How we count every number

Daily calories

Your calorie target is your resting metabolism multiplied by an activity factor, then adjusted for your goal.

Resting metabolism uses the Mifflin–St Jeor equation, which was built by measuring 498 healthy adults with indirect calorimetry and explains about 71% of the variation between people.

The activity factors (1.2 to 1.9) are the convention used with this equation rather than a value taken from one study. For reference, the FAO/WHO/UNU framework groups adults into 1.40–1.69 (sedentary or light), 1.70–1.99 (moderately active) and 2.00–2.40 (vigorously active); the app's lowest factors deliberately sit below that floor for people who barely move.

Because it is a population average, your real expenditure can differ by several hundred kilocalories. If your weight does not move the way the target predicts after two or three weeks, trust the scale over the formula.

Losing and gaining weight

Choosing Lose subtracts 500 kcal a day. The 2013 AHA/ACC/TOS obesity guideline prescribes exactly this: a 500 or 750 kcal daily energy deficit, which for most people means roughly 0.5 kg a week.

Choosing Gain adds 350 kcal a day. The surplus is deliberately small: in trials on trained athletes, a larger surplus added more fat without adding proportionally more muscle.

Maintain adds nothing.

Protein

The app targets 2.2 g of protein per kilogram of body weight.

A meta-analysis of 49 studies and 1,863 people found that gains in muscle and strength from protein flatten out at about 1.62 g/kg/day, with the confidence interval reaching up to 2.2 g/kg/day. The app deliberately uses the top of that interval, so a heavy training week is covered rather than under-fed.

For context, the ISSN position stand puts the general range at 1.4–2.0 g/kg/day for exercising adults, and 2.3–3.1 g/kg/day for trained people eating in a calorie deficit.

Higher protein is not automatically better, and people with kidney disease should not follow these numbers without a doctor.

Fat

Fat is set at 25% of your calorie target, which sits in the middle of the Acceptable Macronutrient Distribution Range of 20–35% of energy for adults, published by the Institute of Medicine.

Fat carries 9 kcal per gram, which is why the gram number looks small next to carbs.

Carbohydrates

Carbohydrates are whatever calories are left once protein and fat are taken out. They are not targeted directly.

This keeps the three macros adding up to your calorie target exactly, and it usually lands inside the Acceptable Macronutrient Distribution Range of 45–65% of energy.

Fibre

Fibre is set at 0.35 g per kilogram of body weight, which for most adults lands between 25 and 35 g a day.

EFSA considers 25 g a day adequate for normal bowel function in adults and notes further benefit above that. The Institute of Medicine expresses the same idea per energy: 14 g per 1,000 kcal.

BMI

Body mass index is your weight divided by your height squared. The bands come from the World Health Organization: below 18.5 underweight, 18.5–24.9 normal, 25.0–29.9 overweight, 30.0 and above obesity.

BMI does not know the difference between muscle and fat, and it says nothing about where fat sits on your body. Trained, muscular people frequently read as overweight while being nothing of the sort. Treat it as one crude number among several, never as a diagnosis.

Water

This one is different from the rest, and it is worth saying plainly: the hydration goal is our own estimate, not an equation taken from a published study.

It starts from your lean body mass, allows 40 ml per kilogram of lean mass and 20 ml per kilogram of the rest, nudges the result slightly for age and height, then caps it between 1.5 and 4 litres and rounds it to glasses of 250 ml.

For an external reference point, EFSA sets adequate total water intake at 2.0 litres a day for women and 2.5 litres for men — counting all drinks plus the water in food, not just what you log here.

Thirst, urine colour and your climate tell you more than any formula. Some conditions require fluid restriction, and there the number in this app does not apply at all.

Food quality flags

When the app flags a food as high in sugar, saturated fat or salt, or scores the quality pillar in the Nutrition Report, it compares your logged food against public dietary limits.

Sugar: WHO recommends free sugars stay under 10% of total energy, and suggests under 5% for further benefit. Saturated fat: the Dietary Guidelines for Americans set a limit of less than 10% of daily calories. Sodium: the FDA Daily Value is less than 2,300 mg a day, and 1 g of salt is about 393 mg of sodium.

These are population guidance for healthy adults, not personal limits set for you.