13 Surprising Reasons for Chronic Fatigue and Solutions to Combat It

London, United Kingdom Jul 24, 2026 ALN: Feeling lethargic even after a full night’s sleep? From not enough fiber to too much sitting, experts explain why your get-up-and-go has got up and gone.

You need to open the window

The very air you breathe could be an issue. “Close the door, shut the window, add a partner and a heater, and by 3am a typical bedroom sits at 1,500 to 2,500 parts per million of carbon dioxide,” says Dr. Jemma King, author of Sleep First: Sleep Smarter, Think Sharper, Feel Better. “Research shows that above 1,000 ppm sleep efficiency drops, deep sleep reduces and salivary cortisol rises on waking. You’re sleeping, but your nervous system is mildly activated all night.” Luckily, it’s an easy fix: open a window – even 2cm will do the job, according to King.

Your creatine stores are low

This supplement isn’t just for bodybuilders. What we think of as “energy” is a molecule called adenosine triphosphate (ATP), produced by mitochondria. It stores and then delivers energy to cells. As you age, you have fewer mitochondria, so your body struggles to produce enough ATP.

Creatine can help. “When creatine is combined with phosphagen (a compound linked to energy), you get phosphocreatine, which regenerates ATP,” says Justin Roberts, professor of nutritional physiology at Anglia Ruskin University. As well as older adults, research consistently shows benefits for regular exercisers, women, vegans, and vegetarians (as creatine largely comes from meat and fish), says Roberts. Research shows supplementing can improve mental fatigue and reduce fatigue during exercise.

In terms of sleep, in three separate studies people taking 5g daily showed improved mood and cognitive function after a poor night’s sleep, slept for longer, and experienced improved sleep quality. Look for micronized creatine monohydrate and take 3-5g daily to increase muscle stores of ATP over two to four weeks. You cycle creatine, so try taking it for six weeks, then come off it for two to four weeks, and repeat.

You’re not getting outdoors enough

“Emerging evidence suggests that exposure to daylight improves our sleep and blood sugar control,” says Dr. Brendan Gabriel, whose research at the University of Aberdeen focuses on metabolic biochemistry. It’s all down to our circadian rhythms. “We have a body clock in nearly every cell in our body,” says Gabriel. “One of the most important is the brain’s suprachiasmatic nucleus, which is most responsive to daylight. Getting exposure to outdoor daylight helps our body distinguish between day and night, which can improve sleep quality.”

You need to eat more fiber

A massive 96% of people in the UK don’t meet daily fiber recommendations of at least 30g. But a fiber-rich meal can help to slow the release of sugar into your bloodstream, giving you longer-lasting, steadier energy, says Dr. Emily Leeming, research fellow at King’s College London and author of Fibre Power: Transform Your Energy and Feel Amazing. She thinks we’re confused and discouraged by “a rather unfortunate PR run that fiber hasn’t been able to shake off. We think fiber is brown stodge.”

Time for a fiber rebrand, then. She suggests we all add “the BGBGs to our diets – beans, greens, berries, grains, and seeds – and nuts. Make those the foundation of your meal, then add other things.”

You sleep but you don’t rest

Getting eight hours of sleep but still exhausted? “We live in a world that equates our worth with productivity,” says Zahabiyah Yamasaki, author of Protect Your Energy. She believes we need to stop rushing when we don’t have to and start to “move at a slower pace, be intentional about commitments, and choose presence over productivity. That might mean closing your eyes rather than reaching for your phone, or sitting quietly looking out the window. Over time, these small shifts help make rest more accessible.” So nap, listen to a podcast, stretch, read, sit in nature, turn down a plan, cuddle your pet.

You’ve sworn off smoothies and fruit juice

Foggy head? A lack of polyphenols could be to blame. “These antioxidants give pigment to fruits and vegetables – the deep purple of an aubergine, the redness of a strawberry,” says Leeming. We get most of ours from tea and coffee, but dark chocolate, black beans, and herbs and spices are particularly concentrated sources, alongside berries.

Leeming points to research showing polyphenol supplements help with oxygen and nutrient delivery to the brain, improving reaction time and mental fatigue. But you don’t need to supplement, just eat the rainbow – or blitz it. “A small study gave people a 400ml smoothie containing blueberry, strawberry, raspberry, and blackberry, or a placebo, and tracked them across a workday. The berry smoothie people maintained accuracy and response times throughout the day.”

