Amy Stephens
MS, RDN, CSSD, CDCES
Licensed dietitian
specializing in sports nutrition
and eating disorders
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Should Athletes Use a CGM? A Look at the Benefits and Drawbacks
- By Amy Stephens RDN CSSD, Sports Dietitian
A Continuous Glucose Monitor (CGM) is a medical device designed to deliver real-time measurements of glucose (sugar) levels in the body. Although it is mainly utilized by individuals with diabetes to regulate their blood sugar, it has also become increasingly popular among athletes and health enthusiasts. While these devices offer a wealth of data, it’s crucial to consider how that information will be applied effectively. Here’s how it works and its main components:
How CGM Works
- Sensor Insertion: A small sensor is inserted under the skin, typically on the abdomen or the back of the arm. This sensor measures glucose levels in the interstitial fluid (the fluid between cells) rather than directly in the blood.
- Continuous Monitoring: The sensor continuously measures glucose levels, usually every few minutes, providing a real-time view of fluctuations throughout the day and night.
- Data Transmission: The sensor sends glucose data to a receiver or a smartphone app via Bluetooth or other wireless technologies. This allows users to see their glucose levels in real-time, track trends, and receive alerts for high or low levels.
- Calibration: Some CGMs require periodic calibration with a fingerstick blood glucose meter, while others do not, depending on the model.
Components of a CGM System
- Sensor: The small device that is placed under the skin to measure glucose levels.
- Transmitter: A component that attaches to the sensor and sends the glucose data wirelessly to a display device.
- Display Device: This could be a standalone monitor, a smartphone, or a smartwatch that receives the data and displays glucose readings.
Benefits of Using a CGM
- Real-Time Data: Provides continuous monitoring, allowing users to respond quickly to fluctuations in glucose levels.
- Trend Analysis: Helps identify patterns in glucose levels in response to food, exercise, stress, and other factors.
Popular CGM Brands
Some well-known CGM systems include:
- Dexcom: Offers a range of CGM products with various features, including a mobile app for tracking.
- Freestyle Libre: Known for its simple sensor application and a focus on ease of use.
- Medtronic: Provides integrated systems that often work in conjunction with insulin pumps.
Using a Continuous Glucose Monitor (CGM) can be beneficial for athletes, especially those involved in endurance sports or those with specific dietary and training goals. Here are some key considerations for athletes thinking about using a CGM:
Potential Benefits of Using a CGM for Athletes:
- Real-time Glucose Monitoring: CGMs provide continuous, real-time glucose data, helping athletes understand how their blood sugar levels fluctuate throughout training and competition.
- Optimizing Nutrition: By tracking glucose levels, athletes can fine-tune their nutrition strategies to enhance performance, avoid crashes, and ensure they’re fueling adequately before, during, and after workouts.
- Identifying Patterns: Athletes can identify how different foods, hydration levels, and exercise intensities affect their glucose levels, allowing for personalized dietary adjustments.
- Avoiding Hypoglycemia: For athletes, especially those in sports with high energy demands, monitoring glucose levels can help prevent hypoglycemic episodes, which can impair performance.
- Recovery Monitoring: After intense workouts, monitoring glucose levels can provide insights into recovery and metabolic response, helping athletes optimize their post-workout nutrition.
- Managing Stress Responses: CGMs can help athletes understand how stress (from training, competition, or other life factors) affects their glucose levels, allowing for better stress management techniques.
Considerations and Potential Drawbacks:
- Cost: CGMs can be expensive, and not all insurance plans cover them, making them a financial consideration for many athletes. Dexcom (Supersapien) may cost $300-400 for the device and $150-200 for the subscription. Freestyle libre (Lingo) costs about $75 per sensor, each one lasting up to 14 days. Additional costs include: $150 per month, plus a one time $60 fee for the reader.
- Learning Curve: Athletes may need time to learn how to interpret CGM data effectively and integrate it into their training and nutrition regimens.
- Over-reliance: There’s a risk of becoming overly focused on glucose levels, which might lead to anxiety or second-guessing nutrition and training decisions.
- Not for Everyone: While CGMs can provide valuable information, they may not be necessary for all athletes, especially those who do not have blood sugar management issues.
- Lag time: CGMs placed on the arm (Freestyle Libre) measures glucose in interstitial fluid, which can be delayed compared to blood glucose, especially during rapid changes (like after eating or during exercise). This lag is generally about 5-10 minutes, so the device might not immediately capture sudden spikes or drops.
- Factors Affecting Accuracy: Certain factors, like dehydration, sensor placement, compression (from lying on it or tight clothing), and high temperatures can reduce accuracy. Users also tend to get better readings when it’s kept at a consistent temperature.
- Stress affects blood sugar readings: Other factors that can lead to fluctuations in blood sugar, apart from food, include stress hormones like cortisol and adrenaline. These hormones may rise during periods of illness, physical or mental stress, medication use (such as steroids), menstrual cycles, or hormonal imbalances. Analyzing CGM data can make it challenging to differentiate between fueling and the body’s normal response to stress.
Conclusion:
Ultimately, the decision to use a CGM should be based on individual goals, health conditions, and the nature of the sport. Athletes interested in using a CGM should consider consulting with a sports nutritionist or a healthcare professional to tailor the use of glucose monitoring to their specific needs and training goals.