What Are Calories? 

Calories are a measure of energy, used to measure how much energy a food provides.^1–3 One thousand “small” calories (cal) equals a kilocalorie (kcal) which is commonly used in food labels. 

How Many Calories Do You Need?

The number of calories an individual needs daily differs based on a few factors.⁴ Typically adult males and females require 2,600-2,800 kcal/day and 2,000-2,200 kcal/day, respectively.⁵ However, the caloric requirement changes depending on one’s age, sex, height, weight, physical activity level, and pregnancy/lactation status.⁴ It is normal for caloric needs to decrease with age as basal metabolic rate reduces, and thus caloric consumption should be adjusted appropriately to maintain weight. Additionally, depending on one’s need to maintain, gain, or lose weight, caloric intake can be adjusted. For instance, it is thought that lowering caloric intake by 500-600 kcal/day can result in 0.5 kg weight loss/week, although other factors can greatly influence the degree of weight loss.⁶ You can check your daily caloric needs using an online calorie calculator by entering in your age, gender, height, weight, and activity level. 

How Do You Count Calories? 

Counting calories can be done easily when purchasing packaged foods and drinks.⁷ The U.S. Food and Drug Administration (FDA) requires manufacturers to detail caloric and nutritional facts on the “Nutrition Facts” label found on packaged food and beverage items. Calories are displayed as number of calories per serving, with serving size indicated above. You can measure how much of a particular food item you are eating and calculate how many calories you are consuming. Then for each meal throughout the day, add up the calories to calculate how many calories you are consuming per day.

Figure 1. U.S. FDA. What’s on the Nutrition Facts Label. 2023.

If a food is not packaged or labeled, you can still estimate the number of calories by using scales or cups to first determine the amount of food you plan to consume and then calculate how many calories it contains. The U.S. Department of Agriculture’s National Nutrient Database provides detailed information on caloric and nutrient content of individual food items. You can also find various apps that can assist with counting calories. The U.S. FDA also requires large restaurants and food establishments to have caloric information available on their menus, making it easier for you to count your calories even when you are eating out.⁸