If you're unfamiliar with the term "carb flu," know that it doesn't mean catching the actual flu virus from a piece of bread, a packet of french fries, or a plate of spaghetti. Instead, it refers to the flu-like symptoms that may result from cutting all carbohydrates out of your diet. We've all been there: It's easy to feel bloated, run-down, heavy, and generally ugh. So you make it your mission to go carb-less; you'll be a full-on Atkins convert, right?
Fast-forward a few days, and you start feeling worse than you did at the beginning. You might experience headaches, fatigue, mental fogginess, or muscle aches. (Basically, it feels like you've come down with something, even though you haven't. And even though you're eating lots of other carb-empty foods, it seems like you're completely devoid of energy and life.) That, my friends, is "carb flu."
Keep reading to see what two expert nutritionists have to say on the issue, as well as what they recommend to fix it!
What Causes Carb Flu?
According to nutritionist Isabel Smith, carbs are kind of a double-edged sword. If you eat too many of them, you may feel bad, and if you eat too little of them, you may also feel bad. "Often, people can feel crummy if they eat no carbs, but that's pretty hard to do if you're trying to eat healthier, as vegetables and fruit contain carbs." Because of this, us health nuts "usually still eat a good amount." So if you think you're experiencing carb flu symptoms, it's possible you might not be eating a well-rounded diet of enough fruits and veggies.
Dana James, nutritionist, and founder of Food Coach NYC agrees. "Vegetables are carbohydrates, so if you're cutting those as well, these symptoms are from a lack of magnesium and B vitamins, which are required to create energy," she says. The only way to fix it is, you guessed it, eating more veggies. "Start eating more vegetables. Make the minimum four cups at lunch and dinner. That will give you enough glucose to restore your blood sugar levels which will reverse these symptoms. And add in fruit. Keep it to one cup twice a day."
How to Swap Carbs for Veggies
Smith says she wouldn't necessarily refer to this sluggish condition as carb flu, though "you can feel less energetic for sure if you're someone who eats a lot of carbs and suddenly cuts them out." Instead of going cold turkey on your carb intake, try gradually decreasing it. "Generally switching to better sources of carbs is the way to go, and then cutting back," she says.
Think healthy foods like squash and sweet potato. And be wary of carb-less diet fads. Smith says she doesn't mind eating carbs at all (just not too many of them). "I don't necessarily think people should cut carbs (except on a few certain occasions—body-building and maybe a ketogenic diet!)—but instead swap processed carbs for whole grains, or eat more vegetables that may be starchy because they contain more nutrients."
How Long Will It Take to See Results?
So let's say you are eating a plethora of fruits and veggies every day, but you stopped eating bread and pastries and refined starches. What then? According to James, "If you're cutting processed carbs, then it can be a short-term withdrawal effect, which reverses quickly." In fact, she says it should be no more than three days of this sluggishness before you feel back to normal. That happens once your "body learns to use fat as fuel, not carbs."
Good for you if this is the track you're set on. James says that vegetables "should be your primary source of carbs. Your body does not need other forms of carbs, but life without them can feel restrictive and austere." So if you do need to have a chunk of bread or a bite of a croissant every now and then (like we do), keep portions small. James recommends 1/4 cup at lunch and dinner for weight loss and 3/4 at lunch and dinner for weight maintenance. There's only one caveat. "If you're an intense exerciser," James says, "then you'll need the carbs for fuel unless you have excess body fat that it can convert to glucose for energy."
Bostock ECS, Kirkby KC, Taylor BV, Hawrelak JA. Consumer reports of "keto flu" associated with the ketogenic diet. Front Nutr. 2020;7:20. doi:10.3389/fnut.2020.00020