Few things are as essential as nutrition, yet few things can feel as nebulous. Even the question of how to lose weight is contested by experts, who say there’s more to it than just eating less and exercising more.
How many calories should you eat in a day? There is no single answer to this question, either, experts say. It depends on variables including gender, age, weight and activity level.
But the U.S. Department of Agriculture puts out rough calorie ranges as part of its dietary guidelines report, published every five years.
Women need 1,600 to 2,400 calories a day, and men need 2,000 to 3,000 calories, according to the USDA’s latest “Dietary Guidelines for Americans” report, released in 2020.
Daily calorie needs for kids under 2 years old are between 700 and 1,000 calories. Children 2 to 8 need between 1,000 and 2,000 calories, the report says. Daily calorie intake estimates vary widely for older children and teenagers, with a range of 1,400 to 3,200.
The USDA posts an online Dietary Reference Intake calculator that makes individualized daily calorie intake suggestions based on your information, along with daily macronutrient, vitamin and mineral intake recommendations.
While online calculators provide calorie rough intake estimates, Caroline Susie, a registered dietician and spokesperson for the Academy of Nutrition and Dietetics, recommends consulting a dietician to best figure out your calorie needs and how to meet them. Health goals and medical history can factor into formulating a recommended diet in a way that can’t be picked up by an online calculator.
A calorie is a unit of energy in food. One gram of carbohydrate or protein equals about four calories, and one gram of fat contains 9 calories.
One way to lose weight is by reducing calorie consumption, but experts warn against cutting back too much. Susie said she comes across people on extreme calorie-deficit diets who consume less than 1,000 calories a day.
“It’s just not enough to keep you fueled long term,” Susie said. “And what’s scary is that when it’s so extreme and too low, you put yourself at risk for certain vitamin and nutritional deficiencies.”
Taking in too few calories can stunt your metabolism.
“I see a lot of people under-eat because they do a ridiculous calculation online,” said Christina Barth, a health and nutrition professor at Arizona State University. “And they wonder why they’re not losing weight. Well, when you cut your calories too low, your body slows down. Your metabolism slows down.”
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