Emergent Fitness: Carbs: How Much Is Enough?

Warning: A long post awaits you! (But it's a good one)

Dietary carbohydrates are often the source of a considerable amount of debate.

*Should we cut carbs for weight loss?

*Do we need carbs for muscle building?

*How much is too much?

*How little is too little?

If you were to take a diverse group of people (experts or lay) and ask them to qualify and quantify answers to the above questions, you would most assuredly get a diverse set of answers. Context means everything when we ask questions having to do with "shoulds" and "should nots."

Rather than give a universally relevant qualitative and quantitative answer to these questions, I'm going to give a more subjective answer (this is all I can do really).

If we condense the context of this issue to people who participate in regular weight training and to those who have an interest in building muscle and/or losing fat, making pertinent recommendations is a little more doable.

Problems with Super Low Carb Diets

In terms of muscle building and exercise performance, going extremely low carb may be a bad idea. When you lower carbohydrate consumption, you necessarily have to rely more heavily on proteins and fats for fuel. While it certainly is possible for your body to use fat and protein as fuel sources, carbohydrates are a superior option if you're performing any sort of high intensity/explosive activity (such as lifting weights) (1).

Fat as a fuel source is better suited to low-moderate level activity. Anything that requires a long term endurance effort (done at a low level of exertion) will cause your body to preferentially burn fat as fuel. If this sort of activity was all you were doing, a high fat, low carb diet would work just fine. However, as a study from the Journal of Applied Physiology, conducted by L. Havemann et. al., reveals, a low carb diet may compromise high intensity efforts (2). The test subjects were tested on their endurance and high intensity sprint performance. While all subjects performed equally in terms of endurance, the low carb group experienced "compromised high intensity sprint performance, possibly by increased sympathetic activation or altered contractile function."

Dietary protein, as opposed to fat, can be converted into glucose within the body, but this process is rather inefficient and more of a survival response to low blood sugar. When liver glycogen levels get low, your body needs to find another source of glucose, and it inevitably turns to your muscle (1); moreover, your body, in an effort to survive, will start breaking down your actual muscle tissue. Your muscle glycogen (the glucose stored in your muscles) is only burned locally from activity-specific use of the contractile elements of your muscle. It cannot be used to fuel other bodily needs such the maintenance of blood sugar (3). The amino acids which comprise your muscles, however, are free game. Thus, it's incredibly important that we consume enough carbohydrates on a regular basis to keep liver glycogen stores adequately supplied.

Furthermore, in work done by Benjamin et. al., researchers determined that, at least for novice trainers, carbohydrates may be a more important nutrient than protein for recovery from weight training (4). I should note, however, that the sort of weight training the researches tested was eccentric in nature; whereas most weight trainers put a greater deal of emphasis on the concentric portion of the lift. Nevertheless, this research reveals that we should not ignore the important role carbs play in exercise recovery and performance.

Is There an Upper Limit?

Going further, though, we have to consider whether there's an upper limit to the amount of carbs necessary to optimize training and muscle growth.

In an experiment conducted by Van Zant et. al., test subjects were given either a relatively high or low carb diet, then tested on their performance on isokinetic leg extensions and contractions, and on the bench press (5). The researchers didn't find any real variation in performance for either group; however, this result may have been the case because the lower carb group was getting approximately 42% of their calories from carbs, and the higher carb group was getting approximately 62% of their calories from carbs. Also, fat comprised 40% and 20% of both groups calories respectively. These percentages for the ratio of carbs to fat fall very neatly within the lines of proposed dietary ranges for weight trainers; thus, the relative significance of this study is questionable (at least in terms of its intended purpose). However, I do think we can establish from this study that, since no additional benefit was seen from consuming more than 42% of calories from carbs, we might say that no more than that amount is necessary. For a person whose maintenance energy needs are 2,800kcals, that would mean consuming no more than 295g of carbs on average.

Another study conducted by Hatfield et. al., revealed similar results to the aforementioned (6). Subjects were tested on their performance for repetitive jump squats, and they were assigned either to a low or high carb diet. No difference was observed in performance, but, like in the study above, the low carb group was not really assigned a low carb diet per se. Rather, they were assigned 4.4g of carbs per kg of body weight. For a 175 pound man, that would come out to 350g of carbs. Once again, despite the fact that this study didn't reveal much in terms of what the researchers were initially looking for, for our purposes we can see that there may be something to this idea of a limit to how many carbs are necessary for optimal performance.

What About Fat Loss?

Aside from muscle building, however, we should also look into the effects of carbohydrate consumption on fat loss.

A research study conducted by Volek et. al., offers us some clues (7); but, only if we read between the lines a bit. The researchers conclude that a low carb, hypocaloric diet (wherein carbs make up 15% of calories consumed) can lead to superior fat loss and preservation of lean mass, when done in conjunction with regular weight training. Notably, however, the higher carb groups they looked (groups which experienced a greater loss of lean mass) at had only 25% of their calories coming from fat. I've established before that fat should ideally comprise 30-35% of your energy needs, and, moreover, I tend to think the amount of fat this percentage entails should remain constant, even when cutting calories. Thus, if 100g of fat is 30% of your maintenance energy needs, if you cut calories to lose weight, you ought to maintain that 100g of fat (while also keeping protein levels elevated), and you should thence cut calories by lowering carbohydrates. However, we should strive not to lower carbs so much that we run into the above mentioned issues which can arise with lower carb diets.

