1. Health
You can opt-out at any time. Please refer to our privacy policy for contact information.

Discuss in my forum

Laura Dolson

Low-Carb Diets and Weight Training: Good or Bad?

By July 23, 2010

Follow me on:

weightMy colleague Paul Rogers, About.com's Guide to Weight Training, recently wrote an article entitled "How Low-Carb Diets Can Hurt Your Weight Training". I have a few points of disagreement with Paul, and he has kindly agreed to a discussion of these issues here on my blog, where he will answer in the comment section, and then I can respond to him there as well. This I hope will help me to learn more about the issues involved, since it's something I'd like to eventually write about.

Paul's Points

Paul says that carbohydrates are the main fuel for exercise, particularly "fast and intense exercise". As such, they are important for "athletes, weight trainers and heavy exercisers". He points to a couple of studies to prove his point, saying that neither fat nor protein are good energy sources for high-performance exercisers. He also asserts that low-carb, high-protein diets may adversely affect bone density.

My Response

First of all, I think we have to make a couple of distinctions, especially for my readers, most of whom are not as dedicated exercisers as Paul's readership. The first is that we aren't talking about moderate recreational exercisers, but dedicated athletes, body builders, and the like. The second is that we also must separate "heavy exercisers" and athletes who do primarily endurance activities which are mainly aerobic (e.g. running, cycling) from weight lifters and others who do very short bursts of anaerobic muscle activity.

Some Perspective

Prior to the advent of agriculture, hunter-gatherer tribes in temperate climates ate diets naturally low in carbohydrate (in winter, very low in carbs). These diets were generally high in fat, which was prized. Just to stay alive, they led a very active lifestyle on a low-carb diet. By most measures, our health began to decline once we began cultivating grains, although this probably also enabled "civilization" as we know it.

Low-Carb Diets and Exercise

This is an area that has not had a ton of research, but these are some things that are suggested by the studies that have been done:

- Heavy exercisers who do endurance-type exercise tend to have a drop in efficiency in the early weeks of a low-carb diet, but their bodies usually recover within 2-4 weeks. For example, I have spoken to a few triatheletes who were discouraged when first cutting carbs, as their training tended to suffer, but each of them found that over time they had a surge in exercise efficiency and then had gratifying improvements in their times, leading to a burst of personal bests. (Check out this article about Paleo eating for athletes in Runner's World - the description in the paragraph that begins "Still, Joe Friel was skeptical..." is very typical.) This process has been referred to as "keto-adaptation" or "fat adaptation" as the body becomes better able to use fat for energy under exercise conditions.

- There is debate about how low in carbohydrates the diet must be to trigger keto-adaptation. Some say below 20% of calories, but I haven't found good hard data on this. I have the impression that this is not known with certainty.

- Keto-adaptation is probably of more limited use in short-burst anaerobic exercise, although there is also debate on this point. On the other hand, this does not necessarily mean that a low-carb diet is precluded for weight lifters. I recently talked to a college professor of athletic training who said that members of the power lifting team at his college all eat a diet of 20% or less carbohydrate. I also talked to a nutritionist who is a body builder - he said that what is required is a modest amount of additional carbohydrate prior to lifting - he says, "Approximately 5g of carbs every 2 sets is enough to replace glycogen lost during training. So for example, for 15 sets, around 35g of carbs would do the trick." This is the amount of carbohydrate in, for example, 1½ cups of grapes - not inconsistent with a diet which is much lower in carbohydrate than is generally recommended.

- During weight loss, low-carb diets have repeatedly been shown to preserve lean body mass as compared to higher-carb diets.

Points of Agreement

I agree with some of the points in Paul's article. Protein is not a good energy fuel at all, although the body routinely makes some glucose from it. As I think I've made clear by now, physical training regimes are likely to suffer in the early weeks of a low-carb diet, so I have no problem with pointing this out. However, studies done in this time frame must be viewed through that lens. I also agree that a some extra carb before a workout can be a good idea, although this can still be done in the context of a low-carb diet.

