Low Carb vs High Carb Diets for Building Muscle

Welcome to the 39th episode of Vegetarian Health and Longevity from Hurry The Food Up and Sports Nutritionist James LeBaigue.

Many of us are looking for that elusive “optimal diet” to build muscle and lose weight.

It’s a big topic, and let’s be honest, we’re often tempted by whatever’s trending—whether it’s keto, low carb, or something else entirely.

And as a sports nutritionist, people often ask me whether low-carb diets are the best for building muscle, because they’ve seen claims that it helps to promote strength while stripping away body fat.

But are these low carb diets actually superior for building muscle, or are you better focusing on a more traditional diet?

By the end of this episode, you’ll know the key takeaways and what you should work on to ensure you’re in the best position possible to build muscle.

You can find it on YouTube below or you can listen to it here on your favourite provider.

If you missed last week’s epodcast about an important research update for vegetarians then you can listen to or read it here.

With a busy life, I want strategies that deliver results with less effort.

I’m no stranger to hard work, and I have a good mindset when it comes to prioritising the long-term, even if it means I don’t see as much progress in the short term.

But if there’s something that could help me get more benefit in a shorter timeframe, is safe, realistic and evidence-backed, I’d be a fool not to follow it.

High-Carb Diets: The Traditional Choice

For years, high-carb diets have been the go-to recommendation for athletes. Carbohydrates play a key role in replenishing glycogen stores in your muscles and liver, and this is crucial for sustaining high-intensity training, allowing you to perform at your best during workouts or competitions. 

Without adequate glycogen, it’s almost impossible to train consistently at high intensity, and when it comes to growing muscle, it’s considered likely that you won’t be able to lift as heavy or regularly as you would otherwise.

However, not everyone agrees. Critics argue that high-carb diets may not be as effective for fat loss or strength gains as alternative approaches like low-carb, high-fat diets.

Low-Carb Diets: The Contender

Low-carb diets, including ketogenic approaches, have gained significant traction in recent years. Advocates claim that cutting carbohydrates forces the body to burn fat for fuel, which can enhance fat loss.

Some people also prefer it because it makes it easier to maintain a calorie deficit, because the more restricted approach lends itself to easier weight loss than if all foods were available.

Proponents even suggest that low-carb diets optimise hormonal responses, such as improving insulin sensitivity and increasing fat-burning potential.

But this isn’t the whole story. While low-carb diets might work well for certain individuals or specific goals, they come with notable drawbacks, especially for people looking to build muscle. 

The primary issue is glycogen depletion, which we’ve spoken about. Without adequate carbs, your glycogen stores are likely to be on the lower side, which can hinder your ability to perform high-intensity or high-volume training. This can lead to fatigue, reduced performance, and slower progress towards your goals.

The Science: What Does the Research Say?

Now, let’s move to the evidence. A 2024 study called “Effectiveness of high-fat and high-carbohydrate diets on body composition and maximal strength after 15 weeks of resistance training” provides some fresh insight into this debate. 

The researchers recruited 48 men, averaging 25 years of age, and split them into two groups. One group followed a low-carb diet, consuming fewer than 10% of their daily energy from carbohydrates. The other group followed a high-carb diet, where carbs accounted for 70% of their daily caloric intake. Both groups engaged in the same structured resistance training programme over a 15-week period, and their calorie intake was standardised.

Both groups experienced fat loss, with the low-carb group showing slightly greater reductions in body fat on average. The high-carb group had increased their muscle strength, while the low-carb group saw a slight decline. 

These two results are fascinating, and need a bit of exploring.

The researchers primarily measured body composition changes via bioelectrical impedance. While these tools can be useful, they are also very sensitive to changes in body water fluctuations. Low-carb diets are notorious for disrupting this because they lack glycogen storage. Water is stored with glycogen, so when someone undertakes a low-carb diet, they typically lose a lot of weight quite quickly, but it is usually water weight.

This is why people who swap onto keto diets typically see such dramatic losses at the start; but it’s not fat loss and it’s not sustainable.

The researchers also used waist circumference as a tool to measure body composition changes, and they found this was similar across both groups.

The high carb group made statisticall improvements in their squat, deadlift and bench press, suggesting that this diet was superior if improving muscle strength is the primary goal.

These findings align with longer-term studies, which have generally shown that both low-carb and high-carb diets are effective for fat loss, with no significant differences when all else is equal.

However, when it comes to performance, the evidence consistently favours higher carbohydrate intake and it’s hard to get around that.

If you’re trying to lose weight by the way, you can check out a free week’s weight loss meap plan as part of TVPF. We’ve made it easy for you to get started by providing a plan with recipes with step by step instructions and a grocery list, so all you have to do is buy the food and cook our easy but tasty recipes.

We’ve worked out the macros so that you don’t have to, so that you can focus on the things which I have no doubt are taking up your brain power!

You can download this free meal plan here.

Practical Takeaways

So, what can we take away from this? For most people, particularly those who are active and aim to train at a high intensity, a high-carb diet is likely the safer bet. Aiming for around 50% of your daily energy intake from carbohydrates is a good starting point. This should ensure your glycogen stores are topped up and ready to support consistent, high-quality training sessions.

It’s also crucial to maintain a high-protein diet, regardless of your carbohydrate intake. Research suggests that consuming 1.4-2.2 grams of protein per kilogram of body weight daily helps preserve and build muscle mass, as well as supporting recovery. 

For example, if you weigh 70 kilograms, that would mean eating at least 100 grams of protein per day. Protein remains non-negotiable, whether your focus is on fat loss, muscle gain, or both.

For those considering a low-carb approach, it’s worth understanding the potential risks. While low-carb diets may lead to slightly greater fat loss in the short term, they could compromise muscle strength and performance. 

This trade-off might not matter if your primary goal is fat loss and you don’t engage in high-intensity training. But if you want to build muscle or perform well in the gym, these risks become more significant.

You also have to look at the long-term realities.

Can you follow a low carb for months at a time, or even forever? Most people I know who have tried this find it very difficult due the restricted food choices, and it’s not something I would recommend to the average person because of the lack of research on the long-term safety.

Examples From the Field

It’s important to acknowledge that there are successful athletes and coaches on both sides of the argument. High carb diets are essential for endurance athletes, especially when aiming for peak performance during events like racing.

On the other hand, some strength athletes and bodybuilders have found success with low-carb approaches, particularly when their training volume is lower, or they’re in a cutting phase.

The key takeaway is that context matters. Your diet should align with your training demands and personal goals. If your workouts rely on sustained effort and intensity, carbohydrates are indispensable. 

If you’re training less frequently or focusing purely on fat loss, a low-carb approach might work for you if you prefer that dietary pattern, but it won’t lead to better results in the long term compared to a high carb diet.

Final Thoughts

Ultimately, there’s no definitive answer to whether low-carb diets are superior. Both high-carb and low-carb approaches can help you lose weight, but when it comes to simultaneously losing fat and gaining muscle, high-carb diets seem to have the upper hand. 

They support better glycogen storage, training intensity, and muscle strength, making them the better choice for most active individuals.

The most important thing is to figure out what works for you. If you’re unsure where to start, my recommendation would be to prioritise carbohydrates for energy, keep your protein intake high, and adjust based on your performance and how you feel.

Alright, that’s it for this week. If this podcast helped you, please don’t forget to spread the word or leave a review, we’d really appreciate it!

---

And finally, here is the easiest way to sign up to try our meal plans (free).

And a list of our vegetarian meal plans (also all free).

And finally finally: More vegetarian podcasts this way!

Studies used in this podcast:

Effectiveness of high-fat and high-carbohydrate diets on body composition