IIFYM Flexible Diet – Calculating Daily Macros In Your Meals To Reach Your Fitness Goals

IIFYM, short for If It Fits Your Macros, is a simplified approach to dieting where you can basically eat ANYTHING you want as long as it fits into your daily calorie allowance and daily macros (macronutrient) split of protein, carbohydrates and fats. You start by calculating how many grams of protein, fat and carbohydrates you need to eat each day, then track your food intake to make sure you meet these macros. Similar to counting calories but easier, IIFYM you can eat it…

Sound too good to be true? While IIFYM, also known as flexible dieting, is designed for people who want to lose weight and build muscle without feeling restricted, the plan does require smart choices to be effective. You could get all your carbs and fats from cheeseburgers and donuts, but you would never reach your fitness goals.

Calculating Your Macros

YOUR metabolism, activity level and lifestyle play a role in how much energy you actually burn and how much of each macronutrient you should be eating. There are four steps to calculating YOUR macros:

  1. Calculate your Resting Energy Expenditure (REE). [You may see this as BMR]

  2. Calculate your Total Daily Energy Expenditure (TDEE), the number of calories you burn.

  3. Divide this calorie total into the correct proportion of protein, fat and carbs.

  4. Track your macros and adjust as needed based on how your body responds.

The Math

For males: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5 = REE

For females: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) – 161 = REE

To convert your REE to TDEE requires estimating your activity level:

Sedentary – If you sit at your desk and crash on the sofa (normal everyday activities) your TDEE = REE X 1.2

Light Activity – If you participate in activities that burn an additional 200-400 calories for females or 250-500 calories for males, your TDEE = REE x 1.375

Moderate Activity – Activities that burn an additional 400-650 calories for females or 500-800 calories for males, your TDEE = REE x 1.55

Very Active – Your activity level burns more than 650 calories for females or more than 800 calories for males over and above your sedentary amount your TDEE = REE x 1.725

Once you know your TDEE,

If you want to gain weight – eat 10-20% more than this.

If you want to lose weight – eat 10-20% less than this.

For weight maintenance – eat this amount.

Calculate Your Macros

Macro ratios vary by your goal, but generally for weight loss, start with 10-30% carbs, 40-50% protein, 30-40% fat then adjust accordingly. Keep in mind that:

  • 1g Protein = 4 Calories

  • 1g Carbohydrate = 4 Calories

  • 1g Fat = 9 Calories

Simple Example

If your TDEE is 2800 calories and you choose a high protein 50/30/20 split (protein/carbs/fat),

  • 2800 x .50 = 1400 calories 1400/4 = 350 grams of protein

  • 2800 x .30 = 840 calories 840/4 = 210 grams of carbs

  • 2800 x .20 = 560 calories 560/9 = 62.2 grams of fat


If you are confused or just hate math, there are many macros calculators and tools available online. If you need help tracking, there are also helpful apps available including MyFitnessPal, My Food Diary and MyMacros.

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