IIFYM Explained: A Simple Guide To Flexible Dieting

What is IIFYM?

IIFYM (If It Fits Your Macros) is a nutrition system that requires you to break down and track your entire diet in terms of the three macronutrients (Protein, Fat and Carbs). By adjusting your daily intake and ratios of the three types of macronutrients, you can adjust your body’s metabolism and muscle building potential.

IIFYM is also known as flexible dieting.

Have you ever wondered if there was a way to eat whatever you want, whenever you want, and still get the body you want? Of course you have, you’re human.

That’s exactly what IIFYM is designed to accomplish.

Flexible dieting is a structure of dieting based on giving your body what it needs to function and change, whether your goal is to lose fat or gain lean muscle and improve performance.

The focus of this system is quantity, not quality; The quantity of macros, aka macronutrients, in order to manipulate your body’s composition.

Every day you eat a specific amount of calories. Those calories are made up of macronutrients: proteins, fats and carbohydrates. IIFYM is simply finding the amount of calories you should be eating every day to reach your physique goals, and at what ratio of proteins, fats and carbohydrates those calories should be.

What are macros?

“Macros” is slang for Macronutrients – Protein, Fat, and Carbs. Macronutrients are what drive your body’s engine; they are your fuel.

A macro refers to either a Carbohydrate, Protein, or Fat molecule. Each one of these is a substrate that is broken down in your body and used for energy. Each macro is measured by mass in grams (g) with an energy unit measurement known as a calorie (kcal).

1g of carbohydrates (carbs) = 4 kcal
1g of protein = 4 kcal
1g of fat = 9 kcal

So IIFYM is about having a macro budget based on your calorie intake, meaning you have a set number of carbs, protein and fats you are allotted each day. Technically under this system you can eat whatever you want as long as it fits within that budget.

Yes, I said WHATEVER YOU WANT. Though let’s review why you shouldn’t just start eating pure junk under your macro plan.

Let’s be clear, if you avoid healthy foods you risk creating deficiencies and numerous health problems. I recommend the 80/20 rule: 80% whole, real foods and 20% foods you enjoy. This way you get to enjoy yourself while getting everything you need like fiber and micronutrients (vitamins, minerals, and antioxidants) and still achieving results.

IIFYM shouldn’t be used as an excuse to binge on junk foods devoid of nutritional value just because it fits your goal macro ratios. Your results will undoubtedly suffer as you lose out on the nutritional value of natural, whole foods. For example, only eating poptarts to meet your carbohydrate requirement would not be recommended. Try to eat a majority of natural, whole foods, and allow yourself to splurge on the junk a small percentage of the time.

Finding your ideal macronutrient ratio for your goals

First things first, let’s establish what your goals are. Your goals will determine whether or not you need to increase or decrease your daily caloric intake. They will also determine where you need to adjust the amount of each macro category.

Step 1: Define your physique goals

If you want to lose weight, you will need to decrease your caloric intake. If you want to gain weight, you will need to increase your caloric intake.

The amount of calories you consume in a day is the most important nutritional metric to consider when it comes to gaining or losing weight. The total amount of calories you eat in a day is made of the three macronutrient types: proteins, carbohydrates and fats.

Everybody is different, however most of us want to lose body fat and improve our body composition (the amount of body fat to muscle). To find the optimal macronutrient ratio for you, follow the next steps below starting with your goal daily calorie intake.

Step 2: find your ideal daily caloric intake

In order to find your ideal caloric intake, we need to find your base metabolic rate (BMR) and your TDEE (total daily energy expenditure AKA how many calories you consume daily). Don’t worry, this is very simple :)

To find your BMR first plug in your current weight, height and age into this calculator.

To find your TDEE take your BMR and plug it into this easy equation based on how active you are:

Sedentary = BMR X 1.2 (little or no exercise, desk job)
Lightly active = BMR X 1.375 (light exercise/sports 1-3 days/wk)
Mod. active = BMR X 1.55 (moderate exercise/sports 3-5 days/wk)
Very active = BMR X 1.725 (hard exercise/sports 6-7 days/wk)
Extr. active = BMR X 1.9 (hard daily exercise/sports & physical job)

This new number is your estimated daily caloric intake. For a more accurate number use the apps we list later in the article and track your diet for 4-7 days and take the average.

