A calorie is defined as a specific unit of energy; a unit requirement that must or should be consumed per day to support both normal growth and maintenance. Also referred to as joules, the mammal consuming the amount of calories identical to the amount of energy used has achieved an energy balance. One which has consumed less energy units than what is used is in a negative energy balance and conversely one which has consumed more than used is in a positive balance.
Often misleading, a calorie is based upon specific heat capacity, or energy, not fat proliferation. There are a multitude of biochemical pathways which convert fuels (foods) which we consume into fat and to associate calories as a negative factor in foods is a bit premature. In mammals, caloric values of metabolic fuels are expressed in kilocalories. The major types of metabolic fuels and their caloric values are:
Fatty acids= 9 kcal/g
Amino acids = 4 kcal/g
Ketone bodies= 4 kcal/g
Carbohydrates = 4 kcal/g
Any fuel recognized has calories. As an example, 4 liters of gasoline contains 31,000,000 calories.
The general confusion with the calorie and the often associated fat production (lipogenesis) and storage which is associated with it arise primarily from the feeding-fasting cycle. It is important to define the fact that humans are intermittent feeders. Consideration of metabolism and the biochemical use of metabolic fuels should take this into account. When we are able to define these metabolic characteristics, it becomes evident that the direct association of calories and lipogenesis has arisen from a lot of misinformation. Think in the terms of the use of fuels by humans as that compared to the fuels used by a fire. In both cases, the fuels donate electrons to oxygen, thus converting to CO2 and the oxygen to water. The generation of heat does not consequently mean the biosynthesis of fats.
Immediately following a meal, humans are defined as being in the fed state. The metabolic fuels used by the tissues and primary structures are taken from the ingested and absorbed food molecules. The fasting state occurs several hours after ingesting a meal, or when insufficient amounts of food are consumed. This fasting state is when the metabolic fuels used by the structures are derived from mobilized storages of fuel molecules. This is usually what occurs when individual’s diet
When we observe the foods most commonly associated with high caloric values, we will also see a correlation of high amounts of sugar arranged with that food. This includes fats, which possess a glycerol backbone. The molecule Acetyl-CoA plays an important role in the balance of both fat and carbohydrate metabolism and does so by transferring the carbon portion of one given fuel source to a biochemical pathway within our body. Please keep in mind that the higher the “carbon loading” within a fuel source (such as simple sugars), the greater activity of the transference of carbon by acetyl-CoA occurs into various biochemical pathways, including lipogenesis.
These biochemical pathways, from insulin activation and requirements, to the Krebs cycle, which produces the energy molecule (ATP) within our cells, all require necessary support in the form of particular ions to substrates. Without these support mechanisms in place or in most cases, their diminished biochemical activities, the lonely calorie often incorrectly takes the blame for being the culprit for bad health (weight gain).
Many of the healthiest foods for mammals contain high amounts of calories. These are ingested in relatively substantial amounts on a routine basis by many indigenous cultures worldwide and yet these societies display very little, if any, obesity. Some may consider the vigorous activity within the lifestyle of these societies as having a role in how the calories are utilized, but this is not always the case. The foods (fuels) consumed by these cultures are generally in their whole form, which conveniently provide the other components necessary for the correct utilization of the amount of carbon within the food. Tropical fruits, for example, have a tremendous amount of calories, yet the societies found in the geographical regions where the fruit grows traditionally have no obesity (industrialized modern day diets are now finding their way into these cultures, unfortunately changing this). Fruits in their whole form encompass the vast array of bioflavonoids and substrates required to correctly utilize the carbon. These substrates support the biochemical pathways as mentioned earlier (acetyl-CoA, Krebs cycle, etc) which shuttle the carbon into the correct pathways for energy utilization. The same holds true for grains when in their whole form.
Generally people ask “How many calories are in that” or state “I am on a calorie restricted diet”, with the intent to loss weight. This inevitably puts the individual in a fasting condition or worse; a starvation mode; both being relatively risky scenarios if maintained for a prolonged period of time. Remember, energy requirements are also dictated by the biochemical pathways within the body, not just its physical activity.
“I don’t understand, she doesn’t exercise at all and she’s thin. I exercise all the time, eating next to nothing and can’t lose an ounce.” How many times have we heard this one? Does this scenario support the high calorie claim? The premise of this article is to invite the reader to consider all variables associated with bad health (weight gain in this case) and the media’s claim that high caloric foods are detrimental to health. It is the state of the food; denatured and manipulated which induces negative health consequences, not the calorie. A calorie is simply energy.
- By Kevin Meehan