What 100+ Years of Research Reveals About Carbs, Energy & Performance
The advice to load up on carbs before a big game or event has been present for decades. Even my middle-school soccer team would have a hefty pasta dinner the night before a tournament to make sure we could dominate the next day… or so we thought.
A new, comprehensive scientific review in Endocrine Reviews, spanning 100+ years and 160+ studies, challenges some common assumptions about how carbohydrate intake truly affects metabolism and physical performance.
Thankfully, the paper doesn’t make simplistic claims about carbs being “good” or “bad.” Instead, it synthesizes more than a century of research on carbohydrate ingestion during exercise and its relationship with fatigue. Turns out, it’s not quite what we’ve been told.
The big takeaway? A light, steady stream of carbs seems to be more effective than a night-before binge. Read on for what that looks like.
What the evidence actually shows
One of the long-held beliefs in sports nutrition is that muscle glycogen stores—the carbohydrate stored in muscles—are the key determinant of how long you can sustain activity.
But the review highlights something more nuanced: fatigue in prolonged exercise appears to be closely tied to declining blood glucose levels rather than muscle glycogen depletion alone.
In other words, keeping blood glucose stable, especially during long or intense efforts, may be central to sustained performance. Carbohydrate intake before or during exercise helps maintain that glucose availability, which in turn can delay the point at which the brain signals the body to stop due to low fuel.
How to use carbs for better performance
While a carb-heavy meal the night before can add to our muscle glycogen stores, that’s not necessarily linked to improved performance, and it’s not actually helping our circulating blood glucose levels. Even worse, it can cause high peaks and low valleys, which over time can increase the risk of prediabetes.
Also surprising is that the amount of carbohydrates needed to regain steady blood glucose (usually between 15-30 grams per hour) is much lower than the loaves of bread and bowls of pasta touted in carboloading phases of years past—it could be as small as half a banana or 15 grapes. Higher amounts weren’t found to offer bigger benefits. So whether you subscribe to low-carb or keto principles in day-to-day life, sprinkling carbs into your training can have a positive effect.
Why this matters
With one in three U.S. adults1 up against prediabetes (and 81% not even knowing it) a little extra education around carbs can’t hurt. It’s easy to assume that anyone carboloading is an athlete who is already at a lower risk of prediabetes, but research has proven otherwise. One study even found that three out of 10 endurance athletes were prediabetic (without even knowing it).
This is a total reframe of how we think about carbohydrate needs and physical activity. Rather than viewing carbs strictly as a fuel source to be “spent,” this review underscores their role in supporting energy stability, especially when gluconeogenesis (the liver’s production of glucose) can’t keep pace with demand.
For people experimenting with low‑carb or ketogenic approaches, this doesn’t negate potential benefits such as improved metabolic flexibility or enhanced fat oxidation, but it does remind us that the context of activity level, goals, and individual metabolic response matters.
The takeaway
Rather than framing carbohydrates as inherently harmful or essential across the board, the latest science suggests a refreshingly balanced POV. Carbs can play a strategic role in preventing performance‑limiting drops in blood glucose, particularly during extended or demanding physical activity. And, we can skip the advice that a whole plate of carbs gives our muscles superhero-like qualities for a big event.
As with all nutritional strategies, personalization is key.