IIFYM - flexible diet that would help to achieve your goals?

Have you heard about IIFYM? This is the abbreviation of the phrase "if it fits your macros". It refers to a form of diet where you can eat almost anything as long as your food is healthy and does not exceed the daily macronutrients intake.


However, some athletes have slightly distorted this trend and built their own meal plan on unhealthy dishes that fit into their daily number of macronutrients. This is a key mistake in IIFYM. In this article, you will learn how IIFYM works in practice, and whether it is really possible to achieve your goals with the help of flexible eating.


What is IIFYM?

IIFYM is a type of flexible diet that was designed to make it easier for athletes and people trying to lose weight. While sticking with IIFYM, it is important to monitor the intake of macronutrients, therefore, the ratio of proteins, fats and carbohydrates. This provides more flexibility, allowing you to enjoy "forbidden foods" once in a while. Of course, only if they fit into your daily macros. [1]


What is IIFYM?


The IIFYM flexible diet was developed by Anthony Coll after he was himself frustrated with many of the traditional diets he had tried. IIFYM is a new type of diet, as it focuses not on the calories, but on macronutrients. Macronutrients or macros are the three main sources of energy for our body. Namely [1]:

  • proteins having 4 calories per gram
  • carbohydrates that have 4 calories per gram
  • fats that have 9 calories per gram 


The principle of the IIFYM diet is based on the fact that the ratio of calories consumed and burned is a crucial factor for reducing or gaining weight. However, it is important to keep the proportion of calories from each macro. [2]


So if you decide to stick with IIFYM, follow these simple steps [1]:

  • Calculate macros - determine the amount of grams of protein, carbohydrates and fats that you need to consume daily to achieve your goal
  • Stick to the ratio of macros - you need to determine how many macronutrients you consume at each meal and monitor your daily intake to make sure that you do not exceed it


Mostly people who want to lose a few kilograms and cannot give up their favorite dishes are attracted to IIFYM. [1]


IIFYM diet


How to calculate macros?

If you are interested in a flexible diet, first you need to determine the daily need of macronutrients. You can use any online macro-calculator, or you can also calculate your it yourself. How to do it? [1]


1. Calculate your BMR

BMR is the basal metabolic rate that can be calculated using the equation. Based on your age, gender, height and weight, you can calculate your BMR and thus you will receive a number that expresses how much energy your body consumes at rest. To perform calculations manually, use the following formulas. [1] [5]


BMR calculation formula

  • women - BMR = 655.1 + (9.563 x weight in kg) + (1.85 x height in cm) - (4.677 x age)
  • men - BMR = 66.47 + (13.75 x weight in kg) + (5.003 x height in cm) - (6.755 x age)


How to calculate macros?


2. Calculate your TDEE

If you exercise, multiply your BMR by the activity coefficient. You will get your total daily energy consumption or TDEE.


TDEE calculation formula [17]

  • minimum physical activity - TDEE = BMR x 1.1
  • 1 - 3 workouts a week - TDEE = BMR x 1275
  • 3–5 workouts per week - TDEE = BMR x 1.35
  • intensive workouts 5+ per week - TDEE = BMR x 1,525


3. Set your goal

Stick to IIFYM according to your goals, therefore [1]:

  • if you want to lose weight, reduce your calorie intake by 15 - 25%
  • if you want to gain weight, increase your calorie intake by 5–15%


Set your goal, IIFYM diet, GymBeam


4. Determine your required macronutrient intake

The final step is to determine daily required macronutrient intake. This means that you need to calculate how much protein, fat and carbohydrates you should consume.


  • protein - you should take between 0.7 - 1 gram of protein per 0.5 kg of body weight 
  • fats - you should take between 0.25 - 0.4 g per 0.5 kg of body weight
  • all remaining calories determine carbohydrate intake [1]


After completing all the calculations, you get a personal IIFYM plan, which indicates how many grams of protein, fat and carbohydrates you need to consume each day. [1] For example, 1,531 is the BMR of a 25-year-old woman that is 175 cm tall and weighs 70 kg and therefore, she needs to consume 1,531 calories at rest. However, she trains 3 times a week and therefore she also needs to calculate TDEE. The result of her TDEE is 1952 calories per day.


However, her goal is to lose weight and therefore she needs to reduce her daily calorie intake by 20%, which is 390 calories. Her daily intake to achieve the goal should be 1562 calories. Her daily requirement of macronutrients is 140 g of protein, therefore, 560 calories. She also needs to consume 56 g of fat, which is 504 calories. Therefore, carbohydrates intake should be 498 calories.


If you do not want to spend time a lot of on the calculations, you can also use online applications. Find out about the best apps in our article.


IIFYM meal plan


IIFYM meal plan

IIFYM does not focus on the source of calories, but rather on the importance of macros. Therefore, sometimes you can have your favorite pastry, pizza or ice cream, however, generally your diet should consist of healthy food. Thus, IIFYM provides a constant calorie intake, which can be adjusted and varied depending on your taste.


