A human being needs around 2000-calories daily, and human race consumes more than 12 trillion calories (6 billion humans x 2000-calories) every day, the spare calories left after doing the basic activities are utilized to either build proteins mostly before the age of 30, or to build fats mostly after the age of 30.
Calorie Consumption Pattern Before 30 :
Over 30, the body has its own laws that work differently from that way we experienced before 30.
From birth to full growth in the early 20s, the hormonal balance in our bodies is dominated by the anabolic hormonal orchestra that utilizes most of the consumed calories to build the body organs.
The anabolic - building - hormonal orchestra is composed primarily of Growth hormone, Sex hormones (mainly male sex hormone), together with Thyroid hormones.
Growth hormone and Calorie Regulation :
Growth hormone derives calories basically from fats (fatty acids), spares carbohydrates and build proteins. This is explained as follows :
* Growth hormone suppresses storage of calories in the form of fats by fat cells, through :
1- It stimulates fat cells to increase calorie production through stimulation of triglycerides breakdown and releasing fatty acids to be oxidized.
2- It decreases the ability of fat cells to store calories through suppressing their ability to take up and accumulate lipids.
* Growth hormone directs the body to consume calories in production of proteins, through stimulating the liver and other tissues to secrete insulin like growth hormone which is the key player in muscle growth, as it stimulates amino acid uptake and reduces their oxidation, thus preventing them from being used as a calorie source.
* Growth hormone carbohydrate sparing effect, preserves them to be stored in the "on-call" or "stand-by" form, i.e. Glycogen, so that they serve as the calorie store for prompt demand by the muscles and the Red Blood Corpuscles, moreover this effect helps maintain blood glucose within the normal range, and maintains supply of sufficient amounts of essential sugars required for structural purposes.
Sex Hormones and Calorie Regulation :
* Testosterone ( male sex hormone) stimulates protein metabolism, promotes burning of fats, and accelerates muscle growth, producing fat free muscle of greater size.
* Absence of Estrogen ( a female sex hormone) receptors in the brain of experimental rats, were found in a recent study in Rockefeller university, to lead to less calorie expenditure. The rats also developed several hallmarks, including glucose intolerance and resistance to insulin.
Calorie Consumption pattern After 30 :
1- Levels of Anabolic Hormones :
* Growth Hormone:
At the age of 25 -the peak time for growth hormone- the total secreted amount is 600 mcg/day. It decreases by age and goes down to 15 percent of this amount at the age of 60-70, this ratio can be accelerated by unbalanced diet to happen at 40-50. Rough estimation of its level at different ages is as follows:At the age of 20, growth hormone secretion is 500 mcg/day, at the age of 40, growth hormone secretion is 200 mcg/day,at the age of 80, growth hormone secretion is 25 mcg/day.
* Sex hormones :
The high level of testosterone in males starts to decline in the third decade and this decline proceeds with age, leading to marked lower levels of bio available testosterone in substantial proportion of elderly men compared to the young adult male range.In females, all hormones abruptly decline after menopause.
2- Calorie consumption pattern :
After 30 , there are different factors influencing calorie consumption pattern, these are :
# Decreased levels of anabolic hormones.
# Decreased expenditure of calories with sedentary life.
# Abundance of nutrients that are in less demand.
# A battery of catabolic hormones, that degrade body tissues, primarily the muscles. They are present all the life time, yet some of them are not endocrine in nature ( not submitted to age changes ), they are available on demand in stress conditions ( fight or flight ), examples are: Cortisol and Epinephrine.
This new situation dictates the body to convert surplus calories into a storage form that meets the following criteria :
# It delivers the substrate for calorie production in a form that can be acted upon by the predominant hormones ( many of them derive calories from fatty acids, e.g. Epinephrine, Cortisol and Glucagon).
# It is an efficient storage form on weight basis, to store a lot of calories that are neither used for building tissues, nor consumed in physical activity.
The form that fulfils these criteria is FATS.
The base line is that whenever you need to consider changing your eating behaviour, you should start with the scientifically calculated calorie needs per day. You have to count 2000 calories every day.