• Continuous glucose monitors overestimated blood sugar levels in non-diabetic people in a small study.
• More health-conscious people are wearing the devices that were FDA-approved for over-the-counter sale last year.
• While useful for diabetics, most people who can regulate their blood sugar don't need CGMs, experts said.

Continuous glucose monitors overestimated the blood sugar levels of non-diabetic people in a small study, calling into question how useful the buzzy devices are for the average person.

Researchers from the University of Bath, UK, compared the results of one brand of CGM with the gold-standard finger prick test when measuring the blood glucose levels of 15 non-diabetic people.

CGM patches provide data on blood sugar with a delay of up to 20 minutes using a sensor placed under the skin with a small needle. Because of the way they collect blood from users, the researchers hypothesized that they may give different results to finger-prick tests.

They found that the CGMs consistently overestimated blood sugar levels by 30% after the participants consumed fruits in various forms: including whole, blended, and smoothies by a brand available in UK grocery stores. The results were published in The American Journal of Clinical Nutrition on Wednesday.

The authors said the smoothie company Innocent Drinks funded the study but had no other involvement.

CGMs were designed for diabetics. But in recent years they have grown in popularity among health-conscious people interested in how different foods affect their blood sugar levels, in the hope of preventing chronic diseases and maintaining a healthy weight.

Last March, the US Food and Drug Administration changed their approval of CGMs from prescription-only to over-the-counter, meaning anyone could buy one.

Javier Gonzalez, a professor of nutrition and metabolism at the University of Bath and the study's lead researcher, said that CGMs are "fantastic tools" for people with diabetes.

"However, for someone with good glucose control, they can be misleading based on their current performance," Gonzalez said. "For healthy individuals, relying on CGMs could lead to unnecessary food restrictions or poor dietary choices."

The authors acknowledged that the study was limited because they tested one brand of CGM, and the relatively small number of participants meant the results might not be relevant to the wider population.

Non-diabetics should take blood sugar readings with a pinch of salt

Experts not involved in the study agreed that CGMs may be causing unnecessary worry in non-diabetics.

Nicola Guess, an academic dietitian and researcher at the University of Oxford who specializes in the dietary prevention and management of type 2 diabetes, said the study suggests that CGMs may wrongly lead non-diabetic people to believe they have pre-diabetes.

This is not the first study to flag inaccuracies with CGMs, so non-diabetic people should take the data they provide with a pinch of salt — or not use them at all, Guess said.

Responding to the study, Adam Collins, an associate professor of nutrition at the University of Surrey, UK, referenced his own ongoing research, which found that two CGMs worn on different arms of the same person logged different data.

Guess previously explained to BI why, if you don't have diabetes or pre-diabetes, blood sugar fluctuations are nothing to worry about.

"When we're considering CGMs in healthy people, it is perfectly normal for your blood glucose to go up and down. It shouldn't be flat, so don't aim for flat. And I think that will help a lot of people relax," Guess said.

There's no evidence to suggest that a blood sugar rise is always followed by a stark drop or causes hunger either, she said.

Charles Brenner, a biochemist who chairs the Department of Diabetes and Cancer Metabolism at City of Hope in Los Angeles, told BI that data from CGMs can cause people to be more alarmed than they need to be.

However, CGMs may have some uses for non-diabetics. BI's Gabby Landsverk previously spoke to an endurance athlete who used one, with the help of a sports dietitian, to learn that she had more energy if she ate more food, including complex carbs, and ate earlier in the day.

And a woman who was pre-diabetic told Landsverk tracking blood sugar levels helped her understand the foods that best suited her lifestyle, helping her to lose weight.

• Jonathan Wolf was a tech exec who ate a lot of ultra-processed foods before cofounding a nutrition company.
• Wolf improved his diet by making small changes over a few years.
• They include eating fewer UPFs and switching from milk to dark chocolate.

When Jonathan Wolf co-founded the nutrition company ZOE eight years ago, his diet was "not great." He was eating lots of ultra-processed food and tons of sugar, he told Business Insider.