Sworn off smoothies or juice over sugar concerns? “Your blood sugar going up is a very normal response,” says Leeming. “It’s when it stays elevated out of range for a long time that it’s problematic – 150ml of fruit juice is a good source of polyphenols and is one of your five a day.” And include berries. “Blending fruit with seeds gives less of a blood sugar response than something like a banana.”

You need a brain dump

While you sleep, your brain is putting in a shift. Dr. Jemma King provides an analogy: “Imagine all the events that happen during the day get documented and put into a manila folder that’s stacked on the desk of your personal librarian, who works through the night, deciding what to keep and what to discard. Usually, this happens smoothly, but sometimes folders need the boss to decide, and you’ll be woken at 3am with a burning thought that makes you feel stressed. The stress hormone cortisol has a half-life of at least 30 minutes, so if you engage with that thought, you have at least until 3.30am before your stress levels go back to a ‘sleep-permissive’ level.”

Help your midnight librarian by spending a few minutes in the early evening creating a list of what you’ll address tomorrow. “Be sure to add times,” says King. “For example: call Sammy’s teachers at 10.30am; call my tax accountant at 11.15am.”

You’re eating too late

Ideally, you need to clear your plate by 7.30pm, especially on steak night. “Protein – particularly big chunks of meat – takes four to six hours to leave the stomach,” says King. “Fat slows it further, while digestion raises core body temperature and draws blood toward the gut, pushing against the nocturnal cooling trend needed for deep sleep.” This is why eating within three hours of bedtime decreases the quality of your sleep. “Your body doesn’t like digesting and repairing at the same time, and will opt to get rid of meat over replenishing maintenance.” Eat heavier protein and fat at lunchtime, and build evening meals around veggies, lighter protein such as fish, chicken, or tofu, and plant-based carbohydrates.

Your sluggish bowel is making you, well, sluggish

“There is two-way communication between your gut and your brain via the vagus nerve, and 80-90% of that communication goes in the direction of gut to brain,” says Leeming. “If things are sluggish, that can make you feel lethargic because your gut is communicating back to your brain that things are not optimal.” According to one study, there’s an incredibly simple fix: eat two kiwis a day (skins optional – the research was done without). “There are different types of fiber, and the particular type found in kiwis helps to draw water in to soften the stool and move it through.”

You’re too focused on protein

Protein is definitely having a moment – the UK market for it is expected to be worth £643m by 2031. But sacrificing carbs to make way for more protein could be detrimental. As sports dietitian and personal trainer Kerri Major says: “If this puts carb intake too low for someone’s activity levels, it can impact energy.” As a general rule, for a steady energy releasing meal, half your plate should be made up of colorful veggies, a quarter carbs, and a quarter protein, alongside some healthy fats.

Your bed needs airing

There’s a reason you sleep soundly in those fresh hotel bedsheets. “Mite droppings, fragranced laundry powder, and synthetic fibers can all trigger low-grade inflammatory responses, producing nocturnal congestion, itching, and microarousals you don’t consciously remember,” says King. “People with house dust mite allergies are far likelier to report insomnia.” Wash your bedding weekly using fragrance-free detergent, put dust mite covers on your mattress and pillows, and air your bed for 10 minutes in the morning.

You’re sitting too much

Our ancestors spent their days hunting and gathering, rarely sitting, so from an evolutionary perspective, “long hours of being sedentary sends a message that something is wrong,” says King. “One theory suggests that in order to conserve energy to fight potential sickness and to promote sleeping to heal, our brains will make us feel sleepy, despite not actually being ill. It will also make us withdraw and isolate so we don’t infect the other tribe members.” Every 30 minutes, stand and move for two minutes. “A 10-minute walk after lunch lowers postprandial glucose and supports afternoon energy.”

You need a blood test

Has your GP ruled out iron or B12 deficiency, or thyroid problems, asks Dr. Linia Patel, dietitian and author of Food for Menopause? Iron deficiency, she says, produces “a heavy, physical exhaustion and breathlessness on exertion, heart palpitations, pale skin, and that frustrating inability to get through the day despite adequate sleep. It can also trigger restless legs, disrupting sleep further.”

B12 deficiency fatigue “feels more neurological, so brain fog, poor concentration, low mood, tingling in the hands or feet, and a deep, bone-level weariness.” Thyroid problems, whether under or overactive, cause tiredness. “An underactive thyroid brings sluggishness, weight gain, and feeling cold; an overactive one can cause anxious, wired exhaustion.” Request a blood test from your GP.