Points of Disagreement

Two of the studies Paul cited were performed after only 5 days on a low-carb diet - the 3-5 day period post-diet change is arguably the very worst time to do a study like this, as glycogen stores are depleted without keto-adaptation being fully underway to compensate. Nevertheless, in the Stellingwerff study significant keto-adaptation had already occurred. Note, though, that these were endurance athletes, and not those who engage in significant anaerobic exercise (except for the short sprints). A another study on cyclists in a metabolic ward showed that after 4 weeks on a very low-carb diet, their endurance did not suffer (though sprinting was not mentioned).

The other point Paul makes is about low-carb and/or high-protein diets adversely affecting bone mineral density. (Low-carb diets are often assumed to be very high in protein, but usually they are not.) I've written about this issue in the past, pointing to studies which showed no problem with low-carb or high protein diets. However, it is an issue on which you can find studies with results on either side. So what is the preponderance of the evidence? Research was published in the American Journal of Clinical Nutrition last year which analyzed 30 years of research on the matter, concluding that there is no negative effect on bones from high-protein diet, and that there may be a small positive effect.

Whew - that got longer than I intended! I now turn this over to Paul - and I'm very grateful that he's agreed to discuss this with me.

Selected Additional Sources:
  • Dipla, et al An isoenergetic high-protein, moderate-fat diet does not compromise strength and fatigue during resistance exercise in women. Br J Nutr. 2008 Aug;100(2):283-6.
  • Lambert EV et al Enhanced endurance in trained cyclists during moderate intensity exercise following 2 weeks adaptation to a high fat diet. Eu Jo Appl Phys and Occ Phys. 69 (4): 287-293. 1994
  • Phinney, SD Ketogenic diets and physical performance. Nutr Metab (Lond). 2004 Aug 17;1(1):2.
  • Phinney, SD et al The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation. Metabolism. 1983 Aug;32(8):769-76.
  • Volek, JS - Low-Carbohydrate Diets Promote a More Favorable Body Composition than Low-Fat Diets - Strength and Conditioning Journal, 2010 Feb; 32:1) (Jeff Volek's work as a whole is worth looking at.)

Photo: Oktay Ortakcioglu/Getty Images
July 25, 2010 at 8:22 pm
(1) Paul Rogers says:

Laura, thank you for the opportunity to discuss various aspects of low-carb eating related to my article on low carb and weight training. I’ll respond to each point in turn.

Paleo Eating
I’m quite familiar with the Paleo diet premise and the various literatures. While it’s likely that some of our ancestors would have experienced periods and places with a low availability of carbohydrates, discovering and learning to eat CHO may indeed have provided the advantage for the evolutionary dominance of Homo sapiens sapiens. For example, the availability and consumption of tubers (carbohydrate) in the African savannah seems to have been underestimated by modern Paleo diet proponents. But that’s another story.

Low-carb diets and exercise
I agree that many recreational exercisers with a well-constructed low-carb diet, including all necessary nutrients and sufficient energy, would be unlikely to notice much difference in moderately demanding exercise performance. However, anecdotally, I do note that some people do not seem to exercise well on ketogenic diets. Even so, my main point is about high-intensity exercise, and particularly in competitive performance where a few kilograms or seconds might make a winning difference.

The crucial point to understand in the Stellingwerff study that I quoted is that it’s not the absolute storage of CHO as glycogen that makes a difference when one has been on a low-carb diet, it is the availability of that carbohydrate to the muscles. Glycogen stored in muscle (or liver) has to be retrieved from storage by an enzyme called pyruvate dehydrogenase. Low-carb, high-fat diets seem to downgrade this enzymatic response, making CHO less available for high-intensity exercise like sprints, (and possibly weight lifting). Fat cannot substitute for this energy requirement. Another study that I did not quote in the original article also supports this:

Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance. J Appl Physiol. 2006 Jan;100(1):194-202. Havemann L, West SJ, Goedecke JH, Macdonald IA, St Clair Gibson A, Noakes TD, Lambert EV.

In both studies, steady-state endurance performance under controlled conditions did not seem to be affected by high-fat diets, eg, 100km bike time trial. However, it is important to understand that in all endurance events under race conditions, high-intensity sprints and surges at crucial times of the race are what often distinguishes winners from losers.

