Formula for Caloric Intake

There are many calorie equations online that can help you figure out how much to eat per day. They're based on fairly generic formulas, which give you an estimate for how many calories you need to eat ⁠— but they aren't completely accurate.

Calorie equations are fairly easy. (Image: serezniy/iStock/GettyImages)

Calculate Your Calorie Intake

Food contains energy. That energy is counted by units of measurement called calories. The actual unit of measurement you see on food labels is a kilocalorie, which means that there are actually 1,000 calories per calorie that you eat.

To figure out how many calories food contains, scientists employ a tool called a calorimeter. The calorimeter measures heat exchange. There's a chamber where food is heated, which is surrounded by water. The calorimeter measures how much the water temperature is raised from the heat of the food.

Will calorie counting help you lose weight? Most likely, yes. The number of calories in your diet is an important factor if you want to gain, lose or even maintain weight. To lose weight, you have to consume fewer calories than you burn.

To gain weight, the opposite is true. Even if you simply want to maintain your weight, you have to consume as many calories as you burn. This is known as energy balance.

Using a calorie tracking app on your phone is the best way to measure your calories. You can try to tally everything up over the course of the day, but it's much easier to use an app like MyPlate that can store all the information for you.

The app not only stores information about calories, but it can also track your nutrient intake as well. It also has a database that contains nutrition information about a wide variety of foods, so that there's less guesswork involved in tracking your total calorie intake for the day.

A calorie tracking app helps you keep track of your intake for the day, which is half the equation for weight loss or gain. However, these apps do more than track calories. They can give you an estimated number of the number of calories you should eat per day to hit your fitness goals.

Using formulas, the app can estimate how many calories you're burning per day. Using that number, it can tell you how much to eat. To figure out how many calories your body burns per day, the apps take into account how many calories you burn from exercise and how many calories you burn at rest, known as your resting metabolic rate.

Your resting metabolic rate is the number of calories your body burns per day just to stay alive. This number is relatively high, often higher than the number of calories you burn per day through activity. Throughout the day, your brain, heart and other organs are also using energy to do their jobs.

Recommended Calorie Equations

There are a few formulas that measure your resting metabolic rate. A small July 2018 study published in the Journal of Strength and Conditioning Research shows that for athletes, the Harris-Benedict Equation was the most accurate for males. For females, the Cunningham Equation was the most accurate.

The Cunningham Equation, while fairly accurate, uses the amount of muscle mass in your body to calculate your resting metabolic rate, since muscle mass makes a large contribution to the total number of calories you burn while resting. The drawback is that it's extremely hard to figure out how much muscle mass you have in your body. For that reason, the Cunningham Equation probably isn't the best to use.

The Harris-Benedict Equation is a simpler calorie formula. It uses your age, height, body weight and gender to estimate the number of calories you burn at rest. However, it doesn't take into account how much muscle mass you have, which means it's not entirely accurate. It's still useful in giving you an estimate, and accurate enough to be the best formula to use.

The Mifflin St-Jeor Equation, like the Harris-Benedict Equation, actually has two different equations: one for males and one for females. Both require your age, height and weight as well. In some populations, the Mifflin St-Jeor equation is the best available, according to a July 2018 study published in Frontiers in Endocrinology.

In the study, the researchers looked at obese Caucasian subjects who had health risks like diabetes and high blood pressure. In this population, the Mifflin St-Jeor equation was superior to the Harris-Benedict equation.

Calculate Your Activity Level

Once you've figured out your resting metabolic rate by using a predictive formula, you can add your activity level. There are two main types of activity you do: exercise and non-exercise activity thermogenesis (NEAT). Rough estimates for the number of calories you burn in a workout can either be found online or on the cardio machines you use at the gym. Some heart rate monitors also give you a calorie-burn estimate.

NEAT is the term used to describe the number of calories you burn from activities that aren't related to exercise. For example, taking the garbage out or washing dishes burns a small number of calories, although these small tasks add up throughout the day.

Your workout and NEAT numbers add up to total the number of calories you burn from activity, which is then added to your resting metabolic rate. After tallying up these numbers, you can figure out how many calories you burn per day.

Depending on your fitness goals, the next step is to figure out how many calories to consume. Whether you want to lose, maintain or gain weight, keep in mind that the magical number for a pound of fat is 3,500 calories.

There are about 3,500 calories per pound of fat, which means that if you want to lose a pound you need to burn 3,500 calories. Of course, there are fluctuations in water weight and other factors that make your weight go up and down, but if you want to lose pure fat, that's what it takes.

To burn 3,500 calories you should look at a span of days or weeks ⁠— it won't happen in one day. If your total calorie expenditure is 2,000 per day and you eat 1,500 calories per day, you're burning 500 calories per day. Over seven days, that's 3,500 calories or one pound of fat. The reverse is true if you want to gain weight.

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