Understanding Macro Nutrition

By Body Satva Team         www.bodysatva.com

www.bodysatva.com

The way our body handles the macronutrients, carbohydrates, proteins and fats is very fascinating. Here we shall try to present a layman’s way to understand this complex and fascinating series of mechanisms.

The demands of survival during periods of famine have caused various adaptations due to which we have survived through the ages. The way human beings handle money, could be a very useful analogy to understand the complex processes. The body spends energy the way an ‘absolute miser’ would spend money. Intake of macronutrients can be considered as earnings. This ‘absolute miser’ has devised various means of storing his wealth. He never ever spends more than what is necessary. Even if there are huge stores of wealth, he will cut down expenditure drastically to preserve and increase the stores. This ‘thrifty’ habit of the body served us well over the ages. Today, it is turning into a liability because the huge stored wealth catches the eye of the taxman.

Let us view Insulin, a hormone secreted by the pancreas, as the ‘Chief Banker’ of the body. 

Dietary carbohydrates are broken down to glucose and used by the body for energy. If glucose levels in the blood are more than the immediate need (pocket money), Insulin will send it to the liver and muscles for storage as glycogen (money in the savings bank). If even more glucose is available, Insulin will convert it into fats for storage in adipose tissue (fixed deposits).

If you exercise regularly muscles will use more glucose and there will be less glucose available for storage. Now why do we need to exercise!? The body, as we said earlier, is an absolute miser and has devised very clever ways of spending very carefully. Every muscle cell has entry points for glucose (and other nutrients) called ‘insulin receptors’. Insulin has to push glucose into the cell through these receptors. The glucose is then carried to the ‘mitochondria’ by other proteins. The mitochondria will use it for conversion to energy, only when the Insulin at the receptor signals it to do so. If the muscle is not used regularly, the miserly body will shut down the receptors to avoid wasteful expenditure of energy. Regular exercise will keep the receptors open and functioning. Intense exercise will lead to more receptors being opened.

Lack of exercise results in shutting down of receptors and may cause defects of insulin receptor signaling. This process is called ‘insulin resistance’. Insulin Resistance leads to Metabolic Syndrome, Obesity, Type 2 Diabetes and diseases of the heart.

Fat is used for energy and also as building blocks for making cell membranes and for the synthesis of hormones and many other compounds in the body. The insoluble fat is carried in the bloodstream inside carrier protein complexes called ‘lipoproteins’. The lipoproteins are also carriers of cholesterol, which are essential for many functions. Excess cholesterol gets deposited inside the arteries and causes atherosclerosis. The main carrier of cholesterol is called Low Density Lipoprotein or LDL or Bad Cholesterol. The carrier that transports cholesterol away from the tissues is called High Density Lipoprotein or HDL or Good Cholesterol. Exercise improves the levels of HDL.

Fat can be used directly by skeletal muscles and the heart muscles. Excess fat gets stored in the adipose tissue. Any miser would prefer to cut down expenditure rather than use up his fixed deposits. The body also does the same thing and recent discoveries show that the body tries to hold on to its deposits by a complex mechanism involving at least 10 different chemical messengers!
This is one of the reasons why dieting never produced good results, unless it was accompanied by regular exercise.

Saturated fats get stored easily and are involved in many inflammatory pathways. Omega 3 fatty acids or poly unsaturated fatty acids (PUFA) are needed for many vital functions and are involved in anti inflammatory pathways.

Till recently the focus was mainly on carbohydrates and fats, since most of the chronic diseases were due to metabolic imbalances of these two macronutrients. Insulin the ‘chief banker’ was involved all the way in regulating storage and expenditure. Developments in Sports Medicine and Aging Studies have uncovered the role of insulin in protein metabolism also.

Proteins are made up of 22 amino acids, out of which 8 are called essential because we have to compulsorily get them from our diet. The remaining can be made in the body if other amino acids are available. Proteins form the muscles and other structural components of the body, including bone and hair. All enzymes are made of protein and many hormones are proteins, including Insulin itself.

Now it is to be expected that such a valuable asset will not miss the eye of the ‘Chief Banker’.

Proteins are broken down to amino acids by the digestive enzymes and then absorbed by the body. Once again only those muscles which are exercised get a larger share of the amino acids. Insulin has a role here also. Remember, no wastage of resources!! As a wise banker who manages liquidity of some assets, the body uses amino acids for energy when carbohydrates are depleted and fat is not yet mobilized from the stores.

Muscles act as the store house for amino acids. A pool of amino acids is maintained inside the muscle cell. When sufficient levels are available muscle synthesis occurs. When the levels are depleted muscle degradation occurs to maintain the amino acid pool, probably for emergency use.

Insulin is known to reduce muscle protein breakdown [1]. Its role in muscle protein synthesis is not so clear. Isn’t this fascinating? Insulin levels are more when glucose levels are high. If glucose is available the body spares the valuable amino acids, through Insulin. Wow!!

A recent study shows that “a flooding dose of essential amino acids (EAA) stimulated the fractional synthesis rates (FSR) of skeletal muscle protein” and “However, when nonessential AA (NEAA) were used as a flood, FSR was not increased. The stimulation of muscle protein synthesis by EAA is an interesting display of human design.” [1]

In conclusion, our body uses energy sparingly and stores valuable nutrients for future use. Physical activity is one of the most important factors to ensure optimal energy expenditure and protect us from the harmful effects of too much storage. When combined with a balanced diet of macronutrients in correct proportions, regular exercise can delay or prevent many of the acquired diseases and also prolong youth.

Prolong Youth by leading an ‘enlightened and balanced life’

Reference:
1. Benjamin F. Miller, Exerc Sport Sci Rev. 2007;35(2):50-55. ©2007 American College of Sports Medicine

Disclaimer

Body Satva Team has taken maximum care to ensure authenticity of the information provided, by sourcing from reputed medical journals and books. Body Satva Team urges members to seek professional advice before commencing any regimen of diet, exercise and medication.