Calories, protein & hydration on GLP-1s

GLP-1 Macro & Calorie Calculator

This calculator sets calories and protein-first macronutrients for adults on glucagon-like peptide-1 (GLP-1) weight-loss therapy (semaglutide or tirzepatide). It uses the Mifflin-St Jeor equation for basal metabolic rate (BMR), multiplies by activity for total daily energy expenditure (TDEE), subtracts 500 kcal for a deficit target, anchors protein at 1.4 g per kg of goal weight, allocates 25% of calories to fat, and fills carbohydrates with the remainder, plus fluid and fiber benchmarks. Prescription drugs require medical supervision; not medical nutrition therapy.

By Jeff Beem

Updated June 25, 2026

Personal stats

Units

Age

Sex (BMR constant)

Current weight

Used for BMR, TDEE, and hydration estimate.

Height

Activity & meds

Activity multiplier

Light activity 1–3 days/week

Medication (context)

Selection documents your protocol; energy math uses stats above, not dose.

Goals

Goal weight (muscle preservation anchor)

Muscle preservation target scales at 1.4 g protein per kg of this weight.

Muscle preservation target

STEP trial optimized, protein emphasis aligns with intensive lifestyle support models used alongside GLP-1 therapy in trials such as STEP.^[1]

GLP-1 deficit target

Dietary fat allocation

46.3 g

25% of target calories (~416 kcal)

Carbohydrate remainder

207.4 g

Non-protein, non-fat energy (~830 kcal)

Hydration (fluid oz)

133 oz

~3933 ml

Dietary fiber target

30 g

GI-friendly benchmark on GLP-1 therapy; titrate if bloating.

Equations

\mathrm{BMR} = 10W + 6.25H - 5A + s

W=\mathrm{kg},\; H=\mathrm{cm},\; s=+5\ \mathrm{(men)},\; -161\ \mathrm{(women)}

\mathrm{TDEE} = \mathrm{BMR} \times \text{activity factor}

\text{Target kcal} = \mathrm{TDEE} - 500

P_{\mathrm{guard}} = 1.4 \times \text{goal weight (kg)}

[1] STEP combined pharmacotherapy with lifestyle support; protein-forward planning aligns with that model, not a prescription.

Notice

For orientation only. GLP-1 medications require medical supervision; do not change therapy based on calculator output.

How to use this calculator

Enter age, sex, height, and current weight in 01. Set activity multiplier and medication (context only) in 02. Enter goal weight in 03 for the 1.4 g/kg protein anchor. With defaults (female, age 42, 198 lb, 5 ft 6 in, goal 165 lb, light activity ×1.375), results show BMR ≈ 1,575 kcal, TDEE ≈ 2,165 kcal, deficit target ≈ 1,665 kcal, protein ≈ 104.8 g, fat ≈ 46.3 g, carbohydrate ≈ 207.4 g, hydration ≈ 133 oz, and 30 g fiber. Heed low-calorie or macro-balance warnings when shown.

Reading your GLP-1 macro targets

The results column shows a protein-first macro plan, a TDEE-based calorie target, hydration from current weight, and a fixed fiber benchmark. Medication selection in section 02 does not change the math.

Example: 198 lb → 165 lb, female, light activity

With defaults in sections 01–03 (age 42, female, current 198 lb, height 5 ft 6 in, goal 165 lb, activity Light (×1.375), medication Zepbound for context): basal metabolic rate (BMR) ≈ 1,575 kcal, total daily energy expenditure (TDEE) ≈ 2,165 kcal, and the GLP-1 deficit target ≈ 1,665 kcal/day (TDEE − 500). That target sits above the ~1,200 kcal female floor, so no low-calorie warning appears.

Muscle preservation and macro tiles (results column)

Goal weight 165 lb (≈ 75 kg) in section 03 drives the green “Muscle preservation target” card: protein = 1.4 × goal kg ≈ 104.8 g. The “Dietary fat allocation” tile sets fat to 25% of the 1,665 kcal target ≈ 46.3 g. “Carbohydrate remainder” fills what is left after protein and fat ≈ 207.4 g. Prioritize protein at meals; fat and carbs flex around that anchor.

Hydration and fiber tiles in the results column

The widget reads current weight from section 01 for the “Hydration (fluid oz)” tile: 198 × 0.67 ≈ 133 oz (~3,933 ml). The “Dietary fiber target” tile is fixed at 30 g on this page for bowel regularity when gastric emptying slows; titrate upward with water if bloating appears.

