Nutrition Basics: Macronutrients

Running Sport Diets

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I have gotten into my fair share of “discussions” regarding nutrition. As a coach and a simple observer, I could see that certain fads were just not healthy in the long term. I couldn’t explain it from a data standpoint, but my intuition always told me that any extreme swing in a nutrition plan couldn’t be healthy long term. I know how to write workouts and place them in the right place in a training plan, but that only takes you so far. Looking at my athletes, most of them know how to string days of training together, but don’t know how to deal with the details of training. So, I decided that I needed more data to accompany my intuition and decided to earn a nutrition coach certification. This certainly doesn’t make me a dietician, but certainly more equipped.

The question now becomes, “where the heck do we start?”

I don’t want to get into a major physiological discussion, but I do think it’s incredibly important to understand the role of macronutrients (fat, carbs, protein) in the body and how we utilize them to fuel our exercise.

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Role of macronutrients:

Carbs (CHO) are subject to a lot of scrutiny these days. Blamed for making people fat and unhealthy. The truth of the matter is fat will also make you fat and unhealthy. Protein will also make you fat and unhealthy. If you overeat any combination of these three, you will become fat and unhealthy.

From a simple view CHO are readily available and primary source of energy in the body. Your brain prefers carbohydrates, but also helps maintain body temp and internal organ function. Utilizing carbohydrate as a fuel also indirectly helps you preserve and build muscle mass (so that your body doesn’t have to break down tissue to do so). Your body likes carbs and needs carbs to support a healthy body and exercise. It’s the type, volume, and timing of eating carbs that get people hung up. There’s also some individuality based on body type you are,  that we will get into another time.

How CHO is metabolized in the body:

  1. Glycogenesis- taking glucose and storing it as glycogen
  2. Glycogenolysis: Taking stored glycogen and converting to glucose
  3. Glycolysis: Taking glucose and turning it into pyruvate
  4. Krebs Cycle and Electron Transport Chain: Produce Acetyl-CoA to ATP, CO2 and H2O
  5. Gluconeogenesis: Turning non CHO sources to glucose. This can be
    1. Pyruvate from glycolysis
    2. Lactate from glycolysis
    3. Most amino acids
    4. Glycerol from triglycerides

Ok, so are carbs bad?

Well no, absolutely not- as long as we are eating the right volume and the right kinds. As far as volume, that depends on what we are doing and our body type. For now, let’s look at the type. The big thing is fructose, or as we tend to see it, high fructose corn syrup. It is certainly true that if you overeat this stuff, you set yourself up for a whole host of potential problems. Current research is suggesting that over 50g of fructose per day is the threshold. HOWEVER, whole food sources like FRUIT, does not contribute to this number because of their water, fiber, and vitamin content. In America, we are obsese, and there’s no way around it. We are inactive and we eat a ton of junk.

Over 20% of the average American caloric intake comes from sweeteners.

So what does 50g of this look like in real life?

  1. A 32oz soda = 50 g
  2. 32 oz sports drink = 50g
  3. 1 bag of Skittles = 24g
  4. Honey nut Cheerios and orange juice = 45g
  5. Grande Frap = 39g
  6. Gas station protein bar: 25g

You can see how easy it is to over consume these products and contribute way to much to our daily needs. However, to say that we need to go low carb is relative. Within a standard deviation of mean intake, 68% of people fall. 18% of people probably need more CHO than average and 18% probably need less. For most people, it’s about going low processed sugar and simply eating more real food.

Fat is also a nutrient that sometimes gets a bad rap, but fat is crucial for plasma membranes, hormones, transport of other nutrients, and of course, fuel. There are a number of mechanisms that fat is metabolized in the body.

