What and how much should you eat?

What are your calorie needs?

A calorie is a measure of energy. Your body uses energy while breathing, regulating temperature, digesting food, working, walking and exercising. Your total expenditure therefore consists of much more than the calories burned during a workout.

Resting expenditure is not the same as maintenance

Resting energy expenditure is the energy your body would need at complete rest. Maintenance needs are higher and also include daily movement, work, exercise and food processing. When we refer to a deficit of 10, 15 or 20 percent, this is a percentage of estimated total maintenance—not resting expenditure.

Which equation does the calculator use?

The calculator estimates resting energy expenditure with the Mifflin–St Jeor equation. This equation uses age, height, weight and sex. It was originally developed using indirect calorimetry and is still widely used as a practical prediction equation (Mifflin et al., 1990).

The result is then multiplied by an activity factor to estimate total daily expenditure. Research shows that prediction equations are useful starting points but may differ substantially from an actual measurement in individuals. Even a comparatively reliable equation can be more than ten percent off for some people (Madden et al., 2016; Thom et al., 2020).

How do you match calories to your goal?

Fat loss: eat less than total maintenance

To lose body weight and body fat, average energy intake must be lower than total expenditure. The calculator therefore subtracts a percentage from estimated maintenance.

A larger deficit may produce faster weight loss on paper, but can also increase hunger, fatigue, reduced training performance and risk of losing lean mass. The calculator therefore offers moderate options of 10, 15 and 20 percent.

Maintaining weight

At maintenance, average energy intake roughly equals expenditure. Maintenance is not one magical exact number; it is a small range in which average body weight remains mostly stable across several weeks.

Gaining weight and building muscle

For weight gain, the calculator uses a modest surplus of 5, 10 or 15 percent above maintenance. More calories do not automatically mean more muscle growth. Without appropriate resistance training, sufficient protein and recovery, a large surplus mainly raises the chance of additional fat gain.

Different dietary distributions can produce weight loss. In the DIETFITS trial, average 12-month weight loss did not differ significantly between a healthy low-fat and healthy low-carbohydrate diet. This does not mean every diet feels the same for every person, but it does show that one mandatory macro distribution does not exist (Gardner et al., 2018).

What are macros and how do you divide them?

Macros is short for macronutrients: protein, carbohydrates and fat. These nutrients provide calories and also serve different functions in the body. The calculator first sets total calories, then calculates a practical protein amount, reserves a portion for fat and assigns the remaining calories to carbohydrates.

Protein

Protein supplies amino acids for building and repairing body tissue. The calculator uses a higher practical target for people performing resistance training than for non-lifters. During fat loss, the amount is raised somewhat to support retention of lean mass. Meta-analyses indicate small but relevant benefits from higher protein intake alongside resistance training, with average additional benefits in many healthy trainees levelling off around 1.6 grams per kilogram per day (Morton et al., 2018; Nunes et al., 2022).

Fat

The calculator allocates about 28 percent of calories to fat by default. This is not a perfect ratio for everyone, but a balanced starting point. Fat is not merely energy: it supplies essential fatty acids, forms part of cellular structures and supports absorption of fat-soluble vitamins. A separate Academy article will explore this in more depth.

Carbohydrates

Remaining calories are assigned to carbohydrates. Carbohydrates are a practical energy source and can support intensive training. You do not need to remove carbohydrates to lose fat. Overall energy balance, food quality, satiety and adherence are more important than banning one nutrient.

What if you do not eat meat, fish or animal products?

Calorie and macro targets can also be achieved with a vegetarian or fully plant-based diet, although the foods used to achieve them change. Protein may come from tofu, tempeh, legumes, seitan, soy, grains, nuts and seeds. A varied plant-based diet can supply sufficient protein and essential amino acids when total energy and protein intake are appropriately planned (Mariotti & Gardner, 2019).

Macros alone do not guarantee adequate micronutrients. A fully plant-based diet requires extra attention to nutrients including vitamin B12, iron, calcium, iodine, zinc, vitamin D and omega-3. A systematic review found that intake or status of several of these nutrients may frequently be lower in vegans (Bakaloudi et al., 2021).

Do you need to weigh your food?

You can eat healthily without weighing every food. Nevertheless, temporary weighing is often useful when you have little insight into portions. Many people do not know how much oil, pasta, rice, nuts, cheese or sauce they actually use. Small errors per product can create a large difference across a full day.

By weighing and recording accurately for several weeks, you learn what portions of 50, 100 or 200 grams actually look like. The goal is not lifelong dependence on a kitchen scale, but gaining knowledge. Systematic reviews indicate that dietary self-monitoring can be an important component of behavioural weight-loss programmes (Raber et al., 2021).

Can you later eat intuitively?

Yes. Once you know recurring foods and portions well, you can increasingly rely on routines and visual estimates. You can return to more accurate weighing when your goal changes, progress stalls or portions have gradually increased. Digital tracking can make this process easier, but it mainly works when the tool is actually used consistently (Patel et al., 2021).

Why keep a food diary?

A food diary shows not only what you planned to eat, but what you actually ate. That difference matters. Drinks, oil, sauces, snacks and small extras are easy to forget, even though they can add up over an entire day.

Especially when you are just starting, it helps to record your foods and amounts for several weeks. You learn which meals provide more or less energy, how much protein you actually consume and which habits keep returning. Research on self-monitoring shows that recording food intake can be a useful part of behavioural weight-loss programmes (Raber et al., 2021; Patel et al., 2021).

Use it as a learning tool, not as punishment

The goal is to build insight. You do not need to record every food forever. Once you know your usual meals and portions, you can rely more on routine. The PowerVita App can keep your food diary organised and show how your daily calories, protein, carbohydrates and fat develop.

Why weigh yourself regularly?

The calculator can only estimate your needs. Your weight trend shows what happens in practice. Daily weighing can provide many data points, provided you do not react to every isolated number. Body weight changes from day to day because of water, salt, carbohydrates, digestive contents and training stress.

Preferably weigh in the morning, after using the bathroom, before eating or drinking and under comparable conditions. Then calculate a seven-day average. Compare weekly averages rather than Monday with Tuesday. A cohort study of ten thousand smart-scale users found an association between more frequent weighing and more favourable weight change, although such an association does not prove that weighing itself causes the result (Vuorinen et al., 2021).

How to discover what you actually need

1. Use the calculator to select an initial calorie and macro target.
2. Weigh and record food as accurately as possible, including oil, drinks, sauces and snacks.
3. Weigh yourself under comparable conditions and calculate weekly averages.
4. Keep the approach reasonably consistent for at least two to four weeks.
5. Assess whether average body weight is moving towards your goal.
6. If necessary, adjust cautiously—for example by about 100 to 200 kcal per day—and measure again.

Energy expenditure also changes with body size, body composition, activity and life stage. Large-scale doubly labelled water research shows that the pattern across the lifespan is more nuanced than the simple idea that metabolism automatically slows dramatically every year (Pontzer et al., 2021).

Conclusion

A good calorie and macro calculation provides direction but is never the final answer. The equation estimates needs from general information. By temporarily weighing food, following body weight as a trend and evaluating the result after several weeks, the estimate becomes increasingly personal.