What a CGM can teach you about exercise after 45

Why exercise matters more for glucose after 45

Skeletal muscle soaks up a large share of the glucose from a meal. As muscle mass declines with age and activity drops, there is less 'storage space,' and glucose stays higher for longer after eating. Insulin resistance tends to creep up for the same reason.

The CDC recommends that adults get at least 150 minutes of moderate activity a week and do muscle-strengthening activities on at least two days that work all the major muscle groups. A CGM does not change those targets, but it can make their effects visible and personal.

Experiments worth trying

Wearing a sensor for two weeks gives you time to compare similar days. Keep meals fairly consistent and change one thing at a time so you can see what made the difference.

• Eat the same lunch twice, once followed by a 10 to 15 minute walk and once sitting down
• Compare a morning workout with an evening one and look at your overnight readings
• Note how your post-dinner rise looks on a strength-training day versus a rest day
• See whether a late, heavy dinner or alcohol changes your overnight baseline
• Track how a poor night's sleep affects the next day's meal responses

Why glucose can rise during hard exercise

Many people are surprised to see glucose climb during interval sessions, heavy lifting or a race. During intense effort the body releases stress hormones, including adrenaline and cortisol, which tell the liver to release stored glucose to fuel the muscles. This is a normal response and usually settles within an hour or two after you stop.

Steady, moderate exercise such as brisk walking or easy cycling tends to lower glucose while you are doing it. Neither pattern is 'bad.' What matters more is your overall daily pattern and your lab results over time.

Lows during or after exercise

In people without diabetes who are not taking glucose-lowering medicines, true exercise-related lows are uncommon, though readings can dip after long sessions, especially if you trained fasted. Remember that CGMs can lag during rapid changes, and pressure on the sensor during sleep can cause falsely low readings.

If you use insulin or a sulfonylurea, exercise can cause genuine hypoglycemia. You need a prescription CGM with alerts and a plan from your diabetes care team. The FDA has said the first OTC CGM is not designed to alert users to dangerous lows.

Do not train for the graph

A CGM can encourage people to avoid carbohydrates before workouts or to skip intense sessions because they cause a spike. That can backfire. Fueling sensibly supports performance and recovery, and higher-intensity work has benefits for heart and muscle health that a glucose curve does not capture.

Use the data to build habits you can keep, such as walking after dinner or lifting twice a week, rather than chasing perfectly flat lines.

Safety first if you are returning to exercise

If you have been inactive, have heart disease, diabetes, high blood pressure or joint problems, check with your clinician before ramping up. Stop and seek care for chest pain or pressure, unusual breathlessness, fainting or palpitations during exercise.

Making the most of two weeks of data

Data are only useful if you can connect them to what you did. Keep brief notes in your phone or the CGM app: meal times and rough contents, workouts with type and intensity, alcohol, sleep quality and stressful events. Without those notes, it is easy to misread a spike or a dip.

Plan a few comparison days at the start of your sensor wear so you are not guessing at the end. For example, choose two days for a post-dinner walk and two without, keeping dinner similar. At your review, your clinician can line up those days and show you what actually changed.

Finally, remember that the CGM is temporary but the habits are not. Many people wear a sensor for a few weeks, learn which changes matter, and then rely on their routines and periodic lab checks rather than continuous monitoring.

How HealifyMD helps

Your clinician confirms a CGM is a good fit, then reviews your glucose data alongside your labs, medicines, sleep and training notes. You get a written summary with a few practical next steps. The HealifyMD CGM is $189 one-time (one 14-day sensor, clinician visit included) with no membership fee, confirmed at the eligibility review. Labs are priced separately.