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View Full Version : Study: Effects of Energy Deficit Without Reducing Dietary Carbohydrates.


Darryl Shaw
06-03-2009, 06:51 AM
Energy deficit without reducing dietary carbohydrate alters resting carbohydrate oxidation and fatty acid availability.

Abstract
Reduced carbohydrate (CHO) availability after exercise has a potent influence on the regulation of substrate metabolism, but little is known about the impact of fat availability and/or energy deficit on fuel metabolism when dietary CHO availability is not reduced. The purpose of this study was to determine the influence of a postexercise energy deficit, independent of CHO availability, on plasma substrate concentrations and substrate oxidation. Seven moderately trained men (peak oxygen uptake: 56 ± 2 ml·kg–1·min–1) performed exhaustive cycling exercise on two separate occasions. The two trials differed only by the meals ingested after exercise: 1) a high-fat diet designed to maintain energy balance or 2) a low-fat diet designed to elicit energy deficit. The CHO and protein contents of the diets were identical. The next morning, we measured plasma substrate and insulin concentrations and CHO oxidation, and we obtained muscle biopsies from the vastus lateralis for measurement of pyruvate dehydrogenase kinase (PDK)-2 and PDK-4 mRNA expression by using RT-PCR. Despite identical blood glucose (5.0 ± 0.1 and 4.9 ± 0.1 mM) and insulin (7.9 ± 1.1 and 8.4 ± 0.9 µU/ml) concentrations, plasma fatty acid and glycerol concentrations were elevated three- to fourfold during energy deficit compared with energy balance and CHO oxidation was 40% lower (P < 0.01) the morning after energy deficit compared with energy balance (328 ± 69 and 565 ± 89 µmol/min). The lower CHO oxidation was accompanied by a 7.3 ± 2.5-fold increase in PDK-4 mRNA expression after energy deficit (P < 0.05), whereas PDK-2 mRNA was similar between the trials. In conclusion, energy deficit increases fatty acid availability, increases PDK-4 mRNA expression, and suppresses CHO oxidation even when dietary CHO content is not reduced.

http://jap.physiology.org/cgi/content/full/98/5/1612

Greg Battaglia
06-03-2009, 08:18 PM
Makes sense. Create a calorie deficit and the body burns more fat than when calories are adequate, despite macro ratios. I'd be willing to bet if they compared a low-carb diet with an equal amount of calories to the low fat diet with a deficit the low carb would win out in terms of fatty acid and glycerol oxidation. In fact, I'd be amazed if it didn't.

Darryl Shaw
06-05-2009, 06:54 AM
Makes sense. Create a calorie deficit and the body burns more fat than when calories are adequate, despite macro ratios. I'd be willing to bet if they compared a low-carb diet with an equal amount of calories to the low fat diet with a deficit the low carb would win out in terms of fatty acid and glycerol oxidation. In fact, I'd be amazed if it didn't.

You may be right (studies?) but a low carb diet would impair your ability to engage in any form of high intensity exercise thereby reducing your ability to create a significant caloric deficit.

Cassidy Drake
07-25-2009, 07:03 PM
Ummmm, actually that is very far from the truth, as we have discussed here quite a few times. Adaptation period is key.

Derek Weaver
07-25-2009, 08:42 PM
Ummmm, actually that is very far from the truth, as we have discussed here quite a few times. Adaptation period is key.

Not exactly. Low carb diets are fine for weightlifters and can work really well for endurance athletes.... and also can be disastrous for endurance athletes depending on the athlete.

However, a fighter, crossfitter, basketball player, soccer player etc. and just about any other athlete from a sport that relies on a constant series of starts and stops is going to need carbs, though not to the degree mainstream dieticians will try and prescribe.

And yes, i realize I just described CF as a sport.

They're not evil and don't make you fat all by themselves.

Cassidy Drake
07-26-2009, 10:32 AM
Not exactly. Low carb diets are fine for weightlifters and can work really well for endurance athletes.... and also can be disastrous for endurance athletes depending on the athlete.

However, a fighter, crossfitter, basketball player, soccer player etc. and just about any other athlete from a sport that relies on a constant series of starts and stops is going to need carbs, though not to the degree mainstream dieticians will try and prescribe.

And yes, i realize I just described CF as a sport.

They're not evil and don't make you fat all by themselves.

Really? Just what is Mark? Or any other alpinist? My team and I compete in 24hour -10 day adventure races. We all are what we consider low carb.

http://www.gymjones.com/knowledge.php?id=17

Then again I won't be the only one here that doesn't agree with you one bit on that.