Activity multiplier and medication (section 02)

The activity dropdown applies a multiplier to BMR for TDEE (default Light ×1.375). Changing it updates the deficit target card immediately. The medication list (Ozempic, Wegovy, Mounjaro, Zepbound) is labeled “context” in the UI and does not alter calories or macros—only your documented protocol.

Macro balance note in the results panel

At very low deficit targets or high goal-weight protein, fixed 1.4 g/kg protein and 25% fat can exceed total kcal. The widget then shows an amber “Macro balance note” in the results column and carbohydrate displays “—”. Raise calories (smaller deficit), adjust goal weight in section 03, or obtain individualized macros from a registered dietitian.

GLP-1 macro and calorie calculator

This calculator sets daily calories and protein-first macronutrients for adults on glucagon-like peptide-1 (GLP-1) weight-loss therapy using Mifflin-St Jeor total daily energy expenditure (TDEE) minus 500 kcal, plus hydration and fiber benchmarks. Educational only; not medical nutrition therapy.

What this calculator does

The widget estimates daily calories and macronutrients for adults using or considering GLP-1-based obesity pharmacotherapy (semaglutide or tirzepatide). It computes basal metabolic rate (BMR) with Mifflin-St Jeor, multiplies by an activity factor for total daily energy expenditure (TDEE), subtracts 500 kcal for a deficit target, anchors protein at 1.4 g per kilogram of goal weight, allocates 25% of calories to fat, and fills carbohydrates with the remainder. Hydration uses current weight in pounds × 0.67; fiber is fixed at 30 g/day. It does not personalize pregnancy, eating disorders, advanced kidney disease, or elite sport nutrition, and medication dose does not change the math.

BMR (Mifflin-St Jeor):

$\mathrm{BMR} = 10W + 6.25H - 5A + s$
W = weight (kg), H = height (cm), A = age (years), s = +5 (male) or −161 (female).
TDEE and target:

$\mathrm{TDEE} = \mathrm{BMR} \times \text{activity factor}$ $\text{Target kcal} = \mathrm{TDEE} - 500$
Macros:

$P = 1.4 \times \text{goal weight (kg)}$
Fat kcal = 25% of target; carbohydrate kcal = remainder after protein and fat.

How the math works

Start with the default profile: age 42, female, current weight 198 lb (≈ 90 kg), height 5 ft 6 in (≈ 168 cm), activity Light (×1.375), and goal weight 165 lb (≈ 75 kg). Mifflin-St Jeor returns a basal metabolic rate (BMR) of about 1,575 kcal. Multiplying by the light-activity factor gives total daily energy expenditure (TDEE) near 2,165 kcal.

The widget subtracts 500 kcal from TDEE to produce a GLP-1 deficit target of about 1,665 kcal/day. Protein is set first at 1.4 × goal weight in kilograms, which is about 104.8 g (~419 kcal). Twenty-five percent of the calorie target goes to fat (~416 kcal, or about 46.3 g). Whatever kilocalories remain after protein and fat become carbohydrate (~830 kcal, or about 207.4 g).

Hydration uses current weight, not goal weight: 198 lb × 0.67 ≈ 133 oz (~3,933 ml). Fiber is a fixed 30 g counseling benchmark shown in the results tiles. If protein plus fat exceed the deficit target, the carbohydrate line shows “—” and a macro balance note appears; if the target falls below ~1,200 kcal for women or ~1,500 for men, a low-calorie warning appears instead.

Limits of the model

These targets are orientation for adults on or considering GLP-1 therapy, not individualized medical nutrition therapy. Appetite suppression from medication may make a 500 kcal deficit unnecessary or unsustainable without clinical oversight. The protein multiplier, fat percentage, and fiber benchmark are simplified counseling defaults—not substitutes for labs, renal function, or registered dietitian plans. Do not start, stop, or change GLP-1 prescriptions based on this page.

GLP-1 Macro & Calorie Calculator FAQ

What are GLP-1 medications?

