Feeling tired on a regular basis is extremely common. In fact, about one-third of healthy teens, adults and older individuals report feeling sleepy or fatigued (1, 2, 3).

Fatigue is a common symptom of several conditions and serious diseases, but in most cases it is caused by simple lifestyle factors.

Fortunately, these are most often easy things to fix.

This article lists 10 potential reasons why you're always tired and provides recommendations for ways to get your energy back.

1. Consuming Too Many Refined Carbs

Carbs can be a quick source of energy. When you eat them, your body breaks them down into sugar, which can be used for fuel.

However, eating too many refined carbs can actually cause you to feel tired throughout the day.

When sugar and processed carbs are consumed, they cause a rapid rise in your blood sugar. This signals your pancreas to produce a large amount of insulin to get the sugar out of your blood and into your cells.

This spike in blood sugar levels — and subsequent fall — can make you feel exhausted. Craving quick energy, you instinctively reach for another serving of refined carbs, which can lead to a vicious cycle.

Several studies have found that minimizing sugar and processed carbs at meals and snacks typically leads to greater energy levels (4, 5, 6).

In one study, children who ate snacks high in refined carbs before a soccer game reported more fatigue than children who ate a peanut butter-based snack (6).

Luckily, research suggests that some foods may help protect against tiredness.

For instance, both okra and dried bonito broth contain compounds that may decrease fatigue and increase alertness (7, 8).

To keep your energy levels stable, replace sugar and refined carbs with whole foods that are rich in fiber, such as vegetables and legumes.

Summary: Consuming refined carbs can lead to unstable blood sugar levels, which can make you feel tired. Instead, choose whole foods that minimally impact your blood sugar.

2. Living a Sedentary Lifestyle

Inactivity could be the root cause of your low energy.

But many people say they're too tired to exercise.

In fact, in one recent study, this was the most common reason that middle-aged and older adults gave for not exercising (9).

One explanation could be chronic fatigue syndrome (CFS), which is characterized by extreme, unexplained fatigue on a daily basis.

Research suggests people with CFS tend to have low strength and endurance levels, which limit their exercise ability. However, a review of studies including more than 1,500 people found that exercise may reduce fatigue in those with CFS (10, 11).

Research has also shown that exercising can reduce fatigue among healthy people and those with other illnesses, such as cancer. What's more, even minimal increases in physical activity seem to be beneficial (12, 13, 14, 15, 16).

To boost your energy levels, replace sedentary behaviors with active ones. For instance, stand rather than sit down whenever possible, take the stairs instead of the elevator and walk instead of driving short distances.

Summary: Being sedentary can lead to fatigue in healthy people, as well as those with chronic fatigue syndrome or other health problems. Being more active can help boost energy levels.

3. Not Getting Enough High-Quality Sleep

Not getting enough sleep is one of the more obvious causes of fatigue.

Your body does many things while you sleep, including store memory and release hormones that regulate your metabolism and energy levels (17).

After a night of high-quality sleep, you typically wake up feeling refreshed, alert and energized.

According to the American Academy of Sleep Medicine and Sleep Research Society, adults need an average of seven hours of sleep per night for optimal health (18).

Importantly, sleep should be restful and uninterrupted in order to allow your brain to go through all five stages of each sleep cycle (19).

In addition to getting enough sleep, maintaining a regular sleep routine also seems to help prevent tiredness.

In one study, adolescents who went to bed at the same time on weekdays and weekends reported less fatigue and less difficulty falling asleep than those who stayed up later and slept fewer hours on the weekends (20).

Being physically active during the day may help you get more restorative sleep at night. One study in older people found that exercising helped improve their sleep quality and reduce levels of fatigue (21).

Furthermore, napping may help boost energy levels. Taking naps has been shown to decrease tiredness in pilots, who often experience fatigue due to long working hours and jet lag (22).

To improve the amount and quality of your sleep, go to bed at roughly the same time every night, relax before sleeping and get plenty of activity during the day.

However, if you find it difficult to fall or stay asleep and suspect you may have a sleeping disorder, speak to your doctor about having your sleep evaluated by a specialist.

Summary: Inadequate or poor-quality sleep is a common cause of fatigue. Getting several hours of uninterrupted sleep allows your body and brain to recharge, allowing you to feel energized during the day.

4. Food Sensitivities

Food sensitivities or intolerances typically cause symptoms like rashes, digestive problems, runny nose or headaches.

But fatigue is another symptom that's often overlooked.

Also, research suggests that quality of life may be more affected by fatigue in those with food sensitivities (23).

Common food intolerances include gluten, dairy, eggs, soy and corn.

If you suspect that certain foods may be making you tired, consider working with an allergist or dietitian who can test you for food sensitivities or prescribe an elimination diet to determine which foods are problematic.

Summary: Food intolerances can cause fatigue or low energy levels. Following a food elimination diet may help determine which foods you are sensitive to.

5. Not Eating Enough Calories

Consuming too few calories can cause feelings of exhaustion.

Calories are units of energy found in food. Your body uses them to move and fuel processes like breathing and maintaining a constant body temperature.

When you eat too few calories, your metabolism slows down in order to conserve energy, potentially causing fatigue.

Your body can function within a range of calories depending on your weight, height, age and other factors.

However, most people require a minimum of 1,200 calories per day to prevent a metabolic slowdown.

Experts on aging believe that although metabolism decreases with age, older people may need to eat at the top of their calorie range in order to perform normal functions without becoming fatigued (24).

In addition, it's difficult to meet your vitamin and mineral needs when calorie intake is too low. Not getting enough vitamin D, iron and other important nutrients can also lead to fatigue.

