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The last time I checked, #FlexibleDieting resulted in over 4.7 million posts on a popular social-media channel. The top nine posts under this hashtag included four gym selfies, one bathroom-mirror selfie, a girl in a giant hat posing poolside in her bikini, and three pictures of food, which consisted of a banana bread recipe, a comparison of three bars of chocolate, and a Philly cheese steak-nacho dish.

If you’ve come across this popular concept online and encountered images like these, you may be wondering what the deal is with flexible dieting, whether it’s healthy, and if you should give it a try.

Before you do, read on to learn all about this approach and whether or not it might be right for you.

What Is Flexible Dieting?

Flexible dieting involves counting and measuring foods to control calories and intake of macronutrients: protein, fats, and carbohydrates. It originated in the bodybuilding industry, which focuses on ccontrol of body composition, musculature, and presentation. In recent years, it’s gone more mainstream among the general population, particularly those looking to make changes to physique.

Also known as “IIFYM,” or “if it fits your macros” (which has more than 11 million posts of its own), the general idea behind flexible dieting is that it’s OK to follow any eating strategy you like — hence the “flexible” part — as long as the foods you eat fit into your assigned target number of daily grams of macronutrients. Those targets are often set by either a coach or through calculations, although there is no standardized, agreed-upon way to set these targets.  

Whether or not it’s directly monitored, a calorie goal is inherently involved since carbohydrates and proteins contain approximately four calories per gram and fats contain approximately nine calories per gram.

Advocates of IIFYM claim that it’s the most sustainable long-term solution to weight management since it does not restrict any particular food choices and allows the freedom to include things like banana bread, beer, nachos, and Philly cheesesteaks. The philosophy is that there are no “bad” foods.

The Pros and Cons of Flexible Dieting

Let’s be clear about this: Calories and macronutrient breakdown absolutely matter for fat loss, muscle gain, and any body-composition goal. Any successful approach must provide a balance of fat, carbohydrate, and protein that suits your metabolic needs most days — and when averaged out week-to-week.

Whether you achieve that macronutrient balance through the use of flexible dieting, however, is a matter of personal preference — and adherence. Consider these factors before you commit to flexible dieting.

PRO: It provides education and awareness around nutrient content.

The IIFYM approach is a great option for those who have never tracked food intake closely and are willing to give it a go. The sheer dedication to measure and track portions spurs an awareness of food intake that can quickly yield weight loss in those who have never given their dietary approach much attention.

It’s also a great way to learn which foods are high (or low) in protein, fat, carbohydrates, sugar, and fiber. Over time, you learn to eyeball servings with relative accuracy to minimize the need for daily weighing and measuring.

PRO: It’s good for those who are analytical.

For those who like specifics and enjoy a formulaic approach to nutrition, flexible dieting is often a suitable option. Monitoring trends in grams of protein, fat, and carbohydrates, along with calories — and comparing them to changes on the scale — provides trackable data each week.

PRO: It can include foods often left out with other approaches.

By planning ahead and providing structure, flexible dieting can allow for food choices that might not be considered ideal on other nutrition plans. For example, by adjusting macros and calories on the days leading up to (and after) a special event, IIFYM can allow for a few date-night cocktails or that cupcake at a birthday party within a weekly macronutrient or calorie budget.

The freedom to occasionally include less nutritious options can make certain social situations easier to navigate — with the right foresight — particularly for those who do not have a history of disordered eating or food triggers.

Of course, other nutrition approaches can allow for flexibility as well, but this approach tends to be more mathematical and calculated.

CON: It requires a high daily commitment level. 

On the flip side, tracking, weighing, and measuring everything you eat each day can be time-consuming — and can feel anything but flexible. To get the best results, you need to use a food scale, measuring spoons, measuring cups, and other tools to ensure that what you’re tracking is in fact what you’re eating.

This includes tracking every bite you consume — including that chicken nugget off your kid’s plate or those few tastes of homemade spaghetti sauce you enjoyed while cooking. When eating out or attending a social gathering, you’ll also need to track whatever you consume. This hyper-awareness about everything you eat and drink can distract you and your companions from connecting.

CON: Tracked amounts are usually not accurate.

It may be disheartening to realize that the calories and macros you are resting your weight-loss hopes on — and are diligently recording — may not be accurate after all. Some online food trackers use crowd-sourced data (meaning app users are the ones who enter the nutrition information of a given food), and similar portions of the same foods can have wildly different nutrition information in the same database.

