Are Carbohydrates Really the Villain?

Written by Dr. Leandro Cordova, Ph.D. — Co-Founder & Formulation Scientist at Proven Science Nutrition Science First. Results Always.

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After thorough deliberation by the panel of judges, the usual suspects are considered NOT GUILTY for their crimes!

Few nutrients have been put on trial as often as the carbohydrate. Every few years, a new wave of diet culture rolls in and hands carbs the same guilty verdict: bread is "poison," pasta is "empty," rice makes you fat, and fruit has "too much sugar." If you've ever felt a flicker of guilt reaching for a banana before training, you are far from alone.

But after fifteen years developing evidence-based formulas and reading the primary literature line by line, I can tell you the science tells a very different — and far less dramatic — story. Carbohydrates are not the villain. Context is. The quality of the carbohydrate, the amount relative to your activity, and what you do to support your body around it matter enormously. The macronutrient itself was never the problem.

Let's put carbs on the stand properly, look at the actual evidence, and clear up one of the most persistent myths in nutrition — including a connection between carbs and hydration that almost nobody talks about.

Where the carb fear came from

The anti-carb narrative didn't appear out of nowhere. It grew out of a few genuinely real problems that got flattened into one oversimplified rule.

The modern Western diet is flooded with refined, ultra-processed foods: sugary sodas, packaged snacks engineered to be irresistible, and refined grains stripped of their fiber and nutrients. These foods are easy to overconsume, spike blood sugar quickly, and add a lot of calories without much nutritional return. When people cut them out — often through a low-carb or ketogenic approach — many felt better, lost weight, and understandably concluded, "carbs are bad."

The logic error is subtle but important. What actually improved wasn't the absence of carbohydrates as a category — it was the removal of a pile of low-quality, calorie-dense processed food. The benefit got misattributed. Blame the specific foods and the overall pattern, not the entire macronutrient class that also includes lentils, oats, berries, sweet potatoes, and vegetables.

That distinction — between carbohydrate quantity and carbohydrate quality — is where the real science lives, and we'll come back to it.

What carbohydrates actually do for your body

Carbohydrates are, quite simply, your body's most efficient and preferred fuel — especially when the intensity climbs. When you eat carbs, your body breaks them down into glucose and stores what it doesn't immediately use as glycogen in your muscles and liver. That glycogen is your ready reserve: the fuel you tap the moment you sprint, lift, climb a flight of stairs, or push through the last few reps of a hard set.

Your brain is an especially demanding customer. Under normal conditions it runs largely on glucose, which is part of why heavily restricting carbs can leave people feeling foggy, irritable, and flat before they adapt.

For anyone who trains, glycogen is the difference between a strong session and a miserable one. The classic work of Bergström and colleagues demonstrated decades ago that muscle glycogen availability is directly tied to endurance capacity — deplete your stores and your ability to sustain hard effort falls off a cliff.[1] Modern sports-nutrition consensus builds on exactly this foundation. The International Society of Sports Nutrition notes that endogenous glycogen stores are maximized by higher carbohydrate intakes — on the order of 8–12 g of carbohydrate per kilogram of bodyweight per day for hard-training athletes — and that these stores are depleted most by high-volume training.[2]

In other words, the athletes and lifters who consistently perform, recover, and adapt rarely thrive on rock-bottom carbohydrates over the long haul. Fuel matters, and carbohydrate is premium fuel.

Carbs, recovery, and performance

The role of carbohydrate doesn't end when the workout does. Replenishing glycogen after training is a key part of recovery, and getting adequate carbohydrate around your sessions helps you show up ready for the next one.

The ISSN position stand highlights that for prolonged, high-intensity efforts, carbohydrate intake during exercise supports both performance and fluid regulation — and notably, they frame the ideal delivery vehicle as a carbohydrate–electrolyte solution, not carbohydrate alone.[2] That pairing is not an accident, and it's a preview of the hydration connection we'll get to shortly. Even in resistance training, adequate carbohydrate availability supports higher glycogen stores and better training adaptations over time.[2]

Chronically underfueling carbohydrate — a mistake I see constantly in people who've absorbed the "carbs are bad" message — tends to show up as sluggish workouts, stalled progress, poor recovery, disrupted sleep, and in some cases hormonal disruption. The body is remarkably good at telling you when it's running low on its preferred fuel. The trick is learning to listen instead of pushing harder.

The real distinction: carbohydrate quality

Here is the single most important reframe in this entire conversation: not all carbohydrates are created equal, and the evidence is overwhelming that quality is what drives health outcomes.

