Fasted cardio

stealthq

yarwell wrote: »

stealthq wrote: »

You can think of it a bit like no-fee, savings-backed checking accounts. Let's say you have $55 in savings (fat), and $5 in checking (glycogen). Two scenarios:

1) You need $10 and take it out of savings leaving you $45 in savings, and $5 in checking.

2) You need $10 and take it out of checking. You're overdrawn by $5 and the bank takes $5 from savings to compensate, leaving you $50 in savings, and $0 in checking. But, the bank requires you to have $5 minimum in checking at all times. So, it additionally moves $5 from savings to checking to meet the requirement. You're left with $45 in savings, and $5 in checking just like scenario 1).

Except when you pay in $10 (eat) and the the overdraft and minimum are replenished from what you pay in, leaving $55 in savings and $5 in checking, which was approximately what the study I linked to demonstrated.

Scenario 1) would be $45 in savings and $15 in checking after eating. Potentially :-)

Well, if you want to get precise about it, replenishing glycogen stores in a deficit takes a while - up to 48 hrs depending on intake. And the minimum $5 in checking would really be coming from the pay in and not from the bank moving money from savings to checking. Fat doesn't get utilized to create glycogen, after all - it just covers for the energy that would have been available if glycogen didn't need replenishment (glycogen synthesis & potential energy in the glucose and tyrosine). I was trying to simplify by skipping the re-feed portion of the scenarios.

Again, on the time scale OP is talking about, it's a wash.

abtriboy

I prefer fasted. Workout feels better. As long as no too dpletes

Azdak

yarwell wrote: »

Expatmommy79 wrote: »

Doesn't matter. Keep eating at a deficit it will come off. There is no benefit to fasted vs non fasted. CO is CO be it in the morning, afternoon or evening.

http://jap.physiology.org/content/jap/118/1/80.full.pdf expresses a different view, that the transient energy deficit can lead to greater oxidation of fat with pre-breakfast exercise compared to later in the day after meals.

In conclusion, even in energy-balanced condition, 24-h fat
oxidation is increased if exercise-induced transient energy
deficit is significant, which is likely to be observed during
exercise performed before breakfast.

Didn't get a chance to read the whole thing, but thanks for the link. Always good to have science to debate rather than opinions. Off the top of my head, I can think of two factors that might be involved: 1) I believe this study just looked at a 24 HR period. It's one thing to look at fat oxidation under tightly controlled conditions, another to look at actual fat loss over a period of time. The recent study by Schoenfeld et al (http://www.lookgreatnaked.com/blog/my-new-study-on-fasted-cardio-and-fat-loss-take-home-points/) looked at actual changes in body composition between fasted and non-fasted groups and found no differences. 2) The subjects in the study you reported had an average body fat % between 11%-12%. It has been thought/speculated that the one group who might benefit from fasted cardio are people with low body fat levels, because the fasted state does increase fat mobilization, which becomes an issue at those levels.

But a good challenge to reconcile the two different results.

RoxieDawn

Fasted cardio for me too. I am a runner, so if I am running longer than 60 to 70 minutes I start running low (to avoid the wall), I do eat carbs (about 150 - 160 calories) during the run.. But anything less than 60 minutes, I prefer fasted... This is totally a personal preference and your basic needs to train well.

Springfield1970

If fasted means 2/3 hours after a good carby meal then, yes I'm fasted.
I wouldn't dream of doing high heart rate zone stuff if I hadn't eaten for more than that amount of time before.
Why run a sports car on low octane fuel? Body fat can only burn so fast, ie not fast enough for a proper anaerobic workout.
Aerobic is different though. As long as you keep it under lactate threshold.

yarwell

Azdak wrote: »

yarwell wrote: »

Expatmommy79 wrote: »

Doesn't matter. Keep eating at a deficit it will come off. There is no benefit to fasted vs non fasted. CO is CO be it in the morning, afternoon or evening.

http://jap.physiology.org/content/jap/118/1/80.full.pdf expresses a different view, that the transient energy deficit can lead to greater oxidation of fat with pre-breakfast exercise compared to later in the day after meals.

In conclusion, even in energy-balanced condition, 24-h fat
oxidation is increased if exercise-induced transient energy
deficit is significant, which is likely to be observed during
exercise performed before breakfast.

Didn't get a chance to read the whole thing, but thanks for the link. Always good to have science to debate rather than opinions. Off the top of my head, I can think of two factors that might be involved: 1) I believe this study just looked at a 24 HR period. It's one thing to look at fat oxidation under tightly controlled conditions, another to look at actual fat loss over a period of time. The recent study by Schoenfeld et al (http://www.lookgreatnaked.com/blog/my-new-study-on-fasted-cardio-and-fat-loss-take-home-points/) looked at actual changes in body composition between fasted and non-fasted groups and found no differences. 2) The subjects in the study you reported had an average body fat % between 11%-12%. It has been thought/speculated that the one group who might benefit from fasted cardio are people with low body fat levels, because the fasted state does increase fat mobilization, which becomes an issue at those levels.

But a good challenge to reconcile the two different results.

Indeed, the Schoenefeld study was at a calorie deficit with 23 BMI women, so the calorie deficit probably drowns out any effect of exercise timing vs eating especially as they used Bodpod to assess difference in fat.

When you see 1.6 vs 1.0 kg of weight loss against a +/- 6 kg SEM there's not going to be any statistical significance in a small group either, it would be interesting to see a much bigger group run for longer so that any significance could emerge.