  1. Fat transport and lipogenesis- Mostly as free fatty acids
  2. Fat mobilization and lipolysis- breakdown of triglycerides into fatty acids and glycerol.
  3. Fatty acid synthesis- system of enzymes that synthesizes fatty acids
  4. B-oxidation- breaks fatty acids into Acetyl CoA (remember that one?) It’s efficient, but it’s slow and it requires oxygen.
  5. Ketone formation- when CHO is low, the liver can make keytones as a glucose substitute to keep brain, muscles, and blood cells healthy.
  6. Cholesterol synthesis and catabolism

I think most people understand the first four of these. When we exercise at a low to moderate intensity, move around, walk down the hall, take the steps, etc, that fat is a great fuel source for those. However, the 5th option, the ketone formation, is all the buzz these days. With a view of carbs being bad, it makes it easy to think it’s completely fine to substitute the carbohydrate intake with a higher fat intake. However, this system is really viewed as a back up and is not the body’s preferred system and we don’t really know what the long term effects are. The diet was really intended for children with epilepsy. Permanent ketosis can lead to high blood lipids, lowered white blood cells, optic neuropathy, lower bone density. Children ultimately developed hydration problems, constipation, decreased bone mineral density, and kidney stones.

Part of the issue I see with ketogenic diets (and high carbohydrate diets for that matter) is lack of continuity in definitions. I see some where it’s  percentage of 70-75% fat for a diet and then I see others where it’s an absolute limit of 25-50g of CHO per day.

To me this is particularly dangerous as the brain alone needs 130g of glucose to function properly.

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Looking at it from a logical standpoint, I wonder why I would load up on a source of energy that I already have an abundance of, but then limit the source of fuel that I have very limited stock piles of. Even if I burn a higher rate of fat, I am significantly increasing the amount of fat in my diet. Then I wonder how the limit of foods is good for overall vitamin and mineral intake. Now, to be fair, I don’t feel that a daily high carb diet is the way to go for all people either. I do think that somewhere along those extremes is a good middle ground to burn more fat, but not deprive yourself of crucial elements to overall health and performance. I realize I will get a lot of pushback on this from some people who swear by ketogenic diets, and I will welcome that discussion later. However, for now just bear with me as this is just a general discussion of macronutrients.

Protein is the final  macronutrient I want to discuss today. Like the other two we have discussed, it’s vital to everyday health and running performance as long as it’s consumed in the right manner. Protein is crucial to giving our body strength and structure, make enzymes and hormones, helping our immune system, and transportation.

The three protein pathways are:

  1. Protein turnover (synthesis and breakdown)
  2. AA catabolism and deamination
  3. Transamination

In terms of providing energy, we need to look at deamination. In deamination, AA are broken down and the portion that remains is called a carbon skeleton. That carbon skeleton can then be converted into one of the following:

  1. Glucose
  2. Ketone bodies
  3. Cholesterol
  4. Fatty acids
  5. A product needed for Krebs cycle where it would ultimately be resynthesized into ATP

These conversions are all seen as backups to when we are under duress of starvation or fasting and isn’t intended to be the primary source of energy.

When you look at use of energy during a marathon and it’s typically less than 2%.

From an endurance athlete standpoint, how much do we need for optimal intake? A healthy sedentary person needs about 0.8g per kg of body weight. An athlete needs anywhere from 1.2-2.2g per kg of body weight. Endurance athletes would probably fall in the middle of those ranges. I think max rate of digestion is something like 3.6 g/kg. This increased rate isn’t for fuel, but rather to help rebuild and repair the muscle damage we create with heavy training.

At the end of the day, if we eat too much excess dietary fat, it gets stored as fat. If we eat too much carbohydrate we increase carbohydrate oxidation. This impairs fat oxidation and causes more dietary fat to be stored. Finally, excessive protein increases protein oxidation and also causes a decrease in fat oxidation. The end result that if you overeat any macronutrient, your body will store more fat.

When we engage in a certain diet, we ultimately gravitate towards high or low CHO. A lot of old school endurance athletes feel like they need to be 60% and above on CHO intake daily. Now, the new school is suggesting that high amount of daily fat is where it’s at. We also tend to muddy the waters between what is ok for a sedentary person and a person in full-blown marathon training. Either way, if a strategy beyond eating an overall balanced diet is extended for a long period of time, then you definitely increase the risk for many nutrient deficiencies and potential health issues.

Where to go from here?

I think we talk about the definition of diets. We can also discuss the idea of “Fueling the day.” Finally, we can talk about safe strategies to decrease fat weight, maintain muscle mass, and improve performance.



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