Can Not Eating Carbs Affect Your Mood? The Science of Diet and Emotion

November 17, 2025 •

3 min read

The brain relies heavily on glucose from carbohydrates for energy, utilizing approximately 20% of the body's daily energy. Consequently, changes in mood are a common response to restricting carbs, with short-term emotional shifts being quite typical.

Quick Summary

Cutting out carbs can cause temporary mood swings, irritability, and brain fog, especially during the adaptation period, often called the 'keto flu'. These shifts occur as the body switches fuel sources, impacting serotonin levels and energy. Both positive and neutral long-term effects can be observed depending on individual factors.

Key Points

Initial Mood Swings: Rapidly cutting carbs can cause temporary mood swings, irritability, and 'keto flu' symptoms as the body adapts to using fat for fuel.
Serotonin's Role: Carbohydrates support serotonin production, a neurotransmitter that is key to mood. A low-carb diet may decrease serotonin synthesis, contributing to mood changes.
Stable Energy: Long-term ketosis can lead to more stable brain energy and improved mood for some, but this is not guaranteed for everyone.
Electrolytes are Key: Losing electrolytes such as sodium and potassium during the initial phase can cause physical symptoms that directly impact mood and energy levels.
Nutrient Deficiencies: Inadequate intake of mood-supporting nutrients like B vitamins and magnesium, which is common when restricting carbs, can negatively affect mental wellness.
Carb Choices Matter: Consuming complex carbohydrates over simple sugars promotes more stable blood sugar and mood, avoiding the spikes and crashes associated with refined carbs.
Listen to Your Body: Individual responses vary. Monitoring personal mood and energy levels is key. Sustainable dietary habits are crucial for long-term well-being.

Carbs, Neurotransmitters, and Emotional Wellbeing

Carbohydrates influence mood regulation through their effect on serotonin levels in the brain. Serotonin, a neurotransmitter, plays a crucial role in mood, sleep, and appetite. The production of serotonin depends on tryptophan, an amino acid that must cross the blood-brain barrier. When someone eats carbs, insulin is released, which helps clear other amino acids, allowing more tryptophan into the brain to boost serotonin synthesis. Restricting carbs can disrupt this process, potentially lowering serotonin and affecting mood.

The 'Keto Flu' and Immediate Emotional Shifts

Initial mood changes when cutting carbs are often linked to the 'keto flu,' which is the body's adjustment period to burning fat (ketosis) instead of glucose. This phase can last days to weeks and includes fatigue, headaches, and brain fog, contributing to irritability. Sugar cravings and frustration may also occur due to changes in the brain's reward system. These effects usually subside as the body adapts.

Long-Term Impact: Variable Outcomes

Research on the long-term mental health effects of low-carb diets such as keto is mixed. Some studies suggest possible long-term benefits for mental wellbeing, likely due to stable energy from ketones and reduced inflammation. For instance, a 2024 study connected the keto diet to improved calmness and alertness. However, a 2009 study found that participants on a low-fat, high-carb diet experienced greater mood improvements compared to those on a very low-carb diet. A 2016 review indicated that the macronutrient breakdown of the diet may not be the key factor for mood improvements during weight loss.

Potential Causes of Mood Shifts on a Low-Carb Diet

Electrolyte Imbalance: Early water loss on very low-carb diets can deplete electrolytes like sodium, potassium, and magnesium, causing irritability and headaches.
Nutrient Deficiencies: Limiting food groups may lead to lower levels of B vitamins, magnesium, and omega-3s, all of which are essential for brain function and mood.
Gut Microbiome Changes: Alterations in the gut bacteria caused by dietary shifts can impact mood via the gut-brain axis.
Psychological Factors: Cravings, dietary restrictions, and social factors can negatively affect mood.

Strategies for Managing Mood on a Low-Carb Diet

To manage mood on a low-carb diet, consider these strategies:

Hydration and Electrolytes: Stay well-hydrated and replenish lost electrolytes with options like bone broth or supplements.
Nutrient-Dense Foods: Focus on healthy fats, proteins, and low-carb vegetables to get essential mood-supporting nutrients.
Cyclical Carb Intake: Some find a strategic weekly high-carb day helps manage cravings and mood.
Listen to Your Body: Pay attention to your energy and mood. If persistent negative changes occur, a less restrictive approach might be better.

Complex vs. Simple Carbs: The Mood Impact


Feature	Complex Carbohydrates (e.g., whole grains, legumes)	Simple Carbohydrates (e.g., sugar, white bread)
Impact on Serotonin	Provides a slow, steady release of glucose, which encourages a more stable and sustained increase in serotonin.	Causes rapid blood sugar spikes, followed by crashes, which can lead to mood and energy fluctuations.
Energy Levels	Supplies sustained energy over a longer period, preventing the fatigue and sluggishness associated with blood sugar drops.	Offers a quick but short-lived energy boost, often followed by a crash that can worsen mood and increase fatigue.
Nutrient Density	Rich in vitamins, minerals, and fiber that support overall health and are essential for optimal brain function.	Often nutrient-poor, lacking the essential vitamins and minerals needed for proper mood regulation.
Long-Term Mental Health	Associated with overall better nutritional balance and mental health, with a more stable mood.	Chronic consumption can create a cycle of craving and dependence, potentially worsening anxiety and low mood.

Conclusion: Your Mood and Carbohydrates

Not eating carbs can affect your mood, particularly in the initial phase of the dietary shift, as the body adjusts to using fat for fuel, potentially causing irritability, brain fog, and fatigue, which is often termed the 'keto flu.' The long-term effects are less clear and depend on the individual; some report benefits, while others find no significant change. Managing electrolytes, focusing on nutrient-rich foods, and listening to your body are essential steps. For any persistent mood issues related to diet, seek advice from a healthcare professional or a registered dietitian.

Frequently Asked Questions

Irritability is a common side effect during the initial 'keto flu' phase of a low-carb diet. It can be caused by the brain's adaptation to a new fuel source (ketones instead of glucose), electrolyte imbalance, or cravings for high-carb comfort foods.

Initial mood swings and irritability typically last from a few days to a couple of weeks, though individual experiences vary. As the body adapts to ketosis and becomes more efficient at burning fat, these symptoms generally subside.

Evidence is mixed. Some studies link severe carb restriction to temporary mood changes, while others suggest that long-term adherence can help manage mood disorders, potentially by balancing blood sugar and reducing inflammation. Persistent anxiety or depression should be discussed with a healthcare provider.

Consuming carbohydrates increases insulin, which helps the body absorb other amino acids, making it easier for the amino acid tryptophan to enter the brain. Tryptophan is then converted into serotonin, a mood-regulating neurotransmitter.

To combat brain fog, make sure adequate electrolytes (sodium, potassium, magnesium) are consumed, stay well-hydrated, and eat enough healthy fats. Some also benefit from a slower transition into ketosis.

Complex carbs lead to a more gradual rise and fall in blood sugar, providing sustained energy and supporting more stable moods. Simple, refined carbs can cause rapid energy spikes and crashes that contribute to mood fluctuations.

If mood is significantly and persistently affected, consider adjusting the diet. This could mean incorporating more nutrient-dense, high-fiber carbs or trying a cyclical approach. It's advisable to consult a professional before making major dietary changes.