A calorie is a unit of energy. Historically, scientists have defined "calorie" to mean a unit of energy or heat that could come from a variety of sources, such as coal or gas. In a nutritional sense, all types of food — whether they are fats, proteins, carbohydrates or sugars — are important sources of calories, which people need to live and function.
"Our brains, our muscles — every cell in our body — require energy to function in its optimal state," said Jennifer McDaniel, a registered nutritionist dietitian in Clayton, Missouri, and spokesperson for the Academy of Nutrition and Dietetics. "So for one, we want to nourish our body right and our brain right. If we don’t get enough of those nutrients [that calories provide], there are negative consequences, whether its losing lean muscle mass, not being able to concentrate or not having the energy we need on a day-to-day basis."
How many calories should people eat every day?
How many calories a person needs in a day depends on the individual’s activity level and resting metabolic rate, which can be measured at a doctor or dietitian’s office, McDaniel said. “There’s conventional wisdom that men shouldn’t eat fewer than 1,500 calories and women 1,200 calories to ensure that they’re getting a balance of major nutrients and micronutrients.”
What should those calories be?
The official Dietary Reference Intakes (DRI) published by the National Academies of Sciences, Engineering and Medicine recommends that for an adult, 45 to 65 percent of calories should come from carbohydrates, 20 to 25 percent should come from fat and 10 to 35 percent should come from protein. Children need a higher proportion of fat, between 25 and 40 percent of their calories. No more than 25 percent of total calories should come from added sugars.
What are high-calorie foods?
Foods that are considered high-calorie, or calorically dense, have a high amount of calories relative to their serving size, according to the Mayo Clinic. Oils, butter and other fats; fried foods; and sugary sweets are high-calorie foods. While high-calorie foods are often associated with junk food, some are high in nutrients, as well.
Healthy foods that are high in calories include avocados (227 calories each), quinoa (222 calories per cup), nuts (828 calories per cup of peanuts), olive oil (119 calories per tablespoon), whole grains, and, in moderation, dark chocolate (648 calories per bar), according to the USDA Nutrition Database.
What are low-calorie foods?
Foods that are considered low-calorie have a low amount of calories relative to their serving size. Fruits and especially vegetables are usually relatively low in calories. For example, 2 cups of shredded romaine lettuce or spinach have 16 calories, a large stalk of celery has 10 calories, 1 large ear of corn has 123 calories, 1 cup of broccoli has 15 calories and an orange has 70 calories.
Calories and weight loss
Though it is important to consume sufficient calories, counting and cutting calories can help many people shed pounds. Calories are expended through physical activity. For example, running a mile might burn around 112 calories.
It functions like a scale; when you are in balance, the calories consumed are balanced by the calories burned. This means you will maintain your body weight.
When people want to lose weight they often attempt to have a caloric deficit. But even a person with a caloric deficit needs to consume sufficient calories to function and stay healthy. Eating enough calories helps maintain muscle mass during the weight-loss process.
Consuming sufficient calories during the weight-loss process is also important to maintaining a healthy metabolic rate. “Chronic under-eating — eating 800 or 1,000 calories a day over time — lowers your resting metabolic rate, [which impacts] how many calories you burn, and your metabolic machinery.
