IIFYM, or “If It Fits Your Macros,” is a type of flexible dieting that helps people lose weight without feeling overly restricted.

Rather than focusing on calories, IIFYM tracks macronutrients instead — namely protein, fat and carbohydrates.

This allows for much more flexibility since all foods can be enjoyed as long as they fit into your macros for the day.

Here are the basic principles of IIFYM, details on how to follow it and the pros and cons of this approach.

IIFYM Guide

The IIFYM diet was originally designed by fitness enthusiast Anthony Collova after he became frustrated with traditional dieting recommendations.

IIFYM is a new spin on dieting that focuses on macronutrients rather than calories.

Macronutrients, or macros, are the four types of food molecules the body can break down for energy. Three types of macronutrients are tracked in IIFYM:

  1. Protein, which has 4 calories per gram.
  2. Carbohydrates, which have 4 calories per gram.
  3. Fat, which has 9 calories per gram.

Alcohol is the fourth macronutrient, containing 7 calories per gram, but it’s not included in the IIFYM diet.

Following the IIFYM diet is pretty simple, and only requires a few steps:

  1. Calculating your macros: Calculations are used to determine how many grams of protein, carbs and fat you need each day in order to meet your weight goals.
  2. Meeting your macros: Once you know your macros, you just need to stay within them each day. Food intake is tracked and adjusted as needed.

Since all foods are allowed, many people consider this diet a welcome change from strict calorie counting or eliminating entire food groups.

IIFYM is typically used for people who want to lose weight but can be modified for those who want to gain weight as well.

Summary The IIFYM diet involves calculating the amount of protein, fat and carbs to be eaten each day in order to meet your weight goals. Food choices are tracked and adjusted as needed in order to stay within these macros.

The first step in getting started on the IIFYM diet is to calculate your macros.

Most people use the free macro calculator on the IIFYM website, but you can also calculate them manually.

The general process is:

  1. Calculate your basal metabolic rate: Standardized equations are used to determine how much energy your body uses at rest, based on age, sex, height and weight. This is known as your basal metabolic rate or BMR.
  2. Adjust for activity level: The BMR is multiplied by an activity factor to increase calories based on your activity level. This is known as your total daily energy expenditure or TDEE.
  3. Adjust based on weight goals: If you want to lose weight, reduce your calorie intake by 15–25%. If weight gain is the goal, increase calories by 5–15%.
  4. Determine your macros: Protein intake should be between 0.7–1.0 grams per pound of body weight. Fat intake should be between 0.25–0.4 grams per pound of body weight. All remaining calories are allotted for carbs.

For weight loss, the main idea is to reduce calories and increase protein to preserve lean muscle mass while losing body fat.

After doing all the calculations, the final IIFYM plan should tell you how many calories and how many grams of protein, fat and carbohydrates to consume each day.

Summary Online or manual calculations are used to determine the appropriate number of calories needed to meet your weight goal. Then, the ideal ratio of macronutrients is determined based on your current body weight and allowed calories.

Once you know how many grams of each macronutrient you should consume every day, it’s critical to track your food intake to determine whether you meet your macros.

Some popular websites and applications for tracking include:

It’s also recommended to purchase a digital scale and weigh your food in grams, in order to get the most accurate macronutrient calculations.

IIFYM diets tend to be higher in protein and fat and lower in carbohydrates. Therefore, it helps to understand which foods contain the highest amounts of each macronutrient.

Foods High in Protein

  • Animal meats, like beef, chicken, lamb, pork and turkey
  • Dairy products, like cheese, milk, whey protein and yogurt
  • Eggs
  • Legumes, like beans, lentils, peanuts, peas and soy
  • Nuts
  • Quinoa
  • Seafood, like fish and shellfish

Foods High in Fats

  • Avocado
  • Egg yolks
  • Fatty fish, like salmon, sardines and anchovies
  • Full-fat dairy products, like cheese, cream, whole milk and yogurt
  • Mayonnaise
  • Nuts and nut butters
  • Oils from fruits, nuts and seeds
  • Olives
  • Seeds, like chia and flax

Foods High in Carbs

  • Breads, cereals, pastas and baked goods
  • Legumes, like beans, lentils, peanuts, peas and soy
  • Grains, like oats, wheat, barley, rye and rice
  • Fruits, especially bananas, plantains, mangoes and apples
  • Pseudocereals, like amaranth, buckwheat, millet, quinoa, teff and wild rice
  • Starchy vegetables, like potatoes, sweet potatoes, winter squash and corn

While tracking is important, there is no need to stress about hitting your macros exactly every single day.

As long as you don’t go over each macronutrient by more than 5 grams, or under by more than 10 grams, you should still see results.

Summary Weighing and tracking your foods is highly recommended to ensure you are meeting your macros. It is recommended to stay within 5 or 10 grams for each macronutrient for the best results.

While all foods are allowed, it’s easier to meet your macro goals with a diet rich in fruits, vegetables, high-quality proteins, nuts, seeds and whole grains.

Most people will easily meet their macro targets by consuming 80% of their calories from whole foods, and including 4–6 servings of fruits and vegetables every day.

Exercise is encouraged while on IIFYM, but not required. Activity level is accounted for when macros are initially calculated.

Summary It’s generally easier to meet your macros by eating a whole-foods diet with plenty of produce. Exercise is recommended, but not required.

