Is Flexible Dieting, or IIFYM, the Secret to Weight-Loss Success?

Quality over quantity seems to be the new mantra of healthy eating. Experts are encouraging people to eat a diet based on whole foods, and talk of “clean eating” is rampant. Consumers are eating less processed food and seeking products with fewer, simpler ingredients. And it appears they’re less concerned with counting calories, and more interested in making their calories count.

But some are still advocating for a more quantified approach. Enter the ”If It Fits Your Macros” eating philosophy, which first gained momentum among bodybuilders and other athletes but is now catching on with people looking to lose weight, too. The name is a mouthful, so adopters refer to it by the acronym IIFYM. The idea is to help people meet their fitness goals by supplying the right number of calories in the right proportion of macronutrients (or “macros”) — better known as proteins, fats, and carbohydrates — while allowing maximal flexibility over food choices. Followers typically use an IIFYM calculator on a website or app to determine how many calories they need to lose weight, maintain their weight, or gain muscle. Those calories are then divvied up among the three major macronutrients. Plans vary in their distribution; some suggest a breakdown of 40 percent of calories from carbs, 40 percent from protein, and 20 percent from fat, for example. Other versions determine macronutrient goals as a function of body weight, such as 0.8 grams (g) of protein per pound. Individuals aim to hit their specific targets for carbs, protein, and fat every day.

What the IIFYM approach doesn’t dictate is which foods people should eat to meet said targets. Followers can technically live on a diet of fast food, chips, and ice cream as long as they nail their daily macros (hence the plan’s alternate name, flexible dieting). In other words, quality takes a backseat to quantity. Many people enjoy the freedom offered by this plan relative to more restrictive eating regimens like the Paleo diet, because no foods are off limits.
As with any eating regimen, the IIFYM approach has its pros and cons. On the plus side:

• It offers flexibility with food choices. The plan doesn’t exclude any food groups, so you’re free to eat a wide variety of healthy, whole foods. Diversity is good, because it’s the best way to ensure you’re getting all of the vitamins and minerals your body needs to function at its best. And since all foods can fit, you might find it easier to follow at restaurants and social events than more prohibitive food plans.
• It takes calories into consideration. All calories are not absorbed and processed in the same way, so they’re not all created equal. But over the long run, calorie balance determines whether you lose or gain weight: You don’t necessarily need to count calories to slim down, but you do need to be mindful of portion sizes, and of the amount of food you’re eating. So quantity does matter. Even the cleanest diet can make it difficult to shed pounds if you’re loading on calorie-dense foods like oils, nuts, dried fruit, and whole grains.
• It can be a relatively balanced approach. This IIFYM framework doesn’t drastically cut any one macronutrient, unlike extreme low-carb diets or the fat-phobic regimens of yesteryear. Combining high-quality proteins, fats, and carbs at snack- and mealtimes can improve blood sugar control, and a well-balanced macronutrient distribution encourages you to tap into all the major food groups (again, variety is good). IIFYM guidelines don’t require you to combine your macros at individual meals since the timing is completely under your control, so you’ll need to balance them throughout the day if you want to manage blood sugar and provide a slow, steady release of energy.

However, just because your meals fit your macros doesn’t mean they support overall wellness, particularly if you’re busy tallying grams without paying any attention to the entire food package. Here’s where the diet can come up short:

• Ignoring quality is a big mistake. Through the IIFYM lens, all carbs are essentially equivalent, which means an apple or sweet potato has the same value as a handful of Skittles. A burger and fries is comparable to a bowl of beans and veggies cooked in olive oil, because both meals supply a similar mix of fat, carbs, and protein. As these examples illustrate, the macros don’t tell the whole story: Choosing high-quality sources of carbs, proteins, and fats — including vegetables, fruits, legumes, whole grains, and nuts — ensures you’re also getting a broad spectrum of vitamins, minerals, phytonutrients, and fiber, which all play an important role in disease prevention. Prioritizing your daily macro targets with no regard for the types of foods you’re eating may permit you to lose weight or bulk up, but it won’t protect your arteries, control your blood pressure, or moderate blood sugar.
  That said, many plans do include a daily fiber target, which forces you to eat more vegetables, fruits, and other nutrient-dense whole foods. And many people who’ve adopted IIFYM are using the plan to fine-tune an already healthy, minimally-processed diet. These individuals do take the quality of their food choices into account when planning meals. They’re not chowing down on candy, chips, and doughnuts just because they fit their macros. But the point is, the principles behind IIFYM don’t guarantee a nutritious diet. It’s possible to strictly adhere to your macros while eating foods loaded with sugar, white flour, and junky fats that wreak havoc on your insides. Just search #IIFYM on Twitter to see what I mean. Along with plenty of healthy meals, you’ll see many examples of people indulging in towering chocolate cakes, gooey ice cream sundaes, and jumbo cookies full of refined carbs — and often doctored up with processed protein powders to tweak their macronutrient ratio. There’s nothing balanced about that.
• It can provide excess protein. Many calculators recommend a protein intake of 0.8 to 1 g per pound of body weight, or as much as 40 percent of calories from protein, which is more than most people need — even if they’re extremely active or lifting regularly. (The Academy of Nutrition and Dietetics and the American College of Sports Medicine recommend 0.5 to 0.8 g per pound to optimize athletic performance. Recreational exercisers and endurance athletes fall toward the lower end of that range.) Extra protein won’t cause you to build muscle faster. Plus, to meet their sky-high targets, many IIFYMers eat large amounts of animal protein and skimp on plant-based sources, which provide more vitamins, minerals, and fiber. They may also come to rely on protein powders and shakes — processed products that don’t offer the same complex mix of micronutrients and bioactive compounds as whole foods. 
• Tracking can be tedious. Whether you’re looking to lose weight or increase lean body mass, trying to hit specific protein, fat, and carbohydrate targets makes planning your diet more complicated than it needs to be. The truth is that you can eat much more intuitively and still reach your goals by eating a mix of lean proteins, high-quality carbs, and heart-healthy fats at snack- and mealtimes, without tracking every gram. Following a regimented plan can cause some people to become obsessive or so frustrated that they give up altogether. Planning meals around a rigid macro structure also limits your ability to eat mindfully and can interfere with your enjoyment of food, which is important for sustaining healthy eating habits.

When it comes to planning a nutritious, health-enhancing diet, quality and quantity are not mutually exclusive: They go hand in hand, and very often an improvement in one aspect promotes the other. If the idea of IIFYM appeals to you, I encourage you to meet your macros with primarily whole, plant-based foods, including vegetables, fruits, legumes, whole grains, nuts, and seeds, along with lean protein such as fish and poultry. That way, you’ll be looking out for your long-term health as well as your short-term goals.