release catabolic chemicals that break down your muscles.

Cardiovascular excercise use a muscle fibre type called slow-oxidative fibres. Non-cardio excercises such as weight lifting use fast-glycolytic muscle fibres. Slow twitch muscle fibres' preferred energy source is fat; so cardio is good for burning fat. Conversely, Fast twitch muscle fibre types will only use a glucose source. Neither has protein as its preferred energy source.

The only time your body will begin to break down muscle for energy is when the body is in a state of fasting. Then it will not distinguish between muscle or fat and will break down both roughly equally (but its noteworthy that fat yield twice the energy of protein pound per pound).

Its also worth noting that your body will streamline the muscles that you are using for the cardio excercise. This means that if say your quads were excessive in size for a long distance run your body will reduce their size to make them more efficient.

In summary, and in direct answer to your question, your body will definitely not metabolize your muscles when your performing cardiovascular excercises.

Answer 4

If you're exercising regularly, eating healthy and giving your body enough calories per day then no. If however you are burning more calories per day than you ingest then yes you will lose muscle mass. Making matters worse with your metabolism thinking that your going to starve by not getting enough calories it will burn more muscle and turn it into fat cells. So you'd actually be getting fatter, noticeably in the abdomen region, while doing cardio.

Answer 5

I believe it the other way around. Your body eats the muscle first, then the fat.

Answer 6

Take a lap around the grocery store before starting shopping.

Answer 7

Do a few biceps curls each time you pick up shopping bags.

Answer 8

Stick to an even more trim protein/green plant eating plan

Answer 9

If you do not consume enuff calories and protein (soy, eggs, steak) you will loose muscle.

Answer 10

The body breaks doen carbs first then lipids (FATS) then proteins(MUSCLE) as a last resort