Do Calories Matter?
What are Calories?
Calories are a unit of food energy. They represent how much heat energy is required to increase the temperature of one gram of water by one degree Celsius. For the purpose of talking about health, calories indicate how much energy a food or beverage contributes to your diet.
Calories and Weight
The standard assumption is that the average adult needs around 2,000 calories per day to fuel themselves, without gaining or losing large amounts of weight. However, individual factors influence how many calories we truly need to fuel our lifestyles and achieve health goals. For instance, a highly active person who wants to gain muscle mass would need significantly more calories than an elderly person who is sedentary.
When it comes to weight, there are three ways by which your body burns calories. The first is your basic metabolism, which requires most of the calories you get from your diet. Your basal metabolic rate (BMR) refers to how many calories you typically burn to sustain the basic functions of being alive, like keeping your heart beating and your blood pumping. Digestion burns calories through a process called the thermic effect of food. Lastly, leftover calories are used to fuel your daily activities, like exercise or using your brain. 
Calorie needs are determined by lifestyle, activity level, and BMR (influenced by factors like age and sex), as well as health or weight goals. If you eat the same amount of calories you burn, your weight and body composition will remain the same. If you eat fewer calories and have a calorie deficit, you will lose weight. If you eat more calories than you need, you’ll put on weight. These are the mathematics of calories.
Do Calories Matter?
Now that you understand the basics of how calorie needs are determined and how they influence your weight, do calories matter? It’s true that calories matter if your sole focus is achieving a weight goal, but that’s not the whole story.
When it comes to your long-term health, calories ultimately take a back seat to the quality of the foods you consume. While it’s true that you’ll lose weight if you eat less than you need, that doesn’t automatically mean your health will improve if your calories are of poor nutritional quality. Nobody can argue that 1,000 calories of soda are nutritionally equal to 1,000 calories of broccoli, or that they have the same effect on health outcomes.
Decades of research show that the types of foods we eat over the long term have a significant impact on health outcomes. Diets heavily based on packaged foods with poor nutrient density are more likely to result in obesity and related chronic diseases, such as type 2 diabetes, cardiovascular disease, and certain cancers. [2-4]
Diets based on minimally-processed whole foods are health-protective, as they’re rich in essential nutrients like fiber, vitamins, minerals, and antioxidants.  Plus, the latter will help prevent sugar spikes and crashes that may lead to overeating and counteract your intentions.
When it comes down to it, calories mathematically matter when your sole focus is on weight loss or gain, but when it comes to sustainability and long-term health, it’s the types of foods that make up your diet that come out on top.