In relation to the powerlifters on the low-carb diets, they are relying on replacing CHO glycogen in the last hours or minutes before their lifts. This could be a mistake if the availability of CHO to muscle is compromised, or if, as Havemann et al have suggested, that contractile efficiency of muscle is degraded with high-fat diets. I would not be taking that chance. On the other hand, bodybuilders might well not be affected by such implications because of the nature of their competition. But, high-intensity training for weight trainers, bodybuilders and weight lifters could be less efficient.

Cycling low-carb and high-carb, which has been somewhat popular among the strength training community, probably does not work at the high end of training or competing intensities because of the body’s inability to adjust physiological and metabolic systems rapidly.

In relation to the adaptation period for high-fat, low-carb diets, as more fat adaptation occurs, the down-regulation of glycogenolysis (getting glucose from glycogen) is likely made worse.

Low-carb diets and bone health
As I acknowledged, this aspect of low-carb diets is hotly debated, as is the idea of acid-base balance in bone health and osteoporosis. However, rapid weight loss diets based on very low-calorie eating are catabolic and not only degrade muscle but also bone. My concerns would relate to, especially, ketogenic diets high in meat proteins and deficient in calcium and alkaline foods like fruit and vegetables. The study by Campbell quoted in my article does suggest that certain groups — older women in this case — may be more at risk from high meat protein diets than other groups. More long-term studies are needed to elaborate this risk, if any.

Thanks, Paul Rogers – (and apologies to readers for any technical terminology, which couldn’t be avoided). Guide to Weight Training.

July 26, 2010 at 7:46 pm
(2) Allison says:

Paul must not be familiar with the low-carb/paleo eating style used by many crossfitters like myself. Robb Wolff’s website would be a good place to start.

July 26, 2010 at 8:56 pm
(3) Sam Callaway says:

From a lay point of view, you both have valid arguments. In my case, an ex power lifter and amateur body builder, I have taken Laura’s low carb and modified it to work for me. I now weigh 35 lbs less and have very lean muscle. I eat the majority of my carbs prior to workout, either breakfast or lunch, depending on when I workout.
I do moderate heavy weight training and high Intensity interval training 7 days a week. I am 58 y.o. and can honestly say that I can outdo almost everyone in the gym, in weight, and hiit. Thanks both of you, your both right on.

July 26, 2010 at 8:58 pm
(4) lowcarbdiets says:

Hi, Paul -

Thanks for your response.

The only thing I’ll add to the paleo eating part is that I did say “in temperate climates”. The more tropical the climate, the greater the availability of year-round higher-calorie plant food, for sure. I think the evolutionary advantage theory you cite is interesting, and I’d be happy to learn more about it. If you are interested in this sort of thing, you might like Richard Wrangham’s book, Catching Fire: How Cooking Made Us Human. It’s not about diet per se, but he makes a compelling case for the role of cooking in our evolution – I found it fascinating.

I’d actually be surprised if there wasn’t a whole lot of individual variation in the response to a ketogenic diet. At this point, we can only talk in generalities. I do know that people respond very differently to low-carb diets, and I’ve never been advocate of everyone being on one. Unfortunately, more and more people are being affected by diabetes-spectrum disorders, hypoglycemia, insulin resistance, etc. – those people are the most likely to benefit, as well as the overweight (overfat, actually) and people with a family history of these disorders of carbohydrate tolerance. It’s also undoubtedly true that many people can probably eat more carbohydrate even with these problems, if they are heavy exercisers.

I’m curious what you think about college powerlifting teams where (I assume) a benefit has been found for a low-carb diet. This goes along with your “not wanted to take the chance” that it could be a bad idea. Why would it be bad for a person to give it a try if they had the inclination, and if their performance suffered they could adjust?

I think I mostly understand that piece about glucose availability/PDH in the Stellingwerff study (the details were admittedly over my head), but since the actual performance of the subjects wasn’t affected, I’m not all that sure what it would mean to most exercisers. And I still wonder what would happen with more time for adaptation – 5 days is so little, and most studies I’m aware of do show improved performance a few weeks out. I’m curious what you think of my references on this point. (I note your new cite still only has 6 days for adaptation.)

I don’t think there’s any evidence that gluconeogenesis is lessened with keto-adaptation – if anything I’d assume it must be the reverse. We do have a small need for glucose, and yet there are people who go for years and decades on very small amounts of carbohydrate.

