Vital asks a few questions when you set up, then gives you a calorie target and protein, fat and carb targets. None of it is a secret, and all of it is editable. Here is exactly what happens, with the limits of each step.
What it asks
Sex, age, height, weight, how active you are, your goal (lose, maintain, gain, and a few in between), how fast you want to go, and how much protein you prefer. The same math is in the free calorie calculator, so you can try it without the app.
Step 1: resting burn, with Mifflin-St Jeor
Your resting energy expenditure is the calories you burn staying alive. Vital estimates it with the Mifflin-St Jeor equation, with weight in kilograms, height in centimeters and age in years:
Men: 10 x weight + 6.25 x height - 5 x age + 5 Women: 10 x weight + 6.25 x height - 5 x age - 161
Mifflin and colleagues built it in 1990 from measurements of 498 healthy adults aged 19 to 78, using indirect calorimetry. It is an equation fitted to a group, so it can miss a particular person by a lot, and it is less reliable outside that age range.
Step 2: an activity factor
Vital multiplies the resting burn by 1.2 (mostly sitting), 1.375 (light exercise), 1.55 (moderate) or 1.725 (hard training). These are a convention, not measurements. The result is an estimate of what you burn in a normal day.
Step 3: your goal
For losing or gaining, Vital works from a weekly change as a share of your body weight: 0.25%, 0.5% or 0.75% a week for gradual, moderate and fast. It turns that into calories with the usual rule of thumb of 3,500 calories per pound, then takes that many calories off or adds them each day. Because it scales with body weight, a heavier person gets a larger daily change than a lighter one at the same pace. Some goals use a fixed change instead: maintain and general health add nothing, a recomposition goal takes off 150 a day, and a performance goal adds 100. The final number is rounded to the nearest 10.
The 3,500 rule is rough. Bodies adapt, water moves around, and real weight change is rarely as tidy as the arithmetic. That is why Vital's Progress screen compares your actual pace with the pace your plan asked for.
Step 4: protein, fat and carbs
Protein comes from your preference: standard (about 1.6 grams per kilogram of body weight), high (about 2.0) or very high (about 2.4). The ranges follow the sports nutrition literature; the protein article has the sources. Fat is set at 25% of calories. Carbs are whatever calories are left, at 4 calories per gram.
A worked example
A 30-year-old man, 180 cm and 80 kg, moderately active, holding his weight:
- Resting burn: 10 x 80 + 6.25 x 180 - 5 x 30 + 5 = 1,780 calories.
- Times 1.55 = 2,759, rounded to 2,760 calories a day.
- Protein at 1.6 g per kg: about 128 g. Fat at 25% of 2,760 calories: about 77 g. Carbs: about 390 g.
- If he wanted to lose weight at the moderate pace: 0.5% of 176 lb is about 0.9 lb a week, which is about 440 calories a day less, so about 2,320 calories.
The app works in pounds internally, so its results can differ from this example by a gram or two.
Training days
If you schedule workouts, Vital adds a training-day bonus to your calories on those days, 200 by default and up to 600. It is a round, visible adjustment rather than something personalized, and you can set it to zero.
What to do with the number
Treat it as a starting point. Follow it for two or three weeks, watch your weight trend, and edit the targets by hand if the trend says your real needs are different. Vital never locks the numbers.
Sources
- 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
- Jager R, 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
Written November 5, 2026. This is general information, not medical advice. Talk to a doctor or dietitian before big changes to how you eat or train, especially with a medical condition or a history of disordered eating.