You’ve probably seen #IIFYM or #flexibledieting in your Instagram feed, with photos of fit people showing off before-and-after pics, meal prepping, and treats like pizza, pancakes, and even peanut butter Oreos. Sign us up, please!
If It Fits Your Macros (or IIFYM) is a popular diet strategy that balances the accountability of tracking your food with the flexibility of eating whatever you want — as long as it “meets your macros,” aka, the macronutrients of carbs, protein, and fat.
But before you dive in, it’s important to get the facts about IIFYM first:
What Is IIFYM, or If It Fits Your Macros?
The premise behind the IIFYM diet is that you get to eat your favorite foods (within reason!) as long as they fit within your predetermined macronutrient ratios, while still losing weight, burning fat, etc.
It started in bodybuilding circles, as a way for those on strict diets to combat boredom and diversify their food intake.
That you’re able to eat anything you want — meaning no single food or food group is off-limits, and you don’t have to adhere to a narrow, repetitive meal plan — is why this approach is sometimes called “flexible dieting.”
But is IIFYM too good to be true?
The Basics of the IIFYM Diet
With IIFYM, you start by calculating the calories and macronutrient ratios you need to reach your goals. Then, each day, you build your meals (and track them) around your macro ratio with whatever foods you want to eat.
You’re setting a calorie and macronutrient range, but you’re not focusing on every calorie. Instead, you’re ensuring that your food hits a certain ratio of macronutrients by using an online app, meal plan, or your own nutrition knowledge.
“It’s sort of the idea that you’re sticking to a pretty healthy diet, but there is room for treats — and most of those treats aren’t purely one food group or the other,” says Paige Benté, M.S., R.D., C.S.S.D..
But calling IIFYM a flexible diet seems a bit misleading to Benté, since you do have to track your macros.
“I wouldn’t consider strict macro counting to be flexible dieting,” Benté says. “If you’re super specific about your macros, that’s not flexible. To me, flexible dieting leans more toward intuitive eating: Trying to eat healthy, but today if you want a cookie, you have a cookie, and tomorrow if you want more avocado, you have more avocado. And obviously those things are going to affect your macros in different ways.”
There’s a certain amount of accountability required for IIFYM to work. If you spend your carbs on sugary foods, and your protein on greasy pepperoni too many times, you won’t lose weight or reach your goals.
“You could meet your macros just eating chicken, sweet potatoes, and avocado, but you’re going to be deficient in a lot of vitamins and minerals, and you’re going to get bored. So it’s good to have a nutrition plan that offers flexibility to eat what they want, but with a guideline on how to get the right portion for all of those foods.”
So can flexible dieting help you lose weight? “Yes and no,” says Benté. “If you’re eating too many calories and meeting your macros, you’re not going to lose weight. At the end of the day, it has more to do with the amount of calories than the distribution of them.”
It’s important to note that focusing on macros is more commonly used when you have a very specific health and fitness goal (i.e. bodybuilding) versus when you want to lose weight in general. If your goal is simply to lose weight, your focus should be on a balanced overall diet, with an emphasis on healthy, whole foods in the right portions.
How to Calculate Your Macros
If you’re going solo, Benté stresses that it’s important to make sure that you’re getting a balanced diet, so you have to learn how to calculate your macros for IIFYM.
“Balanced macros really have more to do with overall health than some secret equation to tricking your body into losing weight,” she says. “So here at OpenFit, we generally go for a 40/30/30 split (carbs, fat, and protein).”
That’s fewer carbs, but not low carb, she says, with moderate protein and fat. “It’s healthy, balanced macros that are going to get you the right amount of energy and the right amount of protein for muscles, the right amount of fat for cell formation and hormones — and enough to maintain energy for continuing to work out,” Benté explains.
The plans generally follow the 80/20 philosophy, too: Clean eating 80 percent of the time, with treats, cheats, and alcohol in moderation 20 percent of the time.
If you decide to tweak your ratios, perhaps because you’re an endurance athlete, or coping with a slowing metabolism, or are curious about the ketogenic diet, do your homework or talk to a dietitian first.
Is IIFYM right for you? Let’s weigh some of the pros and cons.
The Pros and Cons of Flexible Dieting
Pro: You don’t count every calorie
IIFYM brings awareness of nutrition education, says Mandy Enright, M.S., R.D.N., which is a welcome change after trends like the anti-fat and low-fat everything movement of the ’90s, and the protein craze in recent years.
