Figuring out what and how much to eat in order to adequately fuel your body for optimal performance can feel a bit like searching for the holy grail. Balancing taste, cravings, and how to define which foods are “good for you”, can often feel like a full-time commitment. While some foods are clearly better than others when it comes to health promotion, you may be surprised to learn that your body’s response to specific foods is unique to your physiology. Specifically, the impact of food on blood sugar is a key to determining what foods are good for you; in other words, the foods that work best to fuel your amazing body and enable it (and you) to perform at its best!


Blood Sugar and your Health

Stable blood sugar levels (ie. fairly consistent blood sugar throughout the day) affects energy levels, mood, productivity, and overall sense of wellbeing. Conversely, unstable blood sugar is linked to depression and anxiety, brain fog, cognitive impairment, poor sleep and difficulty managing weight. Many popular diets promise a one size fits all approach. However, studies have shown people have dramatically different responses in their glucose levels after eating identical foods. One study found that some people had equal and opposite post-meal glucose spikes in response to the same food. Another provides further evidence that there is no one diet that works for everyone. Personalized tools are beneficial in helping us make better food choices. Continuous glucose monitoring (CGM) is one such tool that is becoming more mainstream for health promotion. For someone who is curious to learn about the foods that fuel them to perform optimally, CGM is worthy of consideration.


What is a CGM?

Unlike traditional methods of measuring blood glucose like a finger stick glucometer or a blood test, a continuous glucose monitor (CGM) is a small wearable biosensor about the size of two quarters stacked together. It measures interstitial blood glucose levels just below the skin, which is a close proxy to actual blood glucose levels. The data is sent to a smartphone or handheld device where it is logged and interpreted. The sensor typically lasts one to two weeks before it needs to be removed and replaced. CGM’s have been used by diabetics for years as a comfortable and easy way to track their blood glucose throughout the day. A CGM paired to an insulin pump enables insulin to be automatically delivered when blood glucose levels are high. This simplifies the complexity of disease management for diabetics. Recently, CGMs have become more popular amongst non-diabetics to gain valuable insights and catch metabolic dysfunction early. 


Why track my blood sugar?

Besides highlighting sugar consumption, there are many benefits of tracking blood glucose with a CGM. Data from a CGM can be used to illustrate fluctuations in glucose throughout the day, also called glycemic variability. High glycemic variability is associated with poor health outcomes, yet most people do not know their level. Learning about individual responses to different foods can be a crucial piece in the health optimization puzzle.  Armed with this information we can begin to identify and avoid spike triggering foods or behaviors and work towards maintaining stable blood sugar levels. 

As with most data, the information gathered from CGM  is only as good as what you do with it.  We must take action in order to change our habits and bring about long term behavior change. In the Fogg Behavioral Model, from BJ Fogg’s bestseller “Tiny Habits,” three elements must converge in order for a behavior to occur. Motivation, ability, and a trigger or prompt. If you consistently see that your blood sugar spikes after breakfast, you may choose to add a small portion of protein to your breakfast the next day. However seemingly insignificant this is, starting off your day with the right fuel and the right intention for your body can mean the difference between a productive morning and an agonizing one. It’s amazing how making positive changes to any aspect of health improvement can lead to better choices and behaviors in other areas of health. 


Who should use a CGM?

Anyone looking to better manage energy levels, sleep, mood, performance, and more can benefit from using a CGM. It is important to note that a CGM is a wellbeing tool that can provide valuable insights, but doesn’t, and shouldn’t, mean obsessing over diet and data in unhealthy ways. The goal is to use this data to increase visibility into our biological functioning. With the enormous amount of processed foods labeled “healthy”, identifying specific foods that cause a blood sugar spike can be a tough challenge. The benefit of CGM technology is the visibility of many data points throughout the day, opening a window to exactly when your blood sugar is spiking or crashing. This enables you to correlate that spike with specific foods or categories of foods consumed around those data points. 


What should my glucose levels be?

