Dr Libby: The Silent Impact Of Sugar On Your Brain & Metabolic Health

In this special series, guest writer Dr Libby Weaver shares her health insights.

In today’s fast-paced world, it’s easy to reach for convenient food options, which often means ultra-processed foods loaded with added sugars. These choices might seem harmless or just a part of modern life, yet the truth is that they carry long-term implications for our health that can’t be ignored.

What is metabolic health?

Excess sugar is not just about extra calories; it’s a metabolic disruptor. Consistent high sugar intake can lead to fluctuations in blood glucose levels, which can trigger a cascade of health issues related to poor metabolic health. Many people link the term “metabolic health” to their weight, yet this is only a small part of it. Your metabolic health impacts how your body utilises glucose and fat as a fuel and also regulates the levels of glucose and fats (such as cholesterol and triglycerides) in the blood, as well as how much and where body fat is stored. It is also involved in processes like inflammation and blood pressure management.

What are the signs of metabolic syndrome?

When your metabolic health is compromised, it increases your risk of a host of health issues, such as metabolic syndrome (a cluster of conditions including hypertension, high blood sugar, excess body fat around the waist and elevated blood fats), insulin resistance, type 2 diabetes, non-alcoholic fatty liver disease and cardiovascular disease. But metabolic health is not just the absence of these conditions.

Chronic disease is not something that occurs overnight, it happens gradually over time. So metabolic health can decline over a long period – before you may reach the point where a diagnosis of one of these conditions is made. The problem is, this gradual decline is often silent, or at least not with the warning signs you may think it would come with. And because it happens gradually, some of the challenges you experience that indicate your metabolic health isn’t fantastic may start to feel “normal” – such as lacklustre energy and frequent sugar cravings.

Feeling irritable? It might be a sign of disrupted brain chemistry

Beyond the physical, excess sugar has a sneaky way of affecting our brains, too. Consuming high amounts of non-fibre carbohydrates can disrupt our brain chemistry, leading to mood swings and affecting our overall mental health. This is because sugar prompts rapid spikes and crashes in blood sugar levels, which can trigger fluctuations in mood, leaving us feeling irritable or depressed as our body scrambles to rebalance. Plus most ultra-processed, high-sugar foods contain very little or no micronutrients, not what our brain needs to thrive.

Sugar and long-term neurological conditions

Perhaps most alarmingly, there is growing evidence to suggest a link between high-sugar diets and more serious, long-term neurological conditions, such as dementia and Alzheimer’s disease. Alzheimer’s has been linked to the brain’s diminished ability to process glucose and the inflammation spurred by persistent high blood sugar levels, which over time can lead to brain cell damage.

In addition, the immediate gratification that sugar seems to provide is fleeting. The quick spike in energy soon plummets, leaving us tired and often craving even more sugar, creating a vicious cycle that can be hard to break. People also regularly say that once they start eating something sweet, it feels impossible to stop. Or that when they try to reduce their sugar intake their tastebuds have other plans. Often, they feel ashamed of this, and berate themselves after eating more than they intended to. But it’s not a lack of willpower driving this. There are biochemical reasons why sugary foods and drinks are so desirable, and why it can feel so hard to stop after a small taste. Humans have evolved to love the sweet stuff. This is partly because historically the bitter foods we would find when hunting and gathering were more likely to be poisonous and partly because sugar is rich in energy (calories) and provides fuel that our brain uses (glucose).

Why is it so hard to stop eating sugar?

Sweet foods and drinks give our brain a great big hit of a chemical called dopamine. This activates our brain’s reward system, essentially communicating that this is definitely something we want to experience again. When we consistently over-consume sugar, we are activating this reward system again and again – and so our brain starts to adapt. It’s like we build up a tolerance and you may find yourself desiring more and more to get the same feel-good response.

The way sugar affects our brain is one reason we can find it so challenging when we want to change our habits and start to reduce our sugar intake. Yet, it truly is possible! While I am not suggesting that you never consume added sugars again, many people find that taking a break from it completely helps them to reset, particularly if they feel like they are stuck in their habits with their tastebuds running the show. Remember, your brain adapts when you start to over-consume sugar, and there’s also a period of adaptation when you reduce your intake.

Our daily choices make an enormous difference to our metabolic health – let that empower you. The way that we eat, drink, move, breathe and sleep, as well as our perceptions of pressure and urgency (which impacts our experience of stress), can all stack up to either promote better metabolic health, or affect it negatively.

If you need an idea for a change you could make for your health today, try adding in an extra portion of green vegetables each day. Not only does this boost your nutrient intake, incorporating more foods that have a bitter taste (eg greens such as rocket, broccoli etc) consistently, it can also help to shift your taste preferences away from very sweet-tasting foods and drinks.

Remember that small changes and habits can add up over time to have a big impact on your health.

Dr Libby Weaver PhD is a nutritional biochemist, 13 times best-selling author and international keynote speaker. For more on balancing your hormones, visit Drlibby.com

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