Counting Calories 101: How to Count Calories to Lose Weight

Brunette Contemplating Whether To Eat Muffin or AppleTo lose weight, you need to eat fewer calories than you burn.

In theory, this sound simple.

However, managing your food intake in the modern food environment can be tricky.

Calorie counting is one way to tackle this problem, and is commonly used for weight loss.

This is a detailed guide about counting calories, explaining everything you need to know.

What Are Calories?

Calories are a measure of energy, normally used to measure the energy content of foods and beverages.

Technically speaking, a dietary calorie is defined as the amount of energy required to raise the temperature of 1 kilogram of water by 1 degree Celsius.

You use the calories that you eat and drink for essential functions such as breathing and thinking, as well as day-to-day activities such as walking, talking and eating.

Any excess calories you eat will be stored as fat, and consistently eating more than you burn will cause weight gain over time.


Bottom Line: A calorie is a measure of energy. In science, it’s defined as the amount of energy required to raise the temperature of 1 kilogram of water by 1 degree Celsius.

Why Calories Count

Slice of Bread Turned Scales Wrapped With Measuring Tape

It’s quite common to hear that calories don’t matter and calorie counting is a waste of time.

However, when it comes to your weight, calories do count.

This is a fact that has been proven time and time again in scientific experiments called overfeeding studies.

These studies ask people to deliberately overeat and subsequently measure the impact on their weight and health.

All overfeeding studies have found that, when people eat more calories than they burn off, they gain weight (1, 2, 3, 4, 5, 6, 7, 8).

This simple fact means that counting calories and limiting your intake can be effective to prevent weight gain or lose weight, as long as you manage to stick to it.

One review found that weight loss programs that included calorie counting led to an average of around 7 lbs (3.3 kg) more weight loss than those that didn’t (9).

Bottom Line: When you eat more calories than you burn, you gain weight. Counting calories can help you eat fewer calories and lose weight.

How Many Calories Should You Eat?

Scales, a Fork, a Knife and a Measuring Tape

How many calories you need depends on factors like gender, age, weight and activity level.

For example, a 25-year-old male athlete will need more calories than a 70-year-old woman who doesn’t exercise.

If you are trying to lose weight, you will need to create a calorie deficit by eating less than your body burns off.

Use this calculator (opens in new tab) to determine how many calories you should eat per day.

This calculator is based on the Mifflin-St Jeor equation, which is an accurate way to estimate calorie needs (10, 11).

Bottom Line: The exact amount of calories you need will depend on a number of different factors, including your gender, age, weight and activity levels. Use the calculator above to work out your daily requirement.

The Best Apps to Help You Count Calories

Blonde Eating an Apple and Using an App in Her Phone

Due to advances in technology, putting calorie counting into practice can be relatively effortless these days.

Lots of apps and websites are available to simplify the process by providing quick and easy ways to log the food you eat.

Even if you only track your food intake irregularly, studies show that people who do so tend to lose more weight. They also maintain their weight loss better (12, 13).

Here’s a list of some of the most popular free calorie-counting apps/websites:

For more details, read this: The 5 Best Calorie Counter Websites and Apps.


Bottom Line: Using an app or online tool to record your meals and track your food intake is a very easy way to count calories.

How to Weigh and Measure Your Portions

Bowl of Pasta on Red Scales

Portion sizes have increased, and in some restaurants a single meal can provide double or triple what the average person needs in a sitting.

“Portion distortion” is the term for when you view large servings of foods as the norm. It can cause weight gain and hinder weight loss (14, 15, 16).

In general, people aren’t very good at estimating how much they eat (17, 18, 19, 20).

Calorie counting can help you combat overeating by giving you a better understanding of how much you are really consuming.

However, for it to work, you need to record food portions correctly. Here are a few common ways to measure portion sizes:

  • Scales: The most accurate way to determine how much you’re eating is to weigh your food. However, this can be time-consuming and isn’t always practical.
  • Measuring cups: Standard volume measures are slightly quicker and easier to use than a scale, but can still be time-consuming and awkward at times.
  • Comparisons: Using comparisons to common items is quick and easy, especially if you’re away from home. However, it’s also much less accurate.

Here are some common serving sizes compared to household items that may help you estimate your portion sizes:

  • 1 serving of rice or pasta (1/2 a cup): a computer mouse or rounded handful.
  • 1 serving of meat (3 oz): a deck of cards.
  • 1 serving of fish (3 oz): a check book.
  • 1 serving of cheese (1.5 oz): a lipstick or the size of your thumb.
  • 1 serving of fresh fruit (1/2 cup): a tennis ball.
  • 1 serving of green leafy vegetables (1 cup): a baseball.
  • 1 serving of vegetables (1/2 a cup): a computer mouse.
  • 1 teaspoon of olive oil: 1 fingertip.
  • 2 tablespoons of peanut butter: a ping pong ball.

Calorie counting isn’t an exact science, even when you weigh and measure portions.

However, it’s not necessary to be absolutely spot-on with your measurements. Just make sure to record your intake as accurately as you can.

You should be most careful about recording items that are high in fat and/or sugar, such as pizza, ice cream and oils. Under-recording these foods can cause a big difference between your recorded and actual intake.

To improve your estimations, you can try using scales in the beginning to give you a better idea of what a portion looks like. This should help you be more accurate, even after you stop using them (21).

Bottom Line: You can use scales, cups and measures or portion-size estimates to determine how much you’re eating. Scales are the most accurate.

The Quality of Your Diet Still Matters

Cookies on Scales and Fruit on Scales

Calories are useful for tracking how much you eat, but they don’t tell you much about the quality of your diet (22).

When it comes to foods and the human body, a calorie is not necessarily a calorie.

For example, 100 calories of broccoli will affect your health differently than 100 calories of french fries.

This is important because your overall diet and the types of foods you eat have an effect on your health (23, 24, 25).

Additionally, the effects of different foods on hunger, appetite hormones and the amount of calories you burn can vary considerably.

It is best to base your diet on high-quality foods from plants or animals that have been minimally processed.

High-quality foods not only provide health benefits, but they also make it a lot easier to consume fewer calories in the long run.


Bottom Line: Basing your diet on minimally processed foods is beneficial for long-term health and weight loss.

5 More Tips to Succeed With Calorie Counting

Brunette Holding a Food Label

Here are 5 more tips to count calories:

  • Be prepared: Before you start, get a calorie counting app or online tool, decide how you will measure or estimate portions and make a meal plan.
  • Read food labels: Food labels contain lots of useful information for calorie counting. Make sure you check the portion size recommended on the package.
  • Remove temptation: Get rid of the junk food in your house. This will help you choose healthier snacks and make it easier to hit your targets.
  • Aim for slow, steady weight loss: Don’t cut calories too low. Although you’ll lose weight faster, you may feel bad and be less likely to stick to your plan.
  • Fuel your exercise: The most successful weight loss programs include both diet and exercise. Make sure to eat enough to still have energy to exercise.

Bottom Line: Aim for slow and steady weight loss, and make sure you have a plan. Reading food labels and keeping less junk food in the house can also be helpful for success.

Should You Count Calories?

Calories in, calories out” certainly isn’t the only thing that matters for optimal health.

However, when it comes to weight loss, calories do count.

Although it doesn’t suit everyone, you may find that counting calories is an effective way to lose weight and keep it off.