I have been doing some lecturing this week, and part of the information I imparted concerned the potential advantages of eating a diet relatively low in carbohydrate. It’s not uncommon for individuals to ask about the potential effect of low-carb eating on sporting performance. This question is usually rooted in the notion that those engaging in regular sporting activity or exercise need to maintain their stores of a starch-like substance called glycogen (found mainly in the muscles and liver), which provides relatively ready fuel during exercise. Glycogen is a carbohydrate, and so exercisers are often encouraged to ‘carb-load’ in an effort to fill up the glycogen stores so that plenty of ready energy will be available during exercise. People downing plates of pasta the day before a marathon is borne out of this theory.
However, is carb-loading really necessary for most mere mortals? Let’s work through some figures. A 30-minute jog will burn about 250 calories in addition to those that would be burned sat still. A significant proportion of the fuel for this exercise will come from fat. Let’s imagine, that during the jog, 150 of the calories come from carb. Each gram of carb contains 4 calories, so in theory to replenish the glycogen lost during exercise is going to need the consumption of about 40 grams of carb. That’s about the same amount of carb found in a couple of apples.
In other words, for most individuals engaged in recreational exercise that doesn’t go on for hours, glycogen depletion is unlikely to be an issue unless carb consumption is cut to very low levels.
For endurance sports, low-carb eating is potentially more of an issue. If you’re training for a marathon, for instance, and racking up 50 miles or more a week, then glycogen depletion is a real risk. However, one thing that needs to be borne in mind is that when carbohydrate is restricted, the body automatically turns to other fuels (principally fat) to make up the difference. This adaptation can take time, so adopting a low-carb diet is not the thing to do a week before a marathon, particularly if your goal in not just to ‘get round’ but crack your personal best.
At lower intensities of exercise, however, adopting a low-carbohydrate diet does not appear to be an impediment to activity. A major review on the subject concluded that “endurance performance can be sustained despite the virtual exclusion of carbohydrate from the human diet.”[1].
There is no doubt in my mind that the very physically active can tolerate more carb in their diet than those who are not. If this applies to you, then aim to get your additional carbohydrate into the system within an hour or so after a sporting event or training session (this help replenishment of glycogen in the muscles for future use).
If you do feel the need to do this, I would counsel against using bread, pasta and white rice as your carbohydrate sources. Not only are these foods generally disruptive to blood sugar, they also offer precious little from a nutritional perspective. Generally slower sugar-releasing and more nutritious forms of carb include fruit, vegetables and legumes (beans and lentils).
References:
1. Phinney SD. Ketogenic diets and physical performance. Nutr Metab (Lond). 2004;1:2
I wonder if the same advice holds for strength training. Some low carb experts, such as Dr. Jeff Volek, recommend that people doing serious strength training who don’t have much weight to lose consume substantial carbohydrate (including quite a lot of pure glucose) before and after training sessions and eat carbs a day or two during the week as well. Dr. Volek says that’s helpful to replenish muscle glycogen and promote muscle building. I’ve been hesitant to follow his advice, particularly drinking the protein shakes containing all that pure glucose around workouts. But he is undoubtedly a true expert and researcher in this area, a strength trainer himself, and a strong advocate of restricted carbohydrate diets in general. Any thoughts?
“If you do feel the need to do this, I would counsel using bread, pasta and white rice as your carbohydrate sources. Not only are these foods generally disruptive to blood sugar, they also offer precious little from a nutritional perspective.”
The word “not” seems to be omitted from between “counsel” and “using”
Bill – I will second those thought. I think HIT guys like Lyle McDonald and the guy at Lean Gains are of the same opinion. Of the paleo crowd Arthur Devaney seems to be of the same opnion as Dr B above.
Dr B – nice post.
Thanks,
RE Lyle McDonald: See http://www.bodyrecomposition.com/nutrition/how-many-carbohdyrates-do-you-need.html
A low carb ,nutrient rich diet suits me very well, but I`m not an exercise nut.I just keep fairly active and walk a fair bit during the day, not being a car driver.My weight plateaued months ago at a loss of 20lbs, but not complaining. I`ve never felt better.
