Food & Mood: Why I wore a continuous glucose monitor (and why I’d do it again!)

Did you know that the quality of the food you eat has a big impact on your mood? Ever wonder why you get ‘hangry’ or feel hungry again an hour after eating?

One of the biggest everyday health markers that affects everything from mood to energy levels is our blood glucose.

This article looks at continuous glucose monitors and why they can be a fantastic tool for hacking your mood & energy levels and even combatting eating distress.

Glucose: What is it and why track it?

Blood glucose is basically the amount of sugar moving through the miles of blood vessels and veins in our bodies.

The body works to keep blood sugar levels stable, maintaining an energy supply for organs and muscles. Stable blood glucose is great: It maintains regular energy levels creating stability in our bodies and brains – including in our mood.

Unstable blood sugar feeds mood swings and even anxiety – when our energy levels swing around, so does what’s going on in our brain.

Blood glucose should stay within the 4.0-7.8mmol range. How do you know what your blood glucose level is? Well, that’s what the monitor is for…

What is a Continuous Glucose Monitor?

Continuous glucose monitors: A hack for reducing eating distress & food decision fatigue.

Continuous glucose monitors: A hack for reducing eating distress & food decision fatigue.[/caption]

A continuous glucose monitor is exactly what it sounds like – a device that keeps a running measure of your blood sugar levels throughout the day. It’s worn usually on the back of the arm and is about the size of a large coin.

Historically, these devices were used for medical purposes, such as for people with Type 1 Diabetes where blood glucose level can be a real emergency. Now the rest of the world is catching on to the fact that they offer up insights into what’s going on inside your body on an everyday level– and that’s why I wore one.

CGMs are great because they track blood sugar in real time. This means they provide some completely different ways to look at lifestyle and nutrition – and how blood sugar directly affects your physical & mental health in both the short and long term.

Why Might a CGM Help You?

You can manage your blood sugar levels to avoid hypo- (too little) and hyper-glycaemia (too much). This allows you to give your body what it needs and prevent excess or deficiency.

You can also test particular foods to see how your metabolism responds and make changes based on solid information to better feed yourself & create stability in body & mind.

The brain needs food, too. Stable blood sugar helps the brain function optimally.

As a psychotherapist, the most interesting bit for me is seeing how blood sugar affects mood and energy availability. This is something so many of us overlook when we are making food choices – it’s not often we stop and think ‘What does my brain need to eat today?’ but we could really benefit from asking some of these deeper questions around food.

Stable blood sugar supports a stable mood and glucose is the brain’s preferred source of energy so when our blood sugar yo-yo’s our brain can’t do its best for us.
Blood sugar stability happens when you’re feeding appropriately for the activity you’re doing and your body’s resting needs. The body works hard to maintain ‘homeostasis’ which is the stability of all bodily systems for survival. When we overeat, undereat, or eat poor quality food we are creating extra stress for the body and undermining its stability.

Metabolism: Energy management in body & brain

Metabolism is the big collection of complicated processes in our bodies for managing energy. Our bodies do several things with energy:

  • Burning it to produce new tissues like muscle, tendons, and maintain organ function (especially in the brain!)
  • Short-term storage: Some glucose is stored in the liver & muscles for use in the near future
  • Long-term storage: Excess energy is stored as body fat, which is used much later on

So metabolism affects how we feel and perform now, the rest of the day, and into the future. The steadier our metabolism, the better our mental performance, hormonal health, and body composition (e.g. muscle and fat levels).

Metabolic health is what happens when we feed ourselves in line with the demands we put on our bodies. There are two main factors here:

The fuel: Quality of foods eaten, quantity, and timing

The activity: Regular exercise and higher activity levels improve metabolic health

It’s important to always remember this is a balance – eating more isn’t bad, eating less isn’t better. Remaining active and feeding your body what it needs is where metabolic health happens – in the balance between the two.

What can I get from a glucose monitor?