But he began making incremental changes to his diet in 2017, after he met ZOE co-founder Tim Spector, an epidemiologist who studies nutrition and gut health at Kings College London.

Wolf was previously the chief product officer at an advertising tech company. Spector made him aware of how he could improve his diet, including by caring for his gut microbiome, or the microorganisms that live in the gastrointestinal tract. Evidence suggests that a diverse gut microbiome, partly achieved by eating fibrous and fermented foods, is linked to better physical and mental health.

Here are the positive steps Wolf took.

1) Eating fewer ultra-processed foods

In the last 18 months, Wolf has become more aware of and reluctant to eat ultra-processed foods, he said. UPFs are made using industrial processes, and can contain additives such as preservatives and emulsifiers. They were linked to 32 health problems in a recent study, but the authors said further research is needed to confirm there is a link between UPFs and poor health.

Wolf tries to eat fewer UPFs, including by avoiding artificial sweeteners or foods at restaurants that are likely to be ultra-processed.

"We're eating these foods that are made with ingredients that have never been available in the kitchen, that our bodies have never been exposed to before. Whereas our grandparents were eating zero ultra-processed foods," he said. "I suspect it's going to turn out to be a huge part of the health crisis that we're having."

It can be hard to cut out UPFs entirely because they are ubiquitous, particularly in Western countries. Nichola Ludlam-Raine, a dietitian, previously told BI how they can be incorporated into a healthy diet.

2) Shifting focus from excluding to adding foods to his diet

Wolf had stopped eating foods that he was led to believe weren't healthy, such as gluten.

But research on the gut microbiome published in 2021, which ZOE was involved with, showed that a more diverse gut microbiome was associated with better markers of health, including lower blood pressure and a lower chance of having a fatty liver.

Participants who ate a variety of healthy, plant-based foods had more diverse gut microbiomes, the study found.

Wolf realized he needed to eat more whole foods to increase the diversity of his diet and, therefore, his gut microbiome.

3) Working up to eating 30 plants a week

Spector was part of a 2018 American Gut Project study into how many types of dietary fiber, found in plants, are needed for a diverse microbiome. Fruits and vegetables were factored in, as well as other plant-based items such as spices.

It concluded that 30 plants a week appeared to provide enough, which Wolf tries to aim for.

"I did not get there in one step. In fact, it took me years to increase to 30. But I did it steadily, and I think the biggest thing that helped was the realization that tinned food and frozen food can actually be really healthy," he said.

He tries to keep nutritious foods on hand, such as frozen spinach, canned beans, and nuts, so he can easily throw together a meal that contains at least a few plants.

4) Gradually switching from milk to dark chocolate

Wolf was pleased to discover that he could still eat chocolate every day as part of a healthy diet.

"If you're eating a really high-quality dark chocolate, there's a lot of science that says that's actually good for you," he said, partly because it counts as one of your 30 plants a week, contains fiber, and is fermented.

He slowly transitioned from eating milk chocolate, to 50% cocoa, to 60%, and all the way up to 90%. Dark chocolate contains antioxidants, fiber, and polyphenols.

5) Eating fewer foods that spike his blood sugar

Wolf cut down on foods that spiked his blood sugar particularly high, specifically white bread and tea with lots of sugar.

Blood sugar spikes are a safe and necessary part of digesting food. But having consistently high or low blood sugar can lead to a higher risk of chronic diseases, Sarah Berry, professor of nutritional sciences at King's College London, previously told BI.

Wolf replaced white bread with rye bread because it didn't spike his blood sugar as high, and gradually reduced the amount of sugar in his tea.

ZOE sells continuous glucose monitors, which were originally developed for people with diabetes to track their blood sugar levels. However, experts are split on whether they are useful for non-diabetics, and fear they may lead to people avoiding certain foods unnecessarily.

