Does cutting carbs affect sleep?: Unpacking the Low-Carb Sleep Connection

October 15, 2025 •

5 min read

According to one 2023 study on a low-calorie keto diet, 65 percent of participants reported sleeping better after a month, yet many people experience temporary sleep disturbances upon starting. So, does cutting carbs affect sleep? The impact is complex, with initial disruption often giving way to improved long-term rest as your body adapts.

Quick Summary

The process of cutting carbohydrates can cause short-term sleep disruption, often called 'keto insomnia,' due to metabolic and hormonal changes. Factors include shifts in sleep-regulating chemicals like serotonin, electrolyte imbalances, and the body's energy adaptation process. While initial sleep quality can decline, patterns often normalize as the body adjusts.

Key Points

Initial Disruption: The early stages of a low-carb diet often cause temporary sleep problems, or "keto insomnia," as the body adjusts its metabolism.
Hormonal Shift: Reducing carbohydrates can decrease the production of sleep-regulating hormones like serotonin and melatonin by affecting the availability of the precursor amino acid, tryptophan.
Electrolyte Imbalance: Low-carb diets can lead to electrolyte deficiencies (especially magnesium and potassium), which are linked to restless sleep and anxiety.
Altered Sleep Stages: A low-carb diet can increase restorative slow-wave sleep while potentially reducing REM sleep, contrasting the effects of high-carb intake.
Carbohydrate Quality Matters: The type of carbohydrate is crucial; refined, high-sugar carbs disrupt sleep more than fibrous, complex carbs that stabilize blood sugar.
Adaptation is Key: Many initial sleep issues subside as the body becomes "fat-adapted" and metabolic processes stabilize on the low-carb diet.

The Initial Shock: Keto Insomnia and the Transition Period

When transitioning to a very low-carbohydrate or ketogenic diet, the body undergoes a significant metabolic shift from relying on glucose for energy to burning fat and producing ketones. This initial adjustment period is a common cause of short-term sleep problems, a phenomenon colloquially known as "keto insomnia". During this phase, individuals may experience difficulty falling asleep, fragmented sleep, or restlessness.

Several physiological factors contribute to this initial sleep disturbance:

Electrolyte Imbalance: As the body burns through its stored glycogen, it also sheds a significant amount of water, which can lead to an imbalance of electrolytes like sodium, potassium, and magnesium. A deficiency in magnesium, in particular, is associated with sleep disturbances and anxiety. Low sodium can boost the stimulating hormone norepinephrine, further disrupting sleep.
Carb Withdrawal: Some researchers liken the process to a form of withdrawal, particularly for those with high previous intake of refined, sugary carbohydrates. These types of carbs can have addictive-like neurological effects, and removing them abruptly can cause irritability and sleep issues.
Increased Energy: The shift to burning fat for fuel can initially provide a significant energy boost, which, while beneficial during the day, can make it difficult to settle down and sleep at night.

How Carbs Influence Sleep-Regulating Hormones

One of the most frequently cited theories for the link between carbohydrate intake and sleep revolves around the amino acid tryptophan. Carbohydrates, particularly those with a high glycemic index (GI), have been shown to increase the availability of tryptophan to the brain. Tryptophan is a precursor to serotonin, a neurotransmitter that promotes feelings of well-being, and melatonin, the hormone that regulates sleep-wake cycles.

Here's the mechanism:

Carbs and Insulin: Consuming carbohydrates triggers the release of insulin. Insulin helps the body's muscle and fat cells absorb competing large neutral amino acids (LNAAs) from the bloodstream.
Tryptophan Entry: Unlike other LNAAs, tryptophan is bound to albumin and remains in the blood. With fewer competitors for the blood-brain barrier transporter, more tryptophan can enter the brain.
Serotonin and Melatonin Production: The increased tryptophan in the brain is then used to produce more serotonin and, subsequently, melatonin.

When a person dramatically cuts carbohydrates, this mechanism is altered. Lower insulin levels mean less competition is removed, and relatively less tryptophan crosses into the brain. This can reduce the production of serotonin and melatonin, resulting in the disrupted sleep patterns commonly seen in the initial phase of a low-carb diet.

Macronutrients and Sleep Architecture

Different dietary patterns, including varying carbohydrate intake, can significantly alter the architecture of sleep, affecting the duration of different sleep stages. Studies using polysomnography (a comprehensive sleep study) have demonstrated these effects.


Feature	Low-Carbohydrate Diet	High-Carbohydrate Diet
Effect on Slow-Wave Sleep (SWS)	Increases the amount of SWS (deep, restorative sleep).	Decreases the amount of SWS, especially during the first half of the night.
Effect on Rapid Eye Movement (REM) Sleep	Decreases the amount of REM sleep, particularly in the short term.	Increases the amount of REM sleep.
Effect on Sleep-Onset Latency (SOL)	Potentially lengthens SOL (takes longer to fall asleep) in the initial phase, often due to hormonal shifts and electrolyte imbalance.	Can shorten SOL, especially when consuming a high-GI meal a few hours before bed.

