The evidence for using CGMs for people without diabetes
We’re in the midst of a metabolic health crisis in Australia and beyond, and there is plenty of evidence to suggest that CGMs may be a powerful tool in the prevention and reversal of this crisis.
We are in the midst of a metabolic health crisis. The latest stats (2018) from the Australian bureau of statistics, revealed that 67% of Australian adults are either over-weight or obese. A number that has been steadily rising over the past 4 decades. Furthermore 25% of Australian kids fall into that category too.
Metabolic conditions are not contained to the western world as in previous decades; obesity has tripled worldwide since 1975. There are now an estimated 422 million people world-wide who live with type 2 diabetes, and a further 7.5% of the world’s population fall into the pre-diabetic range. Over 70% of these people will be diagnosed as Type 2 diabetic within their lifetimes. These numbers are frightening when you think that type 2 diabetes is an entirely preventable lifestyle related disease, attributed to our modern ways of eating, processed foods, poor nutrition, inadequate movement, poor sleep and excessive mental stress. Add to this the burden of metabolic syndrome, which is estimated to be affecting at least 25% of Australians (a likely under-estimate of the true numbers) and we have ourselves a major health crisis, one that is arguably becoming somewhat normalised.
Normalisation is a pervasive social process in which ideas, beliefs and conditions which were once less common, come to be regarded as normal. This common social process is arguably occurring with regards to ageing and the normalisation of issues such as stress, burnout, obesity, frailty, cognitive impairment, arthritis and metabolic syndrome. The reason why this is risky is that disease is seen as a natural part of ageing, where there is in fact no evidence that this has to be the case. Concurrently over the last 60 or so years we have seen a rise in un-healthy foods and unhealthy habits driven by consumerism, processing of foods, market economics, growing work hours and increasing stress. These two concurrent and un-healthy normalising occurrences have flown under the radar and what we see in the hospitals and General practices across the country is the results of these shifts in our way of life, which is majorly impacting our long term health and well-being.
If we home in on the issue of pre-diabetes, metabolic syndrome and insulin resistance, what we see is that it is becoming increasingly common in younger people, for example children are now being diagnosed with Type 2 diabetes in childhood, an issue which is being mirrored world-wide due to the rise in obesity, whereas this was a rare occurrence only a few decades ago. The AFP article from 2016 revealed a 27% year on year increase between 1990 and 2002. Insulin resistance is found to be almost invariable in those diagnosed with poly-cystic ovarian syndrome, which now affects around 10% of the female population world-wide and up to 20% in Western countries such as the USA. Insulin resistance and metabolic syndrome both have been associated with increased frailty in the aged. Insulin resistance is an independent risk factor for Alzheimer’s disease, cancer death, and is associated with an increased risk of cardiovascular death and all-cause mortality in those without Type 2 diabetes. Pre-diabetes is arguably a mis-nomer as it can be misconstrued as being a pre-disease issue without consequence, but it is well documented that those with this condition are at increased risk of cardiovascular and other complications.
Ok, so I think it is pretty hard to argue with the fact that type 2 diabetes, insulin resistance, pre-diabetes, metabolic syndrome and obesity are all on the rise. So, let’s take a look at the underlying role of metabolism, how we currently diagnose the issues and start asking the question, are we leaving it too late and can more be done to prevent the development of these types of conditions?
What is metabolic health?
So let's start with the basics, what is metabolism and what does it do? Well the best way to describe what metabolism is, is that it is the body's way of responding to the energetic needs for optimal functioning. The metabolism adapts based upon the internal and external environment. The body is constantly honing into its own needs for survival, by tuning into nature, how much light is there, the external temperature and the stress and energetic needs of the system; ie pregnancy, breastfeeding, fever, injury, emotional/social stress, sleeplessness and of course how much glucose, fat and protein there is to utilise in order to service those particular needs. It is a complex, highly adaptive system and the old “calories in” versus “calories out” scenario is an oversimplification of the issue.
