How Essentra sets your targets

Every number Essentra gives you is a calculated estimate from published research, worked out from your own answers. It is not medical or nutrition advice. This page sets out each step, the figure it uses, why we chose it, and where it comes from. The app's About screen lists the same sources in short form.

Last updated: November 2026

The short version

• Calories are your resting energy, plus your everyday movement, plus your training, grossed up for digestion, then adjusted for your goal.
• Protein is set first, per kg of body weight, by goal and training type.
• Carbohydrate follows how much you train.
• Fat takes what's left, and never goes under 20% of calories.
• With Apple Health connected, your watch's own measurements replace the estimates for resting energy, everyday movement and training.

Calories

Resting energy

The energy your body uses at complete rest. We estimate it with the Mifflin–St Jeor equation, from your age, sex, height and weight (Mifflin et al. 1990, Am J Clin Nutr 51:241). A systematic review found it the most accurate of the standard equations (Frankenfield et al. 2005, J Am Diet Assoc 105:775).

We use it with your actual weight at every body size, as the Academy of Nutrition and Dietetics recommends for adults with overweight or obesity (Adult Weight Management guideline, 2014). Some clinics substitute an "adjusted" body weight. We don't: its formula and when to apply it vary between clinics, and we found no guideline that recommends it for resting energy.

How accurate is it at the extremes? At a BMI of 50 and over, Mifflin–St Jeor was within about 1.5% of measured resting energy on average, but only about 57% of individuals came within 10% (Rather et al. 2025, Curr Dev Nutr 9:107538, 198 people at BMI 50+). Below a BMI of 16, no standard equation does well: in 1,726 patients, the best of 28 came within 10% for only about 43% of people (Jésus et al. 2015, *Clin Nutr* 34:529). That's why the app tells you, below a BMI of 18.5 or at 40 and over, to treat its numbers as a rough starting point.

Everyday movement

How much you move outside training: commuting, standing, chores. We use physical activity levels measured with doubly labelled water, the most accurate way to measure what people burn in daily life (FAO/WHO/UNU, *Human Energy Requirements*, 2004, Table 5.1), each at the bottom of its measured range:

1.40 is the lowest level the report finds healthy adults sustaining. Many calculators use 1.2 for a desk day, but no measurement supports a figure that low, and the report calls it too low for anyone living normally. These levels hold across body sizes: in 319 measurements, the ratio of total to resting energy stayed about the same from lean to obese, dipping slightly only in severe obesity (Prentice et al. 1996).

Training

Each session's minutes at the energy cost of its kind, from the Compendium of Physical Activities (Ainsworth et al. 2011, *Med Sci Sports Exerc* 43:1575):

We count only what training adds above rest (the MET minus 1), against your own resting rate rather than a standard one, which comes out a little lower for most adults (Byrne et al. 2005, J Appl Physiol 99:1112). A session with no stated length counts as 45 minutes.

Digestion

Digesting food uses about 10% of what you eat (Westerterp 2004, Nutr Metab 1:5). Neither resting nor active energy includes it, and no wearable measures it, so the estimate is divided by 0.9. When your watch reports its own resting energy, we use that measurement as it is.

With Apple Health

When you connect Apple Health, your watch's 28-day averages replace the resting, everyday movement and training estimates. We read one device at a time, so a phone and a watch aren't counted twice, and we leave out your single highest and lowest days.

Training days and rest days

With a set weekly schedule, each day's calories follow that day's training: a training day adds what its session costs, a rest day doesn't. Protein stays the same every day, and the week adds up to the same total. If you'd rather have one number all week, choose Same every day.

Your goal

Lose weight or gain weight

You choose a pace, as a share of your body weight a week:

Losing 0.5–1% a week keeps lean mass in trained people (Helms, Aragon & Fitschen 2014, J Int Soc Sports Nutr 11:20; Garthe et al. 2011, Int J Sport Nutr Exerc Metab 21:97). Gaining faster than 0.5% a week adds mostly fat (Iraki et al. 2019, Sports 7:154). We convert weight to calories at 7,700 kcal per kg. That overstates long-run loss, because your spend falls as your weight does (Hall 2008, Int J Obes 32:573), so the app says "about" and never promises a date.

