Elite cyclist Tracey Jacobs knew something was wrong when easy training rides started to feel like sprints.
Jacobs, 57, is a former national champion with more than 20 years of training experience, but what were meant to be simple intervals left her bogged down and overwhelmed with fatigue.
“It was frustrating,” she told Business Insider.
As it turned out, the problem was her habit of carb-loading through sugary foods before exercise, which was partly driven by anxiety and partly by the belief that as a lean endurance athlete, she needed a quick source of energy to sustain intense exercise.
The sudden sugar intake backfired, leaving Jacobs feeling heavy at first and then weak. She likened it to putting too much fuel in her car: “You're stuffing your body with food and carbohydrates within an hour, with no time to digest and hydrate,” she said.
Jacobs began monitoring changes in her blood sugar levels with the help of a continuous glucose monitor, an increasingly popular wearable device.
Continuous glucose monitors, or CGMs for short, were approved by the FDA in 1999 to allow people with diabetes to continuously monitor their blood sugar levels. A sensor inserted just under the skin with a tiny needle measures the glucose (sugar) in the fluid surrounding the cells and provides continuous updates.
Until recently, you needed a prescription to get a CGM. The FDA approved it for over-the-counter sale in March. Companies can now sell them without a prescription to anyone, whether that's the 100 million Americans with pre-diabetes or the other 200 million adults who want to stay healthy.
Not surprisingly, the market for CGM has boomed as more people seek personalized solutions to optimize their bodies, and it's predicted to more than double from an estimated value of $6.8 billion in 2023 to $20.2 billion by 2032, according to Global Market Insights.
Jacobs says that the CGM, which a fellow athlete recommended to her, was a game changer: It allowed her to track how her body was responding to food and use that data to perfect her training and performance. It was like tracking your heart rate or knowing your VO2 max, giving you a clearer understanding of your body's inner workings and a sense of control.
Working with a sports nutritionist, Jacobs started eating more complex carbohydrates, eating more, and eating sooner for sustained energy. The fatigue disappeared. “After three hours of riding, I had loads of energy, my muscles were stronger, I didn't tire as quickly, and I could push myself longer and slower,” Jacobs said.
Why is blood sugar important?
Blood glucose level measures the amount of glucose in your blood, which is produced by breaking down the carbohydrates you eat to give you energy.
Keeping blood sugar levels balanced is crucial for diabetics, who can face life-threatening consequences if their blood sugar levels are too low or too high.
But health and wellness companies such as Levels and Nutrisense are increasingly arguing that blood sugar is an important indicator even for people without diabetes, as it's linked to a holistic lifestyle factor, from diet to sleep to exercise.
Through a range of health technology products, these companies aim to give consumers deeper insight into how their daily habits affect their blood sugar levels, helping them analyse patterns and identify behaviours that will help them feel and perform their best.
“Understanding your blood sugar patterns is like getting an MRI of how all the holistic aspects of your daily choices work together to create your metabolic health,” Dr. Casey Means, co-founder of Levels, a health tech company that has an app that syncs with CGMs, told Business Insider.
Controlling your blood sugar levels can also help you address chronic health issues and manage or prevent long-term illnesses.
Gail Pagano, a 56-year-old Florida resident, told Business Insider that she started using CGM through NutriSense after struggling with weight gain and joint pain that she said was nearing pre-diabetes, which her doctor dismissed as a natural side effect of aging.
Gail Pagano said using a CGM has helped her lose weight and reduce her risk of diabetes. Gail Pagano/Courtesy of Nutrisense
“You basically had to get sick to get insurance if you got sick,” Pagano told Business Insider.
After reading about how age-related hormonal changes affect blood sugar levels, she started tracking her own and noticed a pattern: Eating refined carbohydrates like bread caused her blood sugar to spike and made her feel ill. Even seemingly healthy foods like salads seemed to cause problems if they were store-bought.
“It was shocking. Things I thought were safe to eat actually weren't,” she said.