While specific daily ranges for blood glucose have yet to be established, a good goal is to focus on minimizing variations in blood glucose levels throughout the day. If you were to plot your 24 hour CGM readings on a graph, you would want the graph to look less like peaks and valleys and more like gently rolling hills. Peaks and valleys would likely indicate particular foods causing a sharp increase in blood sugar and subsequent crash. With this information we can begin to experiment with different foods, analyze their effects on our blood sugar, and make the necessary changes. As with all wearables, the data is only useful when it drives good decision making. You can find an overview of data on glucose patterns in nondiabetic individuals using a CGM here

How do I obtain a CGM?

Currently in the US a CGM can only be obtained with a prescription from a doctor. They are not difficult to obtain and, as we discussed, can be useful for reasons tied to your unique circumstances and lifestyle. The popular software company Levels Health offers monitors paired with a smartphone app that takes CGM data and gives personalized feedback, insights, actions, and recommends opportunities for improvement in these areas. This will help you see how food, exercise, sleep, and other lifestyle choices affect your health. The CGM device can be obtained through Levels by completing an online medical consultation for a prescription, which is reviewed by a physician within their independent network. While the actual CGM device may be covered by your insurance, Levels is a general health and wellness company and would not be considered a medical provider or covered by insurance. FiT has no partnerships with Levels or any other companies, but we would be happy to help you find one that meets your needs. Some of the brightest minds in health and fitness encourage the use of CGMs for the general population. Peter Attia, MD  says “CGM technology has only been around for a couple of decades and remains prescription-only in the US. It makes sense that there are no completed large-scale studies of its utility in the general population so far. But don’t confuse absence of evidence for evidence of absence.” You can find a current list of the top CGM devices available on the market here


Research is Ongoing

There is still much research to be done regarding optimal blood glucose levels and its impact on health. While these subjects are being studied, the metabolic health crisis is real and effective ways to tackle this epidemic are needed now. “There are many limitations with glucose monitoring, but you have to start somewhere,” says Levels Advisor Dr. Sara Gottfried. “We’re in the midst of a serious crisis here, and the status quo isn’t cutting it. Glucose monitoring is a great place to start.” 


FiT Personal Trainers who have tried continuous glucose monitoring


James Frederick

Using a CGM for just a few weeks was an eye opening experience for me. An interesting shift happens when you suddenly have a wealth of useful information available to you that you never had before. I was able to see my blood sugar trends spanning food consumption, exercise, and sleep. My range was typically between 65-120mg/dl with the biggest spikes to 130-140 generally after consuming alcohol or a starch heavy meal. 


Juliana Oliveira (FiT Trainer)

 Was able to experiment and understand how much a soda would make her blood sugar spike way up then crash. She now practices food balancing, or always having some protein and fat with her carbohydrates. The CGM also provided her insights and awareness about her habits in general.


Jennifer Mulry: (Founder – Buddies in Action; FiT Trainer)

One of the most helpful ways in which I have used blood sugar readings with families is to understand behaviors and potentially provide an explanation for specific behaviors (most I consult with are non verbal). Measurements like blood sugar can communicate valuable information as to what is happening throughout the day. I look to help regulate blood sugar spikes to improve behavior and self regulate. With families, we find continuous glucose monitoring to be a helpful tool to check in a couple times a year and compare it in relation to any sleep issues or behaviors. Mornings are by far the hardest to stabilize, which have led several of my families to switch to a high fat/protein breakfast as well as become strategic about when carbs are given based on the child/adult’s routine. 


Kevin Martin: 

One of the things I found the most interesting while monitoring my blood glucose levels was the effects of not only different types of food on my blood glucose, but also the effect of different types of exercise (strength training, HIIT, Zone 2 cardio) had on my glucose levels. It was also interesting to see how long my blood sugar remained elevated post exercise bout. I was able to combine the information with the food that I was eating, in order to better my sleep quality for the night! I could time my meals so that my blood sugar was at a more normal level before going to bed so that I would not only improve my sleep, but also how I felt in the morning.