As the World Cup kicks off at Atlanta Stadium this week, most fans are watching the speed, touch and tactics of the players. Rafaela G. Feresin will be thinking about something less visible — the nutrition science behind what’s happening inside a player’s muscles by the end of the match.

Feresin is an associate professor of nutrition at Georgia State University's Byrdine F. Lewis College of Nursing & Health Professions, where she directs the Ph.D. program in chemistry with a concentration in nutritional sciences, and teaches a course called Advanced Sports Nutrition. Her lab studies how foods like berries and peanuts affect blood pressure, gut and brain health, mostly in people managing metabolic disorders. But the same biology underlies nutrition for athletic performance — which is why, with the World Cup playing out in her own city, she has plenty to say.

Her interest in food began during her childhood in Brazil, she says, where it was always central to family, culture and health. That curiosity carried her through a dietetics degree, a doctorate and postdoctoral training, chasing the same question throughout: how food shapes blood vessels, inflammation and the brain, whether the subject is a clinical patient or on a national team.

The Heat, the Fade and the Carbs

A 90-minute match in heat and humidity drains the body fast. Players burn through glycogen, the carbohydrate stored in muscles and liver, while losing 2 to 3 liters of fluid through sweat. Core temperature climbs, and blood gets pulled toward the skin to cool the body, competing with muscles for circulation. The result is the familiar late-game fade: slower sprints, weaker passes and foggier decisions. Good pre-match fueling does not erase that fade, Feresin said, but it can help to delay it. Topped-off glycogen steadies fuel supply, and hydration with sodium supports blood flow so the brain can keep making good decisions and help the body to cool more effectively. The sodium matters here because it helps the body hold on to the fluid it takes in.

That does not mean reviving the giant pasta dinners of decades past.

“The image of one enormous pasta dinner the night before is outdated,” she said.

The modern approach favors steady carbohydrate intake the day or two beforehand, plus carbs taken in during play through drinks, gels or fruit. The science has not changed. It has been refined as research provides more accurate guidance.

If Feresin could change one thing about how elite players eat during a tournament, it would not be on game day. She would focus on every other day.

“A lot of players nail nutrition on match day, then coast on training and travel days,” she said.

Her advice is to make fueling deliberate every day, depending on that day’s demands, rather than something flipped on like a switch before kickoff.

“The body keeps no real memory of yesterday’s good meal,” Feresin said. “Consistency is the whole game.”

Fueling the Brain, Not Just the Legs

The mental side of fatigue may matter as much as the physical side. The brain runs almost entirely on glucose, so when blood sugar and glycogen dip late in a game, reaction time slows and decisions suffer. Mild dehydration alone can also dull concentration. One detail surprises people most — simply rinsing a carbohydrate drink in the mouth, without swallowing it, may briefly sharpen focus, because it senses that fuel is on the way.

“Fatigue is partly mental,” Feresin said.

The Habit Worth Stealing: World Cup Nutrition Tips

Not all of this requires an elite team’s resources. Ask Feresin what an everyday athlete could borrow from a World Cup roster, and the answer has nothing to do with exotic supplements. It is about respecting the recovery window.

Pros never skip the recovery snack, not just after matches but even after an intense practice session. Getting enough total calories, protein and carbohydrates across the day is what matters most, and once that is covered, refueling and rehydrating within about an hour of training helps optimize recovery. She breaks recovery into three Rs: refuel, repair and rehydrate. Sleep does the rest.

“ That recovery snack asks very little, it is simple and it is exactly the step most amateurs skip,” she said. “Do it consistently, and it compounds over a season.”

A World Cup of Cuisines

What that recovery snack actually contains, though, depends on who's eating it. A global tournament drawing players from dozens of countries creates a uniquely human challenge: The principles are universal, but the food is personal.

"You meet players where they are," Feresin said.

Rice, pasta or plantain, halal or kosher needs, comfort food from home: The skill is adapting the science to familiar foods, since familiar food sits better in the stomach when stakes are highest.

This relates to another less glamorous part of the job: keeping players from getting sick. Vetting hotel kitchens, avoiding buffets that sat out too long and sticking to bottled water can matter more than any performance tweak. A single stomach bug sweeping a squad before a big game, she notes, can sideline months of preparation.

Mythbusting the Supplement Aisle

Food is not the only thing under scrutiny in a player's diet. Two of the most talked about performance aids, creatine and caffeine, get more credit and more caution than people expect.

"It's not really a bodybuilder supplement anymore. It's a performance supplement," Feresin says of creatine, which fuels the quick bursts of energy that a soccer game demands, such as sprints and changes of direction late in a match. It remains one of the safest supplements studied. Caffeine, in smaller doses, sharpens reaction time, but it lingers for hours, and an evening match with the wrong dose can wreck that night's sleep and undercut recovery.

"We treat it as a precise tool, not a habit," she said.

Beyond the Game

The science behind a late-game fade looks a lot like the science behind a midafternoon slump at a desk. Skipped meals and erratic eating produce the same foggy fatigue, just without the sprinting.

Feresin’s advice holds for everyday Panthers whether they are students, faculty or staff: Eat enough, eat consistently and do not wait until kickoff to get it right.

Whether the goal is a match win, a presentation or a final exam, choosing the right fuel for our brain and body is a proven game changer.