Limits on a deficit

A cut never takes a day under 1,500 kcal for a man or 1,200 for a woman, and never takes more than 750 kcal a day off your maintenance. These are the bottom of the intakes, and the larger of the two deficits, that the 2013 AHA/ACC/TOS obesity guideline prescribes for weight loss: 1,200–1,500 kcal a day for women and 1,500–1,800 for men, or a 500–750 kcal deficit (Jensen et al. 2014, Circulation 129(suppl 2):S102–S138, recommendation 3a, grade A; doi:10.1161/01.cir.0000437739.71477.ee).

Without these limits, Faster on a heavy body asked for far more: about 1,100 kcal a day at 100 kg. Diets of 800 kcal a day or less are "very low calorie diets", which both the US National Heart, Lung, and Blood Institute and the UK's NICE say need medical supervision.

For people who train, a cut also never takes carbohydrate below the bottom of its published range (see Carbohydrate). When any limit holds your cut back, the app says which one, and how fast you'll actually go.

Below a BMI of 18.5, the WHO's cut-off for underweight, Lose weight is still yours to choose. The app adds one line: the weight-loss guideline these limits come from covers adults with overweight or obesity, and resting-energy equations are least reliable at low BMI, so the number is a rough starting point.

Maintain, Recomp and Perform

• Maintain eats at maintenance.
• Recomp (lose fat, keep or build muscle) eats a Gentle deficit, 0.25% of body weight a week, with protein at 2.2 g per kg. Recomposition research describes a slight deficit with high protein (Barakat et al. 2020, Strength Cond J 42:7).
• Perform eats at maintenance, with carbohydrate at the top of its range. The extra carbohydrate comes out of fat, down to its 20% minimum, then out of protein, down to 1.6 g per kg.

Protein

Set first, per kg of body weight. Each figure is the middle of its research range:

All the training figures sit within the International Society of Sports Nutrition's 1.4–2.0 g per kg (Jäger et al. 2017, *J Int Soc Sports Nutr* 14:20), Recomp aside.

Protein never takes more than 35% of the day's calories, the top of the healthy range for adults (Institute of Medicine 2005, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids). At ordinary weights the per-kg figure is well under that, so nothing changes. At very high body weights, grams per kg of total weight can outgrow the whole day (700 g on Recomp at 318 kg), and the per-kg research was done on athletes, not at those weights.

Carbohydrate

Carbohydrate follows how much you train, in grams per kg of body weight, at the middle of each published band:

Endurance bands are from the ACSM, Academy of Nutrition and Dietetics and Dietitians of Canada joint position stand (Thomas, Erdman & Burke 2016, Table 1, from Burke et al. 2011). Strength athletes are at 4–7 g per kg (Slater & Phillips 2011, J Sports Sci 29:S67). Strength work uses far less muscle glycogen than the same hour of running, and no source maps its range onto duration, so we don't extend it. Hybrid is the mean of the two. The figures between the anchors are drawn as a smooth line, so a little more training means a little more carbohydrate rather than a jump.

At low training volumes, runners and lifters land close together, because both start in the same "light training" band. They separate as training goes up.

Fat

Fat takes what's left after protein and carbohydrate, but never less than 20% of calories. The joint position stand gives 20–35% and finds no benefit below 20% (Thomas, Erdman & Burke 2016), and 20% is the bottom of the Institute of Medicine's range. When protein and carbohydrate would leave less, carbohydrate is trimmed to make room.

Everyday sets fat at 30% of calories, with carbohydrate taking the rest.

Everything adds up

Protein and carbohydrate count as 4 kcal a gram and fat as 9. Every plan's macros add up to its calories, to within half a gram of fat from rounding, and we test that across thousands of combinations of body, training type, goal and pace.

What we don't do

• We don't estimate a nutrient a food doesn't report. Missing data shows as missing, not zero.
• We don't diagnose. A number on Essentra describes what you logged or what the research suggests for your inputs, never your health.
• We don't change your goal for you. Where the research is thin for your body, we say so, and the choice stays yours.

Questions about any of this? Email [email protected].