However, to quickly and successfully achieve your fitness goals, you should be aware of the best sources of individual nutrients. High-quality protein foods include  [1]:

  • beef, chicken, turkey, lamb or pork
  • dairy products such as cheese, milk, whey or yogurt
  • eggs
  • legumes such as lentils, chickpeas, beans, peas or soybeans
  • nuts
  • quinoa
  • seafood and fish


IIFYM diet, IIFYM meal plan, GymBeam


Healthy foods that are high in fat [1]:

  • avocado
  • egg yolk
  • some fish such as salmon, sardines or anchovies
  • fatty dairy products


IIFYM diet, healthy food, healthy fats


Carbohydrate-rich products [1]:

  • bread, pastry, cereals, pasta
  • legumes
  • cereals such as oatmeal, barley, wheat, rye and rice
  • buckwheat, millet, quinoa
  • fruits, especially banana, mango and apple
  • vegetables such as potato, sweet potato or corn


Carbohydrates in food, IIFYM meal plan


We mentioned earlier that with IIFYM, the source of calories does not matter. However, this was not always the case; let's see how the idea of flexible diet has changed over time.  


IIFYM in the past and today

Initially, IIFYM’s goal was to provide a little bit of freedom when planning a diet, so that athletes do not have to stick to strict and monotonous eating habits. The main idea of IIFYM was that you can achieve your fitness goal, even if you eat food that does not match the standard bodybuilder diet. [3]


Nevertheless, it was a question of small changes in the meal plan, for example, to choose ordinary potatoes instead of sweet ones or to have a favorite cheat meal once a week. [3] In fact, no one expected that IIFYM could become the official way of eating. The phrase itself was born on fitness forums where people asked questions such as: "Can I have one Kit Kat?" And the answer was always: "IIFYM". [4]


However, the meaning of “IIFYM” was distorted by the time and influence of social networks. Today, many people think that IIFYM means that they can eat anything if the foods they consume match their daily nutrient intake. Therefore, you can often see posts on Facebook, where people eat chicken breasts with ice cream and chocolate bar, claiming that they are losing weight. The idea of IIFYM has become intense that 100 calories of chocolate are considered as valuable as 100 calories of broccoli. And this is a big mistake. [3]


IIFYM in the past and today


A calorie is not a calorie

The problem of IIFYM lies in its definition, because the is not only about consumed macros but also about quality food source. Food and calorie sources are both important for achieving your goal, as well as for your health. However, adhering to IIFYM, people often ate only fast food and sweets, because they could not correctly determine the essence of a flexible diet. However, the IIFYM caused people to eat fast food and sweets because they mistakenly twisted its original idea. What are the consequences?


Of course, at the beginning IIFYM works and you can lose weight with its help. Anyone who sticks to caloric deficit is losing weight, there is no science. Weight loss, however, does not mean loss of fat. The question is how this form of diet can affect your body shape and health.


There is a big difference in what source of fat you choose, be it avocado or fried chips. Clearly, there is no need to completely eliminate fats from the diet, you just need to consume the right fats. For example, omega-3 fatty acids, which are found in fish and have many benefits for human health. On the other hand, saturated and trans fats can cause health problems, such as heart disease or diabetes. The same applies to calories from different sources of protein and carbohydrates. [3]


So how to choose food with IIFYM? We recommend sticking to a diet that includes fruits, vegetables, high-quality protein sources, nuts, seeds, and whole grains. Of course, you can also indulge in your favorite junk food, but don’t build your diet around it. Get inspired by our fitness recipes


A calorie is not a calorie, IIFYM


Pros and cons of IIFYM

To sum up everything about IIFYM, we can simply draw positives and negatives of flexible eating. Let's talk about each of them.


Pros of IIFYM

1. Learn more about macros.

If you start with IIFYM, you will learn a lot about food. For example, a Snickers bar (50 g) has a comparable amount of calories per serving as salmon (154 g). However, both have a different composition of macronutrients. Although both products contain a high proportion of fat, salmon mainly contains healthy omega-3 fatty acids. In addition, Snickers contains more carbohydrates, while salmon contains more protein. Interesting, isn't it? The longer you stick to IIFYM, the more amazing information about food you will learn. [6] [7]


2. Helps to reach your desired goal.

Studies show that protein-rich diets like IIFYM can speed up metabolism and help regulate body weight. [8] [9] [10] In addition, research confirms that reducing calorie intake leads to weight loss in the short term. Given that IIFYM weight loss diet reduces calories by 15-25%, it can lead to a successful weight loss. [11] [12]   


Pros and cons of IIFYM


3. You can eat what you want

Want to eat a hamburger, chocolate cake or other high-calorie dish? No problem, with IIFYM there are no prohibited dishes or products. The great advantage of a flexible diet is its variety, so it is easy to stick to it for a long time. But be careful, we have already mentioned above that even with IIFYM one should not forget about quality products, and not just include only junk food in your diet. 