With the help of a nutritionist, she began to make changes: Pagano, who grew up in an Italian household, was resistant to giving up pasta, but she found that simple habits like making her own noodles and eating protein first allowed her to enjoy some carbs.
Since then, she has lost 50 pounds and her fasting blood sugar, fasting insulin and A1c (a measure of average blood sugar levels) have improved dramatically.
Can monitoring your blood sugar levels really prevent disease?
Pagano isn't the only one struggling to access care in the gray area between health status and diagnosis.
Under the typical healthcare paradigm, you may have to wait months or even years for a routine check-up to find a problem. Companies are positioning CGM as a way to shorten that wait time. What if you could proactively manage your health before you got sick?
“Giving people access to their own health data will give them a clearer understanding of where they stand and whether their choices are having the effect they want, rather than having to wait six months or a year for just a sliver of information provided by their doctor,” Means said.
She said it's not a matter of telling people to cut out carbs or start intermittent fasting, it's about giving people the tools to figure out what works for them.
CGMs are great tools that give you a real-time look at the inner workings of your body, accurately reflecting your blood sugar levels at any given moment and showing you how your blood sugar levels change in response to your specific habits.
The problem is, science can't yet explain exactly what those numbers mean, and while CGMs can help people with diabetes avoid dangerous extremes, it's not clear what happens between those upper and lower limits.
This doesn't mean that Pagano and Jacobs are wrong about the benefits, it just means that we're operating in a scientific grey area.
While endurance athletes can use carbohydrates to fuel long training sessions and tough races, cyclist Tracy Jacobs says she eats too much sugar. Photo by Dane Cronin, courtesy of Groove Subaru/Excel Sports Race Team cyclist Tracy Jacobs
“There's no evidence, but just because there's no evidence doesn't mean it's not true,” Dr. David Klonoff, an endocrinologist and medical director at the Diabetes Institute in San Mateo, California, told Business Insider.
For Klonoff, the risk is that people who invest in CGM will get little in return, or simply a kind of placebo effect, as paying more attention to one's habits can encourage healthier behavior.
Clean Eating Can Be Unhealthy
Some experts worry that letting your blood sugar control your diet too much can lead to extreme and unhealthy eating habits, and constant monitoring of your food can lead to orthorexia, a harmful obsession with so-called “clean” eating.
Fruit isn't something to be scared of. Some social media influencers claim that fruit is unhealthy because it spikes blood sugar levels, but experts say that's an oversimplification that doesn't apply to most people. Johner Images/Getty Images
Social influencers with no medical expertise point to spikes in blood sugar levels and warn that healthy foods like fruit and rice can cause brain confusion, weight gain and a range of devastating health problems.
“Eating disorders and poor relationships with food are significant issues, and we believe that CGM use and tracking may make certain people more vulnerable to these issues,” Dr. Jonathan Little, a professor at the University of British Columbia who specializes in metabolism, told Business Insider.
Research does not support concerns that increased blood sugar levels after meals are a cause for concern for healthy people.
“It worries me when people say, 'This is a pre-diabetic blood sugar level,' or, 'I ate this and my blood sugar went to diabetic levels,'” Klonoff said. “There's no evidence to know that it's bad.”
So should you wear a CGM?
Little predicts CGM will become another standard metric collected by everyday electronic devices, alongside data like steps, heart rate and sleep scores.
As people seek more information about the inner workings of their bodies, health wearables can also become status symbols that showcase your health-conscious credibility.
Not everyone is excited about this looming trend: Diabetics worry that those who need the devices won't be able to afford them, and the technology's growing popularity could make it even harder to obtain. But widespread use could also spur innovation, like over-the-counter options, that could make CGMs cheaper for everyone, as some market reports suggest.
Little and other metabolic experts don't think wearable devices can provide any actionable data beyond what we already know.
Do you want a patch on your arm claiming that nutritious carbohydrates like whole grains and fruit are good for you, or that consuming large amounts of highly processed foods can make you sick over time?
“For a typical exerciser or someone trying to optimize their health, I don't think knowing their blood glucose levels at every hour of the day is all that useful,” Little said.