Following the IIFYM diet has many benefits, especially over traditional dieting methods.

1. It Can Be an Eye-Opening Experience

Since IIFYM focuses on macronutrients, rather than calories, it can be a great educational tool for people who are unfamiliar with the macronutrient composition of foods.

For example, a Snickers bar and 5.5 ounces of salmon have almost the same number of calories, but very different macronutrients.

While the candy bar and salmon both contain a large amount of fat, the Snickers bar is loaded with carbohydrates, while the salmon is packed with protein (1, 2).

It’s easy to see how learning to meet your macros can be an eye-opening experience for someone who has not tracked them before.

2. It Helps You Achieve Your Weight Goals

So far, research is conflicting on whether or not manipulating your macros affects weight loss (3, 4, 5).

Some evidence suggests that diets higher in protein, like IIFYM, can increase metabolism and help maintain weight loss longer, but more studies are needed (6, 7, 8, 9).

Regardless, research has consistently shown that reducing calories does lead to weight loss in the short term (10, 11).

Since the IIFYM diet reduces calories by 15–25% for people who want to lose weight, following the diet should result in weight loss.

Food tracking has also been linked to successful weight loss, so the tracking component of IIFYM may also be beneficial (12).

For those who wish to gain weight on IIFYM, increasing calories and consuming higher amounts of protein should result in weight gain (13, 14).

3. There Are No Forbidden Foods

No foods are forbidden on IIFYM, as long as they fit into your macros.

This can be a great way to teach balance and help people understand where the majority of their protein, fats and carbohydrates are coming from.

Allowing all foods can also remove some of the pressure and guilt associated with other more restrictive dieting methods, making for a more enjoyable experience (15).

4. It’s Flexible and Easier to Stick To

With IIFYM, it’s easy to plan your meals around your lifestyle without feeling limited.

For example, if you know you’ll be dining out, you can look up nutrition information ahead of time and then adjust the rest of your meals for the day as needed.

This flexibility can make IIFYM easier to stick to since you’re less likely to feel restricted.

IIFYM works for all sorts of people, including those following special diets like vegan, vegetarian, paleo or gluten-free.

Since there are no special restrictions, all types of cuisines and cooking styles fit into the IIFYM plan.

Summary IIFYM is a flexible alternative to traditional dieting. Since all foods are allowed, many people find it easier to stick to, increasing the likelihood of reaching their goals.

While there are many benefits to IIFYM, it has some downsides as well.

1. It’s Still a Diet

While IIFYM may be more flexible than other diets, it is still a diet.

An abundance of research has found that diets do not work over the long term, and the vast majority of people end up regaining at least some of the weight they lost (16, 17, 18).

Addressing other factors beyond just diet, like motivation, emotions, sleep and stress may help people keep weight off more successfully (19, 20, 21, 22).

The IIFYM program offers access to online coaches, but these are not required to have any formal training in nutrition or dietetics.

Working with a dietitian or other nutrition professional may be a safer and more effective way to address these factors in a personalized manner.

2. No Emphasis on Micronutrients

With so much focus on macronutrients, the importance of micronutrients like vitamins and minerals is somewhat ignored.

While IIFYM does encourage a whole-foods diet, no tracking is actually done to ensure people are getting enough vitamins and minerals.

Research shows that many fad diets do not provide enough vitamins and minerals, so it’s likely that at least some people on the IIFYM diet are also coming up short (23, 24, 25).

It may be a good idea to analyze your IIFYM diet to make sure you’re getting enough micronutrients. You may also want to consider adding a multivitamin-mineral supplement if needed.

3. Does Not Take Health Conditions Into Account

IIFYM may not be appropriate for everyone, especially people with health conditions that require special diets.

For example, people with diabetes need to monitor their carbohydrate intake, and those with kidney disease must watch their sodium, phosphorus and protein consumption.

It may be possible to modify an IIFYM diet to work with these special considerations, but more detailed guidance from a dietitian or other nutrition professional is recommended.

4. Could Increase the Risk of Disordered Eating for Some

While macronutrient tracking can help people reach their health goals, it may trigger disordered eating in some individuals.

Research has found a strong association between food and fitness tracking and the development of eating disorders, especially in young women (26).

One study found that 73% of college students diagnosed with eating disorders believed that using tracking apps contributed to the development of their condition (27).

It’s important for healthcare professionals to screen for eating disorders before recommending diets such as IIFYM.

Summary While IIFYM is flexible, it’s still a diet. It’s important to ensure you are getting enough micronutrients on this plan and to seek professional guidance as needed. IIFYM may not be appropriate for everyone, especially people with serious medical conditions.

IIFYM is a flexible dieting option for people who want to lose weight and build muscle mass without feeling overly restricted.

It involves calculating how many grams of protein, fat and carbohydrates you need to eat each day, then tracking your food intake to make sure you meet these macros.

However, IIFYM does not track micronutrients, and may not be suitable for people with certain medical conditions or those who are at risk of an eating disorder.

Some people find it difficult to keep weight off long term, and may benefit from working with a nutrition professional for more guidance and support.

Since all foods can be enjoyed on IIFYM, many people find it less restrictive and easier to stick to than other diets.

It can be a great option for those looking for flexibility and balance while achieving their weight loss goals.