How Sugar Impacts Your Energy Levels (and How to Navigate the Festive Season)

Discover how sugar affects your energy and fatigue levels, especially during the festive season, and learn strategies to stay balanced

Fatigue has a way of colouring everything. It shapes how you wake up, how you move through the day, how you think, and how resilient you feel. When you’re already tired, the festive season, with its crowded diaries, disrupted routines and endless trays of sweet treats, can feel both exciting and overwhelming. You want to join in the celebrations, but you also want to avoid the kind of crash that can leave you wiped out for days.

If you’re living with heavy tiredness, burnout, or a fatigue-based condition such as CFS/ME, Long Covid or fibromyalgia, you may notice that sugar hits you harder than it seems to hit others. Even those without a medical diagnosis often find that their energy becomes more volatile at this time of year. And no, it’s not simply a lack of willpower, there are real physiological reasons why sugar can make fatigue feel worse, especially when your baseline energy is already low.

This isn’t about restriction or perfection. It’s about understanding what’s happening inside your body, and learning small, gentle strategies that help you feel more steady and less overwhelmed.

Why Sugar Affects You More When You’re Fatigued

Sugar gives the illusion of quick energy, and in the moment it can feel helpful. The challenge comes afterwards. When you eat something sugary, your blood sugar rises rapidly. Your body responds by releasing insulin to bring those levels down again. If the rise was sharp, the drop is often sharper. And that drop is what leads to the sudden fogginess, hunger, shakiness, irritability and deep tiredness that many people describe as a “crash.”

When your body is rested, these fluctuations are easier to absorb. But when you’re already fatigued, the systems responsible for managing energy, stress hormones, blood sugar and inflammation are working at reduced capacity. What might be a small dip for someone else can feel like a cliff-edge drop for you.

For those living with fatigue-based conditions such as Long Covid, CFS/ME or fibromyalgia, this effect is often amplified. These conditions already involve challenges with energy production, nervous system sensitivity and immune imbalance, all of which make the body less able to cope with sudden sugar highs and lows. But even without an underlying condition, ongoing tiredness lowers resilience. That’s why sugar feels so appealing when you're exhausted, and why the consequences tend to feel more pronounced.

What Sugar Actually Does Inside a Fatigued Body

There are three main processes worth understanding: oxidative stress, nutrient depletion, and nervous system disruption. Each of these can affect energy, and each is made more noticeable when the body is already under strain.

Oxidative Stress — the “too many sparks” effect

A simple way to picture oxidative stress is to imagine your cells creating tiny sparks every time they metabolise food. This is completely normal. Your antioxidants act as fire extinguishers to keep those sparks under control.

But when you take in a lot of sugar, the number of sparks increases dramatically. If you don’t have enough “extinguishers” — which is common when you’re fatigued — those sparks start to build up. This is oxidative stress.

Over time, oxidative stress can dull your energy, irritate your nervous system, increase inflammation, and make your mitochondria (your cellular energy factories) work harder than they’re able to. That’s why a sugary afternoon can lead to an evening of exhaustion, fogginess or heightened sensitivity.

Sugar uses up the very nutrients your body needs to make energy

Processing sugar isn’t effortless. Your body needs magnesium, B-vitamins, zinc, chromium, antioxidants and CoQ10 just to keep up with the spikes. These are the nutrients that help produce steady energy. When sugar intake is frequent, your reserves of these nutrients drop, leaving you even more tired.

Magnesium and B-vitamins are particularly important, because they’re involved in almost every step of energy production. When they’re depleted, even simple tasks can feel harder.

Your nervous system feels the impact too

After a sugar spike comes a sugar dip, and when your blood sugar drops, your body releases stress hormones, especially adrenaline and cortisol, to bring glucose back into the bloodstream. For someone with a sensitive nervous system, this can feel like anxiety, shakiness, feeling “wired but tired,” or struggling to concentrate.

This is why sugar doesn’t just affect your physical energy; it can also influence your emotional steadiness, your sense of overwhelm, and your ability to stay regulated through busy or social situations.

Your immune system has to work harder

High sugar intake doesn’t directly cause illness, but it can temporarily weaken the function of immune cells. Sugar competes with vitamin C for entry into these cells, meaning your immune response can become slower and less efficient. During winter, and especially during a busy festive season, this can add an extra layer of strain.

