# Practical Nutrition/Macronutrients

Macronutrients are nutrients that provide your body with energy and the components it needs to maintain its structure and functions. The main three macronutrients are carbohydrates, fat, and protein. They are called “macro” because they are essential nutrients that the body needs in large quantities.

## Macronutrients Overview
### What Are They Used For?

* Carbohydrates: Carbohydrates are the primary short-term fuel source used and the fuel of choice for high-intensity exercise. They are also important for brain function and intestinal health.
* Fats: Fats are the main source of long-term stored energy and are the primary fuel source for long-lasting low to moderate intensity activities. They are also essential for the absorption of fat-soluble vitamins and the production of hormones.
* Protein: Protein provides a minimal amount of fuel that is used by the body. However, protein helps to rebuild muscles and bones, among many other functions such as hormone production, immune system support, and enzyme production.

### How Much Of Each Macro?

The United States Department of Agriculture (USDA) Dietary Guidelines recommend these Acceptable Macronutrient Distribution Ranges (AMDR) for adults:
* Carbs: 45–65% of your daily calories
* Protein: 10–35% of your daily calories
* Fat: 20–35% of your daily calories

## Calories

A calorie is the unit of energy used to measure the amount of energy in food and drinks. More specifically, it is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius.
Calorie Content of Each Macronutrient :
| Macronutrient | Calories per gram | Notes |
| Carbs | 4 | Same as protein. |
| Fat | 9 | Most calorically dense macronutrient. |
| Protein | 4 | Same as carbs. |

### Kilocalorie? Calorie? Kcal or Cal?

* Kilocalorie (kcal) is 1000 calories.
** Kilocalorie: The amount of energy required to raise the temperature 1 kilogram of water by 1°C
** Calorie: The amount of energy required to raise the temperature of 1 gram of water by 1°C.
* Calorie (cal)
** The food label term referring to kilocalories.
** If food label says “80 calories” it really has 80,000 calories (the same as 80kcal)
*** So, for non-scientific purposes 80cal and 80kcal are equivalent.
* This is weird to think about, but in practice it doesn’t change anything. All units used are scaled so the recommendations are correct on the food labels. The distinction is made for scientific reasons.

### Calculating Calories

To calculate the number of calories in a food, multiply the number of grams of the macronutrient that is present in the food by the amount of calories per gram in that macronutrient. For example, take whole-wheat bread:
If there is 2 grams of fat, 17 grams of carbs, 3 grams of protein in the slice of bread:
(2g of fat * 9 calories per gram) + (17g of carbs * 4 calories per gram) + (3g of protein * 4 calories per gram) = 92 calories.
Harvard Health, https://www.health.harvard.edu/staying-healthy/why-people-become-overweight

### Calculating Macronutrient Percentages:

Continuing on with our whole-wheat bread example (see previous).
We know there is 92 calories in a slice, and those calories are made up of:
* 18kcal from fat
* 68kcal from carbs
* 12kcal from protein
If we want to figure out what percentage of the total calories a certain nutrient contributes: divide the amount of calories the nutrient contributes over the total calories.
So, if we wanted to calculate what percentage of calories comes from carbs in our slice of bread, we’d do

## Lesson Summary

It’s important to eat a variety of foods to get enough of each macronutrient: carbohydrates (short-term fuel source), fat (long-term stored energy), and proteins (rebuilding muscles and bones). Most foods contain a combination of carbs, protein, and fat. Some foods are high in one specific macronutrient, while other foods contain high amounts of two nutrients and fall into two macronutrient groups. We measure how much energy a food gives us using calories. Carbs and proteins contribute 4 calories per gram, while fats contribute 9 calories per gram.
In the following sections, we'll discuss each type of macronutrient and its role in the body. Click the "continue" button to continue to the next section.