Here’s how to tell if your body’s begging for fuel.

By Krissy Brady
May 22, 2019

When you’re on a mission to eat healthier, it’s understandable that you want to break up with as many unhealthy foods as you can. One of the first to go is usually carbs, but many of us unintentionally ghost them on a grander scale than is necessary, and sabotage our health goals in the process.

That’s because not all carbs mess with your health: Complex carbs, like those found in veggies and whole grains, are actually an important part of a balanced diet.

“Carbohydrates are one of the main sources of energy used by the body,” says Texas-based registered dietitian Linzi Cruz, RD. “It’s true an imbalance of carbs can impact weight loss, liver function, and GI metabolism, but too little of them can cause some pretty uncomfortable side effects as well.”

The best way to start incorporating more healthy carbs into your diet after lagging on them for a while is to taper them in slowly, says Cruz. For example, if you’ve previously been consuming a net carb total of 20 grams per day (and/or you were on the keto diet), then increasing your intake by 5 to 10 percent every week or two would be best to give your body time to readjust (and make sure to increase your water intake along the way to avoid constipation).

It’s recommended that complex carbs make up 45 to 65 percent of your total daily calories, according to the Mayo Clinic. So if you’re eating 2,000 calories a day, roughly 900 to 1,300 of those calories should be from carbohydrates (or 225 to 325 grams).

How can you tell if you’ve gone overboard nixing carbs from your repertoire? Here, experts reveal eight signs that your body’s begging you to fuel up.

1. Junk Food Cravings

One of the first signs that your body’s running low in the carb department is ravenous junk food cravings. When the body realizes that it’s not getting the fuel it needs to function properly, relentless hunger cues and cravings take over as your body literally starts to hunt for energy in the form of carbohydrates. “It becomes harder to say no and stay away from junk food because most of it contains carbs,” says Maggie Michalczyk, RD, Chicago-based registered dietitian and blogger at Once Upon a Pumpkin.

2. Fatigue and Brain Fog

While feeling pooped can be caused by many things, it’s a common symptom of not getting enough carbs. Since carbs provide the glucose necessary to fuel the body, you might find yourself feeling exhausted when they’ve been demoted in your diet. Your brain can get pretty lax, too: “It can feel like thoughts seem to be slipping away or that your mind is foggy because some pathways don’t have enough glucose to work at their best capacity,” says Michalczyk.

3. Bad Breath

“When we eat too few carbs, we risk the body relying too heavily on fatty acids for fuel, which can lead to a state of ketosis,” says New York-based registered dietitian Rachel Fine, RD. This is when your body breaks down ketones—what your liver produces from breaking down fatty acids—for energy. Bad breath, or halitosis, is a byproduct of certain chemicals being released in the body when ketones are burned (chemicals that are known to cause fruity-smelling breath).

4. Headaches

A lack of carbs can also trigger low blood sugar, and headaches can strike as a result, says Fine. When the brain notices there’s not enough glucose to go around, it reacts to this change by trying to restore sugar levels, causing a headache. (According to the National Headache Foundation, headaches associated with low blood sugar tend to be a dull, throbbing headache located in the temples.)

5. Bloating and Constipation

Carbs are one of the body’s main sources of fiber (think: fruits, veggies, and whole grains), and because fiber is what keeps the number two train running smoothly, not getting enough can lead to bloating and traffic jams in your GI tract. “A lack of fiber leaves your GI tract constricted and unable to perform the peristalsis process that helps things move smoothly,” says Cruz.

6. Feeling Cold

“Temperature regulation is controlled by hormones in our hypothalamus, the same spot in the brain that controls hunger and satiety,” says Michalczyk. When your body’s running low on carbs, it can throw these hormones out of whack and make it feel like you can never get warm.

7. Mood Swings

Because the brain isn’t getting enough glucose, the hypothalamus (which also controls mood) keeps producing the hunger hormone. “When one hormone is in overdrive telling our body that we’re hungry for energy, it can have a major impact on other hormones—like the ones for a calm mood—and prevent that one from being released like it should be,” says Michalczyk. Cue hanger.

8. Workout Drama

If your go-to exercise routine is a grind to get through, being low on carbs could be to blame. “Carbs are the body’s main source of energy, providing fuel to your muscles,” says Michalczyk. “When there’s not enough in the tank, so to speak, the lethargy and lack of energy can impact your workouts.” Instead of feeling refreshed after a sweat session, you might feel even more exhausted, and in some cases, straight-up ill for a day or two post-workout, says Cruz.

The Bottom Line

Carbs—especially fiber-rich complex ones—are part of a balanced diet and help promote good bacteria in your gut microbiome (which contributes to overall health). If you are experiencing any of these signs or symptoms, try slowly adding fruit, veggies, and whole grains (yep, even pasta!) back into meals.

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