A calorie is a unit of energy. It is measured by the amount of energy needed to raise one kilogram of water by one degree of Celsius. There are 4 calories in one gram of carbohydrates and protein. There are 9 calories in one gram of fat. Oh, that makes total sense, right? Clear as mud? Yeah, I thought so.
Does your body require a set amount of calories? If so, what is it? How do you figure it out? You can't. And you won't. It is not consistent. Did you do the exact same thing today as you did yesterday? I hope not. That would be weird. If you did require an exact amount of calories, why can't you just eat chocolate cake all day and call it good?
Your body does not care how many calories you eat. What it actually cares about are nutrients. For your body to function well, it needs a wide range of nutrients. It needs nutrients from some combination of vegetables, animal protein, quality fat, fruit, nuts and seeds. If it doesn't get those things, you will continue to be hungry. The ratios and amounts will vary from person to person, but the basic premise is the same. For you to not only survive, but thrive, you need nutrients. Not just calories.
Okay, then how do you decide which nutrients you need? This is determined by many things, including, but not limited to:
Age
Sex
Size, weight, frame
Physical output
Mental output
Sleep
A physically active fourteen year old male who is in advanced math and sleeps for 10 hours per night will need very different nutrient and energy inputs then a 54 year old overweight, inactive female who works as an administrative assistant and sleeps for 6 hours per night. How many calories do each of these people need? Turns out, that matters way less than their nutrient intake.
Food is information for your body. Every time you eat, your hormones are being affected. All of the hormones work synergistically and they are going to make you feel normal and well, or abnormal and sick. If either of the people mentioned above eat cereal, bagels, donuts, pizza, pasta, slurpees, frappachinos and ice cream they will function much differently then if they eat omelets, steak and potatoes, salmon wraps, homemade trail mix and tea. But what are most of us eating day in and day out? Real, quality, dense nutrients or just calories? And does it even matter? You tell me.
What's the coolest part in my opinion? Once you start eating the best foods for you, everything else falls into place. Energy increases, mental clarity appears, your skin shines, your hormones and mood stabilizes, your body weight regulates itself and more. What are you going to count? Calories or nutrients?