Today, I want to chat briefly about the concept of Macronutrient Partitioning.  This refers to the breakdown (percentages of total calorie intakes) of carbohydrates, proteins and fats that we eat.  This is a general overview of the topic.  If you want more details, I would suggest that you check out this blog post on Robb Wolf’s site and consider this ebook, which is very well researched and describes the topic in quite easy and practical terms, it’s called carb backloading.
Why consider this? Simple. If how much we ate was the only driving force, then circulating hormone levels would not need to be considered.  This is NOT the case, and as you will see, macronutrient composition can alter hormonal circulatio, which then can determine how the macronutrients are utilized in the body.
All macronutrients are necessary for overall health, optimal performance and maximal longevity!  Here we look quickly at the role of each macronutrient in the body.
1)    Carbohydrate.  This category of nutrient is primarily used for energy.  Interestingly, the body has the ability to create carbohydrates given the right substrates and it can adapt to ketone bodies as fuel as well. This category includes mainly fibre, starch and sugar.  Fibre is primarily indigestible although some has been shown to be broken down by bacteria in the colon to release fatty acids for fuel.  Sugar is the simplest form of carbohydrate energy and is quickly absorbed and enters the blood as glucose.  Table sugar is actually sucrose which is a 50/50 blend of glucose bound to fructose molecule.  Fructose is preferentially stored in the liver and has been shown to lead to central adiposity.  The structure of glucose is shown to the right and is a primary fuel source for anaerobic activity (think high intensity glycolytic activities) via glycolysis and Kreb’s cycle and the electron transport chain one molecule of glucose directly creates a net of 2 ATP (energy molecules).  Glucose is blood sugar and entry of this into the blood stream stimulates secretion of insulin by the pancreas to regulate the circulating levels of this in the blood (CITE).  Most food labeling requires sugar be listed because of its rapid effect on blood sugar (and insulin) levels, however, a large amount of starch, although not as rapid-acting can definitely raise blood sugar (and insulin) for longer periods of time, which can change structure of adipose tissue to become more efficient at storing fat (vs. burning it).
2)      Protein.  These are essential nutrients for the body, as they are building blocks of every tissue and are also used for energy sources.  Certain amino acids are essential as humans cannot synthesize them; all others can be made from the essential ones or by breaking down ingested proteins.  Conditional amino acids are not usually necessary except during times of stress, illness and specific inborn errors of metabolism.  By far the best biological availability and quality of proteins are found from animal sources.  Vegetarian options can suffice but are less than optimal.  Branched chain amino acids can be broken down into Acetyl-CoA and Succinyl CoA and enter Kreb’s cycle to produce energy as the body requires.
3)      Fat (Lipid).  This group includes fats, waxes, sterols, fat-soluble vitamins (A,D,E,K), mono-, di- and tri-glycerides, phospholipids and others.  Their main roles include energy storage, signaling and structural components of cell membranes.  Fats provide the richest source of energy for aerobic respiration, in which two carbon units of fatty acids are released and enter Kreb’s cycle and subsequently the electron transport chain to create energy (i.e. palmitate (C16:0) oxidation results in 106 ATP (13.25 ATP per 2-carbon chain)).


We need to understand the effects of each macronutrient profile on hormone secretion and subsequently on body composition.
A)     High carbohydrate, low fat: This is the USDA, HC norm and given today’s sources of carbohydrates (i.e. highly refined) has been associated with increases in insulin (to the point that the body can become resistant insulin resistant) and increased body fat particularly around the abdominal area (i.e. surrounding the visceral organs).  This is the most dangerous form of obesity and is directly associated with metabolic syndrome.
Elevated insulin:
          Promotes fat storage and stops fat burning.
          Promotes protein synthesis and decreases protein hydrolysis.
          Therefore, it promotes growth of both fat & muscle tissue.
          Can cross the blood brain barrier and when dysregulated it has been implicated in neurodegenerative diseases (i.e. Alzheimers) and psychiatric disorders (i.e. Schizophrenia).
B)      High fat, low carbohydrate: This is a ketogenic diet.  It can take up to 4 weeks for the body to adapt to ketone bodies as a primary fuel source.  This directly oxidizes and burns stored body fat.  Circulating insulin levels are low and therefore the body is shifted into fat burning mode away from fat storing mode.  Many different tweaks have been shown to improve fat burning ability and further hamper fat storing expression (i.e. exercise type & volume, timing and amount of carbohydrate intake, amount and type of protein intake, etc…). 
Therefore, it would seem that for optimal health, performance and longevity we would be best served by doing the following.
1)      Protein:
a.       Aim for around 1 g/ lbs of your ideal body weight daily
b.      Choose the best sources (animal vs. vegetable; grass fed vs. grain fed; consider fats included with protein) 
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Fats:
a.       Aim for 2 g/day of omega-3 (DHA + EPA combined).
b.      Not more than 8 g omega-6 per day.
c.       Get adequate monounsaturated fats (olive, avocado, hazelnut and macadamia nut and oils).
d.      Saturated fats (animal sources + coconut oil).  When carbohydrates are lower, these can be your primary fat sources.  These are the most stable for cooking and least oxidizable.
3)      Carbohydrates:
a.       Keep your total intake to around 100-150 g per day (depending on your body composition goal).
b.      Eliminate sugar and refined grains (i.e. all grains are refined).
c.       Consume your main carbohydrate loads post workout (especially strength training) up to 4 hours after and focus on starchy vegetable carbohydrates primarily. 
Citations

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