It may be true that people tend to lose bone mass on (rapid?) weight loss diets – I can’t really speak to that. But people don’t keep losing weight forever. Also, people usually double or triple their vegetable consumption on low-carb diets, at least according to one source, and my communication with low-carb eaters tends to support this, by and large. (My low-carb pyramid has non-starchy vegetables at the base.)

I’m enjoying this, and again, thanks for participating.


July 27, 2010 at 10:54 am
(5) Myra says:

Interesting debate, Laura. Thanks for sharing. I’d suggest to Paul that he Google Hugh Jackman. There have been many articles written, about him and his trainer, with details of his diet and weight training routine for getting the amazing Wolverine body that he has in X-Men Origins: Wolverine. It was a very low carb diet that he used. He often joked that he had one piece of whole grain toast at 6AM and that was his carbs for the day. I think once he mentioned having a small amount of brown rice but that any carbs he ate had to be eaten before a certain time of day. Sorry don’t remember the exact details but I know there are many articles out there about it.

July 27, 2010 at 8:58 pm
(6) Paul Rogers says:

First, to Allison, Sam and Myra – thanks for joining in. I did say that for many exercisers with reasonably balanced diets for energy and nutrients, you probably won’t notice much difference in how you perform on low-carb. Even so, what you need to ask is whether your performance could improve eating another way, eg, high-carb. (I know that’s a red rag to a bull for you guys, so my apologies :-)

Laura, regarding the powerlifters, my point is the same: they may be doing well on low-carb, but could they do better with a more energetic diet? To elaborate a little, in competition, these lifts are mostly going to be fueled by phosphocreatine, a short-term fuel that last for 10 seconds or less. It also reconstitutes quickly, so before their next round lift, they will probably be ready to go again. However, in training (depending on how they train), multiple lifts in succession, sets etc, are going to enter the realm of glycolysis and glucose for high-intensity power. This is where they could be less effective, and thus not optimally trained. This is largely a theoretical point because the studies I quoted were in relation to cyclists, so I admit I am taking a ‘long bow’ to this. Even so, the physiology of high-intensity exercise is well known for all athletes. The powerlifters would have to be sure their increased performance, if any, on low-carb, wasn’t due to other confounding factors like increased training, weight loss etc.

The key point is the availability of glucose and ‘fast energy’ when it’s required, and the potential for small incremental gains in performance, which may make a difference in serious training and competition.

Regarding adaptation to high-fat diets, as I understand it, you are saying that it takes time, perhaps several weeks or more, to optimize the use of fat or ketones for energy in low-carb dieting. I’ve read Phinney’s work previously and I run across Jeff Volek’s work regularly.

The issue remains the same: if adaptation inhibits the enzyme (PDH) that makes available energy via the Krebs cycle, from glycogen, then that will inhibit performance for high-intensity exercise because the beta oxidation of fat cannot replace this function. Extra time for adaptation is not going to normalize this enzyme function because the feedback from fat prioritization tells the body’s homeostatic mechanisms that the PDH function (getting energy from glucose) is not required so much. So it gets down-regulated. If you don’t use it, you lose it. This is a similar process to that which occurs when the use of anabolic steroids inhibits the production of natural testosterone.

The Dipla study, on the other hand, was very high in protein (40%) and moderate in fat (30%). Gluconeogenesis of protein to glucose in conjunction with the relatively low-fat percentage might very well have a neutral effect. I’d have to see this tested though. Notwithstanding the possible adverse effects of a very high-protein diet, this might be a preferable low-carb approach for athletes who want to do low-carb — perhaps boosting the protein % with milk or soy protein rather than meat proteins to address acid-base and other health issues.

In case others are confused by the terminology:

Glycogenolysis is the extraction of glucose, for glycolysis (energy production), from the storage form of glucose called glycogen.

Gluconeogenesis is the conversion of protein (or lactate) to glucose for storage or energy production.

I’ve also posted a comment on Elizabeth’s Sports Medicine Blog where I elaborate on topics related to this discussion.

