MuscleOnGLPHome/Evidence library
The receipts
The evidence behind the guide
Every recommendation in the handbook, the calculators, and the articles traces back to primary literature. This is that literature, in one place. Filter by topic or search by author, journal, or title.
These are the peer-reviewed studies, trial registrations, and official references cited across this site. Each card links to the source. We include the honest limits too: two entries are preprints that have not been peer reviewed, and several trials are still enrolling. This library is educational, not medical advice.
Showing all 47 studies.
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Changes in lean body mass with established and emerging GLP-1-based therapies and mitigation strategies
The review most of this site rests on. It puts lean mass at roughly 15 to 40 percent of the weight lost on a GLP-1, and lays out ways to blunt it.
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Body composition changes during weight reduction with tirzepatide (SURMOUNT-1 DXA substudy)
A DXA substudy that measured how much of tirzepatide weight loss was fat versus lean tissue, rather than estimating it.
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Once-weekly semaglutide in adults with overweight or obesity (STEP 1)
The pivotal semaglutide trial. Average loss was about 15 percent of body weight, the result that made these drugs famous.
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Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1)
The pivotal tirzepatide trial, with weight loss reaching about 21 percent at the top dose.
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Triple-hormone-receptor agonist retatrutide for obesity (Phase 2)
Early trial of retatrutide, a newer triple-hormone agonist, showing even larger weight loss.
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Retatrutide Phase 3 obesity program (TRIUMPH-1)
The ongoing Phase 3 program that will confirm or temper the early retatrutide results.
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Greater lean-body-mass decline with tirzepatide than semaglutide in routine care
Routine-care scans suggesting more lean-mass loss on tirzepatide than semaglutide. A real signal, but preprint only, so treat it as unsettled.
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GLP-1 receptor agonists and muscle strength changes in older adults
Reports reductions in muscle strength, including grip strength, in older adults on GLP-1s. Strength, not just the scale, is what matters.
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The effects of incretin mimetic therapies on muscle and bone health in older adults: a narrative review
Reviews how GLP-1 drugs affect both muscle and bone, a pairing that gets overlooked in older adults.
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GLP-1 receptor agonist-based agents and body composition: filling more gaps
A commentary mapping what is still unknown about how these drugs reshape the body.
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Comparative effects of drugs for adults with overweight or obesity: systematic review and network meta-analysis
A network meta-analysis that ranks the weight-loss drugs against each other rather than one at a time.
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Protein supplementation and resistance-training-induced gains in muscle mass and strength (meta-analysis)
The source of the protein target. Benefit to fat-free mass leveled off near 1.6 g/kg per day, the low end of the calculator range.
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How much protein can the body use in a single meal for muscle-building?
Why the meal planner spreads protein across the day. Distribution beats loading one large dose, which is hard to eat on a GLP-1 anyway.
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Impacts of protein quantity and distribution on body composition
Reviews how both total protein and its timing shape lean mass, reinforcing the four-meal method.
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Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory
An expert advisory on protein and nutrient targets written specifically for GLP-1 users.
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Dietary intake by patients taking GLP-1 and dual GIP/GLP-1 receptor agonists: a narrative review
Summarizes how much, and what, people actually eat once the medication has cut their appetite.
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Investigating nutrient intake during use of a GLP-1 receptor agonist: a cross-sectional study
Finds many GLP-1 users fall short on protein and key nutrients, which is the problem this site exists to solve.
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Macronutrient, micronutrient supplementation and monitoring for patients on GLP-1 agonists
Practical guidance on which nutrients to supplement and monitor during therapy.
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ISSN position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine
The position stand concluding creatine is safe and effective for lean mass and strength alongside training.
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Nutritional, functional, and psychological considerations for incretin-based therapies: an EASO, EFAD, and ECPO consensus statement
A multi-society consensus on eating well and staying supported during GLP-1 treatment.
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USDA FoodData Central
The reference database behind the protein content of the foods in the guide and food tables.
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Resistance training prevents muscle loss induced by caloric restriction in obese elderly (meta-analysis)
The finding behind the calculator green line. Resistance training offset about 93.5 percent of the lean mass that dieting alone would cost.