Example: A 27 year old, 150lb, 5ft 6in, moderately active woman looking to lose weight and improve body composition (lose fat). BMR = 1,432 kcal. TDEE = 1,432 kcal/day * 1.55 = 2,220 kcal/day

Now that you have your current daily caloric intake, adjust your goal caloric intake based on your goals:

Losing weight: decrease 500kcal per day. This should yield a healthy 1lb loss in body weight per week.

Gaining weight: increase 150kcal per week. This should allow for muscular development while limiting gains in body fat.

Example Continued: Goal is to lose weight/fat. At a 500 kcal decrease her goal TDEE would be 2,220 kcal – 500 kcal = 1,720 kcal/day.

Step 3: find your protein intake

IIFYM foods high in protein
Ok, so now that you have your TDEE calculated, we can break it down into macros. Let’s start with a fixed number, protein.

The amount of protein your body requires is based on the amount of muscle mass that you have, and how you use it. If your main mode of exercise is weight lifting then you probably require more dietary protein than someone who focuses on endurance training. For a good place to start, I would recommend at least .8g of protein per pound of body weight.

.8g protein x body weight = Recommended daily amount (RDA) for protein

If you intend to start out in a calorie deficit then I would start with a higher RDA for protein:

1g x body weight = RDA for protein

Example Continued: RDA of protein = 1g protein x 150lbs = 150g of protein daily

If your calculated RDA turns out to be much higher than what you are currently consuming then I would recommend ramping up your protein intake slowly. Try adding 20g a week until you reach your protein goal. If you start consuming a lot more than you are used to all at once then you will probably experience some serious GI stress if you catch my drift.

While you should be getting a majority of your protein from whole foods, it can be challenging to hit your protein intake. I recommend a high quality protein powder like PrettyFit Whey. It’s the most macro-friendly protein powder with each serving containing 25g of cold-processed whey isolate protein. Each serving has only 100 calories, 0g fat and less than 1 gram of carbs. Plus, it’s 100% all-natural with no fake anything which is awesome.

NOTE: If you are trying to lose fat, your protein intake is now set and constant. When calculating your goal macronutrient ratio, this number will not change as the rest of your macros change until your body composition changes significantly or your goals change.

Step 4: find your fat intake

IIFYM foods high in fats
The amount of fat that you consume in a day is important for many metabolic processes that support your ability to create ATP (energy), your brain function, and your endocrine system (hormones).

Your body type and your gender can make a difference in how much or how little fat you can consume in a day. The amount of fat that you naturally store can have an effect on the way that you mobilize, or utilize the stores of fat that you have. For simplicity, we’ll break this up into three categories: ectomorphs, endomorphs and mesomorphs:

Ectomorph: a naturally lean or slimmer person, they typically don’t require as much fat in your diet, about 25% of your diet.

Endomorph: a naturally heavier individual, they probably utilize more fat from their fat stores for their daily energy expenditure, about 35% of their diet.

Mesomorph:: someone of average body type and stands right between the two above in daily fat requirement, about 30%.

Now that you know which one you are, plug it into the equation below:

Ectomorph (Skinny) = TDEE (the daily caloric intake we found above) x .25 = RDA (recommended daily amount) for fat

Mesomorph (Average) = TDEE x .3 = RDA for fat

Endomorph (Heavy) = TDEE x .35 = RDA for fat

Your RDA will be given in kcal, so to find that number in grams, simply divide that number by 9 (there are 9 kcal in 1 gram of fat).

Example continued: Our example woman is a mesomorph. So here RDA for fat is: 1,720 * .3 = 516 kcal. 516 kcal/9 = ~ 57g of fat daily

Step 5: find your carbohydrate intake

IIFYM foods high in carbohydrates
You now have your calculated protein intake and your calculated fat intake, so the rest is easy. Divide the remaining calories by 4 to get your Carbohydrate intake in grams.

