Monitoring blood sugar levels used to be something only people with diabetes did. But in recent years, glucose has become one of the trendiest biometrics to track for people striving to optimise their health. That’s in large part because of the increasing accessibility of a tool called a continuous glucose monitor, or CGM.

CGMs monitor levels of glucose — the body’s main source of energy — in real time. A tiny needle-like sensor sticks into the skin and reads glucose levels in the fluid between cells. That information is sent to a smartphone, where people can monitor it throughout the day.

The devices were originally developed more than 20 years ago for people with diabetes who rely on insulin shots. Now, there are at least five companies that market and sell apps and CGMs to people without diabetes, claiming that knowing about your glucose levels can help you lose weight and improve your health.

Abbott and Dexcom, the two largest manufacturers of CGMs, are also starting to target nondiabetic users.

Endocrinologists say that CGMs are indispensable for people with diabetes who need to know when and how much insulin to give themselves. They can also be useful for guiding diet and lifestyle changes for people who have, or are at risk of developing, type 2 diabetes — that includes adults over 45, those with a family history of the condition or people whose body mass index classifies them as overweight.

Here are three common claims about the advantages of tracking glucose for nondiabetics — and what the research shows so far.

Aiding weight loss

Brands that sell CGMs frequently say that the devices help with weight loss. Research is underway to test whether this is in fact the case. One company that sells CGMs states that nondiabetic users lost a modest amount of weight (four pounds over 12 weeks), but that’s consistent with many dietary interventions, Dr Sun Kim, an endocrinologist at Stanford University in the UK, said. When she compared CGMs with nutrition counselling in a small preliminary trial, she saw no difference in weight loss.

In theory, avoiding glucose spikes could help with weight loss more than tracking calories alone. When food is digested, glucose is released into the blood stream. That prompts the pancreas to secrete insulin, which helps cells take up the glucose and use it for energy. Excess glucose gets converted to fat, so when more glucose is released during a meal, more of it might get stored as fat.

“This is one of the main mechanisms by which we store fat in our cells and by which we gain weight,” said Eran Segal, a computational biologist at the Weizmann Institute of Science in Israel.

Segal, who is an author of a diet book based on this theory, said the devices provide people with personalised information on how to avoid glucose spikes and lead to greater weight loss than general nutrition counselling. Foods can have varying effects on different people’s glucose levels, so without a CGM, you’re less likely to know just which foods in which meals cause your glucose to spike.

Protecting the heart

Another claim is that swings in glucose levels in people without diabetes could be harmful to heart health, so using CGMs to identify (and then prevent) spikes could result in a cardiovascular benefit.

“But we don’t have any studies that necessarily show us that that’s correct,” said Jennifer Sherr, a paediatric endocrinologist at Yale School of Medicine in the US.

For people with diabetes, persistently high blood sugar and large surges in glucose are known to cause worse long-term outcomes, including heart disease and stroke.

Research has shown that, among nondiabetics, higher glucose levels are also linked to an increased risk of cardiovascular disease. But the studies show a correlation, not a clear causal effect, said Dr Robert Gabbay, chief scientific and medical officer of the American Diabetes Association. It’s not clear whether lowering glucose scores actually results in better health outcomes. “That’s the piece that’s missing,” he said.

Preventing diabetes

The clearest potential benefit of CGMs is for people who are at risk for diabetes. An estimated one in three American adults have prediabetes — meaning their fasting glucose levels are higher than the recommended level (under 101 milligrams of glucose per deciliter of blood) but below the cutoff for diabetes (126 and above). Yet the vast majority don’t know it. Research suggests people with prediabetes have an increased risk of developing type 2 diabetes in the next five years.

While CGMs are not technically used as a diagnostic tool, elevated resting glucose levels or larger than normal spikes after meals are signs something could be wrong. Users can make behavioural changes to lower their risk of developing diabetes using insights from the CGM about what foods make their blood sugar spike and what behaviours keep it stable.

NYTNS