GLP-1 Nutrition Calculator
Explore general calorie, protein, fibre, and hydration estimates to discuss with your GLP-1 prescribing team. This tool does not advise on medication, manage side effects, or provide a clinically validated nutrition prescription.
⚠️ The Muscle Loss Problem
Some studies report that a portion of weight lost during GLP-1 treatment can be lean mass — not fat — when users don't prioritise protein and resistance training.
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The GLP-1 Nutrition Problem No One Talks About
GLP-1 medications are remarkably effective for weight loss — but the rapid reduction in appetite creates a dangerous nutritional gap that most users don't recognise until the damage is done. When you're not hungry, you eat whatever is easiest — usually processed carbohydrates, soft foods, or simply too little of anything.
The result: research consistently shows that 25–40% of weight lost on GLP-1 medications is lean muscle mass, not body fat. This muscle loss crashes your basal metabolic rate, making weight regain almost inevitable once medication stops — and the regain comes back primarily as fat, not muscle.
The solution is straightforward: intentional, protein-first eating (1.8–2.4g/kg/day) combined with resistance training. Both are non-negotiable if you want the weight you lose to be fat, not muscle.
GLP-1 Phase Nutrition Guide
Weeks 1–4
Adjustment Phase
- → Nausea is most common here — eat cold, bland protein sources
- → Hydrate aggressively — GLP-1 disrupts thirst signals
- → Small meals every 3–4 hours rather than large ones
- → Take a comprehensive multivitamin daily from day 1
Weeks 4–12
Active Loss Phase
- → Track protein intake daily — appetite suppression masks deficiency
- → Eat protein first at every meal before anything else
- → Start or maintain resistance training 2–3x/week minimum
- → Weigh weekly, not daily — GLP-1 causes water weight fluctuations
Week 12+
Optimisation Phase
- → Focus shifts to body composition, not just scale weight
- → Increase training intensity to build muscle while losing fat
- → Monitor blood markers (B12, iron, D, magnesium) every 3–6 months
- → Plan your off-ramp strategy with your prescriber
Formula, sources and limitations
How this estimate is produced
Sources
- Semaglutide for managing overweight and obesity (TA875)
NICE
- A new predictive equation for resting energy expenditure in healthy individuals
American Journal of Clinical Nutrition, 1990
- International Society of Sports Nutrition position stand: protein and exercise
Journal of the International Society of Sports Nutrition, 2017
Important limitations
- No cited guideline validates this calculator's personalised calorie or protein output for people using GLP-1 medicines.
- Needs vary with the medicine, indication, dose, symptoms, medical history, and rate of weight change.
A citation describes the source method; it does not mean this website or its implementation has been clinically validated or independently reviewed. See the methodology, editorial policy, and medical disclaimer.