6 signs you're not eating enough to build or maintain muscle, according to a sports dietitian

A dietitian at Centr, the fitness and nutrition app created by Chris Hemsworth, said feelings of hunger and soreness are signs of undereating.

• You need to be eating enough for your body to build and maintain muscle, a sports dietitian said. 
• Symptoms like constant fatigue, sleep loss, soreness, and hunger may mean you've cut calories too low. 
• To prevent muscle loss, make sure you get enough food, including carbs, to fuel your workouts.

If you're trying to build muscle or become leaner, undereating could seriously stall your progress, according to a sports dietitian.

Eating too little is one of the most common mistakes for people trying to build muscle, said Angie Asche, an expert nutritionist at Centr, a fitness and nutrition app created by the actor Chris Hemsworth.

"For muscle growth, you should be in a calorie surplus. People are often trying to build in a deficit and it's very difficult," she told Insider.

Even if you want to lose body fat, which does require a calorie deficit, cutting calories too much can cause you to lose muscle rather than maintaining muscle while burning fat. 

Watch out for clear signs that your body isn't getting enough nutrients as a cue to eat more for better gains, Asche said.

Constantly thinking about food may mean you aren't eating enough

The clearest sign that you aren't eating enough is persistent feelings of hunger and overwhelming thoughts about food, Asche said. 

It may seem obvious to eat when you're hungry, pressure to hit a certain weight or aesthetic can prevent you from fueling appropriately.

"You have to really reframe that thought process," she said.  

If fat loss is a goal, some hunger may be inevitable, but shouldn't be taking over your brain or derailing your ability to focus on other things, according to Asche. 

Also pay attention to the types of food you're hungry for, and make sure you aren't cutting out carbs, fat, or protein, all of which are important macronutrients for fitness. 

"Carbs and protein are the main drivers. Fat is important for calories," she said. 

Undereating can lead to trouble sleeping or intense feelings of hunger at night 

Hunger pangs and food fixation can be especially problematic at bedtime if they're causing you to lose sleep, Asche said. 

Good sleep is crucial for muscle, fitness, and overall health. Experts recommend seven to eight hours a night. 

Low energy throughout the day can be a warning sign

Lingering fatigue for no apparent reason is another way your body signals that it needs more nutrients, Asche said. 

While it's normal to have dips in energy during the day, if you're often feeling lethargic, you may want to consider upping your calorie intake. 

Struggling to make it through a workout is a symptom of undereating

If you suddenly start running out of steam during a workout, you may be overtraining or not eating enough for your body to keep up, Asche said. 

Again, the type of food can be a key factor — if you exercise regularly, you may benefit from having high-carb foods like fruit to provide quick energy for workouts. 

"People assume because they're not an athlete, they don't need carbs. We tend to underestimate why we need carbs even as recreational athletes," Asche said. 

If you're not recovering well from workouts, you may need to eat more

Undereating can also interfere with muscle recovery and growth after exercise. A telltale sign is feeling worn out or having muscle aches that last longer than usual. 

"Maybe you feel sore for way longer than you should," Asche said. 

A food diary can be a helpful tool in evaluating how much you're eating compared to your regular activity to see if you're in balance, she said.  

Loss of menstrual period is a serious sign of cutting calories too low

For athletes who menstruate, losing your period is a major red flag. Chronic undereating can wreak havoc on your hormones, especially for athletes, so lack of normal menstruation is reason to talk to a doctor.