Listen, I’m not a doctor, and I try my best not to pretend to be one, but in my world, one of the biggest fitness myths is that you should cut out carbohydrates if you want to get lean or build serious muscle. Carbohydrates are your body’s primary and preferred source of fuel, breaking down into glucose to power your cells, organs, and brain. They act as a critical energy source, help regulate blood glucose and insulin metabolism, support lipid and cholesterol balance, and feed your gut microbiome. The moment you consume carbs, your digestive tract gets to work breaking them down into glucose for immediate energy, while any extra glucose gets stored as glycogen in your liver and muscle tissue for when you need it later.
In terms of weight loss, plenty of people argue that going low carb helps you drop weight faster. While that might feel true during the first week when you drop a bunch of water weight, research shows that cutting carbs gives you zero magical metabolic advantage for fat loss. Large, rigorously controlled clinical studies, including the landmark DIETFITS trial conducted by Stanford University, have proven that when total calories and protein are matched, low-carb diets and balanced diets result in the exact same amount of fat loss. When you train hard or lift heavy, the case for keeping carbohydrates on your plate becomes even stronger.
“Carbohydrates are broken down into glucose, which is the body’s fastest and most efficient energy ning,” explains Dr. Joey Masri, PT, DPT, CSCS, a Board-Certified Orthopedic Clinical Specialist
When you eliminate carbohydrates from your diet, your body undergoes a rapid metabolic shift to adapt to its new fuel source. Because glucose is your system’s easiest source of energy, removing it forces your body into a multi-stage survival process. First, you burn through whatever reserve glucose is circulating in your bloodstream. Once that is completely gone, your system taps straight into glycogen, which is the glucose stored directly inside your liver and muscle tissue.
As those stored reserves dry up over the following days, you’ll likely experience a cluster of unpleasant symptoms commonly known as the keto flu. This phase brings on brain fog, pounding headaches, intense fatigue, irritability, and painful muscle cramps due to the combination of zero circulating glucose and the rapid loss of essential electrolytes like sodium, potassium, and magnesium
To keep you functioning, your liver eventually begins breaking down dietary and body fat into molecules called ketones so your brain and muscles can adapt to using them as an alternate energy
While adapting to ketones sounds fine in theory, it creates massive performance issues if you regularly lift weights or do high-intensity conditioning. Without adequate carbohydrates, your muscle glycogen stores remain chronically depleted. That lack of stored fuel directly impairs your ability to complete high-volume workouts, like four grueling sets of ten squats. While your one-rep maximum strength might hold up for a single rep, your strength endurance takes a total nosedive, leaving you completely gassed halfway through your workout.
“Oftentimes, people aggressively cut down on carbohydrates, such as the ketogenic diet, but doing so leads to subpar performance in workouts and increased sluggishness,” says Dr. Masri
When your muscle glycogen is tapped out, your body cannot regenerate adenosine triphosphate (ATP) fast enough during intense resistance training sets. That lag in energy production means you hit muscular failure much earlier than usual, forcing you to use lighter weights or cut your sets short.
Beyond sabotaging your actual gym sessions, running on zero carbs slows down your recovery between workouts. Muscle protein synthesis, the process your body uses to repair and rebuild damaged muscle fibers after a heavy lifting session, requires both protein and energy. Carbohydrates trigger an insulin response that helps transport amino acids directly into your muscle cells while blunting the rise of cortisol, your body’s main stress hormone.
If you want to maintain training intensity, support your work capacity, and recover efficiently between heavy sessions, keeping a consistent intake of complex carbohydrates in your daily routine is essential
