Macronutrients… what?

 After a successful fast yesterday and a 5 pound drop between Monday morning and Tuesday morning (that will be mostly water weight with maybe .5 lbs of fat) I am back on plan and feeling pretty motivated. I had decided to cut my carb intake for the next 2 days and do a carb refeed on the 3rd, then cycle my carbs like this for 2 weeks while maintaining my calories at a relatively high level. All this sounding complicated yet? As I’m thinking about doing this it occurred to me that all of this information will be useless to most people because most people barely understand what macronutrients are and what their purpose is in the body.The example I usually use with people is that of building a house: Protein = bricks, carbohydrates = the workers, fats = mortar (most of the time, but I’ll get into that later). This forum gives a pretty good explanation.


Your body’s preference is to use carbohydrate for energy (the workers). Carbs provide 4 calories per gram and are converted into energy easily by your body. There are fast acting carbs (sugars and fruits) and slow acting carbs (Whole grains, vegetables, roots and nuts) and these can both be used depending on the type of energy your body needs. Before a run you can eat a piece of fruit for immediate energy and have a sweet potato for long lasting energy. A measure of how fast a carb is absorbed is the glycemic index with can be looked up for all sorts of foods here.

Carbs also create an insulin response based on the glycemic index as well as the glycemic load (the total amount of carbs). Insulin has a large impact on how your body burns fat and processes carbs and fats, but is a very complex topic that is best addressed on its own. If you want to learn more go here.


Proteins are made up of different amino acids which play different roles in your body. Protein is present in many vegetables, grains, nuts and legumes in small amounts, but larger amounts and complete proteins (with all amino acids present) can be found in meat, eggs and dairy products. Our body is better able to use protein from animal sources but a healthy diet can be created with care using only plant sources (I’ll emphasize that this is HARD TO DO!)

Proteins are used to build muscle and lean tissue in your body, repair organs and can be used for energy, but that is not the bodies preference and it requires more conversions that carbs and can be hard on the liver and kidneys if this is the only source of energy. Proteins also provide 4 calories per gram.


There are different types of fats, mainly; saturated, polyunsaturated and monounsaturated fats. There are also cholesterols and trans fats which have a pretty bad rap. Fats unlike protein and carbs provide 9 calories per gram and are therefore more energy dense. Fats are the main source of fuel for your brain and very low fat diets will decrease mental acuity and make you feel “foggy”. Certain vitamins are also only soluble in fat and foods are generally processed more effectively in the presence of fat. Fat promotes satiety (feelings of fullness) and adds flavour to your food.

There is a lot of talk about “good fats’ v. “bad fats” and in general people would classify saturated, trans and cholesterol in the bad camp and poly and mono-unsaturated fats in the good camps with omega 3’s and CLA being the starts of the show. CLA and Omega 3’s are also present in saturated fats (fats from animals or coconuts and some other plants) if they are good quality (i.e. pasture raised meats).

So that your house of macronutrients with protein as the building blocks for your lean tissues, carbs providing the energy to keep going and rebuilding as things are broken down and fats holding it together by allowing things to be processed and when necessary providing the energy if carbs aren’t available.

 So what do you do with this information now?A good place to start a diet is

  • Protein – at least .7 grams of protein per pound of body weight and higher if you are training (I typically eat 1 gram per pound of body weight)
  • Fats – at least .4 grams per pound of lean body weight (think of what you should weigh here and use that as a guide if you are overweight) and no more than 1 gram per pound 
  • Carbohydrates – Carbs basically make up the remaining calories (calories are a whole different part of the equation which I’ll cover another time)… if you are trying to gain weight then add carbs, if you are trying to lose weight, decrease carbs with a minimum of 1 g per pound of bodyweight in the long term if you are active, lower than that and you’ll have some nasty side effects like grouchiness and bad breath, not to mention possible liver and kidney damage if you are replacing it with saturated fats.

All of these amounts can be manipulated in the short term and all of these are based on averages. So if you don’t get enough protein one day then just eat more the next… it’s ok to do that! A good place to read more is in this forum which also discusses calories and how to determine an appropriate calorie range.

You might have heard a lot of talk about percentages and ratios of carbs: protein: fats but I like to work in grams because when you change your calories, your macro requirements don’t actually change. But if you are staying in the same calorie range then percentages work fine (i.e. the Zone diet is 40:40:30).

So what the heck am I doing?

Well I weigh 140 lbs right now (yes I am posting my weight online) and about 115 lbs of that is lean mass (not fat). So by the calculations above I should be at:

 Protein – 1 gram * 140 lbs = 140 gram/day (at least)

  • Fats – .4 grams * 115 lbs = 46 grams/day min – 115 grams/day max.
  • Carbs – 1 grams * 140 lbs = 140 grams/day (this is the normal minimum given for people who are exercising, but can be lower without damaging muscle as discussed here, though he doesn’t list his sources, his information is reasonable accurate)

However… I am cycling my carbs right now… I do 2 days low carb (between 60-80 grams) and 1 day high carbs (more than 250 grams). Here is what my low carb vs high carb day percentages are:

Low Carb

High Carb-refeed

Remember I talked about averages? Well (250+60+80)/3 days = 130 grams/day which is just shy of my minimum and at my minimum if I calculate at my ideal bodyweight of 130 lbs. This method keeps my body guessing and forces it to use my own body fat for fuel on the low carb days and then on the high carb day I “refeed” my muscles and replenish their glycogen stores (stored carbohydrate energy) so that I don’t start using my muscle protein for energy. It’s an interesting system and requires some food tracking and dedication, but I am excited to see how it works 🙂 I’ll keep you posted. If anyone has questions about macronutrients let me know!


2 thoughts on “Macronutrients… what?

  1. Pingback: Counting calories; the good, the bad, and the ugly | On The Go Fitness

  2. Pingback: Double Digits! A GOOD THING! « Eating at my Desk

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