Why Fasting & Carb Restriction May Be Worsening Your Mood.

The Impact of Extended Fasting on Stress and Mental Health

Skipping meals or fasting for extended periods when associated with nutrient deficiencies (e.g., not eating enough complex carbohydrates) or calorie restriction may seem like a quick way to shed a few kegs or "reset" your system — but his kind of fasting can actually worsen anxiety or depression (Wang et al., 2022). This is especially true for people who already experience anxiety (Tinsley et al., 2021).

When you don’t eat regularly (e.g., 3 balanced meals a day), your blood sugar levels are more likely to drop, this triggers the release of stress hormones like cortisol. These hormones are part of your body’s natural fight-or-flight response, and while these hormones are very useful in short bursts, when they stay elevated for too long (say, when you’re fasting), they can make it much harder to regulate your emotions.

Elevated cortisol levels can contribute to feelings of anxiety, irritability, and fatigue, and can even interfere with your ability to think clearly. In fact, one study found that cortisol fluctuations are linked to mood disturbances, anxiety, and cognitive dysfunction (Wirth et al., 2011).

So, fasting or skipping meals when you're already stressed or feeling low could amplify the very symptoms you're trying to avoid.

The Power of Regular Meals: Stabilising Blood Sugar & Mood

On the other hand, eating regular balanced meals helps maintain stable blood sugar levels, which is crucial for emotional regulation. When your blood sugar is steady, your body has a consistent supply of energy to fuel brain function, which helps you think more clearly, feel more composed, and respond more calmly to stress.

In fact, research shows that people with lower blood sugar levels tend to have more difficulty controlling their emotions, and they are more likely to experience irritability, anxiety, depression, and mood swings (Penckofer et al., 2012; Kelsey Kunik, 2024).

But it’s not just about how often you eat. Consuming meals that include a balance of protein and complex carbs is key for preventing these blood sugar dips, making it easier to manage both your energy and your emotions.

Why Protein and Carbs Are Your Best Mental Health Allies

Now, let’s talk about the dynamic duo: protein and complex carbohydrates. Despite what your aunt or your keto-loving gym buddy might say, carbs are not the enemy. In fact, complex carbohydrates (e.g., whole grains & starchy veggies) play a vital role in managing mental health, especially when paired with protein.

Here’s why:

Protein is crucial for creating mood-regulating neurotransmitters like serotonin, dopamine, and GABA. which help regulate mood, focus, and stress response. GABA is an inhibitory neurotransmitter which slows overactive neural activity promoting a sense of calm and relaxation. Serotonin, often referred to as the “feel-good” neurotransmitter, is especially important for managing anxiety and depression.

Complex carbohydrates, like whole grains, fruits, and vegetables, help increase the availability of tryptophan—the amino acid required to produce serotonin. Without adequate carbs, you may struggle to produce enough serotonin, which can leave you feeling anxious or low. Carbs also help keep your blood sugar levels stable, preventing the mood and energy crashes that often accompany a lack of fuel.

This combination of protein and complex carbs is a powerful tool for boosting brain function, stabilising mood, and keeping you calm and focused throughout the day.

So, What Should You Do?

If you’re dealing with anxiety, depression, or high stress, the best thing you can do to start eating regular, balanced meals. Focus on meals that combine protein (think eggs, meat, or legumes) with complex carbohydrates (whole grains like brown rice, kumara, and starchy veggies). This will provide your brain with the steady energy it needs to stay sharp, focused, and emotionally stable.

When you eat consistently and prioritise protein and carbs, you're not just fueling your body—you're supporting your brain's ability to manage stress, process emotions, and stay on track. No more energy crashes, mood swings, or irritability.

I loose my appetite when I’m low or anxious, so what should I do?

It’s common to feel neasous or not hungry when experiencing low moods or anxiety, but that doesnt mean you shouldn’t eat. In fact, eating the right foods (protein with carbs) will make you feel better. I encourage my clients consider foods that may be gentle on their tummy. And before eating, I suggest they take a some deep controlled breaths to communicate with their nervous system”I am safe and ready to digest”. Eat slowly, continue to breathe, and let your kai support your mind and body like it’s meant to.

A Quick Note on Fasting

Of course, fasting can have benefits in certain situations. For example, it can be helpful under professional guidance for addressing specific health issues, such as metabolic disorders or insulin resistance. However, if you’re struggling with high stress, anxiety, or depression, regular meals—especially those with protein and carbs—are your best bet for managing your mental health.

In general, skipping meals or fasting during times of stress only adds to the problem.

Instead, try to nourish your body with regular meals that contain a balance of protein and complex carbs. Your brain and body will thank you.

References

Firth, J., Marx, W., Dash, S., Carney, R., Teasdale, S. B., &Solmi, M., (2019). The effects of dietary improvement on symptoms of depression and anxiety: A meta-analysis of randomized controlled trials. Psychosomatic. Medicine. 81:265- 268. 

Jacka, F. N., O'Neil, A., Opie, R., Itsiopoulos, C., Cotton, S., &Mohebbi, M., (2017). A randomised controlled trial of dietary improvement for adults with major depression. .British Medical Journal 21,23-26. 

Sarris, J., Logan, A. C., Akbaraly, T. N., Paul Amminger, G., Balanzá-Martínez, & V., Freeman, M. P.,(2015). International Society for Nutritional Psychiatry Research consensus position statement: nutritional medicine in modern psychiatry. World Psychiatry. 14:370–375.

Penckofer, S., Quinn, L., Byrn, M., Ferrans, C., Miller, M., & Strange, P. (2012). Does glycemic variability impact mood and quality of life?. Diabetes technology & therapeutics, 14(4), 303-310.

Wang, Y., & Wu, R. (2022). The effect of fasting on human metabolism and psychological health. Disease markers, 2022(1), 5653739.