Food quality can also affect nutrient content. For example, a cut of grass-fed beef can vary in protein and fat content when compared to a similar cut from a conventionally raised cow. The only way to know the exact number of calories you’re eating with certainty is to test the food with bomb calorimetry in a laboratory setting, which is not realistic.

Even food labels can be misleading, tricking you into thinking you’re consuming fewer calories and grams of carbohydrates than you record. And since the food manufacturer determines what goes on the label in the first place, the accuracy of those numbers is also questionable. Some estimates note that nutrition labels can be off by as much as 20 percent.

CON: Including all foods can still trigger unhealthy habits.

Initially, the freedom to include any and every food in a nutrition plan may sound like a good idea. However, this approach does not work for all people. Certain processed foods can be manufactured to have specific amounts of fats, sugars, salt, and other ingredients to make them hyper-palatable and easy to overconsume.

It’s not uncommon to have a specific food trigger that makes it feel impossible to stop at the predetermined serving size, and a single taste can set a slippery slope into motion. If you’ve ever struggled to stop at just one cookie or just a small handful of chips, only to polish off the entire container, you’re not alone. When this happens, it’s common to feel shame or like you’ve “failed.”

Conventional thinking prioritizes portion control and puts mind over matter, but it does not account for the complex science that can drive the behavior of over-consumption. Trying to will your way out of that spiral is much easier said than done.

For certain people, total avoidance of trigger foods, even temporarily, is often more liberating than trying to toe the line with one bite or serving.

CON: It can shift focus away from nutrient-density.


One of the most important considerations of healthy eating is micronutrient — a.k.a. vitamin and mineral — balance. While it’s not necessarily exciting to talk about things like zinc, vitamin B12, folate, and magnesium when it comes to fat loss, these vitamins are critical to support weight-loss success and long-term maintenance.

When these factors are ignored, the downstream metabolic processes can suffer (including gut health, which dictates much of your nutrient absorption). A perfect macro balance of carbs, fat, and protein won’t save your metabolism from the effects of suboptimal nutrition choices. These micronutrients are a keystone to making sure your macro balance exerts the optimal metabolic effect you desire.

In other words, it’s important to get your micros in line so your macros can work as efficiently as possible.

Flexible Dieting vs. Clean Eating

There’s a notable, growing chasm between the nutrition opinions held by many flexible dieting proponents and those who support a nutritional approach generically referred to as “clean eating.”

Clean eating has no set definition. Generally, proponents of clean eating prioritize unprocessed or minimally processed foods, often with more emphasis on intuition than tracking and counting daily macronutrient intake.

This philosophy typically avoids packaged goods; fast foods; trans fatty acids; artificial sweeteners, additives, and preservatives; added sugars; and refined grains. Some versions go a layer deeper and eliminate gluten, dairy, soy, and other foods that are common, underlying food sensitivities.

As with any debate, those at the extreme ends of the spectrum tend to polarize the discussion and drown out reasonable consideration of a more moderate approach to health and weight loss. In the most simplistic terms (and with some exceptions), flexible dieting is more strongly associated with tracking numbers and working toward a specific body composition, while clean-eating approaches are more closely linked to food quality and improved vitality and health.

Ascribing to a myopic view of any protocol, however, can limit your ability to reach the highest potential in your nutrition programming. Just as justifying a 49-ingredient cinnamon roll at the mall because it fits today’s macro goals will not serve your health and efforts in the long run, mindlessly snacking on a bottomless calorie bomb of dried fruit, coconut, and trail mix won’t serve your efforts either, no matter how “clean” the ingredients.

IIFYM: If It Fits Your . . . Metabolism?

Conceptually, flexible dieting makes sense. No one wants to sign up for any level of deprivation or imagine a life completely devoid of a trip to the ice cream stand or gathering with friends at the local pizza place.

From a psychological standpoint, focusing on inclusion always works better than exclusion as human nature automatically desires precisely what it “cannot” have. That being said, after working with and supporting thousands of people in their transformation journeys, the Life Time nutrition team encourages you to make a few considerations before fully placing all of your eggs into the “if it fits your macros” basket.

First and foremost: What does your internal health look like?

The team of Life Time dietitians spend time coaching clients day in and day out while tracking changes in their lab-testing markers. These metrics offer insights into blood-sugar regulation, cardiovascular health, vitamin and mineral status, and hormone levels.

The goal is to ensure that an individual’s nutrition is serving them from the inside out. In partnership with their medical team, our dietitians and coaches monitor whether their clients’ lab markers are trending into optimal ranges, and whether they’re losing body fat and gaining muscle.

Nutrition coaches also check in with clients every 8 to 12 weeks to see how they’re feeling subjectively: Are they feeling more energetic, sleeping better, and reporting positive changes in mood and outlook? 

