Does Sugar Affect Mental Health?: The Experiment, Challenges, Benefits

I’ve never been one to turn down something sweet. A bar of chocolate to reward myself for a successful grocery shop, some dessert after dinner—since I only indulged a few times a week, I thought it was pretty harmless. 

But after noticing how sluggish, irritable, and foggy I felt after sugar-heavy days, I started wondering: could my sugar intake be affecting my mental health?

With that question in mind, I decided to cut out added sugar for an entire month. No packets of jelly beans, no sweetened boba teas, and no honey in my morning oats. The goal wasn’t just to see how my body felt, but to observe whether eliminating sugar had any impact on my mood, energy levels, and mental clarity.

The result? Let’s just say it wasn’t what I expected. 

Why I Decided to Cut Out Sugar

I don’t eat added sugar every day. Instead, I tend to indulge in a (very) sweet treat twice a week or so. I usually justify it by saying that I “deserve” a treat—to reward myself for a work victory, to celebrate a special occasion, or to comfort myself after a hard day. 

There’s nothing wrong with treating yourself. But I eventually noticed that my sugar binge led to some uncomfortable symptoms, particularly brain fog, poor sleep, and mood swings. 

“Excess sugar intake, especially from refined sources, can cause rapid spikes and crashes in blood sugar levels, which can lead to irritability, fatigue, and difficulty concentrating,” says dietician Jessica M. Kelly, MS, RDN, LDN, the founder and owner of Nutrition That Heals. “Over time, frequent blood sugar fluctuations can contribute to increased anxiety.”   

“Over time, a high-sugar diet may increase the risk of depression by causing inflammation and disrupting brain chemicals like serotonin and dopamine,” adds Marjorie Nolan Cohn, MS, RD, LDN, CEDS-S, the clinical director of Berry Street. “These ups and downs make it harder to manage emotions, making mood swings more frequent.”

A 2017 study, which looked at data collected from 23,245 people, found that higher sugar intake is associated with depression, particularly in men. Participants with the highest level of sugar consumption were 23% more likely to have a diagnosed mental illness than those with the lowest level of sugar consumption.

Other research, like this 2024 study, also suggests a link between depression and sugar consumption—but the authors point out this connection might be because mental distress can lead to emotional eating and make it harder to control cravings.

For the purpose of my experiment, I needed to set some ground rules about the sugars I would and wouldn’t cut out. 

According to Kelly and Nolan Cohn, not all sugars affect mental health in the same way. “Natural sugars found in, for example, fruit and dairy, accompany fiber, vitamins, and antioxidants that are health-promoting and slow glucose absorption,” Kelly explains. “Refined sugars, like those in sodas and candy, can cause rapid blood sugar spikes and crashes which can lead to mood swings and brain fog.”  

Excited to see the results, I began my experiment!

Week 1: The “Oh Wow, Does That Really Contain Sugar?” Phase

During my first week, I didn’t experience changes in my mood, but rather in my behavior and mindset. 

This experiment required me to pick up a new habit: reading nutritional labels and ingredient lists. Although giving up sugar was easy for the first few days, this habit was pretty hard. 

I was surprised to learn that sugar is in a lot of things. Most of my favorite savory treats contained sugar. Even my usual “healthy” post-gym treat—a protein bar—was off-limits.  

“Cutting out sugar can trigger strong cravings since it affects the brain’s reward system, this can lead to withdrawal-like urges, and for some, it can feel very intense,” says Nolan Cohn. Sugar withdrawal symptoms often include headaches, fatigue, and mood swings. 

On day four, I had my first major challenge—I realized I could no longer grab some milk chocolate on the way out of the grocery store. Talking myself out of this was harder than I’d like to admit. 

The biggest challenge for week one? Choosing what to eat in a restaurant. Most menus don’t specify which dishes contain sugar, and there’s a surprising amount of sugar in savory dishes, like tomato-based curries and wraps filled with sugary salad dressings. 

Week 2: A Shift in Mood and Energy

Around the 10-day mark, things started changing for the better.

Even if I don’t eat a lot of sugar in my day-to-day diet and my home-cooked meals, I tend to treat myself—a lot. Food is a go-to source of comfort for me, often to my detriment. My mindset is often along the lines of, “Oh, who cares? It’s just a treat. It’s a special occasion!” 

Because I wanted to stick to the experiment, I had to pause my “treat yo’self” mindset. As I was more mindful of sugar, I planned my snacks better, avoided getting takeout, and practiced more self-control while shopping for groceries. 