One of the most comprehensive analyses ever conducted on this question was a series of systematic reviews and meta-analyses published in The Lancet, drawing on roughly 40 years of observational studies and clinical trials.[3] The findings were striking. People with the highest intakes of dietary fiber had, compared to those with the lowest, a 15–30% lower risk of all-cause and cardiovascular mortality, along with meaningfully lower rates of coronary heart disease, stroke, type 2 diabetes, and colorectal cancer.[3] The data pointed to a target of at least 25–29 grams of fiber per day, with more likely being better, and the dose-response relationship was strong enough that the authors judged the links plausibly causal.[3]

Where does that fiber come from? Whole, minimally processed carbohydrates: whole grains, legumes, vegetables, fruits. These foods deliver fiber for digestion and satiety, a slower and steadier release of energy, and a payload of vitamins, minerals, and beneficial plant compounds you simply won't get from protein and fat alone.

Now contrast that with the carbohydrates that genuinely earn scrutiny. Sugar-sweetened beverages are the largest single source of added sugar in the modern diet, and a robust body of evidence links their habitual intake to weight gain and a higher risk of type 2 diabetes, cardiovascular disease, and certain cancers.[4][5] These are rapidly absorbed, nutrient-poor, and extremely easy to overconsume in liquid form.

So when someone asks me whether carbs are "bad," my honest answer is a question back: which carbs, how much, and in place of what? A bowl of oats, a plate of lentils, and a can of soda are all "carbohydrates," and treating them as the same thing is where the entire villain narrative falls apart.

The hidden connection: carbs, water, and electrolytes

Now for the part that even seasoned gym-goers tend to miss — and it happens to sit right at the intersection of nutrition science and formulation, which is my world.

Glycogen is not stored dry. It is intensely hydrophilic, meaning it holds water alongside it. Research using muscle biopsies has confirmed the long-standing observation that each gram of glycogen is stored in human muscle with roughly three grams of water — a ratio that can climb even higher depending on fluid availability.[6][7] For a well-fueled adult, that adds up to well over a kilogram of water riding along with your carbohydrate stores.

This single fact explains a mystery that trips up nearly everyone who tries a low-carb or ketogenic diet: the rapid "weight loss" in the first week. When you sharply cut carbohydrates, you burn through stored glycogen, and all that bound water is released and excreted. The scale drops fast — but most of that early change is water, not fat.

And here's the crucial part: that water doesn't leave alone. When carbohydrate intake falls, insulin levels drop, and low insulin signals the kidneys to excrete more sodium — a well-established physiological process. As sodium and water are flushed out, potassium and magnesium tend to follow. The result is a rapid depletion of the very electrolytes your body depends on.

This is the true nature of the so-called "keto flu." The fatigue, headaches, dizziness, muscle cramps, brain fog, and irritability that so many people experience in the first days of cutting carbs — symptoms documented in the research literature as appearing early and typically resolving within the first few weeks — are largely not caused by the absence of carbohydrate itself.[8] They are, in large part, an electrolyte and fluid problem masquerading as a carbohydrate problem.

Electrolytes are not optional trace players. Sodium, potassium, magnesium, and calcium govern fluid balance, nerve signaling, and muscle contraction. When they run low, your muscles cramp, your energy sags, your focus scatters, and your workouts suffer — regardless of how well you're eating otherwise.

And this isn't only a low-carb issue. Anyone who trains hard, sweats heavily, or lives and works in the heat loses electrolytes through sweat every single session. Fueling with carbohydrate is one half of the performance equation; maintaining proper hydration and mineral balance at the cellular level is the other. This is precisely why the sports-nutrition literature keeps pointing toward carbohydrate and electrolytes together, not one in isolation.[2]

Hydrate smarter — without undoing your hard work

Here's the trap. The obvious "solution" most people reach for is a conventional sports drink — and most of those pile electrolytes on top of a substantial dose of added sugar. If you've been thoughtful about your carbohydrate quality all day, the last thing you want is to quietly undo that effort with a candy-flavored beverage every time you hydrate. And if you're specifically following a lower-carbohydrate approach, a sugary drink can work directly against your goal.

This is a problem I thought about constantly when we formulated PSN Electrolytes. The goal was to deliver the minerals that actually matter — in the amounts that matter — without the baggage.

Our formula provides sodium (from Himalayan pink sea salt), potassium, magnesium, and calcium, plus coconut water powder and taurine, and it does so with no added sugar — it's sweetened with stevia. That design choice matters more than it might seem. It means PSN Electrolytes fits any carbohydrate strategy: whether you're eating higher-carb to fuel heavy training, cycling your carbs, going lower-carb, or simply sweating hard in the heat and needing to top off. You get the hydration support without the sugar that could compromise your nutrition or your goals.

Everything we make follows the same principle: clinically relevant doses, full label transparency, no proprietary blends hiding the numbers, and third-party testing for quality. That's not marketing language — it's the formulation philosophy the entire company was built on. Science first. Results always.

