One of the big new trends in wellness is people using continuous glucose monitors (or CGMs) as a tool for weight loss, athletic performance, or general health optimization (aka bio-hacking).
These devices, which provide a continuous, real-time read on your glucose levels, were originally developed to help people with diabetes manage their blood sugar. And in fact, this is still the only purpose for which these medical devices have been approved by the FDA.
CGMs still require a prescription in the US, but doctors have the discretion to prescribe drugs and devices “off-label,” for uses other than their FDA-approved ones. Companies that are marketing these devices to the general public generally have an “affiliated MD” to supply the necessary prescription.
How do CGMs work?
To use them, you insert a short filament that’s not much wider than a human hair just under the skin (usually on the arm or torso). This sensor transmits glucose readings to a reader or app on your phone. The sensors themselves usually need to be replaced every two weeks.
I recently sat down with Dr. B. Gabriel Smolarz, a board-certified endocrinologist and specialist in obesity medicine, to chat about CGMs and how they are currently being marketed and used. You may remember Dr. Smolarz from my episode on why weight loss is more difficult for some people than others and how pharmaceutical weight loss drugs can play an important role in their treatment. (Dr. Smolarz also serves as a Senior Medical Director for Novo Nordisk, a company that produces drugs to treat diabetes and obesity.)
In Dr. Smolarz’ practice, CGMs are used almost exclusively by patients who need insulin to manage their blood sugar. For example, your blood sugar level before a meal helps determine how much insulin to administer. A CGM spares patients from having to prick their finger six or more times per day to test their blood sugar. But it’s more than just convenience.
CGMs also help the doctor see patterns and trends throughout the day, at times when a patient would not normally be checking with a fingerstick. For example, are blood glucose levels consistently high after dinner? If so, the mealtime dose of insulin at dinner might need to be increased. Are they dipping too low over night? If so, the amount of long-acting insulin taken in the evening might need to be decreased.
Hacking your blood sugar with CGMs
CGMs are definitely making life a bit easier for people with diabetes and their doctors. But now, a lot of people without diabetes have gotten interested in this technology. After all, for a couple of decades now, we’ve all been absorbing the general message that high blood sugar is bad and that keeping blood sugar low is good. Wearing a CGM would seem to be a great way to put that advice into practice.
For example, someone I work with in the Weighless Program recently started wearing a CGM, mainly out of curiosity. But it seemed to be raising more questions than it answered.
And that is the real problem with the use of CGMs as a tool for optimizing wellness or weight loss. Sure, you get a lot of interesting information. But how do you interpret it? We’ve been told that we need to keep our blood sugar “low” or “steady,” but what exactly does that mean?
- A fasting glucose below 100 mg/dL means that you are not at risk of diabetes. But is a fasting glucose of 90 any better than 95?
- Is a post-meal rise that peaks at 140 worse than one that peaks at 120?
- Is reaching your post-meal blood sugar peak 30 minutes after eating better or worse than reaching that peak after 60 minutes?
- Is returning to pre-meal levels within 90 minutes better or worse than 120 minutes? Does that mean your pancreas is working extra well or that your lunch was too small to get you through the afternoon?
More to the point: If all of these are within the “healthy” range, are there any demonstrable benefits to improving on success? Will it lower inflammation? Does it reduce long-term disease risk? Can it help with weight loss?
As Dr. Smolarz points out, we don’t yet have robust data to show that people have anything to gain from modulating what are considered to be healthy blood sugar levels.
Research may one day provide answers to some of these questions. Until then, though, any advice coming from companies or coaches who are pitching this tool to people without diabetes is, by definition, speculative.
Can CGMs help you improve your diet or health?
For most people, a CGM probably isn’t going to reveal anything that you don’t already know: Refined carbohydrates raise blood sugar more than complex carbohydrates. A big meal will raise your blood sugar more than a small one. Fat, protein, and fiber all tend to reduce the speed at which blood sugar rises and falls.
Sure, you could keep careful notes about how the information you see in your CGM reader corresponds to things like your energy levels or appetite. But you could probably get similar insights simply by keeping careful notes about how various foods and meals affect your energy or appetite.
That said, seeing those responses in real time and having the concrete evidence of how your choices are impacting you could motivate you to change your behavior in way that simply knowing what you should be doing doesn’t. But this motivation doesn’t come cheap.
Non-prescription use of CGMs will cost you $200 – $400/month. And, as my client discovered, it may end up raising more questions than it answers. Some observers have also expressed what I think are valid concerns that the non-medical use of CGMs could even trigger disordered eating behavior in those who are susceptible.
It’s also worth nothing that things other than food affect your blood sugar, including stress, sleep, heat, and exercise. Although a CGM may allow you to observe the impact of these factors, it may be challenging to know how to use that information—because there are so few established benchmarks for people without diabetes regarding what is good, better, or best in those various situations.
But let’s say you’re just curious about your unique blood sugar response. Perhaps you suspect that you are one of those people with idiosyncratic blood sugar responses that aren’t correctly by predicted by the usual dietary advice. Or you want to see if your blood sugar curve during exercise correlates to your performance or recovery. Or, maybe you feel that being able to see the effects of the choices you are making in real time would motivate you to make healthier choices. If you’re willing to spend quite a bit for that information and motivation, CGMs are an option that will probably only become more widespread.
If you do go that route, however, try to keep the information—and any advice you may be getting—in perspective. For people with diabetes, keeping blood sugar within well-established parameters can vastly improve health and longevity. But for those who do not have diabetes or pre-diabetes, there’s no evidence (yet) of a “healthier” version of a “healthy” blood sugar response.
There is plenty of evidence, however, that a good diet—one that includes more vegetables and other whole foods, fewer added sugars, refined carbohydrates, and highly processed foods and that helps you maintain a healthy body weight—will improve your health. No sensor required!