It is worth noting that while some studies show that an initial drop in REM sleep on a low-carb diet can feel jarring, a corresponding increase in deep slow-wave sleep may offer its own restorative benefits over time.

Beyond Quantity: The Importance of Carbohydrate Quality

Not all carbohydrates affect sleep in the same way, and the quality of the carb is often more important than the quantity.

Refined vs. Complex Carbs: A high intake of low-quality carbohydrates, such as added sugars, refined grains, and fruit juices, has been linked to an increased risk of insomnia and poor sleep quality. These rapid-release carbs cause sharp blood sugar spikes followed by crashes, which can trigger stress hormones like adrenaline and cortisol that interfere with sleep.
Fiber-Rich Carbs: In contrast, consuming high-quality, high-fiber carbohydrates from whole grains, fruits, and vegetables is associated with better sleep. The fiber helps regulate blood sugar by slowing absorption, preventing disruptive crashes during the night.

Practical Tips for Improving Sleep on a Low-Carb Diet

If you are experiencing sleep issues after cutting carbs, consider these practical strategies to ease your transition to a new eating pattern:

Replenish Electrolytes: Address potential deficiencies by consuming electrolyte-rich foods and supplementing with magnesium, potassium, and sodium. Magnesium supplements, in particular, can be helpful for improving sleep.
Time Your Carbs: If your diet allows, consider consuming your daily allotment of carbohydrates—preferably from complex, high-fiber sources like vegetables and whole grains—in your last meal of the day. This can help promote tryptophan uptake and stabilize blood sugar for a restful night.
Manage "Keto Flu" Symptoms: Be aware that the initial phase can cause flu-like symptoms, including fatigue and irritability that can disrupt sleep. As your body adapts, these symptoms typically subside.
Optimize Sleep Hygiene: Good sleep practices are vital regardless of diet. Create a consistent sleep schedule, ensure your bedroom is cool and dark, and avoid screens for an hour or more before bed.
Stay Hydrated: Dehydration can be more common on a low-carb diet and can contribute to sleep disturbances. Drinking plenty of water throughout the day is crucial.
Moderate Evening Protein: Consuming too much protein close to bedtime can stimulate alertness due to the amino acid tyrosine, which increases energizing hormones. Try to balance your protein intake throughout the day.

Conclusion: Navigating the Trade-Offs for Restful Sleep

Cutting carbohydrates, especially refined sugars, has a significant and complex effect on sleep. While high-GI carbs can initially shorten sleep onset time, they can also cause disruptive blood sugar fluctuations throughout the night. Conversely, transitioning to a low-carb diet can lead to temporary insomnia and shifts in sleep architecture, but often results in more deep, restorative sleep in the long run. The key to managing this change lies in understanding the metabolic and hormonal mechanisms at play, prioritizing high-quality, fibrous carbohydrates, and maintaining good overall sleep hygiene. For many, a low-carb diet offers a period of adjustment but can ultimately contribute to improved sleep health.

For more in-depth information on diet and sleep, consult reliable resources like the Sleep Foundation.

Frequently Asked Questions

Initial sleep issues when starting a low-carb diet, often called "keto insomnia," can be caused by your body adjusting its metabolism away from glucose, hormonal shifts affecting sleep hormones, and potential electrolyte imbalances, particularly low magnesium.

A sharp drop in carb intake can decrease the amino acid tryptophan's availability to the brain. Since tryptophan is a precursor to serotonin and melatonin, this can result in reduced production of these key sleep-regulating hormones.

Yes, the quality of carbohydrates is critical. High intakes of refined carbs and sugars are linked to poor sleep, while diets rich in fiber-rich, high-quality carbs from fruits and vegetables are associated with better sleep quality.

For most people, initial sleep problems associated with cutting carbs are temporary. The body typically adjusts to the new metabolic state within a few weeks, and sleep patterns tend to normalize and may even improve over time.

You can improve sleep by ensuring adequate electrolyte intake (especially magnesium), timing your carbohydrate consumption to be in your evening meal if your diet allows, and focusing on good sleep hygiene, such as avoiding screens and stimulants before bed.

Yes. When you reduce carbs, your body sheds water and electrolytes like magnesium, potassium, and sodium. Low levels of these minerals, particularly magnesium, can contribute to sleep disturbances and restlessness.

Research suggests that low-carb diets may alter sleep architecture by reducing the amount of REM sleep and increasing deep, slow-wave sleep. The reverse is often seen with high-carb diets.