The IIFYM diet, short for “if it fits your macros,” has become very popular in recent years, and it’s an interesting development because it pretty much did a complete 180 on the fad diet industry – while pretty much every popular diet that’s come and gone enthusiastically rejected calorie counting and claimed that food selection or some other similar variable is what matters for weight loss, IIFYM fundamentally claims that calories are the only thing that ultimately matters for weight loss, and that as long as that’s on point you can essentially eat whatever you like.
IIFYM is often used interchangeably with the phrase “Flexible Dieting,” which similarly prescribes that one doesn’t need to rigidly eat an exclusively “clean” foods diet to lose weight, and that it’s conversely entirely possible to liberally enjoy “junk” food and still lose weight.
And so, the question is: does this diet actually work? The answer is yes, it definitely does, although it isn’t really a type of “diet” per say and is often somewhat misunderstood. Beyond that, it’s a strategy that has it’s pros and cons, like just about everything.
Table Of Contents
- IIFYM Explained: What Are Macros? And What is This Diet of “Fitting” Them, Exactly?
- IIFYM Pro #1: Science Conclusively Supports It
- IIFYM Pro #2: It Removes All Guess Work
- IIFYM Pro #3: No Dietary Restriction
- IIFYM Pro #4: It’s An Excellent Learning Experience
- IIFYM Con #1: It’s Extra Work
- IIFYM Con #2: It Can Enable Poor Eating Habits
- IIFYM Con #3: It Can Cause Social Friction
- IIFYM Con #4: You Can’t Always Track
- Conclusion: IIFYM Is Definitely Worth Trying At Least Once
IIFYM Explained: What Are Macros? And What is This Diet of “Fitting” Them, Exactly?
“Macro” is simply slang for the word “macronutrient.” A macronutrient is simply a descriptor for each of the three main nutrient groups that collectively make up one’s total caloric intake: protein, fat, and carbohydrates (sometimes alcohol is considered a 4th macro because it’s distinct and does yield caloric value as well). This is opposed to the many “micronutrients” we need: various vitamins, minerals, etc.
The IIFYM acronym isn’t so much a diet as it is a general philosophy born literally from the go-to catch phrase “if it fits your macros,” which became a stock reply on various fitness forums to people repeatedly asking if they could eat this or that and still lose weight.
(Indeed the answer for anything is yes you can, as long as you’re in a caloric deficit)
IIFYM was also rebellion of sorts from the longstanding and tired dogma in the bodybuilding niche that a proverbial “clean” diet of chicken breast, broccoli, brown rice, plain tuna, etc. was necessary. Turns out, people started to insist, that you don’t need a squeaky clean (and miserably bland) diet to get lean and ripped, you just need to make sure that your calorie and macronutrient intake are on point. Beyond that, that the “clean” food concept was scientifically and logically ill-defined and ultimately meaningless to begin with.
IIFYM Pro #1: Science Conclusively Supports It
At this point, the relevant body of scientific literature conclusively shows that calorie restriction causes weight loss regardless of what is actually eaten, and that meal timing, food type, meal frequency, or any other variable doesn’t actually cause weight loss when calories are controlled for. The one quasi-exception is that higher protein intake does cause modest but not insignificant weight loss, but that’s explainable by the fact that protein is ~15% less efficiently metabolized than either carbs or fat. Read examine.com’s weight loss page for a full review of said literature.
IIFYM Pro #2: It Removes All Guess Work
Most diets are kind of a vague shot in the dark that may or may not work, and when they don’t, it’s not always clear why. IIFYM, contrarily, is precise: You know exactly the quantity of food you’re supposed to eat, and if the diet doesn’t work, you simply titrate down until it does or realize you somehow violate the laws of physics. The resultant removal of decision fatigue is actually huge relief, many will realize.
IIFYM Pro #3: No Dietary Restriction
This is the big and obvious appeal, there’s nothing your not allowed to eat, and you can enjoy your vices in reasonable moderation. It also makes the social aspect of eating a lot easier, less stressful, or perhaps just feasible to begin with.
IIFYM Pro #4: It’s An Excellent Learning Experience
When people first track their food they’re often shocked by how many calories they’re actually eating, often so via insidiously calorie dense “health” foods such as nuts, avocados, etc. They also learn just how satiating alternative low calorie foods can be.
“Intuitive” eating is often viewed as an opposition to calorie counting, but calorie counting is probably the best way to learn how to successfully eat intuitively. Most people don’t do IIFYM forever, but it makes long term maintenance a lot easier because you learn so much even from doing it just once in your life.
And now, as we said, IIFYM does have some downsides:
IIFYM Con #1: It’s Extra Work
Tracking food is a skill that takes practice and has a learning curve, which can be a challenge to overcome. And even when you get your system down cold, the work of tracking food becomes a sufferable chore at best.
Then there are people who will just never willingly count calories. If we’re looking at obesity as a general problem, there will have to be an alternative solution to address that.
IIFYM Con #2: It Can Enable Poor Eating Habits
It’s tempting to defer to packaged junk food with detailed serving and nutrition facts simply because it’s easier to measure and log. It’s also tempting, especially so after prior stints of begrudged “clean” eating, to overdo the junk food simply because you can.
IIFYM Con #3: It Can Cause Social Friction
Are you going to frantically key in your entree on your smart phone under the table when you should be enjoying a restaurant meal with friends? Or might you skip it all together? If you don’t have a plan in place to deal with the inevitable times you can’t (or shouldn’t) track religiously it will lead to problems.
…and speaking of which, the next issue is that:
IIFYM Con #4: You Can’t Always Track
Say you’re a college student on a dining meal plan, or you’re regularly getting served food made by someone else, then you can’t know what’s actually in it. It’s possible to guesstimate, but even then you need at least a rough idea of the ingredients.
Conclusion: IIFYM Is Definitely Worth Trying At Least Once
The mainly important thing you’ll learn is reconciling eating x many calories to how it makes you feel – this makes intuitive eating thereafter a lot easier to get right. You’ll also learn a lot about the food you eat and which choices make life the easiest while managing your weight. It’s not all or nothing either: if you diligently track, say, 80% of the time and just eat with mindful restraint when you’re at a restaurant or whatever, that’s often plenty enough for people to succeed.
Modern technology makes it easier than ever – download an app like Cronometer and just use their prebuilt database to punch in what you’ve eaten during the day, no pen and notebook required.