GLP-1s: The Real Tradeoffs Nobody Tells You About

At Terra, we like to peek into our body and physiology through the lens of our wearables. Our goal is not to claim the causes behind our physiological changes, but to describe the most consistent patterns seen across users.

In this blog we looked at how people respond to taking GLP-1 medication. This drug is often used to treat type 2 diabetes and obesity and acts by mimicking the GLP-1 hormone produced in the intestine that helps regulate blood sugar by stimulating insulin release and inhibiting glucagon [1].

Although medication effects often unfold over days or weeks, wearables are good at capturing day‑to‑day changes that reflect drug effects like changes in appetite, energy, and autonomic physiology [2].

The Data

We used daily wearable data from 538 users that reported taking GLP-1 medication. Each tag is assumed to mean the medication was taken that day, but we do not assume that a missing tag means no medication was taken. That makes this a conservative, correlation‑only analysis.

We use a within‑person approach (each person is compared to their own baseline) so that we minimize differences that come from individual variability.

We applied strict inclusion rules to reduce noise

• ≥30 days of wearable data
• ≥5 GLP tags
• ≥7 days of pre-GLP baseline

We report results that are statistically significant (p < 0.05) and meaningful (Cohen d > 0.2).

Effect sizes:

• Small: |d| 0.2–0.5
• Medium: |d| 0.5–0.8
• Large: |d| ≥0.8

Activity changes

The largest effect seen in our cohort was a reduction in activity with exposure to GLP.

We performed various analyses to understand both the immediate and long-standing pharmacological effects of GLP.

We compared GLP days to non-GLP days, and we also assumed a 5 and 7-day sensitivity window to test these sustained effects.

Steps drop on GLP days and the days after. These effects are statistically significant with small effect sizes but appear across same‑day, next‑day, and lagged analyses. Effect sizes also increase when comparing the 5- and 7- day active windows.

This means that GLP exposure aligns with lower activity. A plausible explanation is transient side‑effects (e.g., reduced appetite, mild nausea, or fatigue)[3], but the data cannot confirm cause.

Physiological Changes

Minimum heart rate increases and HRV drops after GLP exposure, and does most clearly 2-7 days post GLP intake. This could reflect autonomic adjustments, dose titration or behavioral changes. Causality cannot be determined from tags alone.

What does this mean?

If you are taking a GLP medication and tracking your wearable data, the most likely signal you would notice is a reduction in steps or low‑intensity activity around the time of exposure. Smaller physiologic signals (like minimum heart rate and HRV shifts) are present but would be harder to detect without careful analysis. If your wearable patterns match these trends, that doesn’t prove medication effects, but it suggests your data is tracking similar population‑level patterns.

References

[1] Areesha Moiz, Kristian B. Filion, Michael A. Tsoukas, Oriana HY. Yu, Tricia M. Peters, Mark J. Eisenberg, Mechanisms of GLP-1 Receptor Agonist-Induced Weight Loss: A Review of Central and Peripheral Pathways in Appetite and Energy Regulation, The American Journal of Medicine

[2] Gregory J. Grosicki, Jeongeun Kim, Finn Fielding, Summer R. Jasinski, Christopher Chapman, William von Hippel, and Kristen E. Holmes, Heart and health behavior responses to GLP-1 receptor agonists: a 12-wk study using wearable technology and causal inference, American Journal of Physiology-Heart and Circulatory Physiology

[3] Oshi Health. (2025, August 19). GLP-1 nausea: How to handle GLP-1s' most common side effect. https://oshihealth.com/glp1-nausea/