Glucagon-like peptide-1 (GLP-1) receptor agonists mimic a gut hormone that strengthens fullness signals and slows stomach emptying. Weekly injectables for weight management include semaglutide (Ozempic for type 2 diabetes, Wegovy for obesity) and tirzepatide (Mounjaro for diabetes, Zepbound for obesity). They are prescription drugs; eligibility, titration, and monitoring belong with your clinician. This widget estimates nutrition targets only; it does not prescribe or adjust medication.

Why is protein based on goal weight and not current weight?

Section 03 goal weight anchors the “Muscle preservation target” in the results panel at 1.4 g per kilogram of goal body weight so the protein line does not fall as you lose mass. That pattern is common in obesity-management counseling to limit lean-tissue loss when appetite is suppressed. Kidney disease, heavy training, or other conditions may need a different number from your care team.

Is a 500 kcal deficit safe on Ozempic or Zepbound?

The dark “GLP-1 deficit target” card sets kilocalories to total daily energy expenditure (TDEE) minus 500, a textbook teaching default (~0.5 kg fat loss per week if fully adhered to). On GLP-1 therapy appetite is often lower, so some people land near or below that level without trying. If the target drops below common clinical floors (~1,200 kcal/day for many women, ~1,500 for many men), the widget shows a low-calorie warning; your prescriber or registered dietitian should confirm sustainability.

Why 30 g of fiber?

The “Dietary fiber target” tile in the results panel shows a fixed 30 g per day. GLP-1 drugs slow gastric emptying, so constipation and bloating are frequent complaints. Thirty grams is a practical counseling benchmark for many adults, aligned with general fiber guidance, but increase slowly with fluids. Ask your clinician before pushing fiber if you have inflammatory bowel disease, strictures, or similar conditions.

How is hydration estimated?

The “Hydration (fluid oz)” tile multiplies current weight in pounds by 0.67 (from section 01 current weight). At default 198 lb, that yields about 133 oz (~3,933 ml). It is a heuristic, not a prescription. Sweat, climate, heart failure, kidney disease, and diuretics change needs; thirst, urine color, and clinician advice matter more.

Does my medication dose change these numbers?

No. The medication dropdown in section 02 documents your protocol for context only; dose titration is not modeled. Energy and macro math uses age, sex, height, current weight, activity multiplier, and goal weight. This page does not project weeks to goal—that requires trial-calibrated pacing outside this widget’s scope.

How are fat and carbohydrates split?

After protein is fixed, the widget allocates 25% of the GLP-1 deficit target calories to dietary fat (shown in the “Dietary fat allocation” tile) and assigns whatever kilocalories remain to carbohydrate (“Carbohydrate remainder”). At defaults, fat is about 46.3 g (~416 kcal) and carbohydrate about 207.4 g (~830 kcal) once protein (~104.8 g) is reserved.

What does the macro balance note mean?

When fixed protein at 1.4 g/kg goal weight plus 25% fat exceeds the total deficit target, carbohydrate remainder goes negative and the widget shows a “Macro balance note.” Raise calories (smaller deficit), adjust goal weight for the protein model, or obtain individualized macros from a registered dietitian. The note appears in the results column when protein plus fat kilocalories exceed the target intake.

Sources & citations

References used for the calculation method and definitions. Links open in a new tab when available.

[1]

A new predictive equation for resting energy expenditure in healthy individuals

Mifflin MD, St Jeor ST, et al. Am J Clin Nutr. 1990. Mifflin–St Jeor BMR equation used in this calculator.

[2]

Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids

National Academies macronutrient report; 30 g/day fiber is a practical counseling benchmark here, not an individualized prescription.

[3]

Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults

NHLBI (1998). Historical basis for roughly 500 kcal/day deficit as a teaching target; modern care should individualize.

[4]

STEP 1 Trial: Semaglutide 2.4 mg for Weight Management (NEJM)

Semaglutide with intensive lifestyle support; protein-forward counseling models often reference STEP-style combined care.

Medical Estimation Note

Estimates Only: Nutrition targets use published equations (e.g., Mifflin-St Jeor) and simplified deficit and macro rules. They are not individualized medical nutrition therapy.

Individual Variation: Energy needs, tolerance, comorbidities, and medication response differ. Protein, fluid, and fiber goals should be confirmed with your care team.

Consult Your Provider: Consult your healthcare provider or registered dietitian before adopting a calorie or macro plan, especially on GLP-1 therapy.

Privacy First: All calculations are performed locally in your browser. No health data is stored or transmitted to any server.