IIFYM = Portion Control by Another Name

I am a member of MyFitnessPal.com. I joined with my daughter at the beginning of her adventure in healthy eating because it's online calorie tracker is relatively easy to use. I don't use it for myself any more, though I still occasionally read in the forums. I mention this because I'm not sure if IIFYM or If It Fits in Your Macros is a commonly known concept.

I'm not going to do much research on it, but this site gives a basic outline. To me it sounds like portion control made "cool" for body builders and/or weight lifting enthusiasts. But instead of focusing on calories, you're counting "macros" as in the macronutrients of carbs, proteins and fats. But like simple portion control, you can eat anything you want, so long as you don't eat too much of any macro.

Counting macros rather than calories is generally done (at least in my observation) when someone is looking to alter body composition. Body recomposition is critical in body building, body fat must be minimize and muscle maximized. Hitting specific macro targets is often part of the effort (along with intense weight training.)

Anyway, fast food, junk food, any food is acceptable with IIFYM, so long a person stays within the targets for fats, carbs and protein. Not unlike eating whatever you want throughout the day, so long as your calorie total is appropriate for your size.

To me, focusing on the macros (absent any desire to "recompose" one's body) is an unnecessary complication.

Calories In can't be known accurately either, or it's all about the microbiome

Robb Dunn in Scientific American discusses calories, and how not all calories are treated the same by the body. In addition, different people's body will react differently.

Of course a calorie is a calorie, a calorie is a unit of measure. But in the body, not all source of calories are treated the same, and it's mostly due to our bugs (microbiome). It also has to do with how processed (pre-digested) the food is, as well as differences between people based on genetics.

The microbiome, which is, per Robb Dunn, a relatively new term, encompasses the microbe ecosystem that exists in the digestive tract. your microbial digestive biome will handle different foods differently, but in general, whatever the body can't digest, is left to the gut bugs. In a healthy body, the relationship between the body and its gut bugs is symbiotic, and both side benefit.

Gut bugs like whole foods, because the body can't digest them as completely. So the number of calories estimated for a raw, unprocessed foods are likely higher than the total actually absorbed. Some percentage simply passes right through and is excreted. Nuts and seeds in particular do not get digested well.

Cooked and processed foods are easiest for the human digestive system to process. This means that the calorie totals on processed food packaging has a greater chance of being accurate— that is, if food processors were interested in being completely accurate. Regulations allow the actual average calorie totals on packaged foods to be up to 15% higher than what's stated. Lower calorie counts are desirable from a consumer stand point, guess how companies tend to err?

Cooked meats are also digested better than raw meats. So the folks pointing to a raw diet may have a point... up to a point. You can eat more total calories if you eat them raw, because more of the total simply passes through you unabsorbed. Cooking food is unique to humans, and cooking food is the best way to maximize calorie absorption. From an evolutionary standard, getting more calories easier means energy to develop a bigger brain and time to do (invent) other things.

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