There are millions of people for whom it is almost impossible to arrange two square meals for the families. So they don’t have any choice of what they eat. On the other hand, there are affluent people for whom what to eat or what not to eat is a big problem. They are grappling with obesity problems which are the precursor of so many lethal ailments like heart attack, blood pressure, backache and diabetes. They are always conscious of the calorific value of the foods they consume.

Any student of science or health conscious person is aware that calorie is unit of energy. Our bodies continuously require energy to properly perform normal functions of the body. Even while doing nothing, our body consumes energy called basal metabolic rate.

Calorie and calorie are slightly different. In nutrition science, Calorie with capital C is equal to 1000 calories. Sometimes, Calorie is also called kilo calorie. 1 Calorie is the amount of energy it takes to raise 1 kilogram of water 1 degree centigrade at sea level.

The calorie content of foods consumed  by a human being was determined in the late 1800s by Wilbur O. Atwater, an agricultural chemist. He built a device called a “Respiration Calorimeter” to make direct measurements of heat released by humans from the food they consumed. At 4 feet by 8 feet, Atwater’s calorimeter was big enough to allow a person to step into it. The device measured the amount of heat released by that person, along with the amount of oxygen consumed and carbon dioxide given off.

Using this device, Atwater was able to measure the precise amount of energy contained in thousands of food items. He found that carbohydrates and proteins are worth 4 Calories per gram and fats about 9 Calories per gram. This 4-9-4 system is how labels are determined today. In some cases, dietary fiber is subtracted from the total carbohydrate count because it is assumed that it provides no nutritional calories. Also, alcohol, if present, is accounted for as 7 Calories per gram.

Basal metabolism reactions occurring inside our bodies consume 70% of the calories. Rest 30% if not consumed shall be deposited in the body mostly in the form of fat.