do low carb diets burn muscle and fat?

silverharp

I'm at the little knowledge is dangerous phase , but I've gradually moved to low carbs especially for breakfast and lunch and its working a treat for dropping the weight. At the same time I'm trying to get fit, mostly with a combination of running and cycling. My high point of the week is normally a 3 to 5 hour cycle down to Wicklow at the weekend and I've normally eaten a breakfast smoothie with berries, oatmeal,bananas and honey before I set off

So the 2 pronged question is, does low carbing target muscle mass or otherwise lower your ability to run a 10K say or cycle a 100km? And secondly when I'm doing the longer cycles do I "need" to carb up? I reckon I burn about 1500 calories on the cycle and take in about 1000 calories with the smoothie (I take the rest of the batch with me and eat it during the morning). in my head that's an extra 500 calories over a normal breakfast so a net burn of 1000 calories.

I was thinking of trying a shorter route this Sat. but eat a lower carb breakfast and maybe take a banana with me to see if I notice a difference. The only observation I've made is that on the cycling day I dont think I eat anymore that day so the higher carb breakfast and the cycling doesnt appear to make me want to eat more during the day or make me crave junk carbs.

EileenG

One of the advantages of low carb diets for weight loss is that they tend to be muscle sparing, or at least more muscle sparing than an isocalorie diet that's high carb. If you drop calories low enough, you'll lose muscle on any diet. But the trend now is to use low carb diets for obese patients who are bed-bound, because of the muscle sparing effect.

The problem for you is that fat provides an almost infinite amount of energy, but the conversion rate is lower than carbs. So unless you are very used to low carbing, you may find that once you go above 70% intensity or so, you start to struggle. This may not be a factor for you, since I suspect that on a 3-5 hour cycle, you won't go above that often anyway.

However, what a lot of athletes do here is to eat a small meal with low gi carbs before the workout, enough to bridge the gap between what they might need and what fat can provide. Porridge is a good pre-workout meal here.

Carry a few suitable snacks and see what works best for you.

silverharp

EileenG wrote: »

One of the advantages of low carb diets for weight loss is that they tend to be muscle sparing, or at least more muscle sparing than an isocalorie diet that's high carb. If you drop calories low enough, you'll lose muscle on any diet. But the trend now is to use low carb diets for obese patients who are bed-bound, because of the muscle sparing effect.

The problem for you is that fat provides an almost infinite amount of energy, but the conversion rate is lower than carbs. So unless you are very used to low carbing, you may find that once you go above 70% intensity or so, you start to struggle. This may not be a factor for you, since I suspect that on a 3-5 hour cycle, you won't go above that often anyway.

However, what a lot of athletes do here is to eat a small meal with low gi carbs before the workout, enough to bridge the gap between what they might need and what fat can provide. Porridge is a good pre-workout meal here.

Carry a few suitable snacks and see what works best for you.

Sounds good. The cycling is a good calorie burner and I'll keep an eye on what I eat and see if I notice anything. Good to know that low carbing doesnt burn excessive amount of muscle.

El_Dangeroso

The liver produces ketone bodies during a very low-carb diet and these are used as fuel by the brain and muscles. Ketone bodies prevent muscle protein breakdown. If the muscle is plentifully supplied with other fuels, such as fatty acids and ketone bodies, then the oxidation of muscle protein-derived amino acids is suppressed. So, if the body has enough ketones as fuel, it doesn't need to break down so much protein to produce glucose for fuel.

Beta-hydroxybutyrate (a major ketone body) decreases leucine oxidation and promotes protein synthesis (muscle building) in humans. Leucine has been found to slow the degradation of muscle tissue by increasing the synthesis of muscle proteins.

I have been reading up on this lately, can you tell? :P

But even moderate carb isocaloric diets (as in not ketogenic but still <150g/day) are more muscle sparing than higher carb ones.

--Kaiser--

Temple_Grandin wrote: »

I have been reading up on this lately, can you tell? :P

I dunno, sometimes I think you just make it up

El_Dangeroso

--Kaiser-- wrote: »

I dunno, sometimes I think you just make it up

Damn, you've caught me! I just string a few polysylabic words together and bam! scientific credibility..:cool: