Why you feel so sleepy, and how to boost your energy

Sometimes, even though you think you’ve had enough hours in bed, you may find yourself feeling sleepy during the day. But why? 

Certain health conditions, including narcolepsy and sleep apnea, can lead to daytime tiredness. But so can lifestyle factors like drinking too much alcohol or smoking.

If you’re looking for ways to avoid daytime slumps and boost your energy, you should also consider the part your gut health plays, as well as the food you eat.

At ZOE, we run the largest nutrition study in the world, with over 15,000 participants so far. It’s shown us that when it comes to your body’s responses to food, everyone is different. 

ZOE’s at-home test can help you understand how food affects your blood sugar and blood fat levels, and it also tells you about the makeup of your gut microbiome, which has been linked to sleep quality

Our unpublished data shows that more than 80% of people who closely followed their personalized ZOE nutrition program for 3 months said they had higher energy levels. You can take a free quiz to learn more about what ZOE can do for you.

And read on to discover why you might feel tired and how to boost your energy.

Health conditions that can make you sleepy

As we’ll see below, there are a number of lifestyle factors that can lead to you feeling sleepy, and changing them can boost your energy.

However, there are also specific health conditions that can cause tiredness during the day:

  • Chronic insomnia is a common sleep disorder that makes it difficult for you to fall or stay asleep. Causes can include stress, anxiety, and other mental health issues.

  • Obstructive sleep apnea blocks your airways, interrupting your breathing and lowering the amount of oxygen you get while you sleep. Unsurprisingly, it can lead to broken and poor quality sleep. 

  • Restless legs syndrome is an almost irresistible urge to move your legs, which can stop you getting to sleep. It can also happen while you’re asleep, disrupting your sleep pattern.

  • Narcolepsy affects the rapid eye movement (REM) part of sleep, which is the phase when you dream. It can make you feel extremely sleepy during the day and can also cause uncontrollable “sleep attacks,” where you fall asleep suddenly.

If you think you may have any of these conditions, you should talk to your doctor.

5 tips to boost daytime energy

If you don’t have an obvious sleep condition but still find yourself feeling sleepy during the day, there are lots of things you can try to help boost your energy.

Quitting smoking, cutting down on alcohol, and getting more exercise are all lifestyle changes you may be aware of. 

What you might not know is how important it can be to eat the right foods for your unique body and to take care of your gut health.

1. Look after your gut health

Your gut microbiome is the name for the trillions of bacteria and other microorganisms that make their home in your gut. These bugs process nutrients from the food you eat and produce chemicals that influence a range of functions around your body, like your immune system.

The balance of these different bugs in your gut microbiome is connected to many aspects of your health, including factors that can impact how sleepy you feel.

A 2019 study found that having a diverse microbiome — one with a wide range of different bugs — was linked to better quality sleep and a longer time spent sleeping. 

It also showed that specific types of bacteria were associated with better sleep, and other types of bacteria were associated with worse sleep.

When the “bad” bugs in your gut microbiome outnumber the “good,” it can have harmful effects on how your body manages energy.

Dr. Will Bulsiewicz, gastroenterologist, gut health expert, and author of Fiber Fueled, says fatigue is one of the most common symptoms he hears about in his gut clinic. And he identifies an increase in energy as one of the first signs that gut health is improving.

To improve your gut health, Dr. Bulsiewicz advises avoiding:

  • Alcohol: Excessive drinking can inflame the digestive tract and alter how your gut processes nutrients and compounds.

  • Restrictive diets: The latest fad diet may limit the range of foods you eat, but your “good” bugs need a wide variety of nutrients to thrive.

  • Artificial sweeteners: Reducing calories in this way may seem harmless, but artificial sweeteners provide no nutrients and can alter the makeup of your gut microbiome.