There are great learnings from a CGM including:

  1. A fresh perspective
  2. Cause and effect of food going into the body
  3. Helping unpack food-associations
  4. New goals
  5. Reduce decision fatigue or food anxiety
  • The CGM offers a fresh perspective: It can challenge eating patterns or habits with concrete data. I’d never been able to think about food so specifically before: Having immediate feedback on what I was eating helped clarify how my body responded to certain carbs – including timing, type, and quality.
  • A glucose monitor allows you to see cause and effect. I ate food and it changed my glucose levels. These changes are clear and obvious – you can direct these changes to help you feel and perform better.It’s a great way of seeing how what you eat affects your body and mind. Things like exercise performance, energy levels, and mood all change in line with your blood-sugar levels, and you get to see how you affect those feelings through diet and exercise.
  • Food-associations get challenged when you start measuring their effect on your glucose. Foods you believed were working well for you might not look so good on a CGM. Foods you thought were off-limits might actually be okay. This insight is key to making informed changes to habits, improving choices, and feeling more connected with your body.
  • A CGM offers you health goals. That 4.0 to 7.8mmol range is where your body is happy and functions best. So, when you’re not in that area, you know something needs to shift.
  • Finally, it can help make clearer the best way to feed yourself which can be especially powerful for people with eating distress who find this challenging. It can also help reduce anxiety around food choices or decision fatigue if you feel you have to think hard all the time about what to eat or how much.

Carbs aren’t bad for you

One of the most important things to learn and use is this: Carbs aren’t bad for us.

Carbohydrates and fats both get plenty of bad press, respectively. The important thing is balance and stability. Carbohydrates help us work at our best – the problems of blood-sugar spikes and long-term problems (like Type 2 diabetes) are about poor food quality, toxins and imbalance.

Unstable carb intake – over-eating on mostly poor-quality carbs – is where issues arise. This can include choosing processed carbs over whole foods or adding sweeteners such as refined sugar that jack up the energy content of your food. This can create ‘metabolic instability’ – where your body has to work harder to deal with the excess energy it’s receiving that shoots blood sugar up, then back down again. We don’t need to experience this sort of instability if we feed ourselves with stable energy. This is one of the reasons I loved using the CGM – I got to see my metabolic stability and do a few experiments to find out its limits.

Sugars aren’t all created equal: Understanding food quality

The source of your carbs is critical. If sugars and carbs were all created equal, we’d all be eating sugar from the bag by the spoonful. Why don’t we do that? Because carb sources are wide-ranging, and some are much better than others.

The quality of a carb source depends on what you’re using it for. Usually, however, there are a few factors that make up quality:

  • Carb mix: Starches are slower-digesting and offer stable energy over time, while sugars dump glucose into the bloodstream rapidly – we want to avoid this rapid dump most of the time.
  • Fibre: More fibre means a better digestive and metabolic effect, as well as a sustained, slower release of carbohydrates into the bloodstream.
  • Nutrient density: More vitamins and minerals make for better health, as well as metabolism. Whole foods are especially dense in vitamins and minerals and make for better carb choices.

These are the main factors that you should look for. Not only do they change how carbs effect your blood-sugar levels, but also what other functions it has in your diet and how it supports health.

Why CGMs Are So Useful for Improving Carb Habits

If you try a CGM you will quickly learn that not all carbs behave the same in your body. This is what I loved about using it – I could see how foods affected my mood and my performance. For me, eating a banana on an empty stomach was a learning experience – and here’s why…

Sugar-rich foods cause a rapid dump of carbs into your bloodstream: a huge spike of blood glucose, then a “crash” as your insulin levels are too high, when sugar is burned off. When your blood glucose crashes, so does your mood – this could look like irritability (hangry, anyone?), depression or even anxiety.

This is why we tend to struggle with refined, sugary foods: they don’t produce a consistent energy release. Rather, starchy, fibrous carbs are going to release glucose into your bloodstream slowly, while the fiber itself regulates your energy release and digestive health.

When you have these extremes of high and low blood sugar, you cause similar ups and downs in your energy levels. You’re more prone to mood swings, extremes of mental performance, and you challenge your hormonal wellbeing.

When I ate that banana on an empty stomach, despite its sugar content, I never saw a spike or crash. The fiber slowed the energy release – my blood glucose went up, but it was sustained because whole foods (like fruit) offer a balance of carbs (starch, sugar, and even fiber).

