Low carb and its effect on exercise performance

[Keto]

A recent study has begun to shed some light on this topic - the key conclusion is:

An LC (Low Carbohydrate) weight loss diet shifted fuel utilization toward greater fat oxidation during exercise, but had no detrimental effect on maximal or submaximal markers of aerobic exercise performance or muscle strength compared with an HC (High Carbohydrate) diet.

Here's the full abstract and reference:

Dietary restriction and increased physical activity are recommended for obesity treatment. Very low carbohydrate diets are used to promote weight loss, but their effects on physical function and exercise tolerance in overweight and obese individuals are largely unknown. The aim of this study was to compare the effects of a very low carbohydrate, high fat (LC) diet with a conventional high carbohydrate, low fat (HC) diet on aerobic capacity, fuel utilization during submaximal exercise, perceived exercise effort (RPE) and muscle strength. Sixty subjects (age: 49.2 +/- 1.2 years; BMI: 33.6 +/- 0.5 kg/m(2)) were randomly assigned to an energy restricted (~6-7 MJ, 30% deficit), planned isocaloric LC or HC for 8 weeks. At baseline and week 8, subjects performed incremental treadmill exercise to exhaustion and handgrip and isometric knee extensor strength were assessed. Weight loss was greater in LC compared with HC (8.4 +/- 0.4% and 6.7 +/- 0.5%, respectively; P = 0.01 time x diet). Peak oxygen uptake and heart rate were unchanged in both groups (P > 0.17). Fat oxidation increased during submaximal exercise in LC but not HC (P < 0.001 time x diet effect). On both diets, perception of effort during submaximal exercise and handgrip strength decreased (P </= 0.03 for time), but knee extensor strength remained unchanged (P > 0.25). An LC weight loss diet shifted fuel utilization toward greater fat oxidation during exercise, but had no detrimental effect on maximal or submaximal markers of aerobic exercise performance or muscle strength compared with an HC diet. Further studies are required to determine the interaction of LC diets with regular exercise training and the long-term health effects.

Brinkworth, G. D., Noakes, M., Clifton, P. M., & Buckley, J. D. (2009). Effects of a Low Carbohydrate Weight Loss Diet on Exercise Capacity and Tolerance in Obese Subjects. Obesity (Silver Spring). doi: oby2008559 [pii] 10.1038/oby.2008.559

[Tril]

Thanks for posting this!!!

[Keto]

Thanks Tril

The science of Low Carb interests me, along with making the material more accessible. I'm considering setting up a blog with updates (and translations) of new studies as they're published, just an idea at this stage.

Matt

[Tril]

It's a great idea... I'd love to have a resource for studies that support our way of eating. It would make it much easier to say, "Read this... then decide."

[Motley]

Don't forget that the muscles grow with protein, so strength should not be affected. But muscles need carbs (glycogen) to work, so a low carb diet is not for people that do a lot of sport / athletics.

[Keto]

Just to let you know that my blog is now live and the first post expands a little on what I've written above.

Motley your comments were valuable thank you.

the address is www beyondgrains dot com (still cant post links)

Matt

[Tril]

But muscles need carbs (glycogen) to work, so a low carb diet is not for people that do a lot of sport / athletics.

So totally untrue. Otherwise someone who ate low carb would be incapable of running a marathon (or climb stairs... or go for a walk... or a hike...), right? Then how do explain that they can... and they do?

[merlot]

I did a Google for "burning glycogen stores" and on an old Atkins thread was a poster explaining some very interesting chemistry which suggests an alternative to Motley's comment. At this point, I have no idea what the actual science IS, but the debate is interesting.

Indeed, our own Batlou and of course, Bowulf on YouTube run marathons on low-carb with no ill affects.

Good luck on your blog, Keto! I just went over there and it is a VERY nice looking page, and your "About" is very professional! Good "disclaimers" too. Congratulations on putting it together...it is very high quality!

Toni [of the: "Best I can do is walk maybe 2 miles" peanut gallery!]

[Keto]

Thanks Merlot. I'm glad you like the blog, there's another post coming today that will look at low-carb diets vs. low fat. Next week will be an off topic looking at the impact of marriage on weight (seems there is a fairly clear link!).

Matt

[ozfisho]

I'm in the gym most days for 90 minute solid workouts, so I'll see how this pans out and I'll put something on here telling how I go.

Cheers
Dale

[merlot]

I like the "Impact of Marriage on Weight" topic. I was married in 1962, and unfortunately my husband passed away a little over 4 years ago. But together, we shared a LOT of life together.

Back then, if your guy wanted to lose weight, the "little woman" went out of her way to cook low-cal or whatever the doctor said, for him. When the "little woman" went on a diet...it was her problem. The guys LOVED to eat! How many times did we hear, "Just because YOU are on a diet doesn't mean I have to be on one too!" Nor the kids. So hubby (Dad) stayed heavy and the kids got heavy, Mom struggled to be thin and usually failed!

I'm now 65 and do NOT have a clue what a young adult OR family of today goes through. Even my kids are in their mid-40's!

I will enjoy reading it!

Toni

[tracyred]

yeah, interesting...although i reckon just because *i'm* on atkins doesn't mean anyone else in the fam should be....of course, no one else in my family is a fattie

if they were, they'd be eating my way, or nothin'! i should point out though, before any concerned mothers correct me, that i do limit my kids junk food (we call it "party" food), and sugar. they have one little juice a day for example. they so know the words "too much sugar!" thankfully, i am the only one with a propensity to stack on the weight with carbs. i just make the meal, but skip the potatoes/bread/pasta/rice/whatever. works out very well...thank goodness for dr atkins! I love my roast dinners!

t

ps - gonna check out that blog now

[merlot]

Keto, enjoyed your next article. When I was younger, about 27 years ago, I lost 24 pounds on Weight Watchers. I was only about 38 yrs old, and had hit 150 pounds for the first time in my life EVEN when pregnant! I purchased an expensive health club membership and went to the gym with co-workers quite regularly. In 10 months on WW and several times a week at a gym, I had reached my goal of 126. That was then. Didn't last long, as I went up to my "pound barrier" of 132 quickly, and then inched up. Along the way of life, I gained it all back PLUS 15 over the last 27 years. Quit smoking, got more sedentary...got old.

This go-round I started at 165, no health club membership, an old body, and on Atkins, 15 pounds heavier than my highest above. To date (10 mos), in about the same time I starved on WW, have lost 33 pounds (better than on WW) and with no fancy expensive gym membership...just a little walking my neighborhood.)

Even being older, and having a slower metabolism, I have lost 9 POUNDS MORE on Atkins than WW in a 10 mo period, and my experience in not being hungry, being satisfied, etc. bode well for me to STICK to pre-maintenance and maintenance for a lifetime, compared to WW.

Just my personal story.

Toni

[Kisten]

Hey enjoyed your thread while reading and yes got tips and suggestions also...

[shane]

Thanks for sharing such a nice information about this, i had now idea ,but got many information from your thread ..