wrote:
Working out aerobically while in calorie deficit is going to burn body
fat and dietary protein. There is a limit to the number of calories
you can expend per minute though. When I was first starting out with
low carb it was real tough to burn any faster than about .04 calories
per pound of body weight per minute without feeling stale and tired.

Yeah, but if you keep at it your capacity will generally increase a lot.
It took me a couple months to get to the point that I was good on long
climbs on my bike, but eventually I actually had more endurance than I
ever did on high carb. It actually kind of surprised me, actually, as to
that point I'd never been much on endurance.

From little snippits I've picked up from the infamous Lyle and a couple
other mfw lunatics, it appears that muscle tissue can also use fatty
acids for energy to some extent, and that storage and use of same
improves with conditioning. I've never followed up on that, but perhaps
this is what happens with some people, if not everybody. I understand
that this is a rather under-studied area, which I suppose is why you get
so many different opinions. All I know is that after a couple months
adaptation to exercise on a low-carb diet, my endurance and speed/power
was vastly improved, even over an all-the-pasta-you-can-eat diet.

Of course we're only discussing aerobic exercise here. Anaerobic is
another thing altogether.

If you search for information about fasting and muscle catabolism you
will find some good explanations about the problems of keeping muscle
while in calorie deficit.

Yes, if you add in an ongoing, consistent calorie deficit, that's
another element. Although, many people do sort of naturally (not
intentionally) cycle calories, so that they're hypocaloric for a day or
two, then hyper caloric. Even while losing weight overall. I think
that's one of the dangers of eating too few carbs and getting into deep
ketosis, your appetite reduces to the point you don't give yourself
those hypercaloric days. Probably not good in the long run, and
certainly will not promote mucle retention let alone building.
Personally I'm not into having big muscles, being female and all, just
being reasonably strong.

Although tearing yourself up sprinting or weight lifting to excess is
not going to be very productive without cycling carbs you can tone and
do less energetic cardio workouts to rebuild some of the lost muscle.

But see, you're into anaerobic stuff with sprinting and weight lifting.
I think cycling calories is probably somewhat more important than
cycling carbs, in terms of minimizing muscle loss, although effectively
both probably need to happen if you want gains. One thing I hang on to
is that eating a moderately low-carb way, and doing really awesome
amounts of aerobic exercise (like competatively running around 100
miles/day for day after day) didn't give him that kind of skinny,
scarecrow look a lot of (presumably high carb) long distance runners
get. In all the photos I've seen of him, he looks good, moderately
muscled, not what I think of as the "runner look".

Trying to build muscle while in calorie deficit is always going to be
a compromising venture. Having a carb up every few weeks and ripping
yourself out at full effort may give you a psychological boost that is
worth a week of weight gain though. You get a nice pump from the
extra glycogen in the muscles and some people say it resets metabolism
at a higher rate.

I've never been a big fan of carb-ups, but I also am not very positive
about long-term very low carb eating, either. I think there are a lot of
people eating 20 or 30 g/day and feeling cruddy and tired who could do a
lot better up at 50 or 60 or even higher, and still keep their appetite
in control well enough to lose weight. And frankly, appetite control is
the primary advantage of low-carb dieting. Also, feeling really well is
inductive to a higher activity level. But I know there are a lot of
people who feel their periodic carbups do them a lot of good.

HG