“I want to try building muscle on a low-carbohydrate diet,” a reader told me the other day.
“I’ve just seen a study showing that it’s the best way to lose fat and gain muscle. What do you think about it?”
It would be great if there was one single diet that worked best for muscle growth, fat loss, athletic performance, optimal health or whatever else you can think of.
Unfortunately, in my opinion at least, no such diet exists.
If your goal is to gain the maximum amount of muscle in the shortest amount of time, the diet you follow will be very different to one designed for fat loss.
I’ll explain why in a moment.
First, I want to address a few of the issues with the study supposedly showing that a low-carbohydrate diet is the “best diet” to build muscle and lose fat.
Publishing their findings in the journal Metabolism, a group of researchers from the University of Connecticut tracked changes in body composition in a group of healthy, normal-weight men.
Of the 20 men taking part in the study, 12 switched from their normal diet to a low-carbohydrate ketogenic diet for six weeks. The other eight men continued with their normal diets.
Foods eaten on the low-carbohydrate diet included beef (steak and hamburgers), cheese, eggs, peanut butter, various nuts and seeds, vegetables and protein powder (Super Whey Fuel and Fuel Plex Lite).
Subjects were also told to avoid fruits and fruit juices, dairy products (with the exception of hard cheese and heavy cream), breads, cereals, rice, beans, and sweets.
The men kept a food diary each day of the study (seven days during baseline and 42 days during the low-carbohydrate diet) and the control group kept seven-day records during weeks one and six.
Here’s what daily nutrient intake looked like in both groups during the final week of the study.
Control group
Total calories 1,949 calories
Protein 80 grams (16% of total calories)
Carbohydrate 283 grams (58% of total calories)
Fat 56 grams (26% of total calories)
Low-carbohydrate group
Total calories 2,334 calories
Protein 176 grams (30% of total calories)
Carbohydrate 46 grams (8% of total calories)
Fat 157 grams (62% of total calories)
And the result?
Total fat loss at the end of the six-week study was just over seven pounds in the low-carbohydrate group. The group following their normal diet lost no weight.
The men on the low-carbohydrate diet gained just over two pounds of muscle. The control group, on the other hand, gained just under one pound.
However, while the low-carbohydrate group gained twice as much muscle as the control group, this doesn’t necessarily mean that such a diet is the best way to pack on size.
Protein
For one, there was a big difference in protein intake between the two groups.
A closer look at the food records reveals that subjects on the low-carbohydrate diet ate TWICE as much protein than those in the control group (176 grams versus 80 grams per day).
The extra muscle growth in the low-carbohydrate group was most likely down to the fact they were eating more protein.
What’s more, the low-carbohydrate diet was designed to promote weight loss, rather than weight gain. Muscle growth is usually a lot faster with a diet providing more calories and more carbohydrate than both of the diets tested in this trial.
Taking six weeks to gain two pounds of muscle is nothing to write home about, especially when you compare it to the 5-6 pound muscular gain seen with higher carbohydrate intakes over the same period (such as here and here).
This brings me to the subject of exercise.
In an ideal world, both groups would have followed the same exercise program. But that doesn’t appear to have happened in this study. The only information about the type of training routine used in the research was this…
Subjects were moderately active performing a variety of different aerobic and weight-training routines, but none were competitive athletes. In the carbohydrate-restricted diet group, 1 subject was sedentary, 5 performed regular exercise (2 to 4 times per week for 20 to 60 minutes) and 6 performed a combination of aerobic exercise (3 to 5 times per week for 15 to 90 minutes) and resistance exercise (2 to 6 times per week for 45 to 120 minutes). Subjects were required to maintain their current level of physical activity during the study.
What this means is that all of the subjects in the low-carbohydrate group were following a DIFFERENT exercise program, and we have no idea what sort of exercise the control group was doing.
In other words, any differences in muscle growth between the two groups could have been due to a better training program rather than diet alone.
Even the lead author of the study, Dr Jeff Volek, believes that more carbohydrate is needed if you’re trying to build muscle.
Volek, a former Indiana state champion in powerlifting, is the co-author of numerous articles in scientific journals, with a number of book chapters, research presentations and abstracts wedged under his lifting belt.
Here’s what he had to say on the subject of carbohydrate and muscle growth in an interview with Muscular Development magazine…
“If you are trying to gain weight, my experience is that it is very difficult to prevent weight loss, let alone gain weight, on a strict ketogenic diet. When you start doing higher repetitions like bodybuilders do, at least during some phases of their training, I do think there’s probably going to be some compromise in your ability to do those sets.”
Muscle glycogen
Glycogen is the name given to carbohydrate stored in your body, and is used to provide energy during exercise. When you cut back on your carbohydrate intake, your glycogen stores are also going to drop.
If you train hard on a regular basis without replacing the glycogen your body uses, performance during certain types of exercise can get worse rather than better — hampering your muscle-building efforts in the gym.
But that’s not the only reason low muscle glycogen is a problem.
Not only does low muscle glycogen have the potential to limit your performance in the gym, it also appears to have a big impact on the activity of a number of key genes involved in muscle growth.
Australian researchers, for example, have found that lifting weights with low muscle glycogen levels does not enhance the activity of a number of genes involved in building muscle.
For the study, a group of strength-trained subjects performed one-legged cycling exercise to lower muscle glycogen levels in one leg. The following day, they completed 8 sets of 5 repetitions on the leg press machine, working one leg at a time.
Muscle biopsies from both legs were taken at rest, immediately after the workout, and again three hours later. A muscle biopsy involves using a needle to remove a small slice of muscle tissue, which can then be examined in more detail.
The results show that the activity of several key “muscle building” genes was higher in the leg with normal levels of glycogen compared with the leg where muscle glycogen was lowered.
The figure below shows mRNA abundance for myogenin, myogenic differentiation factor D (MyoD), and IGF-I, immediately before and three hours after a bout of resistance exercise. Filled bars, exercise commenced with normal glycogen levels; open bars, exercise commenced with low glycogen levels.
This is in contrast to endurance training, where Danish researchers have shown that completing some (around 50%) of your training with lowered glycogen levels can actually increase the time taken to reach fatigue during exercise.
In fact, this “train-low, compete-high” approach led to a twofold increase in time to exhaustion compared with subjects starting all their workouts with normal glycogen levels.
What’s the bottom line?
Over time, training with lowered glycogen levels has the potential to limit your gains in muscle mass. Because of this, strict low-carbohydrate ketogenic diets are not the best way to gain muscle, although they do work well if you’re trying to shed fat.
If you want to do a bit of both (i.e. losing fat while building muscle), then some kind of calorie cycling program (such as Tom Venuto’s Holy Grail Program) is going to be the best way to do it.
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