Adam Van Voorhees used to eat orange chicken three times a week — until a round white patch on his arm told him not to.
Like most 22-year-olds, Van Voorhees didn’t pay much attention to what he ate until the alarm on his continuous glucose monitor went off. It told him his blood sugar spiked into prediabetic range after eating at Panda Express. Now he packs his lunch.
Van Voorhees is not diabetic. But he’s wearing a monitor that’s usually worn by people with Type 1 diabetes for a class he’s taking at UC San Diego.
These monitors were once a prescription-only device, but Mary Boyle, a cognitive science professor at UCSD, was convinced the technology could reshape how ordinary people understand their own bodies.
So, when San Diego’s Dexcom started marketing its over-the-counter monitor, Stelo, to the health-obsessed and weight-conscious, Boyle enlisted her students to help study how CGMs could help influence healthier habits.
CGMs offer a window into how our bodies respond to our environment and choices. In real time, someone can see their blood sugar spike after eating a candy bar, and settle after taking a five-minute walk.
The idea is that seeing your body’s response to your choices will lead people to make healthier ones.
This device has proven to be highly effective for diabetics. But the stakes — lost limbs and shortened lives — make behavior change a matter of survival.
Now Boyle’s class, Metabolic Health Analytics, is collecting pilot data for a potential clinical study to see if that logic carries over to healthy individuals, “and the results were pretty surprising,” she said.
Intuitively, most of the data makes sense — “Panda Express isn’t good for you,” she laughed.
But many people are surprised by what their unhealthy decisions actually look like. “A brain affected by Type 2 diabetes is almost indistinguishable from one with Alzheimer’s,” said Boyle. When brain cells become resistant to insulin, they can no longer absorb glucose properly. “The neurons are starving and portions of the brain begin to die.”
And it’s not just food that has deleterious effects on your metabolism and mind.
Sleep, exercise and stress all impact the body and therefore the brain.
Researchers have been studying these variables in diabetics for a long time. But as for healthy individuals, “there’s no research yet,” said Dr. Robert Thomas, an academic endocrinologist and clinical investigator at UC San Diego. “It’s worth studying.”
Each student was given three monitors to test a personal hypothesis — an approach scientists call an N-of-1 experiment. While conventional studies pool large populations to answer a single question, this personalized study was the whole point.
A recent class began with one student unboxing a small plastic Stelo disk. She peeled back the cap to reveal a small silver needle and pushed it into the soft flesh of her upper arm.
In less than a minute, her phone synced to the device and illuminated a line chart that would measure her blood sugar for 14 days. Two Stelo monitors retail for $99, but students didn’t have to pay for the devices because Boyle had a grant from Dexcom.
In front of the class, Boyle called on the students to share their experiences.
Some of the 27 students reported seeing their blood sugar drop in the afternoon. The monitors could see that they were hungry before they felt it.
Being “hangry” isn’t just in your head, some of the students joked, but it’s an actual biological reaction to fuel deprivation.
Student Katie Lam raised her hand.
When Boyle called on her, she started to speak at the pace of her heartbeat — fast.
Lam was measuring how stress impacted her glucose because her anxiety had woken her up at 4 a.m.
That day, she faced a high-stakes exam and an interview; she was stressed and couldn’t sleep. Not only could she feel that fight-or-flight anxiety — she could see her monitor turn red.
“It’s a good reminder to take a deep breath,” she laughed. Lam found that taking steps to relax, whether it be meditation or a five-minute walk, helped her calm down. And when she did, her monitor glowed green.
Boyle then explained how hormones and metabolism go hand-in-hand. For example, even before breakfast, blood sugar surges in the morning because your body emits cortisol — which increases glucose production.
The hormonal impact is another pet project Boyle is working on. Besides college students, she has given monitors to the perimenopausal and postmenopausal women on her rowing team.
Boyle is an evangelist when it comes to blood sugar.
“Understanding this mechanism helps us better understand ourselves,” she said. “Expecting people to change their behavior without seeing what our body is doing is a bit like trying not to go into debt without seeing your bank statement.”
Another student, Jaidy Leyva, ate three chocolate cakes in one day, for the sake of science, of course.
Her brother’s homemade dessert and the cake from Costco didn’t spike her blood sugar, but the Applebee’s triple chocolate meltdown sent her glucose sky high.
“I enjoyed all three cakes the same,” she said. “But my body didn’t like Applebee’s,” she told her classmates.
This is the second year Boyle has conducted this student experiment. Some students fall back into old vices, but many have come back to tell her that they’ve formed healthier habits.
For example, students no longer look at smoothies or late-night snacking the same way, she said, because after seeing the monitor turn red, you are reminded in real time of the inflammation your body is experiencing.
Sometimes these constant reminders of inflammation are stressful, said student Rithika Muttukuru.
“It definitely gives you anxiety. You close the app, and it will sometimes set off alarms. It makes sense for someone with diabetes, if they are hypoglycemic, but to have this alarm going off at like 2 in the morning,” said Muttukuru, “isn’t great.”
Thomas calls this “device burden.”
“Don’t measure something unless you’re going to do something with it,” he said. “I try not to burden people with extra tools and technology without also giving them what are you going to do about it when you get this data.”
Thomas doesn’t believe that people need to wear a monitor all the time, but if they are particularly health-conscious or prediabetic, they could benefit from a once-a-year, monthlong trial.
On the bench outside of Malk Hall, one student was scrolling through her TikTok. Between the blur of dance videos and cats were sponsored posts for supplements, gym routines and knock-off GLP-1s.
“There’s so much advice out there… from doctors, Instagram, everywhere,” said Leyva. But information alone didn’t change her behavior. “What made a difference for me was seeing the CGM show exactly how my choices affect my body… It’s being able to have a relationship with these variables rather than just being told this does that. I can see the effect in real time.”
