Why Are Almost Half of Women Dehydrated Before They Even Work Out?

If you've ever started a workout already feeling off — tired, foggy, maybe a little dizzy before you've done a single rep — you're not weak, and you're not imagining it. A sports-science study released this year found that 43% of women showed up to exercise already dehydrated. Not under-hydrated by the end of practice. Dehydrated before they started. The reason isn't that women forget to drink water. It's that almost nothing about how women's bodies actually hydrate and fuel has ever been studied closely enough to tell them otherwise.

Why are so many women dehydrated before they even start?

The number comes from the Gatorade Sports Science Institute's first "Body of Science" study, which tracked more than 500 women across basketball, soccer, ice hockey, and other sports. Beyond the dehydration, 57% of the women didn't take in enough carbohydrates during exercise, and half of them took in none at all. They also replaced only about 20% of the sodium they lost through sweat, far short of the 50% researchers recommend. "The data from our first 'Body of Science' study is clear," said Dr. Kimberly Stein, senior principal scientist at the Gatorade Sports Science Institute. "These aren't small gaps between what women's bodies need and how they're fueling. They're the difference between feeling your best and unknowingly falling short."

The real problem: sports science barely studies women's bodies

Here's the part that actually explains the dehydration number: only about 6% of sports science research focuses exclusively on women, even though girls' and women's sports participation has exploded over the past fifty years. Most of what we call "hydration advice" — how much to drink, when, how much salt to replace — was built from studies done on men and then handed to women as if bodies were interchangeable. They're not. Hormones shift fluid retention, electrolyte needs, and even how thirsty you feel across the menstrual cycle and through menopause, and generic advice doesn't account for any of it. It's the same pattern that shows up when AI tools meant to help close the gender gap in women's health are still trained mostly on data from men. The data gap comes first. Everything built on top of it inherits the blind spot.

Why this matters even if you're not an athlete

If elite athletes — the most closely monitored bodies in sports — are only now getting studied for hydration and fueling specifically, think about what that means for the rest of us at the gym, on a run, or just getting through a hot afternoon. That exhaustion you've chalked up to "just being tired" might be the same gap at work that shows up for women whose constant fatigue turns out to be iron deficiency instead of a willpower problem. And it connects to something we've written about before: women going through the menopause transition need real protein targets, not vague advice built for someone else's body. Fueling yourself well isn't about trying harder. It's about finally getting information that was built with you in mind.

One thing to try today

You don't need a lab to close part of this gap yourself. About an hour before you work out, drink roughly 16 ounces of water with a small pinch of salt in it, or an electrolyte packet if you have one — not just plain water, and not a sports drink loaded with sugar you don't need. After you're done, check your urine color: pale yellow means you're in good shape, dark means drink more next time. It's a thirty-second habit that gives your body what the research says it actually needs, not what the old guidelines assumed.

"Understanding what female bodies need for hydration and nutrition to perform their best on the court shouldn't be a luxury, and Gatorade is putting in the work to make sure it's not." — A'ja Wilson, 8× WNBA All-Star

💌 Sarah