Putting it into practice

If you take nothing else from this article, take these principles:

Build the majority of your carbohydrates around whole, fiber-rich foods — whole grains, legumes, fruits, and vegetables. That's where the health outcomes live.[3] Match your carbohydrate intake to your activity: train hard and you need more fuel; the harder and longer you go, the more glycogen you'll want on board.[2] Be honest about the genuine culprits — ultra-processed foods and sugary drinks consumed in excess — rather than fearing an entire macronutrient.[4] And whatever your dietary approach, protect your hydration and electrolytes so your body can actually use the fuel you give it, especially if you sweat a lot or you're cutting carbs.

That last point is the one most people skip, and it's often the difference between feeling flat and feeling strong.

When you want a plan built around you

Everything above is the general science. But bodies, goals, schedules, and preferences are individual — and translating principles into a plan that actually fits your life is where real results come from.

If you want that kind of personalized guidance, I recommend the coaching team at Fit by Mi (fitbymi.net). They build individualized nutrition and training plans grounded in the same evidence-based, no-nonsense philosophy we stand behind at PSN — no fad diets, no fear-mongering about carbs, just a smart plan tailored to you and real accountability to help you follow through. If you've read this far because you're ready to stop guessing, that's a great place to start.

The bottom line

Carbohydrates are not the enemy. They are powerful, efficient fuel — and when you choose quality sources, match them to how you train and live, and support your body's hydration and electrolyte needs, they become one of your greatest allies in performance, recovery, and health.

So go ahead and eat the banana before your workout. Fuel your training. Choose your carbs wisely. And hydrate smart, so your body can put every bit of that fuel to work.

Science first. Results always.

Have questions about our formulas or the research behind them? Reach out anytime at contact@psnutrition.com.

— Dr. Leandro Cordova, Proven Science Nutrition

Frequently Asked Questions

Are carbs bad for you?

No — carbohydrates aren't inherently bad. Research shows carbohydrate quality matters far more than quantity. Fiber-rich whole foods like whole grains, legumes, fruits, and vegetables support health, while excess added sugar and ultra-processed carbs are the real concern.

Do carbs make you gain weight?

Carbs alone don't cause weight gain — an overall calorie surplus does. That said, sugar-sweetened beverages and ultra-processed carbs are easy to overconsume and are linked to weight gain, while whole-food carbs tend to be more filling and nutrient-dense.

Why do you lose water weight when you cut carbs?

Your body stores carbohydrate as glycogen, and each gram of glycogen holds roughly three grams of water. When you cut carbs, glycogen and its bound water are depleted, causing rapid early "weight loss" that's mostly water, not fat.

What causes the keto flu?

Keto flu — the fatigue, headaches, and cramps common in the first days of a low-carb diet — is largely an electrolyte and fluid issue. Low insulin prompts the kidneys to excrete more sodium, and potassium and magnesium follow, depleting key minerals.

Do you need electrolytes on a low-carb diet?

Yes. Low-carb and keto diets increase sodium, potassium, and magnesium loss, which drives keto-flu symptoms. Replenishing electrolytes — ideally without added sugar — helps maintain hydration, energy, and muscle function.

References

1. Bergström J, Hermansen L, Hultman E, Saltin B. Diet, muscle glycogen and physical performance. Acta Physiologica Scandinavica. 1967;71(2):140–150. doi:10.1111/j.1748-1716.1967.tb03720.x

2. Kerksick CM, Arent S, Schoenfeld BJ, et al. International Society of Sports Nutrition position stand: nutrient timing. Journal of the International Society of Sports Nutrition. 2017;14:33. doi:10.1186/s12970-017-0189-4

3. Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet. 2019;393(10170):434–445. doi:10.1016/S0140-6736(18)31809-9

4. Malik VS, Hu FB. The role of sugar-sweetened beverages in the global epidemics of obesity and chronic diseases. Nature Reviews Endocrinology. 2022;18(4):205–218. doi:10.1038/s41574-021-00627-6

5. Malik VS, Schulze MB, Hu FB. Intake of sugar-sweetened beverages and weight gain: a systematic review. American Journal of Clinical Nutrition. 2006;84(2):274–288. doi:10.1093/ajcn/84.2.274

6. Fernández-Elías VE, Ortega JF, Nelson RK, Mora-Rodriguez R. Relationship between muscle water and glycogen recovery after prolonged exercise in the heat in humans. European Journal of Applied Physiology. 2015;115(9):1919–1926. doi:10.1007/s00421-015-3175-z

7. Olsson KE, Saltin B. Variation in total body water with muscle glycogen changes in man. Acta Physiologica Scandinavica. 1970;80(1):11–18. doi:10.1111/j.1748-1716.1970.tb04764.x

8. Bostock ECS, Kirkby KC, Taylor BV, Hawrelak JA. Consumer reports of "keto flu" associated with the ketogenic diet. Frontiers in Nutrition. 2020;7:20. doi:10.3389/fnut.2020.00020

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Consult a qualified healthcare professional before making significant changes to your diet, especially if you have a pre-existing medical condition.