4. It is a flexible and simple eating program

If you stick to IIFYM, you do not need to think about what you can eat at social events or on vacation. A flexible diet easily adapts to your lifestyle and daily routine.


Cons of IIFYM

1. Micronutrients are ignored

With so much attention to macronutrients, IIFYM ignores micronutrients, such as vitamins and minerals. People on a flexible diet may not receive enough vital nutrients, namely micronutrients. And this, in fact, is the following disadvantage of IIFYM.


2. It does not take health into account

Since IIFYM does not take into account the importance of micronutrients, we recommend supplementing your diet with vitamins and minerals with food supplements or fruits and vegetables. In addition to macros, you should also monitor consumption and micronutrients.


Moreover, IIFYM is not suitable for everyone. Especially those who suffer from health problems, in which you need to stick to special diets, such as diabetics or patients with kidney disease. If you have a medical condition that requires a special diet, consult your doctor about IIFYM. [1]   


Pros and cons of IIFYM


3. May cause eating disorders

Studies have shown that controlling food intake leads to the development of eating disorders, especially among young women. One study shows that 73% of college students with eating disorders believe that using apps for food diaries led to the development of this disorder. [15] [16]


We summed up main advantages and disadvantages of IIFYM or flexible diet. Whether you take this path or if you prefer a different diet, the choice is always on you. However, it cannot be said that IIFYM is a revolutionary diet. It all comes down to a calorie deficit and sufficient intake of protein, fats and carbohydrates from high-quality food sources.


What do you think about IIFYM? Have you tried this diet? If so, tell about your experience in the comments below and mention your favorite cheat meal. If you find this article useful and you liked it, feel free to share it with your friends.



[1] Erica Julson - IIFYM (If it fits your macros): A Beginner´s guide -  https://www.healthline.com/nutrition/iifym-guide#what-it-is

[2] Paul Salter - IIFYM vs. Keto vs. WTF? -  https://www.bodybuilding.com/content/iifym-vs-keto-vs-wtf.html

[3] Paul Carter -  IIFYM: The good, bad and the ugly -  https://www.t-nation.com/diet-fat-loss/iifym-the-good-bad-and-the-ugly

[4] Kamal Patel - What is IIFYM? -  https://examine.com/nutrition/what-is-iifym/

[5] BMR formula -  https://www.thecalculatorsite.com/articles/health/bmr-formula.php

[6] Nutrition Data - Snickers bar -  https://nutritiondata.self.com/facts/sweets/5461/2

[7] Nutrition Data - Salmon -  https://nutritiondata.self.com/facts/finfish-and-shellfish-products/4231/2

[8] Alle EE, Larsen T M, Claus H, Lindroos AK, Kafatos A, Pfeiffer A, Martinez JA, Handjieva-Darlenska T, Kunesova M, Stender S, Saris WH, Astrup A, van Baak MA - Weight loss maintenance in overweight subjects on ad libitum diets with high or low protein content and glycemic index: the diogenes trial 12-month results. -  https://www.ncbi.nlm.nih.gov/pubmed/24675714

[9] Halton TL, Hu Fb - The effects of high protein diets on thermogenesis, satiety and weight loss: a critical revies. -  https://www.ncbi.nlm.nih.gov/pubmed/15466943

[10] Klaas R Westerterp - Diet induced thermogenesis -  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC524030/

[11] Gardner CD, Trepanowski JF, Del Gobbo LC, Hauser ME, Rigdon J, Ioannidis JPA, Desai M, King AC - Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and association with genotype pattern or insulin secretion: the dietfits randomized clinical trial -  https://www.ncbi.nlm.nih.gov/pubmed/29466592

[12] Fleming JA, Kris-Etherton PM- Macronutrient content of the diet: What do we know about energy balance and weight -  https://www.ncbi.nlm.nih.gov/pubmed/27038809

[13] Curioni CC, Lourenco PM - Long-term weight loss after diet and exercise: a systematic review. - https://www.ncbi.nlm.nih.gov/pubmed/15925949

[14] Fothergill E, Guo J, Howad L, Kerns JC, Knuth ND, Brychta , Chen KY, Skarulis MC, Walter M, Walter PJ, Hall KD - Persistent metabolic adaptation 6 years after “Thhe biggest loser” competition -  https://www.ncbi.nlm.nih.gov/pubmed/27136388

[15] Simpson CC, Mazzero SE - Calorie counting and fitness tracking technology: Associations with eating disorder symptomatology. - https://www.ncbi.nlm.nih.gov/pubmed/28214452

[16] Levinson CA, Fewell L, Brosof LC - My Fitness Pal calorie tracker usage in the eating disorders. -  https://www.ncbi.nlm.nih.gov/pubmed/28843591

[17] What is TDEE and how do you calculate it? - https://superfastdiet.com/what-is-tdee/