Sources & how to read the evidence

This guide was built from the primary literature — randomised trials, meta-analyses, clinical guidelines and drug labels — and graded by how strong the evidence actually is. Where the science is genuinely mixed, it says so rather than picking a side.

How it was built

The approach: Every load-bearing number comes from a named trial, meta-analysis, guideline or regulatory document, with the evidence dots reflecting study design, size, replication and whether findings survived scrutiny. Figures are group averages; individual results vary widely. Doses and thresholds are typical adult figures from the literature, not instructions.
The key sources: Drugs: the STEP program and SELECT (semaglutide); SURMOUNT 1–5 and SURMOUNT-OSA (tirzepatide); the SCALE trials (liraglutide); the pivotal trials for phentermine/topiramate, naltrexone/bupropion, orlistat (XENDOS) and metformin (DPP). Surgery: STAMPEDE, the Swedish Obese Subjects cohort, and 12-year gastric-bypass outcomes. Biology & behaviour: Sumithran 2011 (appetite hormones), Fothergill 2016 (metabolic adaptation), Kevin Hall’s dynamic model and 2019 ultra-processed-food trial, DIETFITS 2018, Tasali 2022 (sleep), the National Weight Control Registry, Burke 2011 (self-monitoring), and the Ashwell waist-to-height meta-analysis.

Educational reference — not medical advice

This guide summarises published research for general education. It is not a diagnosis, a prescription, or a substitute for care, and doses are typical figures from the literature, not instructions. Decide anything here — especially any medication or procedure — with a qualified clinician, and never start, stop, or change a treatment on your own.

The Weight Loss Guide