A Calorie is a unit of energy that measures how much energy food provides to the body. The body needs calories to function properly. The amount of Calories in food gives you energy, protein, carbohydrate, nutrients and fat to fuel your body. When you eat food, your body turns the food into fuel, burning it to produce calories (energy).
The calories in your food come from sources such as carbohydrates, proteins, and fats. For example, a gram of carbohydrate contains 4 calories. A gram of protein also contains 4 calories, where as a gram of fat contains 9 calories, which is more than twice the amount of carbohydrates and protein. This is why a food with the same size serving may have far more calories.
We normally refer to kilocalories as Calories, so when you see 800 calories on a food label it actually means 800 kilocalories, and the same applies when you calculate an activity that burns 800 calories. When referring to food consumption and energy expenditure we refer to them in multiples of 1,000. Thus 1,000 calories = 1 kilocalorie or kcal.
A calorie is the amount of energy (or heat) needed to increase the temperature of one gram of water by 1C. So 1000 calories = 1 kilocalorie, is the energy it takes to raise the temperature of 1kg of water by 1 degree Celsius.
There are 239 calories in 1 kilojoule - A joule is a 1 unit of electrical energy it takes to equal the current of 1 ampere passed through a resistance of 1 ohm for one second. 1,000 joules = 1 kilojoules or kJ. One calorie has the same energy value as 4.186 kilojoules. It takes 3,500 calories to equal one pound of body weight. 1 calorie = 4.2 joules so 1 kilocalorie = 4.2 kilojoules.
The energy value per GRAM of various food components includes:
|Calorie Requirements a Day for Women|
|71 yrs +||1550||1750||2000|
|Calorie Requirements a Day for Men|
|71 yrs +||2000||2200||2500|
If you're at a desirable body weight and have plenty of energy, your calories in food intake is probaly ok. However if you're gaining weight and feel tired a lot of the time, you may want to consider counting your intake of calories in food and changing your daily diet, because as you ingest extra calories your body will convert the excess energy to body fat. Ensure you don't eat less than 1200 calories a day, that's the minimum you need to get your nutrients and stay healthy.
The USDA figures show the average male 5 feet 10 inches in height and weighing 174 pounds, needs 2,900 calories per day - performing light to moderate activity. The average female, 5 feet 4 inches and weighing 138 pounds, needs 2,200 calories per day.
Being overweight or underweight is defined in terms of weight for height, according to the Body Mass Index (BMI).