How the calculator works
First we calculate what your body burns at rest with the Mifflin-St Jeor equation, the most accurate formula for most adults in direct tests. Then we scale it to your daily activity, matched to doubly labeled water studies (NASEM 2023), and add 1–2 workouts a week (in the app, your own training). The result is your maintenance calories: what keeps your weight steady.
Calories to lose weight
To lose weight we plan a deficit for a steady pace of about 0.6% of your body weight a week (0.3–0.9% in the app, where you pick your pace), and never go below 1,200 kcal for women or 1,500 kcal for men. Faster isn't better: it costs more muscle and is harder to keep up.
Calories to build muscle
For muscle gain we add a small surplus of 5–15% over maintenance, at the lower end if you are new to training or carry more body fat. Most of a bigger surplus would be stored as fat.
Protein, carbs and fat
Protein comes first: about 1.6–2.2 g per kg of body weight if you train or are losing weight, 1.2 g if you don't. Fat stays at 20% of your calories or more, and carbs fill the rest, at least 130 g a day.
Calories per meal
In the Yummify app the day is split over your own meal times: about 25% at breakfast, 35% at lunch, 30% at dinner and 10% for a snack, with a little more in the morning when you're losing weight. If you skip a meal, only a little of it moves to the meals ahead, so dinner never turns into half the day. You choose two meals, three, or three and a snack. With a workout time, the meal before it gets a bit more and the first meal after it more, with extra protein. With fasting, your meals sit inside your eating window: two meals get half the day each, three get 40/35/25.
From calculator to plan
Bodies differ, so in the Yummify app your plan also uses your training, diet, body fat and health, and every week it compares what you ate with your weight trend and fine-tunes your target.