As the energy that powers everything we do, calories are crucial to maintaining an optimal, healthy weight.

Mention the word calories and people generally cringe, thinking of those avoid-at-all-cost numbers commonly associated with weight loss or gain. Calories are important for anyone trying to stay in shape, but few people know what a calorie is and how it fits into a smart nutrition plan. The truth is that calories can be beneficial if you know how to use them wisely.

What is a calorie?

A calorie is a unit of heat energy. All foods and beverages have calories, and your body uses calories to power everything that it does, including everyday physical activity like getting dressed and digesting food. Calories also fuel the processes that keep the body functioning, such as respiration, bone and muscle growth, and blood circulation. Unused energy is stored as fat to be used later as fuel when we need it. Regular physical activity is important to burn off fat that has been packed away for a rainy day.

Nutrient-dense calories vs. empty calories

When it comes to nutrition, all calories are not equal. While one calorie from a piece of chocolate is the same as one calorie from a carrot, empty calories generally come from foods filled with solid fats and added sugars, ingredients that undermine our overall health. Nutrient-dense calories provide vitamins, minerals and fiber, in addition to energy.

Foods filled with empty calories can also contain Advanced Glycation Endproducts (AGEs), harmful compounds that accelerate the body’s aging process. AGEs, which are found in sugary and processed foods (as well as browned foods like caramelized dishes), are a key medical marker linked to health concerns such as cardiovascular disease, Alzheimer’s and diabetes. Consuming too many of these foods leads to a buildup of AGEs in the body, creating higher-than-normal levels that accelerate the aging process from the inside out.

Foods low in AGEs typically contain nutrient-dense calories and pack a nutritious punch that can fuel your body and even help you maintain a desirable weight. Naturally low in calories, foods low in AGEs also contain vitamins, minerals and fiber. Good choices are brightly colored fruits and vegetables, which are bursting with phytonutrients that help protect your body at a cellular level and fight AGEs. Whole grains are also low in AGEs.

Take control of your caloric intake

While its important to check the number of calories, be sure to also look for the source of those calories by reading labels when you’re in the grocery store. Is it a high-fructose, sugary additive? Are calories coming from fats? Is this a highly processed food such as a frozen or pre-made meal, or one that contains artificial ingredients? Prepare yourself with the knowledge you need to make healthy decisions when shopping for food. Use an app such as MyFitnessPal to find calorie information before ordering when eating out, and keep a food diary to track calories. When cooking for yourself, you can also poach, steam or use a slow cooker to cut calories and protect against added AGEs when preparing food.

Taking control of your health can be as basic as making a few small, simple choices today. Make calories your friend instead of your foe by arming yourself with the right knowledge and balancing with regular exercise.

Pat Baird, MA, RDN, FAND, is a registered dietitian, nutritionist and a member of the AGE Foundation Advisory Board. An adjunct professor at University of Connecticut Stamford, she is also an award-winning author of five books and a lecturer specializing in the development and communication of information on food, nutrition and health-related issues for consumers and health care professionals.