There are a lot of weird, confusing-sounding acronyms that get thrown around by fitness pros, like WOD (workout of the day), AMRAP (as many reps as possible), HIIT (high-intensity interval training), and DOMS (delayed-onset muscle soreness), for example. But there's one shorthand phrase that you may have seen on Instagram a lot: IIFYM, or "if it fits your macros."
Scroll through the more than 10 million photos on Instagram tagged with #IIFYM, and you'll see meal prep containers, people working out in the gym, and infographic memes about nutrition. But, as you might have guessed, there's more to understanding macros than this hashtag implies.
"Macro" is an abbreviation for macronutrient, says Kelly Pritchett, PhD, RD, CSSD, assistant professor in nutrition and exercise science at Central Washington University. All foods contain a combination of six nutrients (proteins, carbohydrates, fats, vitamins, minerals, and water) that provide us with energy or nourishment to help our bodies work. "Macronutrients are the three nutrients that provide and contain energy and are responsible for performing a physiological function in the body," she says. They are: carbohydrates, which are our main source of energy; fats or lipids, which also provide energy and protect our organs; and proteins, which are often called the "building blocks of human life." Compared to other nutrients, macronutrients are needed in relatively large amounts (hence the name, "macro"), and are usually measured in grams, she says. But this is where things get tricky.
The amount of macronutrients that a person needs to consume in a day depends on several factors, like how active you are, your age, and whether you have medical conditions, for example. The Food and Nutrition Board of the Institutes of Medicine has set macronutrient recommendations for the average American to follow. These guidelines suggest that adults consume 45-65% of their daily calories from carbohydrates, 10-35% from protein, and 20-35% from fat. These are pretty broad ranges, so it's tough to say exactly what this would look like in practice for the average person. But the gist is that if you stick to these guidelines, you'll get essential nutrients like vitamins and minerals. (If you eat a variety of foods when you're hungry, then you probably adhere to these guidelines without thinking about it.)
Macronutrients are the three nutrients that provide and contain energy and are responsible for performing a physiological function in the body.
Kelly Pritchett, PhD, RD, CSSD, assistant professor in nutrition and exercise science at Central Washington University
For all intents and purposes, macros are an easy way for people to understand how much of a certain nutrient we should be aiming for in a day, which can be helpful for people to learn how to plan meals, Dr. Prichett says. "However, these guidelines are not individualized according to the person's goals," she says. For example, for athletes and people who exercise for more than an hour per day, it's more appropriate to determine the number of macronutrients needed based on their weight and daily energy expenditure, she says. In other words, the guidelines are meant to be suggestions; they aren't set in stone or applicable for every single person all of the time.
Somewhere along the way, counting macros became trendy. Lots of body builders count macros because they think consuming a certain ratio of protein and carbohydrates will help them build more muscle. And those looking to lose weight may keep track of their macronutrients as an easier way to determine how many calories to cut. There are calculators, apps, and social media accounts that make it easy to buy into the idea of macros. "But I definitely don't think [counting macros] is necessary or works for everyone," Dr. Prichett says.
Dr. Prichett suspects that people like the "IIFYM" concept because it enforces "the idea that they can eat anything" so long as it fits into their macros. Some anti-diet experts are against this type of eating plan, because they say it's still restrictive (even though people often call counting macros a "flexible eating plan"), and leads people to mentally classify foods as "good" or "bad." The whole idea that you can only eat something if it fits your macros is pretty extreme.
So, what can you do with all of this information? At the end of the day, counting macros is just a diet — and we know that diets tend to do more harm than good. It's important to understand that macros serve a purpose, but are not the end-all be-all determinant of a healthy diet. We eat foods for a variety of reasons, and energy is just one of them. "Sometimes your body may need more of a particular nutrient, so listening to your body is also important," Dr. Prichett says. "Food should be enjoyed, too!"