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A look at the "IIFYM" diet. Does it work? – AFK Supply

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A look at the "IIFYM" diet. Does it work?

If It Fits Your Macros aka IIFYM. What is it, is it just a fad or should I use it?

IIFYM has been one of those diets you probably overheard a health nut talking about at the gym or had seen on a fitness influencer page on the internet. They probably are touting on how great it is and how they have had massive success with it. 

So, kinda sounds like a fad? 

Nope! It can be a very successful diet plan when followed correctly.

Like any other diet out there, it can be successful with a few caveats. But don’t worry, I’m here to explain how to utilize IIFYM successfully and what to look out for.

IIFYM, the basics:

The main idea behind IIFYM is that if you eat a specific set amount of these macros in a day, you can successfully reach your goals whether that is to gain muscle, lose fat, or maintain your current physique. It is a very calculated and to-the-point dieting method for people who like doing things by the numbers.

Macronutrients, or macros for short, are what make up our diet. They are protein, carbohydrates, and fats. Typically, you should be getting 45-65% of your total calories from carbohydrates, 20-35% of your total calories from fat, and 10-35% of your total calories from protein. [1]

REMEMBER: (1) gram of carbohydrates is 4 calories, (1) gram of protein is 4 calories, and (1) gram of fat is 9 calories. [2]

Given this information, let me give you an example to make more sense of all of this.

Example: If you are supposed to be having 2000 calories a day to reach your goal, then 45-65% of those calories should be from carbs. 45-65% of 2000 calories is 900-1300 calories, and remember that 1 gram of carbs is 4 calories. So, all you need to do is divide the 900-1300 calories by 4 to get how many carbs you should be having, which would be 225-325 grams of carbohydrates. 20-35% of those calories should be from fat, which ends up being 44 -78g of fat. 10-35% of those calories should be from protein which gives you 50-175g of protein. Then all you need to do is record how many macronutrients you are getting of each of these throughout the day until you hit those numbers. The macronutrients are on the back of the package of food you are eating. Then you are done for the day and that’s it! 

As you can see, this is a very mathematical, calculated approach to dieting, which if that is your preference, his diet can be great for you. For others it can be very tedious, it really depends on your preferences and lifestyle. 

If you believe this could be good for you, then continue reading for a step-by-step guide on where to start.

Step by step guide on how to use IIFYM:

Step 1. 

Determine how many calories you need in a day using the...

The Mifflin St. Jeor Calculator, [3]

...which is great for this as it takes in consideration your activity level.

Step 2.

Determine whether you want to lose weight, gain weight, or maintain weight:

If you would like to lose weight, then subtract 250-500 calories from the calories you should be getting a day based off the Mifflin St. Jeor calculator.

If you would like to gain weight, then add 250-500 calories from the calories you should be getting a day based off the Mifflin St. Jeor calculator.

If you would like to maintain weight, then make sure you are having no more or less than the calories you calculated from the Mifflin St. Jeor calculator.

Step 3.

Calculate your macros! Take the number of calories you determined you need in a day from step 2 and divide them up into proteins, carbs, and fats. Remember, 45-65% of your calories should come from carbs, 20-35% from fat, and 10-35% from protein. Use the example provided above to calculate them, and don’t forget:

REMINDER: (1) gram of carbohydrates is 4 calories, (1) gram of protein is 4 calories, and (1) gram of fat is 9 calories.

*If you are looking to gain muscle mass, then you should have closer to that 35% of your calories from protein.

*If you are looking to lose fat, then try to adjust your macros so that you are eating closer to that lower 45% range of carbs and/or lower fat range of 20%.

Step 4.

Record a daily log of the calories and macros you are eating at each meal so you can hit the number you calculated each day.

If you stay consistent and hit your macro goals for each day, you will see results.

The only caveat is people think they can eat whatever they want when following this diet if they hit their numbers. While this can be true, you still want to get all your daily vitamins and nutrients in. So, try to have a balanced diet while following IIFYM.

Lastly, if you do not want to write down your macros every day, I recommend giving MyFitnessPal a try as it does all the calculating for you, all you need to do is enter in the food you eat every day, and it will tell you when you hit your daily goals!

As always, please holler if you have any questions. 



This is not medical advice. Consult with your physician before beginning any diet regimen.



[1] Kreider, R. et al. (2010). ISSN exercise & sport nutrition review: Research & recommendations.  Journal of the International Society of Sports Nutrition, 7, 7.

[2] Mary L. Gavin, MD (2021) Figuring out Fat and Calories

[3]  Raffaella Cancello et al. (2018) Analysis of Predictive Equations for Estimating Resting Energy Expenditure in a Large Cohort of Morbidly Obese Patients 

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