With the World Health Organisation reporting that worldwide obesity has more than doubled since 1980, and that in 2008, 1.5 billion adults were overweight with over 200 million men and nearly 300 million women of these obese, it is now more important than ever that people understand obesity, to stand any chance of managing it. Obesity is ultimately caused by a positive calorie imbalance, in our bodies. Therefore, understanding calories is the beginning of the route to weight loss success. Controlling the daily amount of calories consumed or expended is the single most important determinant of whether we lose weight successfully, or gain weight.
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But first, what is a calorie? Scientifically, a calorie is the amount of heat required to raise the temperature of one gram of water by one degree Celsius. This is not the same as the calorie used to refer to nutritional energy. The Calorie in nutrition, which is the amount of energy contained by food is actually a thousand calories, the kilocalorie. That is, the nutritional calorie can raise the temperature of one gram of water a thousand times more than the scientific calorie.
Even though obesity is preventable, WHO reports that 65% of the world’s population live in countries where overweight and obesity kills more people than underweight. In order to overcome the scourge that is obesity we need to understand food and calories, first.
All food, carbohydrates, proteins, fats and alcohol, contains energy measured in calories. Did you know that most of the energy in food ultimately becomes heat and is lost? All the energy needed by cells is ultimately provided by food intake. This energy can be used immediately or stored for later use. Our metabolic rates determines how much and how quickly the consumed energy is used up or stored in the body as fat. To understand weight loss, or weight gain, you need to understand a few principles about calories:
1. Calories can’t be created or destroyed, therefore our bodies need to use up or store the energy from the food we eat.
2. If the amount of calorie eaten is equal to calorie expenditure, it results in neutral energy balance, culminating in no weight gain.
3. If the amount of calorie intake is more than calorie expenditure, it results in positive energy balance, leading to weight gain. The surplus energy that’s not used is not lost, but is transformed into glycogen or fat, stored energy.
4. If the amount of calories consumed is less than energy expenditure, it results in negative energy balance, resulting in weight loss. The increased energy being expended has not been created, but has been transformed from stored fat, which is how we lose fat and lose weight.
It is obvious that the only way to lose weight is to create a negative energy balance, forcing the body to use up some of its energy stores. The opposite holds true, as well. If more Calories are eaten than needed to support the body’s energy needs, the result is weight gain, as the excess energy can’t be destroyed, but is stored as fat in our bodies.