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Weight Loss on GLP-1s

Protein and energy calculator

Estimate resting and total daily energy with Mifflin-St Jeor and a FAO/WHO/UNU activity level, then turn body weight into a protein target from the 2025 GLP-1 joint advisory, the Leidy weight-loss range, the ISSN training range or the PROT-AGE older-adult range, split across eating occasions. Shows the formula, cites every range, and prescribes nothing.

By FormBlends editorial teamAssumptions checked September 4, 2026Runs in your browser; nothing is sent to a server

About you

Mifflin-St Jeor has two constants, one derived from men and one from women. Pick the one your clinician would use.

years
lb
ft
in

Middle of the sedentary or light activity band. FAO/WHO/UNU band 1.40 to 1.69.

Range in the 2025 joint advisory from ACLM, ASN, OMA and The Obesity Society for people on GLP-1 therapy during active weight reduction.

Only used for the per-meal split. On a GLP-1, four to five small occasions is common; the joint advisory suggests small, frequent meals.

Results

Enter age, weight and height for energy. Weight alone is enough for the protein target.

Rough food equivalents (USDA FoodData Central): 100 g cooked chicken breast about 31 g protein; 170 g plain Greek yoghurt about 17 g; one large egg about 6 g; 100 g firm tofu about 17 g; 100 g cooked lentils about 9 g.

Formulashown in full, nothing hidden
REE men   (kcal/day) = 10 x weight (kg) + 6.25 x height (cm) - 5 x age (years) + 5
REE women (kcal/day) = 10 x weight (kg) + 6.25 x height (cm) - 5 x age (years) - 161
total daily energy    = REE x physical activity level (PAL)
protein per day (g)   = weight (kg) x factor (g/kg/day)
per occasion (g)      = protein per day / eating occasions
protein % of energy   = protein (g) x 4 / total daily energy x 100
1 lb = 0.45359237 kg;  1 in = 2.54 cm

Mifflin-St Jeor was derived from 498 healthy adults in 1990 (PubMed 2305711). In the 2005 Academy of Nutrition and Dietetics systematic review it predicted measured resting metabolic rate within 10 percent in more people than the Harris-Benedict, Owen or WHO equations, in both non-obese and obese adults (PubMed 15883556). It still misses by more than 10 percent in a meaningful minority; indirect calorimetry is the only measurement.

The PAL multipliers are points inside the FAO/WHO/UNU 2004 activity bands. They are the largest source of error in the estimate. Weight loss itself lowers energy expenditure, and the GLP-1 trials did not measure it, so treat the total as a starting estimate that drifts downward as weight falls.

Assumptions, checked September 4, 2026

  • 1.2 to 1.6 g/kg/day (or 80 to 120 g/day) is the range in the 2025 joint advisory of the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society for people on GLP-1 therapy during active weight reduction (PubMed 40445127).
  • 1.2 to 1.6 g/kg/day is also the range reviewed by Leidy and colleagues for weight loss and maintenance (PubMed 25926512); 1.4 to 2.0 g/kg/day is the ISSN position-stand range for people who train (PubMed 28642676); 1.0 to 1.2 g/kg/day is the PROT-AGE range for healthy older adults (PubMed 23867520); 0.8 g/kg/day is the adult RDA, a floor against deficiency and not a weight-loss target.
  • The energy estimate is Mifflin-St Jeor multiplied by a FAO/WHO/UNU physical activity level. It is not a calorie prescription. The trial deficit figure (500 kcal/day) is reported because STEP 1 and SURMOUNT-1 counselled it; it is context for the trial curves, not advice.
  • Higher-protein intakes are not appropriate for everyone, including some people with chronic kidney disease. A clinician or registered dietitian should set the target if you have a relevant condition, are pregnant or breastfeeding, or are under 18.
  • Compounded GLP-1 products, where used, are not FDA approved and are not interchangeable with brand products. This tool is about food, not medication.
  • Food protein values are approximate USDA figures for orientation.

This calculator is an arithmetic aid for medication a licensed prescriber has already prescribed. It does not recommend a dose. Confirm any result with your prescriber or pharmacist before use.

Sources

  1. Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990. PubMed 2305711
  2. Frankenfield D et al. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. J Am Diet Assoc 2005. PubMed 15883556
  3. FAO/WHO/UNU. Human energy requirements: report of a joint expert consultation (2004), chapter 5, physical activity level categories
  4. Mozaffarian D et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from ACLM, ASN, OMA and The Obesity Society. Obesity 2025. PubMed 40445127
  5. Mozaffarian D et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory. Obesity 2025. PubMed 40445127
  6. Leidy HJ et al. The role of protein in weight loss and maintenance. Am J Clin Nutr 2015. PMID 25926512
  7. Jager R et al. International Society of Sports Nutrition position stand: protein and exercise. JISSN 2017. PMID 28642676
  8. Bauer J et al. Evidence-based recommendations for optimal dietary protein intake in older people: PROT-AGE. J Am Med Dir Assoc 2013. PubMed 23867520
  9. Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005)
  10. Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med 2021. PubMed 33567185
  11. Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022. PubMed 35658024
  12. USDA FoodData Central

Read before you use it

Guides for this calculator

Protein targets on a GLP-1: the ranges, where they come from, and how to hit them on a small appetite

The 2025 joint advisory range of 1.2 to 1.6 g/kg/day, the position stands and trials behind it, why the per-meal split matters more than the daily total when appetite is low, and who should have a clinician set the number.

Updated September 4, 2026

Energy needs on a GLP-1: what Mifflin-St Jeor estimates, what it misses, and why the number falls

The equation the calculator uses, how accurate it is, the FAO/WHO/UNU activity multipliers, what the trials did with the estimate, and why a GLP-1 makes tracking calories less useful than tracking protein.

Updated September 4, 2026

Educational, not medical advice. Read the medical disclaimer.