However, my husband does a couple of hours at the gym every night as, he`s addicted to it. I`ve tried several times to persuade him to go low carb as it`s quite annoying to have to prepare two different lots of meals, but after a week or so he complains of feeling ill. The weight drops off him, but he doesn`t seem to be able to sustain enough energy for a long workout e.g. circuits, spinning. In the end, he goes back to scoffing bread etc and the weight goes back on. There doesn`t seem to be a happy medium of eating just enough carb to supply energy, wthout overdoing it and gaining weight. Probably `cos the carbs make you hungry.Thoughts?
Enjoying all the articles, thanks.
Dr Briffa,
I follow paleo-style eating relatively closely whilst also engaging in heavy strength training & high intensity cycling each week. When engaging in such high glycogen-drain activities, it is difficult to get adequate recovery of glycogen scores over a 48 hour period unless switching back over to a high CHO eating style. In his book, Paleo for Athletes, Loren Cordain advocates the following;
– High carb 2-3h prior to activity (or very high 10-15mins before)
– High carb over the duration of the activity
– High carb (+ BCAA’s) immediately after activity & for a duration matching that of the preceeding activity. So if I did a 3 hour bike ride, I would be eating high carb for 3 hours after.
One would then return to Paleo-style eating. This is a lot easier to manage when trying to maintain consistency in physical performance, particularly when training with intensity for 5-6d per week.
I am in full agreement, that for your average plodder, there is no requirement to carb load. I would disagree with your comment on using bread, pasta, rice, etc as high carb sources. Whilst I am not a big fan of wheat/gluten sources, I find that oats & rice work really well for me. Whilst the rice in particular hasn’t a particularly good source of nutrition, it is important to be mindful of this & ensure it is eaten with plenty of nutrient dense foods.
Cheers.
Relative to #1 Bill above: I’ve been lifting heavy weights (deadlifts, squats, etc) for 2.5 years and eating really low carb all that time. There are plenty of low carb protein shakes out there. I’ve put on about 15 lbs of muscle and lost about 35 lbs of fat in the last 2.5 years with those protein shakes, low carb, and weight lifting. I’ve read the same thing about carb loading and stuff by Volek, but I haven’t needed it. Just lots of fat and protein for me.
Good luck!
I never felt much need for extra carbs when doing endurance exercise. ~100g /day is plenty for me, and my husband generally gets even less (and he’s faster). There is that initial adaptation period, but it’s fairly short. You could also ease into it more gradually and maybe have less deleterious effect.
Nigel – cheers for the link. I have read that article of Lyle’s before and should have checked before posting. His writing is always informative and a pleasure to read.
Even for strength trainers it seems that Lyle is in the paleo/LC camp of 50g basic (IIRC, LC is actually < 40g), + 10g for about every minute of work/four sets. Looking at my HIT workouts I came out with a similar figure to Lyle’s of about 160g on a (training) day.
Personally I don’t really follow such detailed dietary programs. Half my plate is filled with quality protein, the other half with quality veg (mostly green), and that is it.
Although I have had concerns about eating enough to fuel the exercise, I have never felt under nourished by this approach to eating, and reading Lyle’s advice again has put my mind at rest.
For Sherry,
I also was feeling a little exhausted in the first few weeks of low carbing. After reading many blogs in the nutrition, metabolic conditioning and medical blogs, it became obvious
I was not consuming enough calories in the meat and fats.
I increased my meat and fat consumption by the addition of
more meat and good fats. I added 4 tablespoons of coconut oil daily…each has 130 kcals…14 g fat of which 13 g is saturated fat.
I cook my meat in coconut oil and and some garlic plus I cook
my eggs in coconut oil and if that doesn’t get me my 4 tablespoons, I scoop it out of the container.
My issues with tiredness are gone because I am now consuming enough calories. I am losing body fat weight by eating virtually no carbs and I have increased my strength
and decrease my body fat % down from 30% to 12% and I feel great.
I’ve recently written about a paper published in April that looked at a connected topic; the effects of a low-carbohydrate weight loss diet on exercise capacity and tolerance.
The study looked at obese subjects with results showing that people involved in the study following a low-carb diet burnt fat more efficiently and didn’t experience any negative side effects on their ability to exercise.
The full post and reference can be viewed at:
http://beyondgrains.com/?p=5
Very interesting article. I always thought that it was a bad idea to eat carbohydrates before working out. It always seemed like it was defeating the purpose. I do like how you recommend complex carbs (apples) instead of something more harmful like bread. Thanks.