Rather than focusing on the scarcity of calories (“I only have 1,500 to use today“), you shift to an abundance model (“I get to eat all this protein/four servings of carbs today“).
“Instead of a restriction mindset, you’re working your way up to a certain number of grams for each macronutrient, says Benté. “That positive mindset might be helpful to some people, versus a constant idea of restriction.”
Pro: IIFYM can help you reach very specific fitness goals
IIFYM reminds Enright of how she was trained to work with college athletes: Looking at their activity level, then determining what percentage of carbs to protein and fat they needed during the season, before a game, or for recovery, for example.
Having only calorie (numeric) goal could result in a nutrition imbalance, like eating too few carbs for a distance runner or not enough protein for a weightlifter, for example.
IIFYM focuses on the nutritional ratios you need for your specific fitness goals.
Pro: IIFYM can help you ditch the “good food/bad food” mentality
Adopting a diet like IIFYM can help you view food differently, says Rachel Goldman, Ph.D., FTOS, a licensed psychologist specializing in health and wellness with a private practice in New York.
“If we shift the focus to macronutrients, then we are becoming more mindful of what the food is made up of and how that specific food can help us,” she says.
So if your current plan makes you feel like you can never have a soft-serve cone with sprinkles, you might grow resentful or fixate on that treat. Shifting the focus from calories to macros lets you see that there’s room for all foods — within reason and with planning.
“I think this allows people to shift their thought process about food in general and helps people see how food is truly energy,” says Goldman.
Pro: IIFYM can help you stay on track when you’re away from home
With IIFYM, gone are the days of packing up six days’ worth of healthy foods for a work trip.
Because you’re able to pick and choose the foods that will meet your macros, you can eat at restaurants and social events — as long as there are options that meet your goals and you track your food.
“If you’re just sticking to your macros in terms of percentages and you’re not worried about the calorie number, then yes, it is easier to maintain when you’re at a restaurant,” says Benté, adding that you do still need to be mindful of portion sizes and calorie intake.
Con: There may be too much freedom for some
With the freedom of this diet comes responsibility. While a structured diet plan, for example, may limit treats, IIFYM leaves that up to you. (Yay?)
“You could theoretically be eating a Snickers bar every day and keeping your calories at a certain level and keeping your macros in check,” says Benté. “That’s not as filling as three ounces of chicken, half a cup of rice, and a cup of broccoli.”
While most people will quickly notice that their performance, energy, and digestion are affected by the quality of the foods they consume, if you struggle to hold yourself accountable, you may make excuses for regularly including less nutrient-dense foods.
“You want to be aware that you’re not gaming the system by choosing treats too often,” says Enright.
Con: IIFYM is definitely not intuitive eating
Intuitive eating encourages you to eat with your natural hunger patterns, and not focus on the nutrition facts panel of what you’re eating.
IIFYM uses external cues — macro goals — to guide your food intake, which shifts away from intuition, Enright says.
For people who are used to the freedom of responding to their internal hunger cues, this way of eating may feel too restrictive to sustain in the long-term.
Con: Tracking macros may feel too obsessive
While focusing on macros and eliminating the “good food, bad food” mentality can help create healthier relationships with eating, the diet still involves counting — and that could be triggering for some, says Goldman.
“For some people, counting anything can sometimes trigger an obsession,” she says, adding that she reminds clients that food is energy and has them work with a dietitian to focus on the non-quantitative aspects of what they’re eating.
Goldman also tells clients to focus on getting the most “bang for their buck” by choosing nutritious and healthy foods, since what we eat “will determine how we feel and contribute to both our mental and physical health.”
Con: You need nutrition knowledge
This isn’t a diet for someone who’s new to healthy eating. Though it’s meant to simplify meal prep and planning, it does require more than a basic knowledge of nutrition — as well as a certain level of self-control.
While IIFYM does teach you about nutrition and what constitutes a healthy diet when you’re eating a balanced macro diet, you can’t simply guess, says Benté. “You can’t count macros without counting something! You need to count the grams of each macronutrient very precisely with IIFYM.”
To follow the diet correctly, you may need the help of a dietitian, an app, or some other tool that will help you track and calculate what you’re eating.
The Bottom Line
If you have pretty good self-control, but want the freedom to diversify your overall healthy diet and treat yourself in moderation, IIFYM may be right for you.
If you’re new to healthy eating, still struggling with portion sizes, don’t want to deal with a lot of calculations, or are dealing with emotional eating issues, IIFYM might not be the plan for you.