Going back to the research study, let's take a look at the climax example they give to support their recommendations (all results are with hypocaloric diets):
*Women high carb - Lost 5kg of fat mass & 1kg lean mass
*Women low carb - Lost 5.9g of fat mass & 2kg lean mass
*Women high carb + resistance training - Lost 5.5kg of fat mass & 1kg of lean mass
*Women low carb + resistance training - Lost 8.8kg of fat mass & 0.4kg of lean mass
*Men high carb - Lost 3.4kg of fat mass & 1.4kg of lean mass
*Men low carb - Lost 6.2kg of fat mass & 3.2kg of lean mass
*Men high carb + resistance training - Lost 3.5kg of fat mass & gained 1.8kg of lean mass
*Men low carb + resistance training - Lost 7.7kg of fat mass & gained 1kg of lean mass

As you can see, not lifting weights was clearly associated with a greater loss of lean mass. Also note that the lower carb diet actually resulted in a greater loss of lean mass when compared to the lower fat protocol (that is, when weight training was not performed regularly). However, when we include weight training in the mix, the results change. In women, the low carb diet helped to preserve more lean mass (though participants still lost some) than the low fat diet when in the context of regular weight training. Moreover, the low carb group lost more fat mass.

For the men, similar results were seen when no regular weight training was involved. But, when weight training was performed, the men were actually able to build some lean mass (despite being in a caloric deficit). Now, this is where things get a little hinky. It seems that, for the men who regularly weight trained, the higher carb diet allowed for better muscle building with some fat loss. Meanwhile, the low carb group's results reveal greater fat loss while gaining a little muscle.

What We Need: Some Nuance With a Side of Moderate

While the authors of the study concluded that a low carb diet was superior, they only looked at two extremes. I'm curious to know what would have happened if they would've also included a more moderate diet in their findings. I suspect that a more "middle of the road approach" would have allowed for a better mix of results. I tend to think a diet comprised of enough fat to support maximal testosterone levels and enough carbs to support training would be the best option.

What Should We Do?

Having sifted through this sea of confusion, let's make our return to the safety of dry land.

Out of all the experts I follow, one of the more prolific is Lyle McDonald.

In an article he wrote entitled "How Many Carbohydrates Do You Need?," Lyle tackles this very issue I've wrestled with thus far. If there's anyone as obsessed with such issues as I am, it's this guy, and I have the utmost respect for his work and his research. Below is a chart of his recommended ranges of carbohydrates based on needs and context:

Circumstance	Carbohydrate Requirement¹	Grams for an athlete with 160 lbs. LBM
Physiological Requirement	0 g/day	0 g/day
PracticalMinimum to Avoid Muscle Breakdown²	50 g/day	50 g/day
Practical Minimum for Individuals Who Function Poorly In Ketosis³	100-120 g/day	100-120 g/day
Additional Amount to Sustain Low Intensity Exercise	Minimal approaching zero	Minimal approaching zero
Additional Amount Needed to Sustain Weight Training	5 g carbs. per 2 work sets⁴	5 g carbs. per 2 work sets⁴
Average Recommendations in Bodybuilding Nutrition	1-3 g/lb.	160-480 g/day
Average Recommendations by Mainstream Nutritionists	2-3 g/lb	320-480 g/day
Average Intake for Endurance Athletes	2 g/lb	320 g/day
Recommended Intake for Endurance Athletes	3-4.5 g/lb	480-720 g/day
Practical Maximum for Non-Carb Loading Individuals	4 g/lb	640 g/day
Maximal Intakes for Carb-Loading	~7 g/lb	1120 g/day

Let's Break It Down!

According to Lyle...

*The physiological requirement for carbs is 0g. Carbs are a conditionally essential nutrient and not necessary for survival. There are, however, essential fatty acids and amino acids.

*A minimum of 50g of carbs/day is necessary to prevent muscle breakdown (and this number seems to be pretty universal); however, many people may require 100-120g (also pretty universal) if they find they don't function well at 50g of carbs (I tend to think of 100-120g as a practical minimum for most people given the issues with low testosterone, lack of energy, and poor sleep that can ensue with lower levels of carb consumption. Moreover, 100-120g of carbs are typically what we require to maintain liver glycogen stores).

*Lyle, after doing quite a bit of research and calculating, believes that for every 2 work sets you perform, you'll likely burn about 5g of muscle glycogen (assuming your sets last at least 30 seconds).

Now We're Cooking With Peanut Oil!

Taking all of this into consideration, we may make the following conclusions.

1) On average, consume no fewer than 100-120g of carbs (However, if you're severely obese or insulin resistant I would consider going lower, but that's another issue for another day).

2) To support your weight training, eat 5g of carbs for every two work sets you perfom. I might add that if you do some sort of interval training, I would consider consuming 5g of carbs for every 90 seconds you spend doing high intensity effort.

3) This amount of carbs should allow for more than 30-35%+ of your total calories to be comprised of good fats; something not to be neglected for the sake of performance.

There you have it! Now you know how much is enough. (At least if you managed to get this far along with the post.)