Reviewed by Brian St. Pierre, MS, RD

Calorie manipulation—whether to lose weight or gain muscle—seems simple.

After all, it’s just math… right?

Sort of. But it’s tricky.

Your body is a complex machine. In order to determine how many calories your body needs to achieve your goals, you need to first understand how your body burns (and stores) calories.

Want to find out more about what your body does with calories? Keep reading.

What’s the average necessary daily calorie intake?

The concept of a calorie is grounded in tangible science: One calorie equals the energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.

Caloric needs can vary significantly from person to person, depending on various factors. These factors include your gender-assigned-at-birth, age, height, and overall lifestyle.

Generally speaking, adults require approximately 1,600 to 3,000 Calories per day.

(Yes, that’s a huge range. So obviously, your individual needs might differ.)

The foods you eat and their quantities dictate the number of calories you consume.

Consuming more calories than your body expends leads to weight gain, while consuming fewer calories than your body expends in weight loss—including fat and eventually muscle mass.

Making food choices based on calorie count is a common practice for people striving to lose or maintain weight. Calories are derived from the macronutrients of carbohydrates, fats, proteins, and other sources like alcohol.

The timing and frequency of meals also impact energy use, as your body’s energy expenditure fluctuates throughout the day.

What factors affect how many calories you need per day?

As we mentioned above, several factors influence your daily calorie needs. Let’s go into more detail about these factors and how they work together.

1. Age

As you age, your metabolism naturally slows down, so your body requires fewer calories.

This is why teenagers, with their active growth phases, usually need more calories compared to middle-aged adults.

2. Height and weight

Your physical dimensions (height and weight) as well as your body composition (muscle and fat ratios) play a role in caloric calculations.

Those who are larger—either taller, or they have a higher percentage of muscle mass—may burn more calories at rest and require more calories to sustain their daily needs.

3. Gender and hormones

Gender-assigned-at-birth and hormonal differences significantly influence caloric needs.

Men often have higher muscle mass and a faster metabolism, necessitating more calories.

Affected by hormonal fluctuations, women may experience appetite and energy expenditure variations throughout their menstruating years.

4. Activity level

Your lifestyle and activity level have an enormous impact on caloric requirements.

Those with physically demanding jobs or who engage in vigorous exercise will naturally burn more calories and need a higher intake to maintain energy balance.

Of course, the reverse is true for those who have sedentary jobs (such as desk jobs) and don’t intentionally exercise much.

5. Medical conditions and medications

Certain medical conditions, like thyroid disorders, can affect your metabolism and alter your caloric needs.

Additionally, certain medications might influence appetite, energy expenditure, or nutrient absorption, further impacting your daily calorie needs.

6. Basal Metabolic Rate (BMR)

Your basal metabolic rate represents the energy your body expends at rest to perform essential functions like breathing, circulating blood, and maintaining body temperature.

BMR is influenced by genetics, muscle mass, and age, all of which contribute to your daily caloric requirements.

We’ll discuss BMR and how it works alongside other body processes in greater detail below.

7. Goals

Whether you aim to lose weight, gain muscle, or maintain your current physique, your goals shape your caloric needs.

Weight loss typically involves a controlled reduction in caloric intake, while muscle gain demands additional calories to support growth and repair.

What processes affect how you burn calories?

Here are the various ways your body burns calories.

Exercise Activity Thermogenesis (EAT)

EAT refers to the energy your body expends during intentional physical activity, such as walking, running, lifting weights, fitness classes, or any other exercise you incorporate into your routine.

Contrary to common belief, EAT constitutes a relatively small portion of your total energy expenditure—approximately five to ten percent on average.

(Like everything, this percentage can vary.)

For most individuals, while EAT is undoubtedly beneficial for overall health and well-being, its direct impact tends to be minimal; the broader context of your overall energy expenditure matters more.

Non-Exercise Activity Thermogenesis (NEAT)

Non-Exercise Activity Thermogenesis (NEAT) encompasses the calories burned through your everyday physical movements outside of structured exercise routines.

It’s the energy your body expends when you engage in activities like cooking, cleaning, shopping, or even fidgeting—actions that don’t fall under planned exercise or sports.

Despite its inconspicuousness, NEAT holds remarkable potential to influence your metabolic rate and calorie burning. NEAT can contribute up to 15 to 30 percent of your daily caloric expenditure. While it’s not a substitute for vigorous workouts, that’s a noteworthy portion of the calories you burn every day.

