Should I track my blood glucose levels with a continuous glucose monitor? : NPR

The device itself is small, but the hype around it is huge.

While continuous glucose monitors are only a quarter of the size, the companies that sell them make a big claim to their health benefits. It can “revolutionize health.”

A candidate for President Trump's surgeon general, Dr. Casey is a prominent supporter of ongoing glucose monitoring. She co-founded a company that distributed devices and sold apps to help people use them.

The monitor is a painless patch that inserts the needle into the skin. Every few minutes, it sends a signal to your phone app with a blood sugar estimate. (It measures sugar concentration between your skin cells. This is roughly correlated with your blood sugar level.) This app helps you maintain logs of everything you eat.

Research shows that this technology is changing the care of people with diabetes. “It revolutionized the lives of them and their families,” says Elizabeth Selvin, a researcher of diabetes at Johns Hopkins University.

However, in March 2024, the Food and Drug Administration approved the first serial glucose monitor for people without diabetes. Currently, two companies are creating them: Dexcom and Abbott. Each patch lasts about two weeks and costs around $50, so long-term blood sugar tracking costs around $100 a month.

The key question is, do they actually help people who have no diabetes or prediabetes improve their health?

theory

After eating a carbohydrate-containing diet, blood sugar levels in healthy people rise and peak, and return to baseline gently.

“These peaks and troughs are the usual physiological responses to carbohydrate consumption in people without diabetes,” says Sarabury, a nutritionist who is a professor of nutrition at King's College London. Berry is also the chief scientist at Zoe, who distributes continuous glucose monitors (CGMs) and data interpretation apps. “You don't need to flatten these curves,” she says.

But if these peaks become too frequent and too high, Berry says, it can cause problems. This can increase your risk of obesity, cancer, cardiovascular disease, and type 2 diabetes. Also, Berry says they can starve between meals, so they'll eat more on their next meal.

The idea behind glucose monitoring is that it helps identify specific meals and meal sizes that produce extreme peaks. After that, if you change your diet, that shift can help you lose weight, reduce your risk of diabetes, or simply feel better.

Survey results

Two major studies tested this theory in randomized controlled trials. In this study, people wore glucose monitoring patches for a period of time while tracking what they eat on the app. The researchers used the data to design an individualized diet aimed at lowering blood sugar levels. Scientists then tested how much this CGM-based diet stacked up on a standard low-fat or Mediterranean diet.

At the population level, the findings are mixed. In one study at the Wiseman Institute of Science, CGM-based diets did not help people lose weight more than simply following a Mediterranean diet. However, it helped them lower their blood sugar levels further, scientists reported in the Journal Diabetes Care.

In the second study, we compared CGM-based diets to low-fat, high-grain diets. Researchers at New York University found that on average, both diets resulted in the same amount of weight loss and slight improvements in blood sugar levels. However, Colin Pop, who led the study, said the overall findings did not tell the entire story. These conclusions only show average responses across the population, says POPP.

“If you look at the individual levels, it's very different,” he says. For some people, the glucose monitoring approach has been extremely helpful. Some people lost a lot of weight. “We came back and said, 'You changed my life. I've lost 30 pounds and I feel good.' Others in the study gained weight. ”

So scientists are trying to figure out who will benefit from this technology.

If glucose monitors are useful

1. If you are very sensitive to carbohydrates

Nutritionist Karen Kennedy has been helping people interpret and understand their glucose monitoring data for five years. In her experience, these devices can help you discover increased sensitivity to carbohydrates.

“They eat brown rice, quinoa, beans, rice, or oatmeal, and their blood sugar levels are consistently very high,” she says.

This monitor will help you realize that a low-carb diet helps you better manage your blood sugar levels. “There's not zero carbohydrates, it's low carbohydrates,” Kennedy says.

“They change their diet and then their blood sugar drops dramatically,” says Kennedy. “If they can maintain that new diet, they will feel better and lose visceral fat.”

2. If you need more motivation to eat healthy foods

Many people already know what they need to do to improve their metabolic health. But put this advice into practice – that's difficult, both Kennedy and NYU POPP say.

Rapid feedback from a continuous glucose monitor can give you a nudge to actually implement nutritional advice. “It's motivation,” Pop says.

For example, one of Kennedy's clients is clearly required to add protein and fat to their breakfast.

“They said, 'Sorry, but this is my breakfast and have been working for me for 30 years.”

The client then wore patches for a week and saw how that breakfast shot very high blood sugar. They quickly changed breakfast, says Kennedy. Soon, the client was able to see how this new breakfast improved blood sugar levels.

“They didn't have to wait a few months and go to the doctor to see it work,” she says. “The agency can motivate you.”

3. If you need more awareness about food

A study at NYU found that some people benefited from a CGM-based diet. When Popp and his colleagues delved deep into the data, they found one of the key elements of this success. It's whether the person consistently logged their meals to the device's app in a six-month experiment.

For some people, simply documenting what they eat can help them improve their diet and their blood sugar levels, says Popp. “I always say to people, 'Looking at what you're doing can play a big role in your health.'

“And you don't need to accurately record your food,” he adds. “What's important for most people is simply the act of documenting it.”

“We know that awareness helps people lose weight,” adds Johns Hopkins' Selvin. “And it doesn't have to be in the app. I have a colleague who uses a small pocket notepad. It adds accountability” – it's cheaper than glucose monitoring.

Before purchasing a device, experts say take caution.

Many people find the data confusing and useless.

“A lot of people came to me and said, 'I've been using the device for three or 12 months and have all of this data, but I don't know what it means. I don't know how to lower or improve my blood sugar,” says Kennedy.

POPP means people need to be truly educated about what data means. But this education is still mystical to scientists and doctors at this point, so far, so far, that education has been.

If you are staying within normal range, for example from about 70 mg/dL to 140 mg/dL, scientists still don't understand the meaning of peaks and troughs.

“There are no real standard guidelines for good or bad peaks in non-diabetic patients,” says Popp.

Data can be misleading.

First, the devices are not very accurate or accurate, and our bodies don't always respond in the same way to the same food. One recent study in the American Journal of Clinical Nutrition found that the same diet gave very different measurements on two different days. Another small study in the same journal found that serial glucose monitors overestimate people's blood glucose levels compared to direct measurements of blood glucose.

Second, the data can make people worried about eating healthy foods that cause normal blood glucose variability. Popp, for example, has a friend who has begun to worry about blueberries as his blood sugar levels have risen slightly before he declines.

“I don't want to make food tags 'unhealthy'. That's what led to what I perceived as a tiny blood sugar spike. ”

Third, some people can have what looks like normal blood sugar levels, but they still have insulin resistance, explains Kennedy. In this case, their bodies compensate by overproducing insulin. To understand this, you need to see your doctor and check your insulin levels.

“Continuous glucose is a useful metric,” she says. “But it's one metric and you need to use it in the context of lab outcomes and other signs and symptoms.”

Edited by Jane Greenhulg