Metabolism is constantly changing and rather than aiming for a high metabolism, it is ideal to have a highly adaptive metabolism, one that can respond to one’s needs. The metabolism is a whole body system, it involves a range of different hormones from the thyroid to the sex and stress hormones, it is dependant upon the circadian rhythms, timing of movement and energy requirements, light and sleep, emotional and mental stresses as well as food choice, nutrient density and food timing. So you can see that there is a lot to it beyond your food choices. Its main role is to keep the body in balance, which is why balancing your glucose levels can be a great way of witnessing in real time your metabolic health.
As a GP, the way we diagnose whether you have Type 2 diabetes is by ordering a HBA1C test. This test is essentially a reading of your average glucose levels over a 3-month period. The impact of the result is based upon what percentage you get. The result is deemed normal if your HBA1c is less than 5.7%, you are deemed pre-diabetic if you sit between 5.7-6.4% and you will be diagnosed with Type 2 Diabetes if your results sits above 6.5%. Where the HbA1c test is limited clinically is that it doesn’t allow the doctor to see if you are having excessive glucose variability nor how high the highest reading was or how low the lowest reading was? The second way to diagnose is to take a fasting glucose reading, if this is over a certain number, then the diagnosis can be made.
The last way in current general practice to diagnose Type 2 diabetes is to do a glucose tolerance test. This is done on a fasting blood and then a 75 gram load of glucose is given to the patient and readings are taken every hour up to 3 hours. If the reading falls into the high category the diagnosis can be made. None of these tests check for insulin resistance nor high glucose variability. The reason for why this is important is that these 2 variables are significantly under diagnosed and associated with poor outcomes overall and chronic cardiovascular diseases as outlined above.
The evidence of using CGMs for non-diabetics
So, of course I can now hear you asking, well why are we not checking people for glucose dys-regulation? Well to be frank, we don’t and this is why the CGM technology may just be the game changer we are all looking for! Note; a CGM is a small device that measures the blood glucose levels in the interstitial fluid. The device is easy to apply, sits of the back of the upper arms and can measure the levels every 5 minutes, continuously for 2 weeks.
CGM technology has made the ability to check for glucose variability much easier. Glucose variability is the % indicator that reveals how many highs and lows the person may be experiencing, with higher variability associated with increased risk of all -cause mortality, cardiovascular events, such as ischemia, retinal damage and peripheral vascular disease. So even though we try to avoid high glucose reading in those with Type 2 diabetes, it is also known that high and frequent levels of glucose variability is problematic for non-diabetics as well.
So, it begs the question, what is prevention? Is it waiting for the disease to occur, picking it up early and then trying to implement changes to fix the issue or does true prevention lie in helping people manage weight, support fitness, optimise sleep, understand how to optimise their diet and maximise mental health before a disease develops? Being diagnosed with type 2 diabetes isn’t someone’s fault, but it is their responsibility and taking responsibility early, and finding ways to support the health of your body before a disease occurs is not only an individual’s duty, but the role of a well functioning society as well.
So surely it is a matter of simply telling someone what to eat, how much exercise to do, how much sleep to get and not to worry too much, right? Well to be honest most people know what they need to do, they know they should stop watching Netflix, go to bed early, join the gym and eat more salads, but many people don’t and the answers as to why are still far from accurate. So what to do? Sit on our hands, and wait? Pray? Bombard people with more information? Well, to be fair the answers are still not clear and possibly what works for one person, may not work for another.
So, what if we were to give people early access to how their metabolism works? What if there was an option to look at the way different foods affect your blood glucose levels, how sleep impacts them and what effect exercise has? What if you could see how your glucose levels responded to a bowl of pasta compared to a steak and salad meal? How does a bowl of processed cereal compare to an omelette for breakfast? What if by using a continuous glucose monitor (CGM) you can see in real life, the effects of your lifestyle choices on your metabolic response? Could it be the secret sauce that offers you the motivation, resolve and knowledge that is unique to you?
