GLP-1 medications can drive rapid weight loss, but without the right system, muscle, strength, and energy can suffer. Here’s what the evidence shows.
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The Eternal GLP-1 Monitoring Program was built by an interdisciplinary team spanning obesity medicine, nutrition, exercise physiology, and performance, designed to ensure GLP-1 use improves health without sacrificing muscle, strength, or long-term resilience.
This program reflects how we practice medicine at Eternal. Coordinated. Data-informed. Grounded in physiology.
Our role is to ensure that while body weight changes, muscle, strength, recovery, and long-term health are protected.
They can, but muscle loss is not inevitable.
GLP-1s reduce appetite and slow gastric emptying. For many people, that leads to a large drop in calories and protein intake. When weight loss happens quickly and energy intake is too low, the body may break down lean tissue along with fat.
Clinical and sports-nutrition data show that without enough protein, resistance training, and monitoring, a meaningful portion of weight lost can come from muscle rather than fat.
The scale cannot tell you:
That’s why body-composition tools like DEXA scans, along with strength and performance markers, are used in sports and clinical settings to monitor weight loss safely.
Most online GLP-1 programs don’t measure any of this.
Many people on GLP-1s simply aren’t hungry enough to eat what their body needs, especially protein.
Evidence-based protocols for muscle preservation during weight loss typically include:
Without these, fatigue, strength loss, mood changes, and stalled progress are common.
I’m losing weight, but I feel weaker. Is that normal?
It’s common, but it’s a signal worth paying attention to. Declining strength can indicate under-fueling or lean mass loss, even if the scale is moving.
Can I just do cardio?
Cardio alone does not preserve muscle. Resistance training is the primary protective stimulus for lean mass during weight loss.
Do GLP-1s affect mood or motivation?
They can. Appetite suppression, rapid body changes, and under-fueling may contribute to mood changes in some individuals, which is why mental health screening and follow-up matter.
What are some other key risks?
With muscle loss comes a decline in strength, this must be monitored alongside body composition.
Additionally, micronutrient balance is often put at risk with decreased eating and should be measured frequently.
2.5 hours, hundreds of insights, twice per year and tracked over time.
After a dynamic warmup we’ll use functional movement and balance tests to measure your range and quality of motion as well as your core stability and muscle control.
Next, we measure your ability to produce force and how quickly you can apply it. We use force plates and targeted exercises to identify imbalances and guide your training.
To identify your aerobic and anaerobic thresholds, you’ll do a Lactate Ramp test. You’ll move through stages on a treadmill or bike, with a quick finger prick after each.
Finally you’ll roll right into your VO2 max test, which measures your aerobic capacity (VO₂ max) or how efficiently your body uses oxygen during intense exercise.
After a dynamic warmup we’ll use functional movement and balance tests to measure your range and quality of motion as well as your core stability and muscle control.
Next, we measure your ability to produce force and how quickly you can apply it. We use force plates and targeted exercises to identify imbalances and guide your training.
To identify your aerobic and anaerobic thresholds, you’ll do a Lactate Ramp test. You’ll move through stages on a treadmill or bike, with a quick finger prick after each.
Finally you’ll roll right into your VO2 max test, which measures your aerobic capacity (VO₂ max) or how efficiently your body uses oxygen during intense exercise.
Located in at the base of the Golden Gate Bridge in The Presidio with ample parking, our San Francisco performance center is where you'll want to put in the work.
A plan built around your goals, so results improve how you move, feel, and perform.
