Why muscle is the real risk on a GLP-1
GLP-1 medications work by quieting appetite, which is exactly why they drive weight loss. The catch is that when total intake drops fast, the body pulls amino acids from muscle to cover its needs. Losing muscle lowers your resting metabolism, weakens you, and makes the weight easier to regain later. Protein is what tells the body to spare muscle and burn fat instead.
The number, by goal
- Active weight loss: 1.2–1.6 g/kg. This is the evidence-backed band for preserving muscle while in a calorie deficit.
- Maintenance: 1.0–1.2 g/kg once your weight has stabilized.
- Muscle gain: 1.6–2.0 g/kg if you are training to add lean mass.
- Hard floor: never go below 1.2 g/kg while the GLP-1 is suppressing your appetite, regardless of goal.
Use adjusted body weight, not scale weight
Naive calculators multiply your raw scale weight by a protein factor, which overshoots for anyone carrying significant excess weight. The clinical standard is adjusted body weight: it starts from your ideal weight for your height, then adds a fraction of the difference. That gives a target your body can actually use, instead of an inflated number you will never hit on a quiet appetite. Our calculator applies this automatically when your weight is more than 115 percent of ideal.
Split it across meals
Your daily total is only half the answer. Muscle protein synthesis is driven per meal, and the body can only use so much in one sitting. Aim for 25 to 40 grams per eating occasion across three or four meals. On a GLP-1, where you may only manage small portions, hitting that per-meal target is often harder than the daily number, which is why a concentrated shake or two becomes the practical backbone of the day.