CGM technology has also made the ability to check for glucose variability accessible and easier. So even though we encourage those with Type 2 diabetes to avoid high glucose reading, it is also known that high and frequent levels of glucose variability is problematic for everyone. Glucose variability is the % indicator that reveals how many highs and lows the person may be experiencing, with higher variability associated with increased risk of all -cause mortality, cardiovascular events, such as ischemia, retinal damage and peripheral vascular disease.
A recent article published in the American based journal Clinical Diabetes, in 2020 surveyed a group of diabetic CGM users to ascertain the impact of using a CGM on food and exercise choices. What it found was that in those who were using it, 90% of them felt that it contributed to better lifestyle choices, 47% of users felt it made them more likely to exercise if their sugars were going higher and 87% felt that wearing a CGM influenced their food choices and helped them make healthier choices. Arguments could be made that these people already had a diagnosis and would therefore be more motivated to change. However, in a recent study, of non-diabetic people, published in PLOS Biology, it found that by wearing a CGM, a significant number of participants did in fact, have abnormal glucose regulation. The CGM was a critical factor in revealing this underlying abnormality, which would not have been uncovered, using the standard single point in time blood tests. What this means, is that our current ways of measuring glucose intolerance and type 2 diabetes, is sub-standard and that we are at risk of missing the diagnosis in non-symptomatic, seemingly healthy people.
Vively’s data provides anecdotal evidence
In fact, at Vively we are seeing the same trend. Between August 2022 - December 2022, Vively collected over 500,000 glucose readings and discovered a higher-than-expected rate of potential metabolic dysfunction. For example, more than 66% of users have an estimated Hba1c of 5.7% or greater, which by our current standards would put them in the pre-diabetes category. These figures are being found in users who have not reported any known metabolic dys-function. Obviously more research is needed and it is not standard to diagnose a metabolic issue in a person from CGM data alone, but the trend is definitely something worth looking more closely at.
The use of CGM in non-diabetics may become the way doctors will diagnosis glucose dys-regulation and metabolic syndrome in the future, without having to wait until the fasting blood test becomes abnormal, and considering we have an epidemic on our hands, as well as a pandemic, health costs and prevention will be high on every government’s agenda world-wide.
So, if this is the case, why is it such a stretch to employ this “data collecting device” in people without the diagnosis of Type 2 diabetes? And if we were to employ this data collecting device earlier, would the user be able to reverse the dys-regulation more easily and prevent the long term devastating effects that type 2 diabetes often face, such as dialysis, blindness or amputation? The answer has not yet been researched, and more investment is clearly needed.
Medicine is changing and so are patients. Many patients with lifestyle related disease ideally need to become increasingly and intimately involved in their own care. In the past, the major reasons to go to the doctors was to either get a diagnosis, treat an infectious disease or deal with a trauma. Current medicine reveals the most common conditions that result in a visit to the GP, are for lifestyle related diseases, stress and mental health. So, in the past when making a diagnosis was a core role of the doctor, nowadays, the doctor is also obliged to teach their patients about the factors that led to the lifestyle disease and in doing so must become, nutritionist, counsellor, psychologist and coach.
One of the fundamental tenets underlying a condition such as Type 2 diabetes, is that it is linearly progressive, meaning that once the condition has occurred, if a person fails to alter the lifestyle factors that have impacted the diagnosis, it will progress in a fairly predictive way. In fact, it is well known that glucose dys-regulation and higher than hyperinsulinaemia will be expressed for up to 15 years prior to “full-blown” diabetes diagnosis is made. Therefore, we should be trying to document glucose dys-regulation and insulin resistance early to promote interventions that increase the risk of reversing the underlying metabolic dysfunction and help the person prevent this devastating chronic disease.
