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The evidence base

Research

LeanSync is programmed against peer-reviewed findings in GLP-1 pharmacology, body-composition change, and resistance training. These are the studies our decisions are built on.

We cite studies, not vibes. Every claim on our landing page traces to a primary source or a recent systematic review. Below is the core evidence base, organized by question.

How much lean mass is lost on GLP-1s?

  • STEP 1 — Wilding et al., N Engl J Med 2021. Semaglutide trial reporting weight loss and body-composition change; updated by 2024 systematic reviews.
  • SURMOUNT-1 DXA substudy — Jastreboff et al., Diabetes, Obesity & Metabolism 2025. Tirzepatide body-composition at one year (n≈160).
  • Network meta-analysis — Metabolism 2024. Pooled lean-mass outcomes across 22 GLP-1 / GIP trials.

What happens after discontinuation?

  • STEP 1 Extension — Wilding et al., Diabetes, Obesity & Metabolism 2022. One-year follow-up after discontinuation; weight regain disproportionately as fat.

What preserves muscle under caloric deficit?

  • Lundgren et al., N Engl J Med 2021. Structured exercise plus GLP-1 protected lean mass at one year.
  • Jensen et al., EClinicalMedicine 2024. Resistance training as the differentiating factor in lean-mass retention.

Clinical guidance

  • Joint statement — ACLM, ASN, OMA, TOS, 2025. Muscle preservation during weight loss.
  • AACE 2025 clinical practice guideline.
  • ACSM 2024 position stand on resistance training during pharmacologic weight loss.

Full citations with DOIs and our working notes are being prepared. Have a study we should be reading? Send it to research@leansync.fit.