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ACSM position stand: resistance training prescription (overview of reviews)
The current expert prescription for how to program sets, reps, and load to build and keep muscle.
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LEAN mass preservation with resistance exercise and protein during semaglutide/tirzepatide (LEAN-PREP)
A registered trial testing training plus protein directly in GLP-1 users. The kind of GLP-1-specific evidence the field still needs.
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Free-weight versus machine-based strength training on maximal strength and hypertrophy (meta-analysis)
Free weights and machines build muscle about equally, so you can train with whatever you have.
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ACSM position stand: progression models in resistance training for healthy adults
The classic guidance on how to progress a program over weeks and months instead of stalling.
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Association of cardiorespiratory fitness with long-term mortality
Higher fitness tracked with lower long-term mortality, part of why training is about more than muscle.
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World Health Organization 2020 guidelines on physical activity and sedentary behaviour
The WHO baseline for weekly activity, including muscle-strengthening work on two or more days.
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Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts
More daily steps tracked with lower mortality, the evidence behind the walking targets.
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Compatibility of concurrent aerobic and strength training for muscle size and function (meta-analysis)
You can combine cardio and lifting without cancelling out muscle gains, if you set it up sensibly.
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The role of intra-session exercise sequence in the interference effect (meta-analysis)
Examines whether doing cardio before lifting blunts strength gains, which informs how to order a session.
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Creatine supplementation during resistance training on lean tissue mass and muscular strength in older adults (meta-analysis)
Creatine added to training increased lean tissue and strength in older adults, the population most at risk of muscle loss.
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Weight regain and cardiometabolic effects after withdrawal of semaglutide (STEP 1 trial extension)
About two-thirds of lost weight returned within a year of stopping. The reason the off-ramp matters as much as the ramp-up.
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Trends in 1-year persistence and adherence among initiators of weight-loss-indicated GLP-1 receptor agonists
Shows how many people stop these drugs within the first year, which makes planning for the stop essential.
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Weight cycling and its effects on muscle mass, sarcopenia and sarcopenic obesity
Repeated loss-and-regain cycles can erode muscle over time, so the muscle you keep now protects you later.
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Sarcopenic obesity: a review
Reviews the overlap of low muscle and high fat mass, the outcome muscle preservation is meant to avoid.
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Sarcopenic obesity and weight loss-induced muscle mass loss
Looks specifically at muscle lost during weight loss in people who already have sarcopenic obesity.
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Gastrointestinal tolerability of once-weekly semaglutide 2.4 mg (STEP 1 to 3 pooled analysis)
GI side effects clustered during dose escalation and declined after, which is why timing meals around a dose helps.
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Creatine supplementation and kidney function: a narrative review
Controlled trials show no harm to kidney function in healthy people. Creatine raises the creatinine marker without changing the kidney.
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Treatment for constipation
Government guidance on managing constipation, a common complaint once appetite and fiber intake drop.
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Wegovy (semaglutide) prescribing information
The official FDA label for semaglutide, the primary source for dosing and warnings.
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Zepbound (tirzepatide) prescribing information
The official FDA label for tirzepatide, the primary source for dosing and warnings.
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Special considerations when using GLP-1 receptor agonists in obesity and type 2 diabetes in older adults
Reviews the added cautions for prescribing these drugs to older adults, where muscle loss carries more risk.
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A new predictive equation for resting energy expenditure in healthy individuals
The Mifflin-St Jeor equation that the calculator uses for basal metabolic rate, validated as most accurate for healthy adults.
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Human energy requirements: physical activity level (PAL) values
The standard activity multipliers used to scale resting metabolism up to total daily energy expenditure.
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Caloric equivalents of gained or lost weight
The origin of the 3,500 kcal per pound rule of thumb behind the timeline estimate. A first approximation, not a promise.
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Quantification of the effect of energy imbalance on bodyweight
A dynamic model showing weight loss slows over time as metabolism adapts, which is why the calculator flags its timeline as an estimate.
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Put the evidence to work
The complete handbook
The studies above are the foundation. The handbook turns them into a system you can follow: protein targets built for a gone appetite, home and gym training routines, and a maintenance phase for after you stop.
See the full handbookNew research lands weekly. Follow the research roundups for the studies we add as they publish.