Continuous Glucose Monitors as a Tool for Weight Loss: Separating Hype from Reality
Wearable glucose monitors, otherwise known as Continuous Glucose Monitors (CGMs), have been around for over a decade as a diabetes management tool. Recently, these devices have also become popular among metabolically normal, non-diabetic individuals as a weight loss tool. Many diet service providers market CGMs as a wearable that can help manage blood sugar levels, reduce cravings, promote healthy eating habits, and encourage physical activity. As a clinical researcher who developed clinical trials for CGMs during my time at Verily (Google’s former life science division), I can say that these devices excel at tracking blood sugar levels. However, their direct usefulness in helping one shed pounds is a bit more complicated than advertised.
A CGM’s primary function is to help the user manage blood sugar levels. By tracking blood glucose levels in real-time, individuals can see how their blood sugar responds to different foods and activities. Changes in blood sugar levels in response to a given food can differ across individuals. For example, some individuals may have a genetic predisposition to insulin resistance, which can result in some types of bread causing larger blood sugar increases in one individual more than in another. On the other hand, individuals who are physically active may be able to process glucose more efficiently, resulting in lower blood sugar levels after eating the same food. Using the CGM, the user can identify how specific foods and activities affect blood sugar and make more informed choices to manage their blood sugar levels more effectively.
While this information is certainly helpful, CGM-based diet companies often exaggerate the benefits of using a CGM for weight loss. They will claim that personalized nutrition information allows for better-tailored advice on diet and lifestyle changes to optimize blood sugar control and promote overall health. They also state that using a CGM increases diet compliance by reducing cravings. When blood sugar levels are unstable, people may experience cravings for sugary or high-carbohydrate foods. By using a CGM to stabilize blood sugar levels, one may be less likely to experience cravings and more likely to stick to their diet plan. While this claim may be true for some individuals, it is important to note that both cravings and diet noncompliance are more often caused by psychological or social reasons, such as stress eating or dining with friends at a restaurant and a CGM does not address these issues. In fact, research has shown that the main reasons for non-adherence to a diet are low self-control, lack of information, the tendency to eat out, and inaccessibility to healthy food. In other words, sticking to a diet has little to do with blood sugar levels for most people.
While using a CGM can encourage a basic understanding of nutrition, it cannot compensate for a lack of knowledge. For those who lack proper education on nutrition, they may not understand how caloric, fatty, or deficient in nutrients certain foods can be even if these foods do not cause a blood sugar spike. This could still lead to the overconsumption of calories and eventually weight gain. The main purpose of a CGM is to aid individuals in understanding how their blood sugar responds to different foods; it does not teach someone basic nutrition or define what constitutes a healthy diet — both of which are arguably more critical for overall health and weight loss than merely avoiding blood sugar spikes. In fact, eating a healthy, balanced diet alone can lead to weight loss even without tracking blood sugar levels.
Also, keep in mind that a CGM can only provide insight into one’s blood sugar levels, it can’t measure calorie intake. Even when blood sugar levels are reasonable and stable, consuming more calories than the body burns will still result in weight gain. A high calorie meal that has no carbs but is both high in fat and protein may register little to no blood sugar increase on an CGM, which might give the user a false sense of confidence that they haven’t eaten that much.
It is important to understand that while a CGM is a powerful tool for managing blood sugar levels, it is not a magic bullet for weight loss. Managing blood sugar undeniably plays an important role in sustaining good health and can indeed assist in weight management. However, for most people, its direct impact on weight loss might not be as significant as addressing emotional overeating triggers and mastering the core principles of healthy nutrition. For equivalent or even lower costs per month, consulting a nutritionist would provide better benefits, as they could teach one proper nutrition and how to handle overeating triggers.