In order to keep your energy levels up, avoid drastic cuts in calorie intake, even if your goal is weight loss. You can calculate your calorie needs using the calorie calculator in this article.

Summary: Your body requires a minimum number of calories in order to perform daily functions. Consuming too few calories can lead to fatigue and make it difficult to meet nutrient needs.

6. Sleeping at the Wrong Time

In addition to inadequate sleep, sleeping at the wrong time can reduce your energy.

Sleeping during the day instead of at night disrupts your body's circadian rhythm, which are the biological changes that occur in response to light and darkness during a 24-hour cycle.

Research has found that when your sleep pattern is out of sync with your circadian rhythm, chronic fatigue may develop (25).

This is a common problem among people who perform shift or night work.

Sleep experts estimate that 2–5% of all shift workers suffer from a sleep disorder characterized by excessive sleepiness or disrupted sleep over a period of one month or more (26).

What's more, even staying awake during the night for a day or two can cause fatigue.

In one study, healthy young men were allowed to sleep either seven hours or just under five hours before being kept awake for 21–23 hours. Their fatigue ratings increased before and after sleep, regardless of the number of hours they slept (27).

It's best to sleep during the night whenever possible.

However, if your job involves shift work, there are strategies to retrain your body clock, which should improve your energy levels.

In one study, shift workers reported significantly less fatigue and better mood after being exposed to bright light pulses, wearing dark sunglasses outside and sleeping in total darkness (28).

Using glasses to block blue light may also help people who perform shift work.

Summary: Sleeping during the day can upset your body's natural rhythm and lead to fatigue. Try to sleep at night or retrain your body clock.

7. Not Getting Enough Protein

Inadequate protein intake could be contributing to your fatigue.

Consuming protein has been shown to boost your metabolic rate more than carbs or fat do (29).

In addition to aiding weight loss, this may also help prevent tiredness.

In one study, self-reported fatigue levels were significantly lower among Korean college students who reported eating high-protein foods like fish, meat, eggs and beans at least twice a day (5).

Other studies have found that high-protein diets tend to produce less fatigue among weight lifters and people who perform resistance training (30, 31).

What's more, research suggests that fatigue may be reduced by branched-chain amino acids, which are the building blocks of protein (32).

To keep your metabolism strong and prevent fatigue, aim to consume a high-quality protein source at every meal.

Summary: Consuming adequate protein is important for keeping your metabolism up and preventing fatigue. Include a good protein source at every meal.

8. Inadequate Hydration

Staying well hydrated is important for maintaining good energy levels.

The many biochemical reactions that take place in your body every day result in a loss of water that needs to be replaced.

Dehydration occurs when you don't drink enough liquid to replace the water lost in your urine, stools, sweat and breath.

Several studies have shown that being even mildly dehydrated can lead to lower energy levels and a decreased ability to concentrate (33, 34, 35).

In one study, when men worked out on a treadmill and lost 1% of their body mass in fluid, they reported more fatigue than when they performed the same exercise while remaining well hydrated (33).

Although you may have heard that you should drink eight, 8-ounce (237-ml) glasses of water daily, you may require more or less than this depending on your weight, age, gender and level of activity.

The key is drinking enough to maintain good hydration levels. Here are some common signs of dehydration.

Summary: Even mild dehydration may reduce energy levels and alertness. Make sure to drink enough to replace fluid lost during the day.

9. Relying on Energy Drinks

There's no shortage of beverages that promise to provide quick energy.

Popular energy drinks typically include the following:

• Caffeine
• Sugar
• Amino acids
• Large doses of B vitamins
• Herbs

It's true that these beverages may provide a temporary energy boost due to their high caffeine and sugar contents (36, 37).

For example, a study in sleep-deprived healthy adults found that consuming an energy shot led to modest improvements in alertness and mental function (37).

Unfortunately, these energy drinks are also likely to set you up for rebound fatigue when the effects of caffeine and sugar wear off.

One review of 41 studies found that although energy drinks led to increased alertness and improved mood for several hours after consumption, excessive daytime sleepiness often occurred the following day (38).

Although the caffeine content varies widely among brands, an energy shot may contain up to 350 mg, and some energy drinks provide as much as 500 mg per can. By comparison, coffee typically contains between 77–150 mg of caffeine per cup (39).

However, even at smaller dosages, drinking caffeinated beverages in the afternoon may interfere with sleep and lead to low energy levels the following day (40).

To break the cycle, try cutting back and gradually weaning yourself off these energy drinks. In addition, limit coffee and other caffeinated beverage consumption to early in the day.

Summary: Energy drinks contain caffeine and other ingredients that can provide a temporary energy boost, but often lead to rebound fatigue.

10. High Stress Levels

Chronic stress may have a profound effect on your energy levels and quality of life.

Although some stress is normal, excessive levels of stress have been linked to fatigue in several studies (41, 42, 43).

In addition, your response to stress can influence how tired you feel.

One study in college students found that avoiding dealing with stress led to the greatest level of fatigue (43).

While you may not be able to avoid stressful situations, developing strategies for managing your stress may help prevent you from feeling completely exhausted.

For instance, large reviews of studies suggest yoga and meditation can help relieve stress (44, 45).

Engaging in these or similar mind-body practices may ultimately help you feel more energetic and better able to cope with stress.

Summary: Excessive stress can cause fatigue and reduce your quality of life. Practicing stress-reduction techniques may help improve your energy levels.

The Bottom Line

There are many possible causes for feeling chronically tired. It's important to rule out medical conditions first, as fatigue often accompanies illness.

However, feeling overly tired may be related to what you eat and drink, how much activity you get or the way you manage stress.

The good news is that making a few lifestyle changes may very well improve your energy levels and overall quality of life.