Weight Loss is Math (Part 1) - Calories & Macros
Part 1 - Energy Balance & Macronutrients
If I oversimplify (setting aside the nuances of micronutrients, genetics, etc.), weight loss is fundamentally a math problem.
To understand this, we have to get on the same page on two core concepts: energy balance and macronutrients.
Energy comes from the foods and drinks we consume. Their calories is what gives your body the fuel to function - walking your dog, lifting boxes, playing with your children. The more you move, the more energy your body demands. Conversely, the less you move, the less energy your body demands, and any excess calories consumed gets stored in your body. Over time if we consume excess calories on a regular basis, those calories becomes fat to be stored and used for later. So this means that in order to lose fat (which is what actually most people mean when they say they want to “lose weight”), our output has to be more than our input. There are two ways to achieve this - we can either move more, or we eat less. We are going to focus on the eating part today.
To understand how calories are made up, we need to understand macronutrients. Three main macro nutrients make up calories in food and drinks - protein, carbohydrate (often referred to as carbs in short) and fat. They each play a role in our bodies:
Protein’s main role is to grow, repair and maintain our body tissues
Carbohydrates get broken down into glucose and provide us with energy for many bodily functions, including but not limited to muscular contraction during exercises
Fats are our longer term more endurance energy source. They protect our organs and are also critical for our brain function.
Each gram of macronutrient has certain amount of calories:
1g of protein = 4 calories
1g of carbs = 4 calories
1g of fat = 9 calories
To calculate the calories of the food you eat, you multiply the calories per gram of macronutrient and the number of grams on of the food, and add the results together.
Total Calories = Grams of Protein x 4 + Grams of Carbohydrate x 4 + Grams of Fat x 9
Take this Nature Valley Sweet & Salty granola bar as an example:
4g protein x 4 cal per protein = 16 cal
20g carbs x 4 cal per carb = 80 cal
8g fat x 9 cal per fat = 72 cal
16 + 80 + 72 = 168 cal (or 170 calories listed on the package*)
*In Canada, foods with more than 50 calories are rounded to the nearest multiple of 10 cal
So now you know the basics of macronutrients and how calories are calculated, how much should you eat to achieve your goals? Check out Part II for a short guide on how to set targets.