What About Sugar-Free Options?

The natural thought is: “I’ll swap to sugar-free and avoid the spike altogether.” But non-nutritive sweeteners (NNS), such as sucralose, aspartame and acesulfame-K, are not always the simple solution they appear to be.

They don’t raise blood sugar, but they may:

disrupt the gut microbiome
increase cravings
alter appetite and fullness signals
create digestive discomfort
interfere with glucose regulation in some people

Some people tolerate them well, while others find they increase hunger or cause unsettled digestion. If your gut, immune system or nervous system is already sensitive, it’s worth approaching sweeteners with curiosity rather than assuming they are automatically “better.”

Gentle Ways to Navigate the Festive Season Without Feeling Drained

The goal during the holidays isn’t to avoid sugar entirely. It’s to support your body so that you can join in, enjoy the moments that matter, and avoid the deep dips that make everything feel harder. Small tweaks often make the biggest difference.

Before events: arrive nourished, not depleted

Turning up hungry almost guarantees a sugar spike later. A small protein-rich snack before you leave home, a yoghurt, a handful of nuts, hummus and oatcakes, or a boiled egg, can stabilise your blood sugar, calm your nervous system, and help you feel more grounded when you walk into a busy room.

A glass of water beforehand helps too. Dehydration can mimic cravings and make your energy feel uneven.

During events: balance, not perfection

Once you’re surrounded by food and people, the aim is simply steadying your body while still enjoying the experience. Begin with a balanced plate, some protein, some colourful foods, some slower-release carbohydrates. This cushions your system before desserts and richer foods appear.

If you do choose something sweet, have it as part of your meal rather than on an empty stomach. Pairing dessert with something savoury or protein-based, or simply eating it after your main course, slows the glucose spike and reduces the post-event crash.

Give yourself permission to pause. A ten-minute breather between courses or second helpings gives your body time to register fullness and can prevent unconscious overeating driven by blood sugar swings.

After events: reset gently, without judgement

What happens after an event can make the biggest difference to how you feel the next day. Rehydrating helps your body rebalance. Herbal teas like ginger, peppermint or cinnamon support digestion and help your nervous system settle.

A small magnesium-rich food, a few almonds, some dark chocolate, spinach, or pumpkin seeds, can soothe your system and support sleep.

Most importantly, be kind to yourself. One meal, one party, or one dessert doesn’t undo your progress. Stress and guilt themselves drain energy far more than sugar ever will.

Simple, Supportive Swaps for the Season

You don’t need to overhaul your diet, just make small swaps where they feel easy.

If you love chocolate, choose a richer, higher-cocoa option and savour a couple of pieces rather than grazing mindlessly. If you enjoy hot drinks, try cacao with cinnamon instead of a sugar-laden hot chocolate. Sparkling water with cranberry or a kombucha can feel festive without sending your blood sugar soaring.

When baking, reducing sugar by a third, adding oats or ground almonds, or using spices like cinnamon and vanilla can create the same enjoyment with a gentler impact.

These aren’t rules. They’re options, tools you can pick up or put down depending on how you feel.

Why This Matters

Supporting your energy isn’t about denying yourself pleasure. It’s about creating a foundation that allows you to enjoy the festive season without paying for it with days of exhaustion. Understanding how sugar affects your body gives you back a sense of control, especially when fatigue has made life feel unpredictable.

Whether your tiredness is due to a demanding year, a busy mind, parenting, work stress, perimenopause, Long Covid, CFS/ME, or something else entirely, your body deserves support, not pressure. These strategies help you honour your limits, maintain more stable energy, and feel more like yourself during a season that can otherwise tip you into overwhelm.

You don’t need to be perfect. You don’t need to say no to everything. You simply need to support your body in the way that feels kind and sustainable.

About Claire

Claire Thomas is a Nutritional Therapist, NLP Practitioner, and Phlebotomist with a background in Children’s Nursing. She specialises in supporting ambitious women who feel exhausted, burnt out, or stuck in survival mode. Through personalised nutrition, mindset coaching, and functional testing, Claire helps her clients increase their energy levels, find clarity, and do more of what they love. Based near Cullompton, Devon, she works both in-person and online through her clinic, Nourish to Soar

Categories: : boost your energy, cfs/me