Eating low-carb has been popular since the Atkins Diet blew up back in 1972—and the current buzz about the benefits of the super low-carb ketogenic diet proves the low-carb trend isn’t going anywhere.
The question on many people’s minds: Would we all be better off without any high-carb foods? There’s no black-and-white answer, really; different people thrive on different types of diets. But there are some surprising side effects most of us can expect to experience after a breakup with bread and pasta.
1. You Lose Weight Quickly
Oftentimes people go low-carb because they want to lose weight—and when you cut out high-carb foods like bread, that happens fast. That initial drop on the scale those first few days is just water weight, though. “Carbs hold onto water like a sponge,” says Deborah Malkoff-Cohen, R.D., dietitian and certified diabetes educator in New York City.
When you stop eating carbs, your body starts using the carbs it has stored up in your body to keep functioning, ‘wringing out the sponge’ and releasing water as it does so. Start noshing on carbs again, and you’ll put that water weight right back on.
2. You Feel Tired At First
Carbs, which you break down into a form of sugar called glucose, are your body’s preferred source of energy. While you get a slow and steady boost from complex carbs (like potatoes and oats), which take longer to break down into glucose, simple, quick-digesting carbs (like white bread and rice) hit your bloodstream in sugar form fast, spiking your energy only to send you crashing later.
Regardless of whether you usually eat a lot of simple carbs—and ride the blood sugar rollercoaster that comes with them—or coast along the complex-carb freeway, cutting down on your total intake will probably leave you feeling pretty drained at first, says Toni Marinucci, R.D., registered dietitian in New York City.
When your body doesn’t have enough glucose to run on, it eventually turns to its backup generator—a state called ketosis—and burns fat instead. Your blood sugar and levels of stored glucose in your liver and muscles (called ‘glycogen’) have to drop significantly to get you there, though, and you’ll likely feel pretty awful as they do. (If you can hold out until you get there, most people feel better a few days into ketosis.)
3. And Crabby, Too…
You can expect not to feel your happiest when you’re depriving yourself of an entire food group—especially when you’re passing up on the bread basket during dinner out with friends. But the emotional impact of cutting carbs goes deeper than that: Eating carbs actually increases your brain’s production of the mood-regulating chemical serotonin (often called the ‘feel-good hormone’), says Malkoff-Cohen. The less serotonin you pump out, the more likely you are to feel bummed out.
4. You Might Even Feel Like You Have The Flu
Ever heard of something called the low-carb or ‘keto flu’? Yeah, it’s a real thing—and it’s not fun. When you cut down on carbs significantly, you might deal with flu-like symptoms like drowsiness, achiness, and nausea, says Malkoff-Cohen.
A lot of these issues have to do with your brain, which typically uses tons of glucose because it has so many nerve cells. When your brain doesn’t have enough glucose to run full-steam-ahead, but hasn’t transitioned to using fat, your neurons (nerve cells) don’t function properly and you feel terrible.
Plus, people on low-carb diets often lose out on electrolytes like sodium and potassium, which can lead to some of those flu-like symptoms, as well as issues like heart palpitations and muscle cramps, Malkoff-Cohen adds.
The low-carb flu should subside once you’re a few days into ketosis, but if you’re not quite low-carb enough to make the shift (like 20 to 30 grams of net carbs a day, ‘low’), symptoms might stick around.
5. You Have Trouble Going No. 2
Complex carbs, like whole-wheat bread and other whole grains, contain fiber, which keeps our digestive systems regular. If you cut out complex carbs and don’t make up for that lost fiber with other foods (like vegetables, legumes, and nuts), you might fall short of your needs and have a more difficult time going to the bathroom. (Men should aim for 38 grams of fiber per day; women should aim for 25.)
6. Your Workouts Feel Pretty Meh
Just as putting the kibosh on carbs can tank your overall energy at first, it can also leave you feeling like garbage in the gym. Marinucci typically recommends snacking on something carb-y (like a granola bar or piece of toast) about 30 minutes before working out, to provide your body with quick fuel.
Lower-intensity exercise (like jogging) may not suffer much when you slash carbs, because your body can power it pretty easily with fat. However, you’ll likely have a harder time pushing through higher-intensity workouts (like strength training or sprint intervals), which rely heavily on carbs. Without those carbs, your body will have to use glycogen or even break down muscle tissue to scrounge up the energy you need.