For people not in those groups, evidence is thin that knowing how your glucose levels respond to certain foods is advantageous for health, in part because the spikes often aren’t that large.
“I think most people, when they hear about it, it sounds super cool,” said Dr Sun Kim, an endocrinologist at Stanford University. But people who are young and healthy “generally get bored wearing them because nothing’s really changing.”
Here are three common claims about the advantages of tracking glucose for nondiabetics — and what the research shows so far.
Aiding with 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 (1.8kg over 12 weeks), but that’s consistent with many dietary interventions, Kim 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 which meals cause you to spike.
However, other experts, including Michael Bergman, a professor of medicine at New York University Langone Health who researches diabetes prevention, and Kevin Hall, a senior investigator at the National Institute of Diabetes and Digestive and Kidney Diseases, said the idea that avoiding glucose spikes could help with weight loss “is controversial” and “probably not correct.”
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 pediatric endocrinologist at Yale School of Medicine.
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 1 in 3 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.
“It’s really very important to identify individuals at a much earlier point than we do currently, and I think using these devices is one way to approach it,” Bergman said.
In order to improve health, knowing your glucose levels isn’t enough — you have to actually do something about it. Some experts, including Bergman and Gabbay, said real-time feedback about how different meals affect glucose levels can motivate people to alter their diet. Others, such as Kim, said that even with the devices it’s hard to get her patients to change their behaviour.
Worth trying, for some
For people who are young and healthy, there isn’t clear evidence that spikes in glucose (which are much smaller than those experienced by people with diabetes) are detrimental to health. So while some people might be curious to see if manipulating this aspect of their biology changes how they feel, several experts said the potential benefits probably don’t justify the cost.
For people who are at risk for diabetes, which is a substantial portion of the population, the calculation is different. For this group, “I absolutely think that they are worth it,” Sherr said.
This article originally appeared in The New York Times.
Written by: Dana G. Smith
©2023 THE NEW YORK TIMES
