GLP-1 Protein & Macro Calculator

How the calculator works

None of the arithmetic is difficult. What matters is that every coefficient in it traces to a peer-reviewed source.

• BMR (Mifflin-St Jeor 1990, PMID 2305711) [1]:
  Male: 10×W(kg) + 6.25×H(cm) − 5×age + 5
  Female: 10×W(kg) + 6.25×H(cm) − 5×age − 161
• TDEE (FAO/WHO/UNU 2001 PAL multipliers) [13]: BMR × {1.2, 1.375, 1.55, 1.725, 1.9} — running from sedentary at the bottom to extremely active at the top, through light, moderate and very.
• Caloric deficit [10]: a shortfall of 500 kcal a day is the usual 0.45 kg (1 lb) a week under the old 3,500-kcal-per-pound approximation, which is the figure the calculator shows. Hall 2011 (PMID 21872751) shows real loss on a fixed deficit is slower than that rule and tapers over time, because the body adapts as it gets lighter.
• Protein tier selection (see below).
• Per-meal split (Mamerow 2014, PMID 24477298) [5]: spreading protein evenly over 3 meals raised muscle protein synthesis across the day by roughly 25%, against loading it into one.

The protein tier ladder

Five tiers, and each one is somebody's published recommendation rather than a round number:

• 0.8 g/kg/day — the RDA, which covers a sedentary adult holding steady and almost certainly does not cover anyone losing weight on a GLP-1.
• 1.0-1.2 g/kg/day — what PROT-AGE 2013 [2] asks of a healthy older adult at maintenance.
• 1.2-1.6 g/kg/day — PROT-AGE again where illness or training is involved, ESPEN 2014 [8] for older adults with disease, the bottom of the ISSN 2017 [4] range for active people, and the range the 2025 joint advisory [14] notes for active weight loss. This is the tier anyone on a GLP-1 gets.
• 1.6-2.0 g/kg/day — the ISSN 2017 [4] figure for active people, used here for hard-training people in a deficit who are not on a GLP-1.
• 2.0-2.4 g/kg/day — the high arm of Longland 2016 [3], which added lean mass across 4 weeks of severe deficit plus lifting; Mettler 2010 [7], holding lean mass in trained athletes while losing weight; and Helms 2014 [6], which puts contest-prep protein at 2.3-3.1 g/kg of lean body mass rather than of total weight.

The GLP-1 target

Say you are on a GLP-1, or about to start one: the target becomes 1.2 to 1.6 g/kg a day of body weight. No GLP-1 trial has tested a protein dose. A 2025 advisory issued jointly by four US obesity and nutrition groups [14] notes 1.2 to 1.6 g/kg a day proposed during active weight loss, or about 1.5 g per kg of fat-free mass when body composition is known, and advises against prolonged intake at or above 2 g/kg a day. The Neeland 2024 review [9] says the right amount is not yet clear.

Body-composition scans inside the pivotal trials found lean tissue made up about a quarter of the weight lost in SURMOUNT-1 [12] (tirzepatide), with the same 75/25 split on placebo [15], and roughly two-fifths in STEP-1 [11] (semaglutide; DXA substudy, NEJM supplement). That share reflects losing weight more than the drug itself, and protein and resistance training are the levers for it.

What this calculator does NOT do

• It cannot see your body composition. The 2025 advisory [14] warns that actual weight can overstate protein needs in people with obesity, so on a GLP-1 with a BMI of 30 or more the target is worked from an adjusted weight (ideal weight plus 40% of the difference) instead of your full weight; below that it uses your weight as entered. If you have a DXA scan, about 1.5 g per kg of fat-free mass is the figure the advisory gives, and it also offers a flat 80 to 120 g a day as a simpler target.
• It knows nothing about your kidneys. With chronic kidney disease — an eGFR under 60 — the higher tiers are a conversation for your nephrologist before they are a plan.
• It writes no meal plan. Targets are all it produces, and the plan is yours to build — ideally with a registered dietitian.
• It stands behind the conversation with your prescriber, never in front of it, and least of all where diabetes, kidney disease or anything else bearing on nutrition is involved.

Important disclaimer

Educational only. This is neither medical advice nor a dietary prescription. Every published recommendation behind it was drawn from healthy adults and healthy older adults, which means none of it transfers cleanly to chronic kidney disease, advanced liver disease or a metabolic disorder. With any of those, take the targets to a registered dietitian or the clinician who prescribes for you before acting on them. Each coefficient is cited to the primary source it came from, so any of them can be checked.

Related tools and research

• Semaglutide and muscle mass loss — the muscle-loss problem this calculator exists to work against
• GLP-1 BMI calculator — where you start, and where each trial endpoint would put you
• GLP-1 weight loss calculator — week-by-week trial projections