Friday, February 15, 2013

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Calorie and calorie counter

When people talk about the calories in food, what do they mean? A calorie is a unit of measurement — but it doesn't measure weight or length. A calorie is actually a unit of heat energy. That's right. We think of calories as just things that are in food and all foods have calories. But your body sees calories as energy and it's energy to produce heat. And heat energy is what really fuels our body just the same way that gasoline is what fuels your car's energy. When you hear something contains 100 calories, it's a way of describing how much energy your body could get from eating or drinking it.




Are Calories Bad for You?


Calories aren't bad for you. Your body needs calories for energy. But eating too many calories — and not burning enough of them off through activity — can lead to weight gain. Most foods and drinks contain calories. Some foods, such as lettuce, contain few calories (1 cup of shredded lettuce has less than 10 calories). Other foods, like peanuts, contain a lot of calories (½ cup of peanuts has 427 calories).


You can find out how many calories are in a food by looking at the nutrition facts label. The label also will describe the components of the food — how many grams of carbohydrate, protein, and fat it contains.


Here's how many calories are in 1 gram of each:


 carbohydrate — 4 calories

 protein — 4 calories

 fat — 9 calories


That means if you know how many grams of each one are in a food, you can calculate the total calories. You would multiply the number of grams by the number of calories in a gram of that food component. For example, if a serving of potato chips (about 20 chips) has 10 grams of fat, 90 calories are from fat. That's 10 grams x 9 calories per gram. The number of calories people should eat each day depends on several factors, including their age, size, height, sex, lifestyle, and overall general health. A physically active 6ft 2in male, aged 22 years, requires considerably more calories than a 5ft 2ins sedentary woman in her 70s.


Recommended daily calorie intakes also vary across the world.


According to the National Health Service (NHS), UK, the average male adult needs approximately 2,500 calories per day to keep his weight constant, while the average adult female needs 2,000.


The NHS stresses that rather than precisely counting numbers (calories), people should focus more on eating a healthy and well balanced diet, being physically active, and roughly balancing how many calories are consumed with the numbers burnt off each day. According to the United Nation's Food and Agriculture Organization (FAO), the average person's minimum calorie requirement per day globally is approximately 1,800 kilocalories.


Daily calorie consumption varies considerably around the world (countries in gray indicates "no data available")



Calories and Kilocalories :  It's easy to get confused about calories and kilocalories since, in a nutrition context, values are actually given for the number of kilocalories in a food, but referred to simply as calories.

In scientific terms:

1000 calories = 1 kilocalorie



The human body and energy usage


For the human body to remain alive, it requires energy. Approximately 20% of the energy we use is for brain metabolism. The majority of the rest of the body's energy requirements are taken up for the basal metabolic requirements - the energy we need when in a resting state, for functions such as the circulation of the blood and breathing.


If our environment is cold, our metabolism increases to produce more heat to maintain a constant body temperature. When we are in a warm environment, we require less energy.


We also require mechanical energy for our skeletal muscles for posture and moving around.


Respiration, or specifically cellular respiration refers to the metabolic process by which an organism gets energy by reacting oxygen with glucose to produce carbon dioxide, water and ATP energy. How efficiently energy from respiration converts into physical (mechanical) power depends on the type of food eaten, as well as what type of physical energy is used - whether muscles are used aerobically or anaerobically.


Put simply - we need calories to stay alive, even if we are not moving, and need calories to keep our posture and to move about.

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