Health literacy is a critical factor for many people in understanding the impact of nutrition on health, and understanding their own empowerment and behaviour required to successfully reverse certain conditions. A recent study published in the Journal of Diabetes Science and technology in 2007 set out to reveal the difference in blood glucose responses to a variety of different meal compositions. For many it would be obvious that a meal high in refined carbohydrates such as a processed breakfast cereal would impact the post prandial blood glucose levels more than a meal high in fibre, protein and healthy fats, however because of the excessive advertising of processed food stuffs, confusing health messaging, targeted messaging to children and the poorly understood 5 star health rating system, many people are understandably confused as to what to eat, what is healthy and what isn’t. The use of the CGM may be a game changer for those with poorer health literacy.
Most people are aware of the saying “one man’s meat is another man’s poison” but how this impacts the individual is a common source of confusion, made worse by the fact that the key stakeholders espousing nutritional advice, tend to standardise their advice and recommend the same food pyramid for everyone. A one size fits all approach. Even though most learned health professionals will agree that a one size fits all approach is rudimentary, yet the ability to individualise a person’s diet is limited by a lack of personalised data. A study published in Cell in 2015 highlights the different glucose responses with the same meals in different people, paving the way for some exciting predictive opportunities that may potentially revolutionise our understanding of personalised nutrition. Studies have begun to look at the role the gut biome plays in food choice, cravings and satiation to name a few.
Glucose variability, glucose dys-regulation, and reactive hypoglycaemia can all be features of conditions such as pre-diabetes, obesity, metabolic syndrome, PCOS and type 2 diabetes. Whilst a person’s overall average glucose can appear normal, the highs and lows are often overlooked, fail to be picked-up or not captured by single point in time data collections, such as finger prick blood test and even glucose tolerance tests. The CGM can pick up lows as well as highs. Recurrent or frequent hypoglycaemia can be a risk factor for cardio-vascular events and for type 2 diabetes, and it can functionally impact a person’s sense of well-being.
In the 2021 Australia talks survey, 60% of Australians are currently trying to lose weight. Only 24.5% of Australians met the recommended daily exercise requirements, and approximately 49% of Australians report that their jobs were mainly sedentary. Add this to over 15% of Australians suffering sleep apnoea and nearly half the population report at least two issues with their sleep. The physiological impacts of lifestyle and long-term health are extra-ordinary by these three key factors alone.
The research is still early
CGM technology is relatively new and research is still burgeoning. Therefore, we don’t yet have solid evidence to ascertain whether wearing a CGM has any negative impact, psychologically, emotionally or puts the users at risk of a mis-diagnosis. We also don’t know if the use of CGM in non-diabetics negatively affects a person’s relationship to food, whether disordered eating may increase or whether the impacts are short lived and therefore statistically not relevant long term. We also lack international consensus for hypoglycaemic levels, which may have unknown implications, and the true impact on behaviour change is yet to be fully explored.
In addition, blood glucose levels are impacted by a multitude of variabilities, for example the impacts of broken sleep, shortened sleep hours, lack of REM sleep, co-morbidity, exercise intensity, quality and length, food quantities and qualities, underlying nutritional status in the user, environmental toxins, supplements, medications and emotional stress to name a few. When considering the permutations and combinations at play, the research suggests that support from a health professional and proper interpretation of the data may be a critical factor in the successful long term outcome regarding behavioural modification.
As I aforementioned, the numbers of people with metabolic impairment is not slowing down, in fact the predicted number of people suffering metabolic syndrome, pre-diabetes, PCOS, type 2 diabetes are rising year upon year. This is causing immeasurable financial, practical and societal impact on our health care systems. So, if we are truly talking prevention, and not merely screening or early detection, then the potential of using CGM technology intermittently may offer the user a chance to learn with more individualised accuracy the impact of their particular lifestyle choices on a critical parameter such as blood glucose levels. Most of us are aware that improving diet, developing a regular exercise program, optimising sleep and minimising stress are all critical factors for improving health and preventing disease, so using a technology that can provide data on how these key factors all inter-relate. By making CGMs more widely accessible to the public, patiens, practitioners and the government will have a powerful tool for better understanding and addressing this crisis.