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Scientific sources

These are the formulas, references and food databases behind Renzy’s numbers, with a link to each source and what it is used for. If one does not feed any calculation in the app, we say so.

Disclaimer: Renzy is an informational tool, not a substitute for medical advice. Consult a healthcare professional before starting any diet if you have health conditions, are pregnant or breastfeeding.

Total daily energy expenditure (TDEE)

Your resting energy use comes from the Mifflin-St Jeor equation (weight, height, age and sex) and is multiplied by an activity factor: from 1.2 if you barely move during the day to 1.9 if your activity is very high.

  • Mifflin MD, St Jeor ST, et al. (1990)

    Equation for resting energy expenditure from weight, height, age and sex. Renzy uses it to work out your calorie target.

    PubMed

  • Harris & Benedict (revised, Roza & Shizgal 1984)

    Revision of the classic equation. Renzy does not use it for your target: it is listed because the calculators and articles compare it with Mifflin-St Jeor.

    PubMed

  • WHO/FAO/UNU — Human Energy Requirements (2004)

    WHO report that defines the physical activity level (PAL): daily energy use as a multiple of resting energy use. Renzy uses that idea with the activity factors common in calculators (1.2 to 1.9), not with this report’s tables.

    FAO

  • EFSA — Dietary Reference Values for Energy (2013)

    European reference values for energy. Background reading: it does not feed any calculation in Renzy.

    EFSA

Macronutrients and protein

Protein comes from your weight and your goal; fat is 25% of calories (22% if you only do endurance sport), within EFSA’s 20-35%; carbs are the rest.

  • ISSN Position Stand — Protein and Exercise (2017)

    Range of 1.4 to 2.0 g per kg a day for active people. Renzy sets 1.8 g/kg if you want to lose or gain weight or you do strength training, and 1.4 g/kg if you want to maintain; above a BMI of 25, per kg of the weight you would have at a BMI of 25.

    JISSN

  • ACSM/AND/DC — Nutrition and Athletic Performance (2016)

    Joint position of the American College of Sports Medicine and the Academy of Nutrition on macros during physical activity.

    ACSM

  • EFSA — Dietary Reference Values (general)

    Official European ranges for carbohydrates (45–60% energy), fats (20–35%) and fibre (>25 g/day).

    EFSA

  • NIH Office of Dietary Supplements — Omega-3

    Reference for what Renzy’s tips say about omega-3 (oily fish). It does not feed any calculation.

    NIH ODS

Food databases

The scanner estimates with AI and then checks each food against our own table of values per 100 g taken from USDA and BEDCA: if one is far off its value, it is corrected. Barcode products bring their label data from Open Food Facts.

  • USDA FoodData Central

    Public database of the US Department of Agriculture. Many of the per-100 g values Renzy checks the scanner’s estimates against come from here.

    USDA

  • BEDCA — Base de Datos Española de Composición de Alimentos

    Spain’s official food composition database. The values for many typical Spanish foods in that same table come from here.

    BEDCA

  • Open Food Facts

    Collaborative database of packaged products. When you scan a barcode, the label data comes from here; if the product is not there, you can type it in yourself.

    OFF

Weight loss and gain

To lose weight, Renzy takes 500 kcal a day off your energy use at the normal pace (275 at the slowest and 750 at the fastest, never more than 25% of your energy use and never below the safety minimums) and works out kilos per week with the classic rule of 7,700 kcal per kilo. It is an approximation: over time weight comes off more slowly (Hall, below).

  • Hall KD et al. — Quantification of energy imbalance on bodyweight (2011)

    NIH model showing why the classic rule (3,500 kcal per pound, about 7,700 per kilo) promises more loss than actually comes over time: as you lose weight, energy use drops. Renzy uses the classic rule for the estimated date.

    NCBI

  • American Heart Association — Losing Weight

    AHA guide to safe, sustainable calorie deficits. Renzy’s normal pace (500 kcal a day) works out at about 0.45 kg a week.

    AHA

  • WHO — Healthy Diet (fact sheet)

    General WHO recommendations for a healthy diet. Each plate’s score uses its limits on free sugars, salt and saturated fat.

    WHO

Hydration

The water amount Renzy suggests (in Settings and in the water calculator) is an estimate of 35 ml per kilo of body weight that goes up with activity and, in the calculator, with heat. It does not depend on sex. The references below are there to compare it with.

  • EFSA — Adequate Intake of Water (2010)

    2.0 L a day for women and 2.5 L for men, including water from food. It is there to compare with Renzy’s estimate; the app does not track the water you drink.

    EFSA

  • NIH/IOM — Dietary Reference Intakes for Water

    Complementary US reference. It explains why you need more water in the heat or with hard exercise; it does not feed any calculation in Renzy.

    NIH / IOM

Missing a reference or think a citation is wrong? Write to us at hola@renzy.app.