Information tool, not medical advice. Do not decide your medication dose or any change of treatment from this website. Ask your doctor. Text size
Modern Obesity Treatment

Calorie guide methodology

The calorie guide is an information tool, not medical advice. Every number is a range, never a single exact value. The equations come from published studies (see sources). The activity multipliers, the size of the deficit, the lower intake limits and the width of the range are a conservative choice by the website author and are not taken from a single guideline. The guide does not replace a doctor or a dietitian.

1. When the calculator does not calculate

The calculator does not calculate for anyone under 18 or when an exception is ticked: pregnancy or breastfeeding, insulin treatment, an eating disorder. Missing or implausible data only prompts the user to complete it (height 120 to 230 cm, weight 30 to 400 kg, age 1 to 100).

2. Resting energy expenditure (BMR)

The first formula that applies to the data entered is used:

  • From measured lean mass: BMR = 370 + 21.6 × lean mass (kg), if lean mass is at least 20 kg and lower than body weight.
  • From body fat (5 to 70 %): lean mass is calculated as weight × (1 − fat / 100) and the same formula is used.
  • Without a measurement: Mifflin-St Jeor, 10 × weight + 6.25 × height − 5 × age + 5 for men and … − 161 for women (weight in kg, height in cm).

The formula 370 + 21.6 × lean mass comes from Cunningham (1980) and is often called Katch-McArdle in practice.

3. Activity and total expenditure

Total expenditure (TDEE) is BMR × multiplier. The activity level is chosen by the average number of steps per day (five bands after Tudor-Locke and Bassett: under 5,000, 5,000 to 7,500, 7,500 to 10,000, 10,000 to 12,500 and over 12,500 steps). The multipliers are 1.2 (sedentary), 1.3 (light), 1.45 (moderate), 1.6 (active) and 1.75 (very active). They are deliberately cautious because activity is commonly overestimated at higher body weight.

4. Deficit and lower limit

The deficit is the smaller of: 22 % of total expenditure, or 750 kcal. The target intake is total expenditure minus the deficit. Intake never falls below 1,500 kcal for men and 1,200 kcal for women. If the target would be lower, the calculator uses the limit and says so.

5. Intake range

A range is built around the target intake: ±7 % without a body composition measurement, ±4 % with measured lean mass or body fat. Limits are rounded to 10 kcal, the lower limit never falls below the floor and the upper is always at least 20 kcal higher.

6. Protein

Ideal body weight by the Devine formula: 50 kg (men) or 45.5 kg (women) + 2.3 kg for every inch of height above 152.4 cm. Adjusted weight, when above ideal, is ideal + 0.25 × (weight − ideal), otherwise actual weight. The protein range is 1.2 to 1.6 g per kg of adjusted weight, rounded to 5 g.

7. BMI

BMI = weight / (height in metres)², to one decimal place. With a BMI below 25 the guide notes that it targets a higher BMI.

8. Check after a few weeks

The expenditure estimate is only an estimate. After a few weeks compare it with how your actual weight changed and discuss the result with a doctor or dietitian.

9. Intake goals and nutrient breakdown

The calculator offers three goals. Weight loss is the intake from steps 4 and 5. Maintenance is the estimate of total expenditure (TDEE) with the same range (±7% or ±4%). Weight gain is total expenditure plus a small surplus: the smaller of 10% of expenditure and 300 kcal a day, again with the same range. When treating obesity, gaining weight is usually not the goal, so for weight gain the website advises consulting a doctor.

The nutrient breakdown (the expandable part of the result) is calculated from the middle of the chosen intake range:

  • Protein: g per kg of adjusted weight: weight loss 1.2 to 1.6; maintenance 1.0 to 1.4; weight gain 1.4 to 1.8. Spread over 3 to 4 meals.
  • Fat: 20 to 30% of energy (9 kcal/g). The lower bound is from EFSA, the upper from WHO. Saturated fat less than 10% of energy.
  • Carbohydrate: the rest of the energy (4 kcal/g) after protein and fat. Free sugars less than 10% of energy.
  • Fibre: at least 25 g a day (EFSA, WHO).
  • Fluids: total intake including water from food 2.0 l for women and 2.5 l for men (EFSA).

The protein ranges lie within the ranges of the cited statements (0.8 to 1.6 g/kg on GLP-1 treatment; 1.4 to 2.0 g/kg when training to build muscle). The exact numbers within those ranges are the website author's choice. The breakdown is approximate and does not replace the advice of a doctor or a dietitian.

Sources

Citations were checked in the Crossref database on 9 November 2026.

  • Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247. doi:10.1093/ajcn/51.2.241
  • Cunningham JJ. A reanalysis of the factors influencing basal metabolic rate in normal adults. Am J Clin Nutr. 1980;33(11):2372–2374. doi:10.1093/ajcn/33.11.2372
  • Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650–655. doi:10.1177/106002807400801104
  • Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr. 1958;6(5):542–546. doi:10.1093/ajcn/6.5.542 (basis of the 7,700 kcal per kg simplification in the adjustment)
  • Spreckley M, Ruggiero CF, Brown A. Bridging the nutrition guidance gap for GLP-1 receptor agonist therapy assisted weight loss: lessons from bariatric surgery. Int J Obes. 2025;50:265–267. doi:10.1038/s41366-025-01952-w. It summarises the joint advisory of ACLM, ASN, OMA and TOS (Mozaffarian et al., 2025) with protein of 0.8 to 1.6 g/kg/day. Our range of 1.2 to 1.6 g/kg of adjusted weight lies within it; the lower bound of 1.2 is our choice.
  • Activity multipliers, deficit, lower intake limits and range width: the website author's choice, with no single cited guideline.
  • Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. doi:10.1186/s12970-017-0177-8
  • EFSA. Scientific Opinion on Dietary Reference Values for fats. EFSA Journal. 2010;8(3):1461. doi:10.2903/j.efsa.2010.1461
  • EFSA. Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre. EFSA Journal. 2010;8(3):1462. doi:10.2903/j.efsa.2010.1462
  • EFSA. Scientific Opinion on Dietary Reference Values for water. EFSA Journal. 2010;8(3):1459. doi:10.2903/j.efsa.2010.1459
  • WHO. Healthy diet (fact sheet, updated 26 January 2026, checked 9 November 2026): free sugars less than 10% of energy, fat at most 30%, saturated fat less than 10%, fibre at least 25 g.

Data protection

The calculation runs only in your browser. The data you enter is never sent or stored; see privacy.