What is IIFYM?


“If it fits your macros,” aka IIFYM, is a diet plan where each individual has their own personal goals for how much macronutrients they should consume over the course of a day. It is a form of “flexible dieting,” which allows people to have cheat meals or certain foods they like as long as they fit into their daily macronutrient count.

So let’s back up for a minute… What are macronutrients? The main macronutrients, or macros for short, include carbohydrates, fats, and protein. They are required in a normal diet and are consumed in large amounts. They are the nutrients that our bodies break down for energy. These are different from your micronutrients, which include vitamins and minerals, and are consumed in much smaller amounts.

How do you figure out what macros are right for you? First, you’re going to have to calculate your Total Daily Energy Expenditure, or TDEE. Your TDEE is the amount of calories your body requires to maintain its current state, based on how active you are during the day along with your height, weight, gender, and age. Out of pure convenience, head on over to IIFYM.com to easily calculate your TDEE.

  • Example: I am a 22 year old female, 5’7″ and 145 lbs. I am a student so I am moderately active. My TDEE is 2250 calories per day.

After calculating your TDEE, you must establish your goals to determine how many calories you should eat each day. Are you trying to gain muscle mass? Burn fat? Maintain? Your goals will greatly affect the amount of macros recommended for your diet. To put it simply:

  • Gain weight: add and extra 20% of your TDEE (example: 2250+(2250 x 0.20) = 2700 calories)
  • Lose weight: subtract a maximum of 20% of your TDEE (example: 2250-(2250 x 0.20) = 1800 calories)
  • Maintain: use your TDEE (example: 2250 calories)

Now, we can calculate your macros!

  • Protein is normally set around .825g per pound of body weight. If you’re like me and weightlifting is a part of your exercise regimen, you can set yours at 1 gram per pound of body weight (example: 145lbs = 145g protein per day). One gram of protein = 4 calories… So 580 calories of my TDEE are attributed to protein.
  • Fat is set at 25% of your TDEE. So if I want to lose weight, my fat intake would be 1800 x .25 = 450 calories of fat. Because 1 gram of fat = 9 calories, I should eat 50 grams of fat per day.
  • Carbohydrates are calculated as the rest of your available TDEE (1800-580-450= 770 calories). Because 1 gram of carbs = 4 calories, I should eat about 190 grams of carbs per day.

So in conclusion, a diet for a 145-lb, 5’7″, 22 year-old female wanting to burn fat is as follows:

  • 1800 calories per day
  • 50 grams fat per day
  • 145 grams protein per day
  • 190 grams of carbs per day

Not too bad, right? IIFYM provides simple guidelines to delegating your calories wisely so you can consume all of the macronutrients your body needs. I love IIFYM because if I am missing out on fats or carbs by the end of the day, sometimes I can squeeze in a pop tart or some toast and peanut butter. Being able to diet flexibly makes me feel less guilty about eating one of my grandma’s cookies during a family party or sharing a milkshake with my little brother as long as it is within my macros.

There are plenty of arguments against flexible dieting, and I can understand why. Some claim IIFYM allows you to eat higher quantities of salt, unhealthy fats, and refined carbohydrates. Some also claim clean eating is better, because the ingredient lists are shorter and you are eating less processed food. 

Like I say with just about anything, I think balance is key. Almost 90% of my IIFYM-calorie diet consists of clean and unprocessed foods. I personally try to avoid processed foods as much as possible, but still like to eat my Oikos vanilla Greek yogurt in the mornings. I’m also gluten and oat free, which can make things a little complicated. I think IIFYM is a great tool as long as you are not filling your macros entirely with processed foods, refined carbs, and unhealthy fats. 

  1. Ioannides, Z. A., Ngo, S. T., Henderson, R. D., McCombe, P. A., & Steyn, F. J. (2016). Altered Metabolic Homeostasis in Amyotrophic Lateral Sclerosis: Mechanisms of Energy Imbalance and Contribution to Disease Progression. Neurodegenerative Diseases, 16(5-6), 382-397.
  2. Miller III, E.R., Erlinger, T.P., & Appel, L.J. (2006). The effects of macronutrients on blood pressure and lipids: An overview of the DASH and omniheart trials. Current Atherosclerosis Reports, 8(6), 460-465.
  3. Robert-McComb, J.J., Álvarez Carnero, E., & Iglesias-Gutiérrez, E. (2013). Estimating Energy Requirements. The Active Female. 411-449.

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