Dr. McDougall's Online Discussion Board

I haven't been able to find anything scientific on under what conditions (and said 'conditions' could depend on proximate food consumption, amount of exercise, or any controllable factors) exercise will burn fat as opposed to under what conditions exercise will burn muscle; and what can be done in a weight-losing regime to have more of the fat-burning and less of the muscle-burning.

I assume that strength-exercises build muscle, but am not even that clear about how, physiologically, this happens.

Good question I am interested too - plus anything on what a safe amount to loose each week is. I have heard 1% of current body weight per week, but have also heard that that figure assumed high protein Adkins type diet where muscle loss can be an issue. Then again heard that it doesn't matter on plant-based but no reason for that was given in what I read. I am so confused. Hope Lani can help us!! Sure she can

The body always burns a combo of fat and sugar, with ratio depending on intensity and fitness level. It will break down some muscle at times, but usually only when under duress. To burn significant muscle, you must be seriously underfed, since nearly everyone has enough stored carbohydrate to last more than an hour, especially if you follow this WOE. So exercising in a fasted state, going really hard, or for a really long time, all with no refueling could see some muscle wasting. So, don't do those things. Exercise at an aerobic intensity for an hour or less and you'll be fine.

On a side note, ever see those ex-NFL players that run a marathon or triathlon for charity and notice how much slimmer they are than their playing days? They actually need to burn off muscle to become efficient enough for endurance. They do that by long training in a fasted state.

That is a very interesting question. I did not realize that one could burn muscle from exercise. I was always under that impression that muscle can be built but not burned. I look forward to Lani's answer to this question as well. -Jeff

Elvin wrote:I haven't been able to find anything scientific on under what conditions (and said 'conditions' could depend on proximate food consumption, amount of exercise, or any controllable factors) exercise will burn fat as opposed to under what conditions exercise will burn muscle; and what can be done in a weight-losing regime to have more of the fat-burning and less of the muscle-burning.

I assume that strength-exercises build muscle, but am not even that clear about how, physiologically, this happens.

Hi Elvin,

Our bodies burn a mix of fuel, more or less of one or the other depending on the intensity of the exercise. Hard fast exercise utilizes a higher percentage of glucose in the mix, while at lower intensities the body is able to work aerobically - with oxygen - which can bring more fat for fuel into the mix. But if you are just looking to get leaner, it doesn't matter because what's important is overall energy usage to create an energy deficit.

Remember, it's really the food that's the biggest player in your bodyfat stores. Exercise then compliments the primary driver by creating a better metabolic profile, retains muscle mass, and just plain makes you feel better.

In low fuel situations, muscle can break down. Here's an article you might find interesting:

http://www.unm.edu/~lkravitz/Article%20 ... facts.html

Exercising the muscle through resistance training protects muscle mass.

Lani

Thanks for the article. It summaries everything very well.

schermel wrote:Thanks for the article. It summaries everything very well.

You're welcome!

Lani