• Maya Ramirez, 31, has been attending diabetes camp all her life.
• In 2023, she attended a diabetes camp for adults for the first time.
• Adult diabetes camp gave her community and helped her process the grief of losing her mom.

This as-told-to essay is based on a conversation with Maya Ramirez. It has been edited for length and clarity.

I was born with a condition called congenital hyperinsulinism, which essentially means your pancreas releases insulin to an excessive level. The condition led to the removal of my pancreas at eight months old, resulting in me developing pancreatogenic, or type 3c, diabetes, which is a type of diabetes that happens after your pancreas is compromised or removed.

Diabetes camp as a kid helped me find community

My oldest brother has type 2 diabetes now, but growing up, I didn't have any friends or family with the condition. I didn't have a community and wanted to know other kids who could relate to what I was going through. Things changed for the better at 10 years old when I received my first insulin pump.

The medical device made me feel confident enough to go to sleep-away diabetes camp because it allowed me to better manage my diabetes without my parents' help. Diabetes camp is just like a traditional summer camp for children, but with a medical staff and camp attendees who are living with diabetes — often type 1.

I met several kids my age who were also living with diabetes and built friendships. From that point on, I went to diabetes camp every summer, and sometimes, if my parents would allow it, I would attend multiple camps each summer. One July, I hopped off one bus, went home to do laundry, and then hopped on another bus to attend another camp.

Eventually, I went from camp attendee to counselor. When I was around 16, I became a camp counselor in training, and then at 18, I became a counselor. I took two years off from working at diabetes camps in college, but now I'm working in an administrative role for a nonprofit based in California that supports families impacted by type 1 diabetes with community-building events and camps.

I went to an adult diabetes camp for the first time last year

Even though I'd been to many camps growing up, I attended an adult diabetes camp for the first time at the age of 30 in August 2023 through the nonprofit I work for. When we arrived, they gave us a schedule of activities to choose from. There were educational sessions led by medical staff, nurses, and even therapists.

One of the educational sessions focused on navigating pregnancy with diabetes. We learned about blood sugar management when pregnant, what type of doctor visits we should have, and where to find a support group. I'm at the stage where I may have kids soon, so the session was very informative.

People of all ages were in attendance. You have to be at least 18, but I saw a woman in her 70s when I went. The camp is way up in the mountains in California, and there's no cell service. But we had all the activities you think of when you think of camp — pool time, archery, arts and crafts, and hiking. One night, we had a traditional campfire with skits, songs, and s'mores, which was one of my highlights.

We all slept on giant outside decks. Each deck had a cot with a mattress, and we could sleep under the stars. August in California is typically super hot, so we were pretty toasty. There's something so peaceful and tranquil about sleeping under the stars with the sound of nature in the background. Even though we were in the woods, we had fully functioning restrooms and showers.

A lot of people living with diabetes sometimes feel restricted in what they can eat because some doctors and society, in general, have created a bad stigma about the relationship between diabetics and food. The message is, "Oh, you can't eat this because you have diabetes." At camp, it was instilled in us that we can still eat what we enjoy. We just have to figure out the carb count and administer a proper amount of insulin based on what our body needs. Luckily, the kitchen staff at the camp had a full carb breakdown on all the foods and measurements, so we didn't have to guess.

I processed my mom's death during camp

I lost my mom back in 2018, and when I think about my diabetes journey, I think about my mom. From day one, my mom pushed me to be independent and said, "Hey, it's just something you'll live with. You're not different; you're not weird." She didn't want diabetes to stop me from doing anything I wanted. When she died, I felt lost in life. She was my person.

During one of our adult camp discussion sessions facilitated by a therapist, I opened up about how her death impacted me and the worries I had about navigating diabetes without the person I had talked to most about the condition for my entire life.

The camp discussion finally allowed me to let out all of the feelings I had been navigating for years after losing my mom but hadn't processed out loud. Because of camp, I was able to process my grief around people who not only understood navigating a serious medical condition, but some also understood navigating a serious medical condition while simultaneously grieving a parent.