On my therapist’s recommendation, I paid attention to the uncomfortable feelings that’d usually lead me to eat, and I journaled about them instead. 

I also noticed some changes in my mood—finally! Because I wasn’t eating a lot of sugar and then crashing twice a week, my energy levels felt a bit more stable. This meant that my mood also felt more stable.   

Week 3: Mental Clarity and Emotional Balance

By week three, I was genuinely surprised by how good I felt. 

Not only was my energy and mood a little calmer, I was really chuffed with myself for managing to avoid sugar for such a long time. 

Another win? I realized that sugar-free treats could be just as good as sugary ones. I opted for nuts, dark chocolate, and fruit—all in moderation, of course—and found them to be really satisfying. 

Week 4: The New Normal

I’d love to say I wasn’t really thinking about sugar anymore, but honestly, the Cape Town summer meant that I desperately wanted an ice cream. 

Overall, though, my longing for sugar had decreased rapidly—a huge win in my books. 

The best part? I felt more in control of my choices. By pulling off this experiment, I showed myself that I can do hard things—and that I do have self-control, even when it comes to food. 

What I Learned From a Month Without Sugar

Cutting out sugar for a month was difficult, but it was absolutely worth it. Here’s what I learned:

1. Sugar Really Does Affect My Mood

I always assumed sugar just caused physical crashes, but it directly impacted my mood and patience. Without my twice-weekly sugar binge, I felt more emotionally balanced and less reactive.

2. Sugar Is in Everything

Seriously—check the labels. Even foods that seem nutritious (like yogurt, granola, or protein bars) often sneak in added sugar.

3. My Cravings Were More Mental Than Physical

By week two, I realized I wasn’t physically craving sugar—I was mentally associating it with comfort and stress relief. Breaking that habit was a game-changer, not just for my diet but for my emotional well-being. 

4. Small Changes Make a Big Difference

Giving up sugar was difficult, but it wasn’t the biggest sacrifice in the world—and the benefits made it totally worthwhile. I didn’t expect to feel this much better just by removing sugar. My energy, sleep, focus, and mood all improved, and I wasn’t constantly battling highs and lows.

5. I Can Do Hard Things

Self-trust is a constant struggle for me. I often assume I’ll bail whenever the going gets tough. By sticking with this experiment, I proved to myself that I could do it. Giving up sugar for a month might seem like a relatively small feat, but it drastically improved my self-image.  

Should You Cut Out Sugar Too?

I gained a lot from this experiment, but I wouldn’t say that everybody can or should cut out sugar cold turkey. 

“Cutting out sugar entirely, especially in an extreme or restrictive way, can negatively impact one’s mental health,” Kelly says. “A hyper-focus on avoiding sugar can lead to stress, anxiety, and disordered eating patterns.” 

And, as mentioned earlier, all sugars aren’t created equal (we want to be mindful of added sugars!). “It’s important to note that eating some sugar is OK, especially when part of a balanced overall diet!” Nolan Cohn says. “A registered dietitian can help you determine what’s the right balance for you, and how much you can enjoy without experiencing negative side effects.”

Instead of being extremely restrictive, which can lead to a cycle of restricting and bingeing, Kelly and Nolan Cohn recommend eating sugar mindfully and in moderation. 

Kelly also recommends learning to identify when you’re craving sugar for emotional reasons. “Journal, chat with a friend, draw something, or get some fresh air if the craving is coming from an emotional source,” Kelly suggests. 

If you’re an emotional eater like me, it might be worth working with a therapist or a dietician to help you manage emotional eating. Emotional eating isn’t a problem that’s automatically solved by cutting out any part of your diet—it’s a deeper issue that may require some self-work.

“In short, the best way to manage cravings is a holistic approach by focusing on self-care rather than cutting out or simply not eating sugar,” Nolan Cohn says. 

Will I Stay Sugar-Free?

Not completely. I won’t strictly avoid sugar forever, but I will be more mindful of it.

I’ll still enjoy dessert, but I won’t rely on sugar as a stress-coping mechanism. Instead, I’ll focus on whole foods, balanced meals, and paying attention to how sugar actually makes me feel.

So, would I recommend trying it? If you’re up for the challenge, and if you don’t have a history of disordered eating, this experiment might be worthwhile. Even if you don’t cut sugar completely, reducing it might help you feel more mentally and emotionally balanced. At the very least, it’ll help you become a bit more mindful of what you’re putting into your body. 

And trust me—your future, non-hangry self will thank you.