ZOE scientific co-founder Professor Tim Spector also has five tips for a healthier gut microbiome. These include eating lots of different plants, eating less ultra-processed foods, and regularly eating fermented foods, like yogurt, artisanal cheeses, kimchi, kombucha, kefir, and sauerkraut, which contain beneficial bacteria called probiotics

At ZOE, we’ve identified 15 “good” gut bugs linked to better health and 15 “bad” bugs linked to unfavorable health outcomes. 

The ZOE at-home test analyzes all of the bugs that make up your gut microbiome and tells you which of the “good” and “bad” ones you have at the moment. With the ZOE program, you can find the right foods for your gut, including your personal “gut boosters.”

2. Eat the right foods for your body

Your gut microbiome is just one of several factors involved in the unique way your body responds to food. These food responses also impact your health and energy levels.

After you eat, your blood sugar levels rise before dropping again. Some foods can cause higher rises in blood sugar, such as those containing a lot of sugar or refined carbohydrates like white bread.

These spikes can be followed by dips, also known as blood sugar crashes. They’re associated with a number of symptoms, including the slump in energy you may feel after eating.

Swapping to complex carbs can help avoid sharp blood sugar spikes and dips. But the best foods for your blood sugar levels are unique to you. 

The ZOE program gives you personalized recommendations for the foods that work best for your body, based on the latest science. 

You can take a free quiz to find out what ZOE can do for you.

3. Move more

You might expect exercise to make you feel more tired, but physical activity can boost your energy levels. And adding even a relatively small amount to your routine can have a benefit.

One 2008 study focused on 36 otherwise healthy adults who reported feeling tired during the day, but who usually did very little exercise. They were divided into three groups. Two of the groups started a regular program of either low- or moderate-intensity exercise, while the third group didn’t make any changes.

After 6 weeks, those who followed the exercise programs reported significantly better energy levels than those who hadn’t. And there were similar improvements across both the low-intensity and moderate-intensity exercise groups.

In another small study from 2017, a group of physically active women with chronic sleep deprivation found that taking a break to climb the stairs for 10 minutes boosted their energy levels more than consuming caffeine supplements. 

4. Drink less alcohol

Some alcoholic drinks like red wine may have health benefits in moderation. However, the idea that drinking alcohol will send you off into a deep sleep is a myth. 

A 2021 study involving almost 12,000 people found that alcohol was associated with poor sleep quality, a greater likelihood of snoring, and less time spent actually sleeping. 

Another recent study linked drinking too much to waking up tired and an increased risk of sleep disorders like insomnia in older men. 

If a beer or two is your idea of a treat, that’s OK. But keeping it to a minimum gives you a better chance of feeling less sleepy during the day.

5. Quit smoking

Alongside its well-known links to cancer, heart disease, and other serious illnesses, smoking can also contribute to daytime sleepiness. 

A 2020 study found that the chemicals produced by smoking affect REM sleep, increase the time it takes you to get to sleep, and can lead to you waking up during the night — all of which contribute to daytime sleepiness.

Smoking also reduces the amount of oxygen your blood can carry around your body, which can make you feel more tired

Smoking is highly addictive and can be tough to quit. The National Institutes of Health have some advice for helping you ease off tobacco in a sustainable way.


Feeling sleepy during the day may be due to an underlying sleep disorder, like narcolepsy or sleep apnea. 

Lifestyle factors such as smoking, drinking too much, or not getting enough exercise can have a significant impact, too — and nutrition and gut health could be key.

Research has found links between a healthier, more diverse gut microbiome and longer and better quality sleep. 

Meanwhile, eating foods that aren’t right for you, particularly those high in sugar and refined carbs, can lead to blood sugar spikes and crashes that can cause slumps in your energy.

ZOE’s research has shown that the way your body responds to food is unique and is related to the makeup of your gut microbiome.

The ZOE at-home test analyzes your blood sugar and blood fat responses to different foods, and it tells you about the specific bugs that live in your gut.

The ZOE program then recommends the best foods for your gut health and overall health.

Take a free quiz to find out more about what ZOE can do for you.


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