On the other hand, meals that I expected to be okay – like a roast dinner – were much higher in carbs than anticipated. Parsnips, Yorkshire puddings, and honey-glazed carrots provided a huge quantity of carbs, but also very rapidly-absorbing ones, even alongside fats and protein.

Here is a day of blood glucose tracking showing some ups & downs but still within the healthy range. I was able to diary when I ate & what I ate, allowing me to see cause & effect with clarity.

7 Hints and Tips for Better Carb Habits

There are a few simple changes you can make to lifestyle that will improve your long-term glucose levels. The idea is to keep things as sustainable as possible and only seek to spike glucose levels before and after exercise.

Remember: Carbs are energy for short-term activity, so you should eat the faster-absorbing ones to support exercise performance. Eating sugar while you’re inactive will get stored, probably as body fat! When glucose levels are too high or too low, we run into issues. These hints and tips will be simple changes and reminders that you can apply to your lifestyle and routines to get the best from your diet for mood, consistent energy levels, and better mood-control through the day:

  • Breakfasting: When you sleep, your body is doing a lot of repair and recovery. Your first meal of the day, which may not even be in the morning, should focus on slow-release energy: fats, proteins, and high-fiber carbs (like oats). If you have a sugary first meal, you’re going to spike your glucose levels right away and crash out early in the day. Recent research showed that glucose spikes early in the day affect you ALL day, leaving your blood sugar less stable than if you start the day with fats and protein.
  • Prioritise protein: Protein is great for regulating your blood sugar. It slows the digestion and absorption of all the food you eat. So when you combine protein with carbs, for example, you slow down the release into the blood stream. Make sure all your meals contain a protein source. It’s great for digestion, metabolism, and controlling your blood-sugar.
  • Eat relative to your exercise: Exercise and activity levels determine your carb needs. Increase carb intake when activity goes up and bring it down when you’re less active. This helps maintain good balance, better metabolic health, and builds the great habit of eating for your life!
  • Meal and exercise relationships:  Eat your carbs closer to your workouts – both before and after. This helps use them for both the development of energy stores and then replenishing those stores after exercise. This is particularly important for women – the female recovery window after exercise is small, just 30 minutes, while men recover over 21 hours.
    Make sure your carb intake serves your goals, whether that’s sports performance, stable energy, body fat loss or body composition maintenance.
  • Seek satisfaction not fullness!  When eating, aim for 80% fullness, not 100%. Give the body an opportunity to signal when it’s had enough – if this feels difficult, check out Precision Nutrition’s hand guide to food portions.
  • Better carbs = better life:  Improving your carb sources – preferentially choosing those whole plant foods that you know are good for you – is a huge deal.  Wholegrains, pulses, legumes, and veggies are the place you should look. Carb quality overlaps with other areas, too, like protein, vitamin, and mineral content.
  • Liquid carbs are exercise fuel and nothing else so avoid juices:  Avoid sugary drinks unless you’re doing exercise! And yes, that includes fruit juice!  Juices, sodas, and other forms of liquid calories add up quickly. They don’t help you stay full, and they spike your blood-sugar since they absorb so quickly.  These kinds of food can be used to rapidly increase blood sugar levels during hypoglycaemia. However, they don’t help you maintain healthy balance during inactivity, can destabilise your blood sugar and upset the gut!


The drawback of a CGM? They’re ugly. Fortunately, some savvy companies are now making sleeker designs such as the one by SuperSapiens which is marketed toward athletes but valuable to everyone. Others available include:

Continuous glucose monitors are a chance to get inside the data of your body and use it to understand the impact of your lifestyle. We can track a number of different factors when we use a CGM that make lifestyle change a little more concrete:

  • Maintaining healthy metabolism
  • Ensuring proper fuelling for exercise and good recovery
  • Checking the cause-and-effect of lifestyle change
  • Having a set of goals and systems for your food choices

These changes add up and touch on almost every aspect of your physical and mental wellbeing. That is why I wore a continuous glucose monitor, and it’s why I believe it’s a powerful tool for learning how to:

  • Change body composition
  • Fuel athletic performance & stabilise energy in the body
  • Support emotional wellbeing

If you’re trying to make sense of your metabolism and make feeding yourself easier, it’s a powerful tool that most people aren’t using.