How Many Calories Should You Eat a Day?

Calorie counting can be a tedious practice, as it tends to take the joy out of eating. On the other hand, it can help us become more aware of our daily calorie requirements and the food choices we make to stay on top of a healthy eating routine. When it comes to wellness, self-awareness is key.

To best understand how to determine daily caloric intake, we enlisted the help of two leading nutritionists who will walk you through the necessary calculations and the individual factors to consider when figuring out how many calories to eat in a day.

The History of the Recommended Calorie Count

Calories were first conceived of in the nineteenth century by French physicists. You might recall from chemistry class that a 'Calorie' can be defined as the heat needed to raise the temperature of a kilogram of water one-degree centigrade. In other words, a Calorie is a potential source of energy.

At the dawn of the twentieth century, scientists began introducing the notion of calories as a unit or way to measure dietary intake. In 1918, Lulu Hunt Peters, MD, published what's widely known as the first American diet book, Diet & Health with Key to the Calories. This bestselling book was instrumental in evolving the scientific understanding of calories in a modern context. In it, Peters established counting calories as a method to either gain or lose weight. She popularized the notion that you can lose weight by burning more calories than you store.

In the 1980s, calorie counting experienced a boom. However, the methodology used to calculate calorie intake wasn't as evolved as it is today. "The general system used to determine how many calories a healthy individual should consume regularly was not based on unique characteristics like gender, age, and activity level," explains Richards. Back then, the system provided more of a baseline instead of the more nuanced approaches used today.

Both Bowman and Richards underscore the importance of factoring in individual metrics like gender, age, height, weight, and weekly activity to determine daily calorie intake. "Dietitians will use various equations to calculate this information," says Richards, indicating that a uniform scale doesn't make sense when it comes to understanding individual needs. "It is also helpful to consider any potential physical conditions, health issues, or diagnoses. For instance, someone with a COPD diagnosis will burn more calories than someone with healthy lungs; an amputee will require less a specialized calculation as well."

Currently, many nutritionists determine daily calorie intake by an equation that measures Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDE), both unique to the individual. "Recommended daily calorie intake is typically calculated based on the Mifflin-St Jeor equation," explains Bowman, "and is widely recognized as the most effective and valid method to estimate daily individual calorie needs."

She adds that health and long-term fitness goals also provide insight into hitting that magic number. "The daily calorie requirements for an individual looking to build lean muscle will largely vary from those with a goal more focused towards fat loss or overall weight loss," says Bowman. "Understanding daily calorie needs in addition to the breakdown of these calories as macronutrients (carbs, fats, proteins) is important for creating structure and individualization within one’s daily eating pattern."

How to Determine Your Recommended Calorie Count

When it comes to determining your recommended calorie count, there's an app for that. Bowman recommends you look for a calculator that "utilizes gender, age, height, weight, and weekly activity level." From there, she says, you can generate a daily "calorie estimate making it easy to portion meals and plan a healthy weekly eating routine specific to your goal."

Richards recommends the following equation to calculate your Basal Metabolic Rate (BMR), which she explains "is a generalization of how many calories you should consume based on gender and activity." Bowman adds that BMR is "the amount of calories required for daily function at rest."

Adult male: 66 + (6.3 x body weight in pounds) + (12.9 x height in inches) - (6.8 x age in years) = BMR

Adult female: 655 + (4.3 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years) = BMR

Multiply your BMR by the appropriate activity factor, as follows:

1. If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2
2. If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375
3. If you are moderately active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55
4. If you are very active (hard exercise/sports 6-7 days a week): Calorie-Calculation = BMR x 1.725
5. If you are extra active (tough exercise/sports and physical job or double training): Calorie-Calculation = BMR x 1.9

 Again, lifestyle factors heavily into determining your daily caloric intake. "The weekly eating routine of an athlete with a nutritional focus of performance will largely differ from the daily caloric needs for someone training for weight loss," explains Bowman. "By determining our specific daily calorie needs, we’ll start to gain greater awareness not just around the type of food we should be consuming regularly but also the total calories required for optimal energy balance to meet our goal and avoid training plateaus."

Other Considerations

Additional lifestyle factors need to be taken into consideration to assess your recommended daily caloric intake accurately. "Lifestyle factors such as sleep and hydration are extremely important in meeting target goals, and while they do not directly influence one’s estimated daily calorie consumption, they are essential to long-term training progress," notes Bowman.

To keep track of calories, explains Richards, " You'll need to look at nutrition labels and look up nutrient content on all whole foods. Add up each calorie from each food item or beverage consumed during the day." 

To get a more dynamic sense of calorie intake, Bowman also emphasizes the importance of breaking calories down using a macronutrient ratio. "For greater individualization, nutritionists and dieticians can also provide a breakdown of what an individual's estimated daily macronutrient ratio (carbs, fats, protein) should be for a goal of fat loss, lean muscle development, or health maintenance. For example, an individual looking to build lean muscle while shredding fat would be best suited to high protein meals with little to no processed carbohydrates." Here, she underscores the idea that not all calories are considered equal. "It's important to have both a general understanding of your goal-specific daily calorie needs in addition to the type and quality of food that will benefit your long-term goal," she says.

The gut microbiome is another consideration when it comes to determining daily caloric intake. "Our nutritional choices over time can impact our gut microbiome and affect how well our body may respond to certain foods, particularly carbohydrates," explains Bowman. "Specifically, the way our body utilizes carbohydrates and fats for energy varies from individual to individual. When we become more aware of our daily calorie requirements, we start to build better self-awareness for our food choices and make it easier to stay accountable to a healthy eating routine."

Finally, counting calories is not for everyone. "Anyone with a history of disordered eating should be encouraged not to count their calories as this can be triggering practice," says Richards. Bowman adds that anyone with a history of disordered eating should focus more on "food quality" instead of a specific number.

Final Takeaway

Calorie counting is best understood as a general estimate and, as outlined above, needs to be put into context with other lifestyle factors. Richards explains the practice can be useful but isn't necessary across the board. "So long as you are consuming a balanced diet and stay physically active, you shouldn't worry about being overly concerned with calorie counting," she says.