Environmental conditions, genetics, job type, and lifestyle all contribute to NEAT’s variability from person to person. A sedentary job and an active profession might result in notable differences in daily calories burned.

Research has highlighted NEAT’s role in promoting wellness. A study tracking over 12,000 women for 12 years demonstrated that activities like fidgeting could mitigate the risks associated with prolonged sedentary behavior.

If you want to increase your NEAT, subtle changes like opting for a standing desk at work instead of sitting—which burns more calories per hour—can help.

NEAT’s influence extends beyond just calorie burn—it encourages a lifestyle that values movement throughout the day. This impacts on your overall energy balance—but maybe even your long term quality of life too.

Basal Metabolic Rate (BMR)

BMR, often referred to as your “resting metabolic rate,” represents the energy your body expends to maintain essential functions while at complete rest.

These include vital activities like your heartbeat, respiration, cell regeneration, body temperature maintenance, and all the other foundational biological activities required to sustain life when you’re inactive.

BMR calculators tell us that, on average, BMR constitutes about 60 to 70 percent of your daily energy expenditure. However, accurate BMR calculation requires a 12-hour fast, sufficient sleep, and absolute rest devoid of physical exertion.

Age, body composition, hormones, and body shape influence your BMR:

▶ Children and adolescents exhibit higher rates due to ongoing growth demands, while adults experience a gradual decline as the body shifts from building to breaking down.

▶ Individuals with more muscle have higher BMRs, as muscles demand more energy for maintenance. Conversely, higher proportions of body fat will lower BMR since fatty tissue requires minimal energy upkeep.

▶ Gender-assigned-at-birth also matters, with men generally possessing higher BMRs due to higher average muscle mass.

▶ Hormones, like thyroxine from the thyroid gland, also influence BMR. Thyroxine levels correlate with metabolic rate: Elevated levels increase BMR, while reduced levels decrease it.

Thermic Effect of Food (TEF)

The Thermic Effect of Food (TEF) is how your body expends energy during the processes of digestion, absorption, and metabolism of the food you consume.

Think of TEF as the energy cost your body pays to process the nutrients from your meals.

TEF accounts for roughly ten percent of your caloric intake in a day. So, if you consume 2,000 calories, around 200 calories are expended just through eating and digestion.

The composition of your food profoundly influences TEF. Different macronutrients (carbs, fats, and protein) require varying levels of energy for digestion and metabolism.

Protein and complex carbohydrates have a higher thermic effect, demanding more energy for breakdown. In contrast, fats and simple carbohydrates have a lower thermic effect, necessitating comparatively less energy expenditure.

To delve into specifics, here’s how macronutrients impact TEF:

• Fat: 9 calories per gram; TEF ranges from 0-5 percent
• Carbohydrate: 4 calories per gram; TEF ranges from 5-15 percent
• Protein: 4 calories per gram; TEF ranges from 20-30 percent

This is one of the reasons a high-protein diet has a metabolic advantage and contributes to prolonged satiety. Same with choosing minimally processed, complex carbohydrates over simple carbohydrates.

Fats exhibit the lowest thermic effect, but despite this, healthy fats like those found in avocados, salmon, nuts, and seeds play vital roles in maintaining bodily functions, safeguarding organs, and providing energy source.

Factors like age, insulin resistance, and physical activity levels also influence TEF. For example, physically active individuals experience higher TEF.

And in case you’ve ever wondered, what you eat is definitely more important than when you eat. While some believe a large breakfast boosts daily calorie burn, the impact of meal timing on TEF remains inconclusive.

TDEE: Your Total Daily Energy Expenditure

Total Daily Energy Expenditure (TDEE) is the comprehensive sum of energy your body expends in a single day.

These components, which we’ve discussed above, add up to your TDEE:

As you can see, BMR is the calorie-burning foundation, and is boosted by EAT, NEAT, and TEF.

The sum of these define your daily calorie needs and calories burned.

If you’re working toward a specific fitness goal—weight loss or muscle gain, for example—your TDEE and your calorie needs will change as you progress. As you lose fat or build muscle, your metabolism will adapt to your new body composition, impacting your calorie needs along your fitness journey.

We can help you meet your goals

Knowing—and meeting—your daily calorie needs is integral to many health and fitness goals.

To figure out how many calories you need to meet your goals, try our Weight Loss Calculator or Ultimate Macro Calculator.

Whatever your goals, Precision Nutrition can help you reach them.