Are Low-Carb Diets Fucking with Your Muscle Gains?

So, you’ve cut the carbs, loaded up on fats, and embraced ketosis. You’re shedding fat, your energy feels stable, and you’re on the path to metabolic flexibility. But then, a creeping concern enters your mind—what about the gains, bro? 

Is your body secretly chewing through your hard-earned gains just to keep itself running? 

Possibly!

 Let’s explore the science behind low-carb diets, glucose production, and whether the low-carb approach tanks your muscle gains.

Why Does the Body Still Make Glucose in Ketosis?

You might assume that when you cut carbs, your body just shrugs and moves on. But nope! The human body is wired for survival, and glucose still plays a crucial role in essential bodily functions.

But Carbs Aren’t Essential, Bro. 

It drives me nuts when I hear “But there are no essential carbs, bro.” 

Even in full ketosis, your body still needs glucose. Some tissues and organs cannot run on fat or ketones alone. 

The term essential nutrients refers to your body’s ability to make nutrients on its own. It doesn’t mean you don’t need them to live. Your body can’t make certain amino acids and fatty acids and requires them from dietary sources. Glucose (carbs) is essential to survival. Your body has adapted the ability to make them on its own from other substrates. 

Here’s a quick rundown of who still demands glucose in your body:

• Brain and Central Nervous System (CNS): Your brain can get about 60% of its energy from ketones, but the rest must come from glucose.

• Red Blood Cells (RBCs): These guys lack mitochondria and can’t use fat or ketones for fuel—glucose is their only option.

• Kidneys: The renal medulla, the inner part of your kidneys, has a high demand for glucose because it doesn’t have enough mitochondria to use fat effectively.

• Retinas: Your eyes require a steady glucose supply for optimal function.

• Muscles (during recovery and anaerobic activity): Glycogen replenishment and lactate recycling (via the Cori cycle) require glucose.

How Your Body Still Makes Glucose Even Without Carbs.

Enter gluconeogenesis—your body’s backup for making glucose from non-carbohydrate sources like lactate, amino acids, and glycerol. This is why even on a strict ketogenic diet, you’re not walking around with zero glucose in your bloodstream. YOUR BODY STILL MAKES GLUCOSE on its own because it is “essential” for survival.

What Triggers Gluconeogenesis?

When carb intake drops, your body shifts gears to make its own glucose. The main triggers include:

1. Low Insulin & High Glucagon Levels: Insulin suppresses gluconeogenesis, but when carbs are scarce, insulin drops and glucagon rises, kicking glucose production into gear.

2. Cortisol Release: Prolonged carb restriction can raise cortisol levels, a stress hormone that increases gluconeogenesis. Yes, low-carb diets actually raise cortisol. That adrenaline rush from high cortisol is why some people feel more alert on keto. 

3. Exercise (Especially Intense Training): High-intensity workouts increase lactate production, which the liver converts back into glucose via the Cori cycle.

How Much Glucose Does the Body Make on it’s Own?

On average, the liver produces about 1 mg of glucose per pound of body weight per minute. So, for a 200-pound individual, that’s roughly 12 grams per hour or around 150 grams per day in full ketosis. That’s more than enough to meet the needs of glucose-dependent tissues.

Does Gluconeogenesis Burn Muscle?

The answer is yes and no. 

The body typically prioritizes other substrates before tearing into muscle protein. Lactate, glycerol (from fat breakdown), and even some amino acids from dietary protein all contribute to glucose production before muscle tissue gets touched. 

This works great when you have some body fat to spare, but here’s the rub. When you are on a cutting diet or contest prep and body fat lowers, those substrates become more scarce, and the risk of burning muscle tissue increases. We all have seen that guy on stage at a local show. The keto bro looks like he survived a forced labor camp death march. 

What happens in this situation is the body will start breaking down protein structures and converting it into glucose. You hear the term that carbs are protein sparring. This is what it means. When glucose is present, the body will not catabolize muscle tissue to make its glucose. 

You can smell the dude that is converting protein into glucose. It’s the guy that smells like ammonia. When the body strips proteins of nitrogen to make glucose, ammonia is the waste product and is excreted through your sweat, breath, and urine. 

Can You Build Muscle Without Carbs?

Yes, but it’s trickier. Muscle protein synthesis requires insulin. Insulin requires carbs. Increased glucose and insulin lead to lower AMPK, increased MTOR, and increased IGF1.  Ketosis reduces glycogen stores, increases cortisol, increases AMPK, lowers MTOR, and decreases IGF1. Doesn’t sound like the best environment for growing muscle, does it?

Key Challenges of Building Muscle on Keto

1. Lower Glycogen Stores: Without sufficient glycogen, high-rep and explosive training suffer.

2. Higher Cortisol Levels: Chronically high cortisol can increase protein breakdown.

3. Reduced Anabolic Signaling: Insulin plays a role in muscle growth, and lower levels might slow hypertrophy.

Ways to Maximize Muscle Growth on a Low-Carb Diet

• Increase Protein Intake: Aim for 1.2-2.0g per pound of lean body mass to ensure muscle preservation.

• Use Targeted Keto (TKD): Ingesting small amounts of fast-digesting carbs pre/post-workout can replenish glycogen without kicking you out of ketosis.

• Opt for Cyclical Keto (CKD): Having periodic carb refeeds (1-2 days a week) can replenish glycogen and support muscle growth.

• Consume More Electrolytes: Low-carb diets can lead to electrolyte imbalances, which impact muscle contractions and recovery.

This is sort of the brilliance of carb-cycling. You can go very low carb on certain days strategically and have other days where you push the carbs higher to initiate these processes for muscle growth. 

Ketosis Begins When Glycogen is Depleted

Ketosis begins once glycogen stores are depleted, but this doesn’t mean your muscles are empty forever. The liver and muscles can still synthesize glycogen from gluconeogenesis-derived glucose.

The Cori Cycle: Recycling Lactate into Glucose

During intense anaerobic exercise, muscles produce lactate. Instead of wasting it, the liver recycles lactate back into glucose, which can then be used for energy or glycogen replenishment.

Should You Ditch Low-Carb for Muscle Gains?

This depends. First and foremost, you need to be lean before pushing for muscle gains. Doing a modified keto diet with high days to replenish glycogen or a carb-cycling diet might make sense. Low-carb is a viable strategy if your metabolic health is compromised and if you are overweight. The bottom line is that you should get lean first. Once lean, it makes sense that you should push carbs strategically if you want to grow.