7.3: Sources of Energy 

In the human body, the greater the number of bonds contained within the macromolecule, the greater the amount of stored energy. Fats are larger and contain more bonds; therefore, they have more stored energy than carbohydrates do. With the many conveniences of fast food and high fat content foods, North America has an increasing number of overweight individuals. 

People make food choices for differing reasons. One may be for cultural or ethnic reasons. Using data found on Our World in Data, review some of the information found on Obesity globally. We will select individual countries and research the types of food they tend to eat. We hope to find a connection between typical food choices and obesity rates for that country. 

Carbohydrates

Food is needed to keep the body warm, provide energy to be active, and to stay alive. The main source of energy comes from simple carbohydrates, called glucose. As we learned in the last section, cellular respiration is what happens when the body breaks down the glucose to provide energy. Any glucose that is not used immediately is then converted to glycogen. This starchs like substance is stored in the liver and muscles. When we need energy, glycogen is converted back into glucose.

Contrary to many fad diets, health experts recommend we take in 55 to 65% of our calories in carbohydrates. Athletes will carbo load a day or two before an event in order to have enough stored energy to be used in competition. 

There are many diets that suggest that people reduce the amount of carbohydrates in their diet in order to lose weight. Because carbohydrates are the most direct source of energy, people who are looking to lose weight should not cut these out of their diet. If you want to increase your metabolism in order to lose weight, then you need to build muscle. This does not mean that you need to build big muscles. People with a lot of muscle have a higher metabolism because their body keeps all the muscle cells fueled with energy. Keeping the muscles ready to work requires energy, which means that your body uses more energy -- Another way of saying that your metabolism is higher.

Fat: There when You Neet It

There is a certain amount of body fat that is required in order to insulate the body to conserve energy and to be used as a source of energy. Experts suggest that we take in less than 30% of our daily calories from fat. When carbohydrate stores have run low, the body then uses fat as its source of energy for activities. If you compare the amount of energy provided by fat and carbohydrates, 1 kg of fat will provide twice as much energy as carbohydrates. 

However, why is it not good to eat more fat than carbohydrates?

Saturated and Unsaturated Fats

There are two groups of fats.

Saturated fats 

Those fats that come from animals' fat and some oils

• Cheese

• Milk and other dairy products

• Hamburgers

• Coconut oil

Unsaturated fats

Fat that is found in vegetable oils, nuts, seeds, and some fish . These oils are in liquid form at room temperature. They are considered beneficial because they can improve blood cholesterol, lower inflammation, stabilize heart rates

• Olives

• Peanuts

• Avocados

• Canola

• Sunflower 

• Fish

Protein: The last Choice

Even though one gram of protein contains the same amount of energy is 1 gram of carbohydrates, the body finds it harder to break this down in order to release energy and therefore it takes longer. For this reason, the body will only use a source of protein as energy, when there is only a small amount of carbohydrates or fat left. Protein provides about the same energy per kilogram as carbohydrates and about half the energy provided by fat.

Just because it is a poor source of energy does not mean that proteins should not be eaten. Protein is needed for many regular functions in the body. It has been considered the building blocks of the body. They help to build and maintain body tissues, promote growth and repair. Children, pregnant women and breastfeeding women require higher amounts of protein to maintain optimal health for themselves as well as their child.

Since some people are choosing extreme diets, they need to ensure they are getting enough protein from the right sources. Without the proper amount of protein, their bodies will not function properly. High level athletes in such sports as figure skating or gymnastics will have a restrictive diet. The effects on their health is similar to those who experience scarcity of food in 3rd world countries today. 

Check Your Understanding

What is the first source of energy that the body will use?

List five foods that are high in carbohydrates.

In what situations would the body use proteins for energy?