How to Use a CGM for Fitness: Turn Glucose Data into Performance and Fat-Loss Wins

No. Many people achieve great results without CGMs. A CGM is an optional feedback tool that can speed up learning—especially if you struggle with energy crashes, cravings, or mysterious performance issues. It helps you see how your body responds to specific foods, training, and sleep so you can personalize the basics more quickly.

There is no single ‘ideal’ workout range for healthy individuals. Many people feel good with glucose somewhere between roughly 80–150 mg/dL during training, with gradual rises or falls rather than abrupt swings. Temporary spikes during intense exercise are normal. Focus on how you feel and perform, not hitting a specific number on the screen.

Some rise after meals is normal. What’s more concerning are consistently large spikes (e.g., >160–180 mg/dL), frequent rapid crashes that leave you hungry or shaky, or inability to return toward baseline within about 2–3 hours. If you see those patterns often, experiment with more protein and fiber, smaller portions of refined carbs, and post-meal movement—and consider discussing the data with a clinician.

In most healthy, active people, quality carbohydrates can be part of an optimal diet. Use your CGM to fine-tune type, amount, and timing: favor minimally processed carbs, pair them with protein and fiber, and consider placing larger carb portions around training sessions. The goal is carbs that support performance and recovery without causing extreme swings or persistent high readings.

Many people gain substantial insight from 4–8 weeks of periodic use: enough time to see patterns across workdays, weekends, different training blocks, and sleep schedules. Some athletes or data-driven individuals choose to wear CGMs longer term for ongoing fine-tuning, but it’s not required. The key is using the data to build habits you can maintain even when you’re not wearing a sensor.