You have read a lot about calories here. While understanding the Golden Rule of calorie balance, it became clear that any excess calories consumed over the the amount required by your body will ultimately be stored as energy in the form of fat. You also looked at different ways to find out how many calories you really need and a site that shows you the calorific values of common foods.
Definition:
But what really is a calorie, anyway? A calorie is simply a measure of energy. To be more precise 1 calorie is defined as the amount of energy required to raise 1g of water by 1 °C (even more accurate definitions exist, but this is sufficient for practical purposes). A KiloCalorie is 1000 calories.
It is important to remember that all nutrition information labels in the United States actually refer to KiloCalories when they say “Calories” (usually with a capital C, but sometimes not even that). This is important to know becase in the United Kingdon, the labels clearly mention “KCal” but mean the same thing. So if your can of regular soda is 200 “food” calories, it is really 200 KiloCalories.
Are all calories created equal?
This question is the cause of most of the confusion in understanding nutrition, because we tend to think in terms of “this many calories from fat” and “that many calories from protein”. The truth is there is no difference at all in the calorie itself! A calorie really is a calorie - period. What really is different is the source of that calorie. Why? Because our body expends some energy (called the thermic effect of food) to actually extract energy from food to get to those calories and therein lies the crux of the matter.
It’s easiest for our body to get (extract) calories from fat (just 2-3%), less easy from carbohydrates(about 10-15%) and least easy from protein(sometimes as high as 30%!). On average you can assume that the body expends 10% of the energy in the food you eat just to extract that energy. So now you can see that calories themselves are the same, but since some foods tend to give them up so easily, they should be treated with a greater “weight” or “importance” - that’s all. Calories from fat are no different from calories from carbohydrates except that your body expends more energy getting it from carbs.
Calories from foods:
Typically,
1g of fat = 9 Calories
1g of carbohydrate = 4 Calories
1g of protein = 4 Calories
Note that fats are more than twice as “energy dense” as either carbs or protein. So if a food contains 5g each of fat, carbohydrate and protein, then it has (5X9 + 5X4 + 5X4 = ) 85 Calories with (5X9= ) 45 Calories from fat.
Calories and nutrition:
Although your body treats all calories the same when trying to use them for energy, the source of these calories are important in the context of nutrition because calories from fat are more easily absorbed and stored (especially in dangerous areas like arteries, restricting blood flow and in the stomach near major organs reducing their ability to function optimally). The Food and Drug Administration recommends getting not more than about 30% of your total calories from fat (on a 2000 calorie diet that’s about 600 calories or 67g of fat a day - your situation may vary depending on your daily consumption). Today, many nutritionists are recommending reducing that fat % down to 20 and trying to stick to a 50-30-20 approximation when it comes to getting calories from carbs, proteins and fats.
Additional resources:
- How Calories Work from How Stuff Works.
- What are calories and kilojoules? from CaloriesPerHour.
- The Wikipedia page for Calorie
