How much carbs should you eat for a lean physique?…
Carbs are needed to provide energy for the muscles. When muscle glycogen (carb energy) is low, exercise performance may be altered and the anabolic response may not be as good.
When you eat carbs, your body breaks it down into glucose to be used as fuel or to be stored. About 1g glucose attracts 2.7g of water. So it can definitely result in a poofy look as it gets stored as fat when excess carbs are eaten while being inactive or active.
Carbs however are not the culprit here, as you need to go about this cleverly.
In humans, ∼80% of the glycogen is stored in skeletal muscles.
The thing that you need to do is to eat the correct amount of carbs so that only your muscle glycogen gets replenished and no excess glycogen is left to get stored as fat.
You want the glycogen and water inside of the muscle to make it feel and look swole, and also provide tons of energy for your workout.
Our muscles use glycogen as fuel through an anaerobic pathway during contraction by lifting heavy weights. During interset rest (between sets), our bodies use fatty acids (if you train fasted like me) through an aerobic pathway for energy. So during weight lifting, our muscles aren’t constantly using glycogen. Lets say you do 15 sets per workout and each set takes 30 sec to complete. You then only do a total of 7.5 minutes of work. So then your muscles only use glycogen for 7.5 minutes of your workout. The rest of the time it’s running on fatty acids.
Muscle glycogen concentration is 80–150 mmol/kg ww (14.4 – 27 grams of glycogen per kg).
If you have 22kg of fat free mass you’ll be able to store between 316g and 594g of glycogen in your muscles. The chance that you’ll deplete all that glycogen from one workout is not very likely.
So how much glycogen gets depleted in one workout anyway?
Most of the glycogen is stored in fast twitch muscles. (study) Heavy weights done explosively recruit fast twitch muscles the best.
The largest reductions in glycogen are seen with high repetitions (~10) and moderate training loads (<75%of 1RM) (study).
- 40% reduction in glycogen stores after 8 sets of 6 reps of leg extensions at 70% of 1RM in untrained subjects (study).
- 12% and 24% reduction in glycogen stores after 1 and 3 sets of curls respectively, at 80% of 1RM in trained subjects (study). Muscle glycogen doesn’t deplete in a linear way.
- 44% reduction in glycogen stores after 45 minutes of resistance exercise in untrained individuals (study).
- Well-trained subjects can oxidize more than 3g/min which results in oxidation of 180g carbohydrates during 1h of intense exercise (spinning) – (study).
- 26% reduction in glycogen stores after 5 sets of 6-12 reps of fronts squats, back squats, leg press and leg extensions in trained men. They did 20 sets total and completed the workout in 30 minutes, and rested double the time they took to complete the set (study).
- 26.1% reduction of glycogen stores in the vastus lateralis after 3 sets of 12 RM of leg extensions performed to muscular failure while 6 sets led to a 38% decrease. (study)
Conclusion to these studies
- The more training experience you have, the slower you deplete muscle glycogen.
- Larger muscle groups such as legs take longer to deplete muscle glycogen, whereas biceps (a smaller muscle group) depletes faster.
- Heavier weights (80% of 1RM, 8 reps) deplete muscle glycogen the same as lower intensities. (study)
- Resting too short (like the 20 sets study), will hinder you from going heavy, or from recovering fully for maximal power output and the chances are that the intensities will be too low to use muscle glycogen but rather fatty acids to perform the exercise.
Your muscles don’t get depleted in a linear way, as seen in the graph below. The red line represents a theoretical linear depletion and the blue line represents a more logarithmic curve as it really happens.
But not only muscles use glycogen, but the liver as well. The liver is much smaller (∼1.5 kg) than muscles and the total amount of glycogen the liver takes is ∼100 g.
When to eat carbs
Only after a workout and not before, because on a normal day only∼15% of the ingested glucose is stored as muscle glycogen.
- You need to deplete your muscle glycogen first through a workout, as muscle glycogen replenishing is best when muscle glycogen is low compared to normal or high
- GLUT4 transporters are inversely correlated with the glycogen content in the muscles
- Glycogen resynthesis is 3 times greater after a fast, than training fed with carbs (study)
- Glycogen resynthesis is greater in fast twitch than in slow twitch, so lift heavy and explosively (study)
- After a fasted workout AMPK will be elevated. AMPK increases glycogen transport into the muscle cells. AMPK is only elevated 1-2 hours post-workout
After fasting 16 hours and completing a fasted workout, there are tons of GLUT4 transporters to transport all the glucose into the muscles. That’s why I eat my largest carb meal post-workout.
So how much carbs exactly?
Doing an isolation movement will deplete local muscle glycogen, whereas compound movements deplete greater amounts of muscle glycogen, as more muscles are involved to perform the movement. Doing crazy high volume training (+25 sets) might deplete trained muscle groups, but I don’t do that much volume and don’t recommend it, as the chance for glycogen depletion isn’t likely.
So, lets say you deplete 60% of all your muscle glycogen from a highish volume, full body split… a man with 22kg lean mass will then have to eat between 190g to 356g of carbs to replenish his stores.
- You don’t know exactly how much glycogen gets stored into your muscles
- You don’t know how much glycogen you use during a workout
- You don’t know how full your glycogen stores are to begin with
- Rest, intensity and volume all influence how much glycogen you use
Not enough studies have been done on this area with resistance training and it would be hard to speculate as every one’s workout is different and everyone’s bodies function differently.
Between 190g – 356g is a huge difference, and it’s not per say that you deplete all your muscle glycogen by a certain percentage. It’s all speculation and requires self testing, or the help of a personal trainer to help determine how much carbs you need for optimal workout and recovery.
As you are most likely resting on your off days, there is no need to consume carbs, if adaquate carbs was consumed on your workout day to replenish glycogen stores.
Several studies show that a very low carb diet is superior for fat loss and preserving muscle mass compared to eating more carbs.
- 4.3kg better fat loss for 30g carbs/day vs 104g carbs/day after 9 weeks and fat accounted for 95% and 75% of the weight loss (study).
- 10g of carbs/day resulted in an average of 0.6kg/day weight loss, which 97% was from fat (study).
- 8% carb diet led to a 3.4kg loss of fat after 6 weeks. Adaquate calories was consumed to maintain weight and still weightloss took place (study).
- Higher energy expenditure when following low carb high fat vs high fat low carb (study).
On off days, eat very low carbs and on workout days, eat adaquate carbs to replenish glycogen stores. Very low carbs won’t result in muscle mass lost as seen in the studies above.
- Eat more carbs on a day you train a large muscle group and less when you train a smaller muscle group
- One can eat more carbs due to the supercompensate effect of intermittent fasting and fasted training
- If weight-loss is the goal, carbs are more important than fats to maintain muscle mass
- ∼40% of total macro-nutrients should consist of carbs
- On off days, eat a low carb diet
- On workout days, eat a high carb diet to replenish glycogen stores fast