Macronutrients and Health
Published: November 15, 2013
Macronutrients, in terms of your body composition, include water, fat, protein and carbohydrate. Dietary macronutrients contained in the food you eat include carbohydrates, fats and protein. These macronutrients provide you with energy, but also have other functions in your body.
Although the amount of carbohydrate within your body is small relative to the amount of fat and protein, dietary carbohydrates contribute towards a significant proportion of a healthy energy intake.
Water is also an important dietary nutrient and essential to life, but does not provide you with energy.
These macronutrients are described below in terms of a healthy body composition and dietary requirement.
Water constitutes about 60% of a healthy body, and you cannot survive without a regular and adequate supply of water. Almost all of your body's internal activities take place in a water based environment.
Water is necessary for your body's metabolic reactions such as transporting essential substances to cells and removing waste and potentially toxic substances out of your body.
The amount of water you need depends on your gender, level of physical activity, and the temperature of your environment. You can obtain the water that you need from foods and beverages although some beverages, such as alcohol, may result in increased fluid losses from your body.
Water or fluid requirement varies between 2-3 L/day depending on age, gender and activity level.
Fat is the second major component of a healthy body at about 13 -30 % of total body weight. Within your body, fat is used to provide energy for your body's many metabolic reactions.
There are many different types of fat (lipids) found in your body and as well as providing energy they have several different functions.
Your body can synthesize most fatty acids; however, there are two essential fatty acids, omega-3 and omega-6 fatty acids, which your body cannot make, but which can be obtained from the foods that you eat.
In a healthy diet, fat provides between 20%-35% or your daily energy requirement.
In a healthy body, protein represents between 10 -17% of body weight. Protein is required to build muscle tissue, skin, hair, bone, and for the formation of hundreds of other types of proteins within your body which allow your body to function.
All proteins are composed of amino acids.
Protein can be obtained from a wide variety of food sources such as meat, poultry, fish, eggs, dairy products, legumes, grains, nuts, and vegetables.
The recommended protein intake for adults is 0.8 g/kg of body weight per day. Children, adolescents and very active people require slightly more protein relative to body weight.
In comparison to water, fat and protein, carbohydrate is only present in your body in relatively small amounts. Storage of carbohydrate (glucose as glycogen) is limited as glycogen holds water and is bulky.
About one third of glucose is stored in your liver and the other two thirds is stored in your muscle cells.
Since glucose is a primary source of energy for your body, and body stores of glucose are mostly depleted during your overnight fast, dietary carbohydrate is a necessary source of glucose for your body.
]Dietary carbohydrates are categorised as simple carbohydrates (sugars) and complex carbohydrates (starches and fibres), and provide the majority of glucose for you energy requirements.
All of the cells in your body use glucose as an energy source so you need to refuel with glucose every day. The average person requires about 130 g/day of glucose to meet their energy requirements.
In a healthy diet, carbohydrate provides between 45% - 65% of your daily energy requirement.
Macronutrients on their own do not provide you with all the nutrients that you need for a healthy and fully functioning body.
Whitney, E. & Rady Rolfes, S. (2005). Understanding Nutrition. Belmont, CA: Thomson Wadsworth
Gropper, S.S., Smith, J.L. & Groff, J.L. (2005). Advanced Nutrition and Human Metabolism (4thEd.). Belmont, CA: Thomson Wadsworth.