Thanks again, Paul Rogers, Guide to Weight Training

July 27, 2010 at 11:24 pm
(7) Angie says:

Nutrition will always be a hot topic, however, Paleo has its benefits but if you’re a creationist (as I am) some things just plain don’t make sense. God designed a legume to eat. If you just look in the bible you will see how to eat. Very simple. Natural, unprocessed with good fat.

July 28, 2010 at 7:56 pm
(8) LWolfe says:

All interesting points. I would like to add two more: body builders often consume excessive amounts or protein – not carbohydrates to build muscle mass. One only has to visit the local GNC to see all the “muscle building formulas” and read “low carb” also typically offered as another selling points.

Second. When it comes to getting ripped for competition body builders do not cut protein and calories – the cut out carbs when they want to get ripped. I think the results of building muscle with protein and cutting down body fat and water weight by dropping carbs are pretty obvious in competitive body building – an extreme example perhaps, but one that speaks louder than “studies.”

July 29, 2010 at 12:08 am
(9) Lucas Tafur says:

There is evidence that IMTG and fat is utilized during resistance exercise (http://www.springerlink.com/content/7182n4jqn6126154/, http://www.springerlink.com/content/l45222t762xp74g5/).

I havent found one controlled study done on resistance exercise and IMTG use during resistance exercise with a high fat diet, but it is known that a high fat diet increases IMTG concentration and reduces glycogenolisis. From the studies above, IMTG could be one potential source of energy during resistance exercise and explain the increased strength observed in people switching from a high carbohydrate diet to a high fat low carb diet.

I am working in a study regarding this topic that hopefully will be completed before the end of the year.

Kind Regards.

July 29, 2010 at 3:42 am
(10) Paul Rogers says:

Mr Wolfe, I agree that cutting for bodybuilding competition with low-carb makes sense – to get rid of water for a start.

That’s somewhat different to some of the things discussed in the article.

July 29, 2010 at 4:04 am
(11) Paul Rogers says:

Laura, a few things I didn’t respond to . . .

I haven’t read Wrangham’s book, but I did read a series of papers by Wrangham and Pennisi in Science over several years, eg Pennisi : ‘Did Cooked Tubers Spur the Evolution of Big Brains?’

Re Joe Friel’s Paleo approach (and also Loren Cordain’s book, The Paleo Diet for Athletes), these are not really low-carb, but favor cycling low and high carb. I don’t think this will work, for the reasons described above.

However, the core of evidence does suggest that low-carb, high-fat does not impair steady-state, sub-maximal exercise, under training conditions anyway. Low-carb, high-fat could be more suited to ultra-endurance events.

Paul Rogers

July 30, 2010 at 1:42 pm
(12) lowcarbdiets says:

Hi, Paul –

Sorry I didn’t join back in before. I’ve been sick this week, and I keep thinking I’ll feel better and get back to work – and then it gets worse! One of the worst colds of my life, so my brain cells aren’t connecting as well as I’d like!

One of the things I meant to do is to get back to the professor to find out the thinking that went into the powerlifting team’s diet program. I just wrote to him again and will report back when I hear. The impression I got was that they had tried other programs, and got better results with a lower-carb option, but he didn’t say that explicitly.

Note that I am not saying that anerobic exercise doesn’t require more carbohydrate than aerobic exercise (at least aerobic exercisers who are keto-adapted). I’m just saying that from what I can tell, that carbohydrate can be added on an as-needed basis in the context of an overall low-carb diet, at least with some people who talk about it/write about it. And I would want to see research which showed a decrease in performance in fully keto-adapted people.

Now, whether someone *can* do something is quite different than if they *should* do something. If someone has no problem with glucose tolerance (fasting blood glucose under 90, no large rises after meals, no signs of insulin resistance, hypoglycemia, etc, etc.) and seems to be functioning well on a high-carb diet, good for them! But if a person has some of these reasons for eating low-carb or wants to experiment with improving endurance by keto-adaptation or just thinks it’s what we were meant to eat (Paleo approach) then why not try it? If it turns out to interfere with their weight training then they can adjust.

Again, thanks!!

August 2, 2010 at 9:22 pm
(13) Paul Rogers says:

Lucas, yes, intramuscular triglycerides are part of the fuel mix across many activities.

