When was the last time you thought about your glucose levels? Chances are you never paid much attention to them at all until the subject started blowing up on social media. While a lot of the chat online seems to stray worryingly close to diet culture, with influencers selling anti-glucose spike formulas and dismissing fruit as a source of unhealthy sugar, there is a more serious, science-backed point here: our blood sugar level is hugely important for our health and wellbeing. In fact, glucose affects almost every part of our bodies, including how we move and work out.

If you’ve ever had a mid-afternoon crash or an energy slump during the day, it’s very likely that it could be down to the glucose levels in your blood fluctuating as they spike rapidly after eating certain foods and then fall.

Before we go any further, it’s useful to first clear up exactly what glucose actually is. The main sugar found in your blood, glucose is the body’s preferred source of energy. Whenever we eat something starchy or sweet, that sugar (in the form of carbs or actual sugar) gets broken down in our digestive system and converted into glucose. This is then released into the bloodstream for our cells to use it for energy.  

If there’s more glucose circulating in our blood than we need, our body converts it to glycogen. Our pancreas releases the hormone insulin and its job is to take excess glucose and store it away. This stored glucose (glycogen) gets held in different areas of the body including the liver, muscles and fat cells. When the body needs that energy, that glycogen gets broken back down into glucose molecules and sent back into the bloodstream again so your body can use it for energy.

It’s a carefully balanced system that works at its best when our blood glucose levels are relatively stable. It’s absolutely normal to have a peak after every meal or snack, but you don’t want giant spikes and super-low dips.

Now, while glucose spikes are a totally natural reaction to eating any foods containing carbs, we don’t want to get into a cycle of having huge spikes and dips – something a 2018 study from Stanford University found happens a lot in non-diabetic, healthy people. Dr Michael Snyder, chair of genetics at Stanford and senior author of the study, found that regular spikes of high blood sugar levels can cause chronic health issues, especially when they happen over a prolonged period of time. The biggest risk, the study found, was that of cardiovascular disease.

You’ll find plenty of hysteria around glucose spikes online at the moment. They’ve been linked to everything from diabetes to sleep issues, and while much of that is scare-mongering, there is some truth to the fact that constant high blood sugar isn’t healthy. One of the people leading the charge against glucose spikes is biochemist Jessie Inchauspé (aka the Glucose Goddess), who warns against staying on what she calls ‘the glucose rollercoaster’. 

“If you have a glucose spike – from a sugary breakfast, for example – your glucose rises really quickly then crashes,” Inchauspé tells Strong Women. “During that crash, you’ll get hungry and crave something else high in sugar. Inevitably, you then eat something very starchy or very sweet, and then you have another glucose spike and crash. Most of us are on this rollercoaster.”

No one wants to constantly be swinging between energy and fatigue – and regularly craving more refined carbs or sugar means potentially missing out on other nutrients like protein, fibre and healthy fats.

“Glucose is very important to our body; every single cell in your body uses glucose for energy. Your eye cells use glucose to see, your finger cells to type and your heart cells to pump. We need glucose to be able to live,” says Inchauspé.

The issues start when we have too much glucose circulating in our bodies with no way to use it all. 

A long line of studies have shown that glucose spikes can effect everything from our mood and our sleep to our skin and the health of our immune system. In the short term, big glucose spikes might cause food cravings, fatigue and brain fog, but in the long term they can impact a whole host of systems in your body.

“When I started analysing decades of research and running thousands of original experiments on myself, I found glucose spikes have different effects on different people. For somebody, it might be nausea, anxiety, fatigue or acne,” says adds Inchauspé.

She compares poor glucose control to bad breathing: “If you’re not breathing properly, it’s going to affect a lot of systems in your body and glucose is similarly pervasive. Every single one of the cells in your body feels glucose spikes. They affect the whole picture of our health – both our mental and physical health.” 

When we exercise our muscles and make them contract, they need energy. The main place they will look for energy first is from glucose in your bloodstream. During high-intensity exercise, glycogen is the body’s main source of energy as it breaks down into glycogen and is released back into the bloodstream.

“If you’re working out intensely, such as doing strength training, HIIT, cardio or any long-distance running where your heart is racing and you’re breathing fast, your body will depend on its glycogen stores for energy,” Dr Folusha Oluwajana, a GP and personal trainer tells Strong Women. “So if your glycogen stores are depleted, then you will also be depleted.”

“If you’re an endurance runner or doing anything more high intensity, you might want to think about making sure you’ve had carbohydrates before exercise to make sure those stores are maintained,” she adds.

In fact, a 2021 study by the Australian Institute of Sport found that exercise was less effective in people who ate a low-carb diet. Participants needed a higher oxygen uptake for the same amount of work and all saw a reduction in their race performance.

Exercise also has an impact on our insulin production. “When you are exercising, your muscles can uptake glucose without needing insulin,” says Inchauspé. “It’s one of the only cases of this and it’s very important because over time if there’s too much insulin in our bodies it can lead to insulin resistance and type 2 diabetes.”

This is why regular exercise has been shown to improve blood sugar control and improve your risk of getting diabetes. And it’s also why we shouldn’t be scared of consuming carbs or glucose. We need blood sugar to function, and we need to have more of it to workout effectively. The key is to make sure that you have enough blood sugar at the right time – and not keep it elevated when we’re just sitting at our desks.

Images: Getty