What is a calorie?
Calories are the measure of how much energy any given food contains:
Carbohydrates contain 4 calories per gram
Protein contains 4 calories per gram
Fat contains 9 calories per gram
Not all calories are created equal
The normal consensus is eating too many calories without expending energy will equate to weight gain. This is true, however there are many missing pieces. High caloric foods such as nuts, animal proteins, and avocados are rich in micronutrients needed to feed your body on a cellular level - not just to fill up your belly. They also tend to keep you fuller for longer, as opposed to processed foods containing refined grains and sugars that are not as satiating.
Calories coming from a 100 calorie sugary snack-pack versus a whole egg for example is quite different. The type of calorie we eat will directly affect the energy (calories) that are expended.
What does this mean? Your body works harder (uses more energy) to break down whole foods because there is more food components such a fiber to break down = burns more calories via digestion. Regarding macronutrients, proteins and fats also take more energy to digest than carbohydrates.
Variables
There are several variables to consider when thinking about how calories are burned in a day:
Thermic effect on food
The energy that is used to digest and assimilate nutrients.
Active energy expenditure
The energy that is used during activity from walking, running, weight lifting, or smaller activities that includes unconscious movements such as fidgeting.
Resting energy expenditure (Basal Metabolic Rate or BMR)
The energy that is used on a daily basis to accomplish basic physiological functions at rest.
Calories and weight loss.
Most health professionals will recommend implementing a caloric deficit to some degree, if the goal is weight loss. However, the real challenge is maintaining a healthy mindset around food, and maintaining healthy eating habits which ensure that you maintain a healthy weight long-term. Many people get stuck in a yo-yo pattern, and gain weight back once they have returned to a more sustainable pattern of eating. Ultra-low calorie diets are not the right approach. Striking the right balance between a gentle deficit, exercise, and building a healthy mindset is key. Always work with a qualified health professional who has experience working with long-term weight management strategies.
Are you an highly active female?
Very active women who engage in extreme exercise in combination with too low calorie intake are at risk of a female athlete triad. This is a combination of menstrual dysfunction, low energy availability (burning more energy than they consume), and decreased bone mineral density. Hormone imbalances may occur as a result.
The bottom line?
Become familiar with proper portion sizes for different ingredients and get to know your caloric and macronutrient requirements. Working with a professional who can help you navigate this is advised. Once you understand your daily requirements for optimal energy and health, you will be able to identify which foods to prioritize on your plate.
Tips to stay organized - Learn to cook simple meals, and consider batch prepping a few meal components for the week.