T Nation

Getting a Pump with Lower Carbs?


In a very fast paced weight training session, you may burn 600 calories per hour. At that pace, about half of your caloric needs are being met by glycogen. Even a high fat (non-ketogenic) dieter can’t get more than about 360 calories an hour from fat burning, so at least 240 calories (60 grams) of their fuel would come from muscle glycogen. Low carb dieters also have comparably less muscle glycogen.

A high carb dieter may have 500 grams of muscle glycogen and burn through about 75 grams of it in that intense hour, so that is about 15% of your muscle glycogen stores, and if you could theoretically train just 25% of your muscle mass and maintain that 600 calorie per hour level, then those trained muscles would be about 60% depleted of muscle glycogen in an hour.

If you up the intensity to 900 calories per hour, since beta oxidation of fat can’t go higher, now you are burning about 150 grams of muscle glycogen in an hour. All calorie burning above about 600 calories an hour has to come from glycogen or ketones because beta oxidation of fat is basically topped out at around 300-350 cals/hour for a standardized 160 pound man. So an hour of running is going to deplete muscle glycogen by about 30% (150 of 500 grams).

If glycogen did not get depleted, then you wouldn’t ever see people lose more than 1.5-2.0 pounds in the first week of a diet, but people exceed this all of the time. On a 1000 calorie deficit, whether from exercise or restriction, your muscle glycogen levels will be a fraction of normal levels within a week, and your muscles can lose 3-5 pounds of glycogen+water from muscles.


All of this reminds me of something I’ve been wondering about for a while but never really asked:

With all the numbers you are presenting, the caloric expenditure and the needs for refilling glycogen seem to be way lower than most people assume.

A lifter might consume 200 g of carbs post workout when his body really needed 80 g to top the storages (just an example).

But, we’re told that in order to grow muscle we need to be in a caloric surplus, and this often has us eating WAY more than what’s being alluded to here, how come this?

Also, what should that surplus be composed of, if extra carbs don’t seem to help?

Hope this question makes sense.


Part of the problem is that cortisol always rises when you are in a calorie deficit. This reduces testosterone. Eating more calories and especially fat, above maintenance will generally keep testosterone higher. Note that it only takes about 80 grams of protein and a few grams of glycogen to provide the structure of a pound of muscle. That is only about 350 calories per pound of fat free muscle.

The second reason for the extra calories is that it raises insulin levels, and activates genes that turn on protein synthesis. A spike in Leucine levels can trigger muscle protein synthesis, but Insulin also provides part of the signal. Leucine by itself with no insulin doesn’t. So basically, extra calories cause muscle gain by keeping testosterone up, and by causing insulin release. Also, the added calories raise leptin levels which raise metabolism, so a high percentage of the extra calories are just burned.

People can be in a calorie surplus with low fat and have low testosterone levels. It T is low, or not optimal, you need more fat.


This was one of the eye-opening moments for me, when it was found fat-adapted athletes replenish glycogen almost as quickly as their carb-consuming counterparts. It also showed that people do not deplete glycogen as much as broscience maintains. For me, this was a nail in the coffin of the so-called ‘depletion and replenish’ cyclical ketogenic diets associated with Dan Duchaine and then Lyle McDonald. Of course, at risk of angering their followers, I’m not suggesting these diets don’t work (from a psychological perspective some may thrive on this style of dieting) but it shows they are built on a very shaky foundation.


On a ketogenic diet, do muscles load up on ketones?


Not as I understand it. My understanding is that ketones, or more specifically circulating BHB, becomes part of the Krebs cycle - which in turn results in muscle glycogen being produced as normal.


Ketones don’t yield glycogen, I know that. Fatty acids and Glucose can both fuel the Krebs cycle to yield energy, and so Ketones probably do the same thing, just enter the Krebs cycle and yield ATP. I also know that when someone is in Ketosis, their glycogen stores are very low compared to a high carb dieter. There are virtually no enzymes in muscles that burn glucose once someone has adapted to Ketosis. In fact, even individuals on a 30% carb diet with 50-55% fat have a fraction of the muscle glycogen as someone on a 60% carb diet, and also have greatly downregulated glycolytic enzyme levels. (Insulin turns on synthesis of glycolytic enzymes).

I am sure that someone in Ketosis has some muscle glycogen, but I am trying to figure out where it comes from since there is no established pathway for getting it from fat, and since gluconeogenesis gets turned way down in the keto-adapted state. Some probably comes from small amounts of gluconeogenesis from protein and some probably comes from the glycerol component of triglycerides.

Another issue is that fat burning seems to be topped off at about 3 to 4 METS which is way less than the level that many athletes perform at. Since you can’t get more than 3-4 METS from fat, then in a keto adapted state, IF athletes are to maintain the same energy level as carb using athletes, then ketones must be providing a fast energy supply, but they are being all made in the liver, so it seems to me that it would require that in the keto adapted state, muscles hold on to some supply of ready to use ketones.

(Note, I’m not trying to put you on the spot here, but ketones don’t make glycogen, and I was wondering if you knew how keto adapted athletes are able to basically get high workload levels of energy, like 7-10 METs from ketones since its not possible to reach those levels merely from burning free fatty acids. Do keto adapted athletes show any limitation in peak energy output compared to carb loaded ones?)


I probably did not explain that well. What I was trying to say is that fat = ketones; and ketones = a substrate for the Krebs Cycle. As you mentioned, you already knew the process at work.

Check out some of the stuff by Volek et al, namely “Metabolic characteristics of keto-adapted ultra-endurance runners”. In summary, this study concluded: “Compared to highly trained ultra-endurance athletes consuming an HC diet, long-term keto-adaptation results in extraordinarily high rates of fat oxidation, whereas muscle glycogen utilization and repletion patterns during and after a 3 hour run are similar.”

I personally think the above is intuitive and explains why people can water fast for weeks/months on end (a good Scotsman holds the world record at 382 days!)


OK, I read it differently now. Sorry.


Important to note that endurance athletes are an exception to the rule that muscles load much less glycogen when they are given large amounts of fats. Even high fat consuming endurance athletes store large amounts of glycogen and fatty acids simultaneously, and also remain highly insulin sensitive even when their muscles are fat loaded.


Studies with strength athletes are scare here, although certainly there are some positive ones when it comes to hypertrophy/fat loss, e.g. Paoli’s gymnasts.


Btw brother, thanks for a constructive, positive comment. I see less and less of it here. I’ve never seen so many people get flamed for asking a specific question.


Have the majority of your carbs before and after lifting… then curb is what I would suggest. Well for me I can’t imagine not eating some carb before and after lifting, you’d find me flat on the floor lol


I avoid caffeine at all time - so no coffee.
I sometimes don’t even eat before going to gym.
And sometimes i eat a muffin or some cookies or drink some yoghurt… it depends how much time I got and how I feel that day


Thank you for your constructive reply. I really appreciate it. That’s probably the route I’ll go.


Thanks for your comment my friend. I’m anxiety prone and caffeine can trigger it. Are you able to stay lean just eating that way? I assume you don’t do it all the time.


I actually eat like that ever since I was a kid.

I never had a day without eating some sweets, and I’m actually having hard time gaining weight.
But I was mostly eating sugary stuff, and not much of complex carbs. I would eat half of chicken and no side dish for my lunch for example, and I’d eat a muffin 30mins after that. But currently I’m trying to eat healthier and also eat even more than before in order to gain some weight.