This is all important because, more often than you might think, individuals with lean body compositions come to us looking for help for everything from poor exercise recovery to intense cravings, constipation, diarrhea, bloating, bottomed-out energy levels and sleepless nights. Aesthetically, they may appear to be in optimal health, but lab work often reveals there is something else going on internally.

Consider these real-life client anecdotes:

  • A 40-year-old wife and mother of four tracked everything she ate (with “perfect” macros) for several years to no avail. Lab tests showed that gluten was the likely culprit for why she was feeling terrible; she also had low iron levels.

    She started focusing on including more iron-rich foods (grass-fed red meat and dark meat poultry), paired with a quality vitamin-C supplement and broad-spectrum digestive enzymes to support breakdown and absorption of iron. She also began avoiding gluten.

    As a result, her energy levels skyrocketed, she was finally able to attain restful sleep at night, and her chronic daily bloating disappeared. She later discovered that including gluten even once per week brought on her previous symptoms.
  • At age 32, a new dad was developing an unwanted “dad bod,” and the psoriasis he had been struggling with was flaring up. Lacking the wherewithal to track everything he consumed, he followed a D.TOX® food approach (free of gluten, dairy, soy, corn, peanuts, and sugar), lost seven pounds in 14 days, and reported an 80-percent reduction in his psoriasis symptoms.
  • A 34-year-old working mom was suffering from debilitating gas, bloating, diarrhea, and fatigue. After being diagnosed with SIBO (small intestine bacterial overgrowth), she adopted a diet low in FODMAPs (a type of fermentable carbohydrate) to complement her medical treatment. It literally made her feel like a new person: Her energy improved after a few weeks of strict avoidance of lactose, wheat, garlic, onion, and other high FODMAP foods.
  • An 18-year-old high school senior was overweight and plagued with acne and horrible PMS symptoms. A food sensitivity test and hormone panel provided invaluable insight that helped guide her to a nutrition plan that excluded dairy. It incorporated more fiber and focused on food quality to minimize exposure to exogenous toxins and hormones.

    The result? A 17-pound weight loss, the disappearance of acne, and normalization of her monthly cycle. She found that avoiding ice cream and takeout food was key to her success, and in her case, it was well worth it.

In all of these cases, a dialed-in macro approach with “flexibility” to include whatever they wanted would not have netted the results these individuals had hoped to achieve. In most cases, the greater the metabolic disruption, the more important the quality of what you eat becomes.

These success stories do not suggest that calories and macronutrients did not matter for their success, but they do serve as examples that highlight the importance of a broader, more comprehensive approach.

To Flex Or Not To Flex

At the end of the day, no one knows your body better than you do. Finding a nutrition approach that works and is sustainable for you is paramount, while enlisting the support of a coach who is dedicated to guiding you through your program can create accountability and invaluable support.

If you’ve tried calorie and macro counting with appropriately set goals, stuck with it consistently for at least a few weeks, are seeing results and feeling great, then flexible dieting may be the right thing for you.

If you are not experiencing the results you had hoped for or notice that you’re not feeling your best, it’s probably time to look deeper. Chronic stress, hormone imbalances, gut health, chronic inflammation, and other metabolic imbalances may be affecting your vitality and body-fat stores. Another approach with a fuller thought may be better for you.

Wrapping Up

Flexible dieting and IIFYM may be a good approach for some, and I’ve seen it work great for those who do not have underlying issues with digestive health, hormone imbalances, or nutrient deficiencies. But a weight-loss plan that ignores your caloric intake and macronutrient levels is lacking the structure and energy balance concepts needed to net results.

As with any hot debate and polarizing issue, finding a middle ground ends up serving most of us well. Instead of religiously tracking food quantities and scale weight for months or years on end with IIFYM — or only focusing on strict standards of “good versus bad” foods without regard for portions and balance — how about instead eating quality, nutrient-dense foods in reasonable balance most of the time?

As it turns out, a moderate approach that considers the importance of both food quality and food quantity often leads to the health and body-composition improvements most people are looking to achieve.

Keep the conversation going.

Leave a comment, ask a question, or see what others are talking about in the Life Time Health Facebook group.

Samantha McKinney, RD, CPT

Samantha McKinney has been a dietitian, trainer and coach for over 10 years. At first, her interests and experience were in a highly clinical setting in the medical field, which ended up laying a strong foundation for understanding metabolism as her true passion evolved: wellness and prevention. She hasn’t looked back since and has had the honor of supporting Life Time’s members and nutrition programs in various roles since 2011.

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