What the studies actually found.
Plain-English summaries of the trials behind semaglutide and tirzepatide: weight loss, muscle, protein, side effects and what happens when you stop. Every number links to its source.
What happens when you stop a GLP-1? What three trials found about weight regain
STEP 1, STEP 4 and SURMOUNT-4 followed people who stopped semaglutide or tirzepatide. Here is how much weight came back, how fast, and what it means.
ComparisonsSemaglutide vs tirzepatide: which leads to more weight loss? What the head-to-head trial found
SURMOUNT-5 compared tirzepatide and semaglutide head to head for 72 weeks in 751 adults with obesity. The weight, waist and side-effect results, plus caveats.
NutritionHow much protein do you need on a GLP-1? What the research says about protecting muscle
Part of the weight lost on semaglutide and tirzepatide is lean mass. Here is what the trials measured, what the 2025 nutrition advisory suggests for protein, and a quick calculator.
Trial resultsHow much weight do people lose on oral semaglutide? What the OASIS trials found
OASIS 1 and OASIS 4 tested daily semaglutide pills for weight loss. Here is how much weight people lost, how it compares with the weekly shot, and side effects.
Trial resultsHow much weight do people lose on GLP-1 medication? What STEP 1 and SURMOUNT-1 found
The two landmark trials behind Wegovy and Zepbound, in plain English: average weight loss, how many people reached 10% or 20%, side effects and what the averages hide.
Trial resultsHow much weight do people with type 2 diabetes lose on a GLP-1? What STEP 2 and SURMOUNT-2 found
STEP 2 and SURMOUNT-2 tested semaglutide 2.4 mg and tirzepatide for weight loss in adults with type 2 diabetes. Here are the results and how they compare.
Health conditionsCan tirzepatide help sleep apnea? What the SURMOUNT-OSA trials found
Two SURMOUNT-OSA trials tested tirzepatide in adults with obesity and moderate-to-severe sleep apnea. Here is what AHI means and how much it changed in a year.
Side effectsHow common is nausea on a GLP-1, and how long does it last? What the research says
Nausea, diarrhea, vomiting and constipation on semaglutide and tirzepatide: how often they happened in trials, when they peaked, and what helped.
Trial resultsDoes GLP-1 weight loss last? What two- and three-year trials found
STEP 5 followed semaglutide for two years and SURMOUNT-1 followed tirzepatide for three. Here is whether weight stayed off and what happened to diabetes risk.
Health conditionsDoes semaglutide help knee osteoarthritis pain? What the STEP 9 trial found
STEP 9 tested semaglutide in adults with obesity and painful knee osteoarthritis. Here is what happened to weight, pain and physical function over 68 weeks.
Health conditionsDoes semaglutide lower the risk of heart attack and stroke? What the SELECT trial found
SELECT followed 17,604 adults with heart disease and overweight or obesity but no diabetes. What semaglutide 2.4 mg did to heart attacks, strokes and weight.
Side effectsDoes semaglutide or tirzepatide cause hair loss? What the research says
How often hair loss was reported in GLP-1 trials, why rapid weight loss is the leading explanation, and what is still unknown about the cause.
Health conditionsCan GLP-1 medicines help fatty liver disease (MASH)? What the trials found
Semaglutide's phase 3 ESSENCE trial and tirzepatide's phase 2 SYNERGY-NASH trial checked liver biopsies in people with MASH. Here is what changed, in plain words.