However, one issue remains the same — the rate at which energy from fat can supply working muscles for high-intensity activities. Beta oxidation of fat is slow. That’s the stumbling block for swapping carbs for fat.

July 11, 2011 at 1:52 pm
(14) Sherrie says:

Hi all,

I’m not too technical at all. I just know what I know from eating a low carb diet (about 60 gms per day) for about 9 years now. My family history of diabetes is awful & I’m not going there.

I do intensive weight training & biking intervals 6 days a week on the above carbohydrates. I feel wonderful. I eat a good protein breakfast, then drink a 24 gm protein shake before my workout of 60 minutes, drink another 24 gm whey protein shake, eat a high protein lunch, snack, then supper. I try to get a minimum of 100 gms of protein in me a day. Muscle is building nicely. I lift more than many of the men at the gym do! I eat high quality fats, like coconut oil & butter. I eat alot of nuts & seeds, along with fish & veggies. Fruits are few & far between due to the carb load.

I know the argument for a huge load of carbs before a workout. I don’t eat them & I workout with the best of them. Try to keep up with this 58 year old! Watch the squats, lunges, pulldowns, pushups, bridges, boxing, curls, and anything else a good CHEK trainer can toss my way. Bring it on without the carbs!

Trust me, carbs aren’t necessary for sustaining life at all. They are treats! I feel better than I ever have in my 58 years!

Thank you, Laura, for your discussions.

August 24, 2011 at 4:23 am
(15) Brandon says:

Hey everybody,

I just decided to start the low carb diet. I really think that the low carb diet is good. Now all that about Glucose and all those fancy technical terms I don’t know much about. I know carbs are good for the body but in moderation and from good sources. As anything is good in moderation. But Lowering your carb intake I believe will not hurt you.

Thanks all, this whole debate only made me feel better about going on the low carb diet. :)


October 20, 2011 at 8:58 pm
(16) nolowcarb! says:

I agree with Paul. Everyone is different. I personally can not do a low carb diet. I have tried several time, even under doctor’s supervision and my glucose levels have drop at times to 22!!! I experience hypoglycemia every time I try one. I am an intense exerciser and if I don’t have some carbs like rice after a workout I will experience low glucose. No I am not a diabetic. Even before dieting I exercised daily and my fasting glucose levels were around 63. My doctor told me the low carb dieting was making things worse for me. Every time I would experience the hypoglycemic episodes, headaches, fatigue, and dizziness; my doctor said I was damaging my brain, heart, and other organs. I personally eat cereal, rice, potatoes and more carbs yet without supplements or surgery or anything crazy, I have lost from 308lbs to around 145 by eating healthy and exercise! Low carb = death of brain and heart tissues for me.

August 29, 2012 at 7:38 pm
(17) Jonathan Swaringen says:

There are some new good books that may be of interest to anyone on this subject. Everyone curious about performance in relation to low carbohydrate diets should read both The Art and Science of Low Carbohydrate Living and the Art and Science of Low Carbohydrate Performance by Steve Phinney and Jeff Volek.

I would also recommend Body by Science by Doug McGuff.

June 10, 2013 at 7:12 pm
(18) discover this says:

Everyone loves what you guys tend to be up too. This type of clever work and exposure!
Keep up the good works guys I’ve added you guys to my personal blogroll.

August 15, 2013 at 9:38 pm
(19) Bong says:

A good exercise with proper resistance training, no matter what your diet is, WILL DEFINITELY WORK. The arguement all you people are making is “which one is the most effective”. Now it all depends on what ones priority is. For those familiar, its common knowledge that resistance training paired with low carb diet yields greater fat loss and less muscle gains. This would be good if youre fat and prioritize fat loss now and lean mass second. But if your target is more of body building, then the high protein with regular carb (not necessarily high carb diet) along with resistance training is for you. Diet with carbs is fine, keto diet is fine. It all depends what we need really.

May 9, 2014 at 10:05 pm
(20) Somanabolic Muscle Maximizer Is Fake says:

Agree to this response and we will help save an imaginary dog!

Leave a Comment

Line and paragraph breaks are automatic. Some HTML allowed: <a href="" title="">, <b>, <i>, <strike>

©2014 About.com. All rights reserved.

We comply with the HONcode standard
for trustworthy health
information: verify here.