The food an individual consumes over their lifetime is composed of a certain combination of fat, protein, and carbohydrate. These three factors are known as macronutrients. It is imperative to obtain them, as well as water and select vitamins and minerals, to supply energy, build and maintain body tissue, and regulate body function.


About 60% of a human’s weight is attributed to water. It aids in multiple functions, including digestion, gas exchange located at the lungs, and is the component that allows many chemical reactions to proceed. In a general sense, two litres of water intake on a daily basis are recommended. However, this amount can be increased if the ambient environment is hot and humid for example, or if physical activity and the consumption of diuretics (substances that raise urination levels) are added to the equation. Lastly, it is noteworthy to highlight that water intake can involve both liquids and foods in an individual’s diet.


Calories can be broken down into three main macronutrients (also referred to as energy sources): fat, protein, and carbohydrate. Alcohol is an additional energy source but it does not carry the same degree of importance as the others.

The macronutrient with the highest energy density is fat, carrying nine kilocalories of energy per gram. It is also an element of cell membranes. As hydrocarbon (an organic compound consisting only of hydrogen and carbon) chains (of the latter molecule) that can differ in length, fats are grouped according to their chemical composition, more specifically, they are classified as either saturated or unsaturated. In terms of saturated fats, single bonds attach each carbon atom in the chain to other carbons. When it comes to unsaturated, at least two carbons are joined to each other with a double bond. The saturated variety is solid at room temperature and is usually found in meats, dairy, coconut oils, and palm oils. While unsaturated fats are liquid at room temperature and can be obtained from fish, avocados, olive oils, canola oils, and vegetable oils.

Listed above, the two different types of fat have significantly contrasting effects on one’s health. The unsaturated kind initiates the production of good cholesterol, known as HDL, and lessens the production of bad cholesterol, named LDL. It is commonly associated with enhanced cardiovascular health as well. Alternately, saturated fats set off an increased accumulation of LDL and have been linked with cardiovascular disease. In addition, trans fat is artificial and man-made, in most cases being created from regular unsaturated fat having been exposed to high heat (for example, during the activity of frying food). This type is solid at room temperature, even though they started off in the unsaturated category. Research suggests that trans fat is as negative, if not worse for the health of the body, as saturated fat. As a result, Health Canada recommends that citizens aim to avoid or limit their consumption of trans fats.

Regarding unsaturated fatty acids, two are essential for proper health, linolenic acid (omega 6) and alpha-linolenic acid (omega 3). Omega can translate to “last”, meaning that the double bond is located right after the third carbon from the end of an omega 3 fatty acid. However, both are important as the body is unable to produce them. They are crucial for appropriate cell membrane structure and function, and greatly help the immune system, inflammatory system, nervous system, and vision. Deficiencies in these fatty acids are connected to reduced growth rates in children, decreased immune function, depression, and dryness of one’s skin. An equal amount of omega 6 to 3 is the suggested optimal ratio between the two. This balance is also significant in preventing heart disease, arthritis, osteoporosis, and cancer. Foods that are rich in omega 3 fatty acids include flax, walnuts, and certain fishes.

Carbohydrate is another energy source and offers four kilocalories of energy per gram. Based on their chemical structure, they can be divided into two groups – understood as either simple or complex. Glucose, fructose, sucrose, and maltose are labeled as simple sugars. In contrast, included on the complex side are starches, such as those found in grains, legumes, and tubers (for instance, potatoes and yams). Complex carbohydrates must be broken down into simple sugars as the digestive process is taking place. This macronutrient is mostly stored in the muscle and liver, and is a key source of energy, especially during high-intensity exercise.

Also providing four kilocalories of energy per gram, protein is used for building tissues (like muscle, hair, and skin), as well as hormones and enzymes. In a general sense, it is not a major contributor to the fuels involved in energy expenditure until the physical activity becomes quite prolonged. Good dietary suppliers of protein are meat, beans, eggs, and nuts.

The information in this article was retrieved from Jennifer L. Kuk (Ph.D.), Michael Riddell (Ph.D.), and Angelo Belcastro (Ph.D.).