Derek Weaver
07-26-2009, 12:04 PM
Not exactly. Low carb diets are fine for weightlifters and can work really well for endurance athletes.... and also can be disastrous for endurance athletes depending on the athlete.
However, a fighter, crossfitter, basketball player, soccer player etc. and just about any other athlete from a sport that relies on a constant series of starts and stops is going to need carbs, though not to the degree mainstream dieticians will try and prescribe.

And yes, i realize I just described CF as a sport.

They're not evil and don't make you fat all by themselves.

Really? Just what is Mark? Or any other alpinist? My team and I compete in 24hour -10 day adventure races. We all are what we consider low carb.

http://www.gymjones.com/knowledge.php?id=17

Then again I won't be the only one here that doesn't agree with you one bit on that.

I think you missed the point I made and I'll just leave it at that.

Cassidy Drake
07-26-2009, 05:44 PM
Didn't miss the point at all. :D

Darryl Shaw
07-27-2009, 05:53 AM
Ummmm, actually that is very far from the truth, as we have discussed here quite a few times. Adaptation period is key.

Fat adaptation is great in theory but the reality is it does nothing for athletic performance where glycogen stores are always the main limiting factor. Even Phinney's study Ketogenic Diets and Physical Performance (http://www.nutritionandmetabolism.com/content/1/1/2) came to the conclusion that "performance is limited by the low muscle glycogen levels induced by a ketogenic diet, and this would strongly discourage its use under most conditions of competitive athletics". The bottom line is that the only people who really benefit from fat adaptation are arctic explorers and anyone else who has to go for very long walks in very cold climates.

"Fat adaptation" for athletic performance: the nail in the coffin? - Louise M. Burke. (http://jap.physiology.org/cgi/content/full/100/1/7?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&author1=burke+lm&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT)

Cassidy Drake
07-28-2009, 06:51 PM
Fat adaptation is great in theory but the reality is it does nothing for athletic performance where glycogen stores are always the main limiting factor. Even Phinney's study Ketogenic Diets and Physical Performance (http://www.nutritionandmetabolism.com/content/1/1/2) came to the conclusion that "performance is limited by the low muscle glycogen levels induced by a ketogenic diet, and this would strongly discourage its use under most conditions of competitive athletics". The bottom line is that the only people who really benefit from fat adaptation are arctic explorers and anyone else who has to go for very long walks in very cold climates.

"Fat adaptation" for athletic performance: the nail in the coffin? - Louise M. Burke. (http://jap.physiology.org/cgi/content/full/100/1/7?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&author1=burke+lm&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT)



That can be said. However having done 24-240 hr race events with my team. I beg to differ. Sure I understand glycogen. I aslo understand that the depletion of it is often over rated, and misplayed. We don't do keto. I am not even what I would consider low carb (150 per day, I weigh 180). Bottom line? No, I have seen it work quite well within the climbing community and adventure racing community. We don't do it in the artic:D That being said, it may come off as me being anti carb. I'm not, I just won't see and havent' seen over the last two years that 300-400 carbs a day is needed for our type of training, which is extremely endurance based.

Not to mention your article and studies use 5 days to two weeks as the adaptation period. Not near long enough when talking to mid or long level endurance athletes. Glycogen can be depleted anytime you don't ingest enough carbs. We do that, but not the way everyone thinks.

Darryl Shaw
07-29-2009, 05:44 AM
Cassidy,

Your CHO intake of 150g/d works out at 1.8g/kg/d which is a very low carb diet and is barely enough to keep your brain ticking over. This falls far short of the of the general recomendation that endurance athletes consume 6-10g/kg/day (depending on training load/volume) but if that's what works for you I'm not inclined to argue the point.

Cassidy Drake
07-29-2009, 12:02 PM
Cassidy,

Your CHO intake of 150g/d works out at 1.8g/kg/d which is a very low carb diet and is barely enough to keep your brain ticking over. This falls far short of the of the general recomendation that endurance athletes consume 6-10g/kg/day (depending on training load/volume) but if that's what works for you I'm not inclined to argue the point.

It ticks fine. See here is the thing. I do it, my team mates do it. I realize I don't post here much. But I am no spring chicken to training or diet what so ever, in fact I have a year long series coming up in the PM.

I know where you are coming from though, and I understand your reasoning. I am saying I have read tons of literature on it, and have used it with enormous success in our training. Does it work for everyone? Of course not, we all have different needs, and I imagine some day someone on our team will need to consume mass carbs to complete our races. Just haven't gotten to that point yet:D

Thanks for the great discussion.

Miranda Sierra
11-15-2009, 05:14 AM
Wow! You guys are all so amazing, keep up the awesome work ^_^