RDA for Carbs = TDEE – protein calories – fat calories

So let’s review our example woman’s new macro ratio:

BMR in calories: 1432 kcal

TDEE in calories: BMR x Moderate Activity level = 1432 x 1.55 = ~2,220 kcal

Goal TDEE: 2220 kcal – 500 kcal (weight loss) = 1720 kcal

RDA for Protein: Body weight (150lbs) x 1g protein (for fat loss) = 150g protein = 600 kcal protein

RDA for Fat: TDEE x Mesomorph (30%) = 1720 kcal * .3 = 516 kcal/9 kcal per gram = 57g fat = 516 kcal fat

Carb intake: 1720kcal – 600 kcal – 516kcal = 604 kcal = ~ 151g carbs

GOAL DAILY MACRONUTRIENT RATIO: 150g protein/57g fat/151g carbs

With proper training progression, these macros should support steady fat loss for at least 4-6 weeks before needing to be lowered again or adjusted for the next phase. This is a simple approach to fat loss and is based on very general rules. If you want to gain weight, or fix your metabolism, or just learn more about diet theory then I suggest you give my article a read: Learn To Be Your Leanest While Eating More Than Ever.

Remember too, the example used is for a moderately active woman. If you work out frequently and consider yourself very active or extremely active, review your goal caloric intake in STEP 2.

Tracking made easy: flexible dieting calculators and apps

Ok, so now you have your macros, you might be wondering how to get this party started. First, buy a cheap digital food scale (Amazon’s a good place to look). Food scales are more accurate and straightforward than measuring cups. Next, download one of these Apps to get started:

1. My Fitness Pal: This is my preferred app for tracking my macros. It has the largest database for food items and a user friendly lay out. You can find anything from estimated chipotle burrito nutrients to verified nutrition labels from the groceries you regularly buy. The food label scanner makes it easy to quickly log new items. Once you track an item it is stored in your history. So once you track for a few weeks you will start to have all of your regular foods in the app, which makes tracking even quicker.

2. My Macros+: My Macros+ was created to be a more in depth app for tracking macros. You can customize your daily macros and macro progressions. This app is usually recommended for more hardcore flexible dieters. But, due to competition, the two apps now feature variations on many of the same features.

The choice is yours. The paid version of either apps offer full customization, and for ease of use the $2 spent could be worth it. Personally I don’t have a problem remembering my macros so I just go for it with the baseline version of My Fitness Pal.

Pro tips to make your IIFYM plan successful

I highly recommend that you plan out most your food for the day the night before to hit your target. That being said, do not stress over exact macros, just try to come within a small deviation of your macros with the accurate calorie total.

Your body does not detect perfect macros so there is no point on getting your macros absolutely perfect. In fact, stressing out about eating perfectly can actually be counterproductive to your physique goals, so don’t freak out if you miss your macros here and there!

The main advantage of tracking your macros, specifically, is that you can take advantage of the ratios that your body prefers. For example, if you are accustomed to weight training and high intensity training, then you could respond better to a higher carb intake. Reducing your fat intake percentage by 5% in order to make room for a higher carb intake could likely lead to leaner and more defined looking muscles and better performance.

Remember, everybody’s natural metabolism and body functions are different. It may take a month or so of tweaking your ratios to find what works optimally for your specific body.

The point of flexible dieting is to enjoy the foods you eat and to take away the stress of restrictive dieting. It’s about being strict, but not restrictive. Give your body what it needs and what it wants. Just make sure to check If-It-Fits-Your-Macros.

About the Author 

GRIFFIN BURKE

Griffin is a certified personal trainer and the founder of Burke Fitness, based in Venice, CA. His private training business focuses on aesthetic based strength training and nutrition for individuals who want to learn the healthy and intelligent way to eat and train. He believes in a balanced approach to training, nutrition, and life where responsibly doing what you enjoy most takes precedence. Griffin spends his free time reading up on the latest research in training theory, enjoying the creative side of life with music, art and cooking, exploring nature, and getting down on the dance floor. If you want to connect with Griffin, feel free to shoot him a question at BurkeFitnessLA.com and link up with Burke Fitness on Instagram (@burke.fitness) and Facebook (@BurkeFitnessLA).