The energy value of a food indicates how much energy the human body can gain through metabolism. The energy value is specified in KJ/100gm or 100 ml. In addition, the specification is open in Kcal. The total energy value of food product results from the addition of the energy content of each nutrient component. These are defined as follows:

1)      1 gm Fat- 31KJ

2)      1 gm Carbohydrates- 17KJ

3)      1 gm Proteins – 17 KJ


·         When we eat food, the nutrients present in it are released by the process of digestion. Digestion starts in the mouth, where the food is broken into smaller bites and mixed with saliva. The food is then passing into the stomach or the duodenum where it is further broken down by chemical action and sent to small intestine where the process of absorption of nutrients begins.

·         The chemical reaction in our body causes the complex molecule present in food to be broken down into simpler molecule.

·          These simple molecules are absorbed by the walls of the small intestine. They enter the bloodstream and are then transported to the various parts of the body. These simple molecules are then burnt by the cells to provide energy.

·         Food contains a number of basic elements such as carbohydrates, proteins, fat and alcohol. These elements all produce different quantities of energy when burnt. The amount of energy produced when 1 gm of any of these elements is burned is known as calorific value.

Calorific value of each of these food elements is given below:

Carbohydrates: 4 calorie

Protein: 4 calorie

Fat: 9 calorie

Alcohol: 7 calorie

·         Carbohydrates are the main source of energy for the human body. When they are broken down they form glucose. Glucose is essential as a source of energy and is also important for maintaining tissue protein. The brain and CNS depend solely on glucose for their energy requirement.

·         Carbohydrates are obtained from foods such as whole grain cereal and breads and pasta, corn, beans, peas, potatoes, fruit, vegetable and milk products. These foods grouped together normally constitute more than 50% of the calorie requirement of the human body. It is recommended that carbohydrates should contribute 60-70% of the total calories is a 6 days diet.

·         The carbohydrates that are found in such foods are called complex carbohydrates. They are slowly broken down into glucose and absorbed by the body. This ensures that healthy levels of glucose are always maintained in the body.

·         Simple sugars are carbohydrates that are obtained by refining naturally occurring sugars. These simple sugars are found in processed food. Simple sugars are readily absorbed by the body. The body glucose requirement is usually exceeded and the supply of glucose doesn’t last over a period of time.

·         Processed foods are also devoid of minerals and other requirement that are required by the body to aid the process of digestion.

Calorific needs:

The 2010 dietary guidelines for American women estimates 1,600 – 2,400 calories, while more generally require 2,000-3,000 calories each day to maintain a healthy weight. Harvard Medical School suggests adults need 13-18 calories/ pound of body weight each day to maintain their weight. Therefore, a 125 pound women needs 1625-2250 calories each day and 16.5 pound man requires 2145-2970 calories per day, according to the US department of health and human resources.

Carbohydrate requirement:

The Institute of medicine recommends adults consume 56.5% of their body calories from carbohydrates. Since carbohydrates contains 4 calories each gm. We can calculate our carbohydrate requirement by dividing 45-65% of your calories needed by you. Sugar and starches get digested to produce glucose, which is the form of energy preferred by every cell in our body. They also have the advantage of being converted into energy faster than fats and proteins. Inside our cells, special structure converts glucose into the chemical that stores and carries energy in the form of ATP. Each molecule of glucose produces 36-38% molecules of ATP. If we eat more carbohydrate than we need for energy, the excess glucose is stored in fatty tissue as triglycerides or in the muscles and liver as glycogen.

Protein requirement:

Adults should consume 10-35% of their energy intake from protein, according to the institute of Medicine. Since protein provide 4 calories per gm of your goal is to consume 20% of your calories from protein we had need to eat. 400 calories or about 100 gms of protein per day when consuming 2,000 calories. High protein foods include lean meats, poultry, seafood, soy products, eggs, dairy foods, legumes, nuts and seeds. Our body prefers not to use proteins for energy because it is specifically needed to build and repair all kinds of tissues. Our muscles, hair, skin, organs, enzymes, antibodies and hormones depend on proteins. If we don’t have enough carbohydrates and fats to meet our energy needs, amino acid from dietary protein are converted into energy.

Fat Requirement:

The Institute of Medicine suggests adults eat 20-35% of their daily calories from fat. Since fat provides 9 calories/gm, calculate your needs by dividing 20-35% of you calorie requirements by 9. Based on these recommendations we should eat 400 -700 calories from fat, or about 74-78 gm of fat, each day when following 2.000 calories diet. To reduce our risk for heart disease, choose healthy unsaturated fats such as vegetable oil, fish oils, humus, avocados, vents, seeds instead of high fat meal like butter and full fat dairy products. When our body runs out of glucose, it turns to fat for energy, when fat has 9 calories in every gm. This is a little more than double the amount in carbohydrate converting fats into energy takes longer than it does to convert glucose into energy because fat must be first broken down into its two components part: fatty acid and glycerol. Each part follows separate pathways to ultimately become available as energy. One common saturated fat; palmitic acid make 130 molecules of ATP for each molecule of fat.

The amount of energy we will get from carbohydrate, protein, fat is measured in calories/gm. Fats have the most energy and protein have the same amount as carbohydrate, but their value as a source of energy is determined by more than the calories gained from 1 gm.



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