Clean Eating vs. Flexible Dieting (IIFYM): Which is Best to Lose Weight & Build Muscle?

by Elliot Reimers, M.S.(C), CNC | Reviewed by Advisory Board

Clean Eating vs. Flexible Dieting (IIFYM): Which is Best to Lose Weight & Build Muscle?

Revisiting the Clean Eating vs. Flexible Dieting Debate

Whether your goal is to lose weight or build muscle, the path is actually quite a bit more straightforward than you might presume: controlling energy balance (i.e. calories in vs. calories out) and exercising accordingly. Yet, the war between clean eating and flexible dieting, aka if it fits your macros (IIFYM), rages on in fitness subculture.

Many IIFYM advocates argue that the ingredients in food don't matter, just the macronutrient composition and calorie content. On the other end of the spectrum are the clean-eating zealots that cling to a select group of "healthy foods," generally things like grilled chicken breast, green vegetables, and brown rice.

So, which is the best approach for your diet plan? Are there "junk foods" that must be avoided at all costs? Should you only care about the calories and macronutrients in food?

The tenets of both IIFYM (flexible dieting) and clean eating get some things right, but they also have a few issues – especially when taken to the extreme. This article will outline the basics of IIFYM and clean-eating diet plans to give you a better sense of what people should focus on for healthy eating.

What is If It Fits Your Macros (IIFYM)?

Let's start by briefly summarizing flexible dieting. Colloquially, this approach goes by the acronym IIFYM, which stands for "If it fits your macros." Essentially, an IIFYM diet means any food is fair game so long as it helps you meet your goals for macros (i.e. protein, fat, and carbs) and total number of calories for the day.

As counterintuitive as the IIFYM diet approach seemed to gym-goers when it became popular in the early 21st century, it is now readily accepted by many former clean-eating apologists. Heck, IIFYM is arguably even more popular than clean eating nowadays.

energy balance

Without question, flexible dieting makes more sense as a dietary approach since it is much more sustainable than restricting your food choices to just those that are considered "clean." There are quite a few compelling studies that show that flexible dieting is superior to clean eating since people who follow the former are more likely to stick to their diet and less prone to binging or "cheating." [1, 2]

In fact, rigid dieting strategies are a major risk factor for developing an eating disorder [3]. This isn't really surprising considering that the overarching theme of clean eating is restricting what you do and don't consume.

But what does IIFYM overlook? Well, mostly micronutrient intake and a few other qualitative features of foods.

Things to Consider on an IIFYM Diet

Vitamins and minerals are essential nutrients despite being devoid of energy (calories). Research on bodybuilders that follow either a flexible-dieting or clean-eating meal plan suggests that many people from both groups fall short of their daily micronutrient needs [4].

So yes, you can eat Pop-Tarts and drink soda while still meeting your macros and calorie goals, but vitamins and minerals will be lacking in the diet if you're relying on "empty-calorie" foods and liquids.

Moreover, not all carbs, protein, and fats are created equal. For example, many processed vegetable oils abundant in packaged foods like chips, salad dressings, and dips — contain a large proportion of omega-6 fatty acids that have pro-inflammatory effects in higher doses [5]. Consequently, getting most of your fat intake from these food sources skews the ratio of omega-3 to omega-6 essential fatty acids in the body, creating an unfavorable inflammatory response [6]. Eating plenty of "healthy fats" is crucial for everyone, no matter what diet they follow.

Similarly, consuming most of your protein intake from soy protein will not have the same physiological effects as ingesting whey protein [7]. Sure, a modest amount of soy protein in the diet is fine, but where your protein comes from absolutely does matter — especially if you're trying to build muscle or lose weight.

TL Grass-Fed Whey Protein Isolate

The above examples illustrate the point that food is not just a source of calories and macros. Even when you follow an IIFYM diet, food tracking is important to ensure you're getting a proper balance of vitamins and minerals, as well as essential fatty acids, dietary fiber, and complete protein.

The total number of calories and macros you consume is ultimately what dictates energy balance, and therefore weight loss or weight gain, but that doesn't mean that all foods with equal macros and calories elicit the exact same physiological response. Still, IIFYM gets people to focus on the most critical aspect of their diet: portion control. As such, it's the ideal way to establish healthy eating habits that are sustainable and flexible.

Clean Eating: Why Strict Diets Often Fail

At the end of the day, the food you eat should be promoting your health and fitness.  For this to happen, you should be avoiding the extremes of taking in too much of a particular nutrient and/or being deficient in another nutrient, as well as meeting your daily goal for caloric intake.

Many self-proclaimed "nutrition experts" in the fitness world preach the health benefits of eating strictly “clean foods." Ironically, people that latch onto this obsessive control over food intake develop highly-restrictive behaviors that are unhealthy in the grand scheme of things. Not to mention, when you deprive yourself of food you genuinely enjoy for so long, you end up giving into temptation and binging on "junk food" (which results in a vicious cycle of losing weight and gaining it back). 

When it comes to diets, restriction isn’t necessarily a good thing if you're trying to adopt healthier eating habits. For example, what makes a 4-ounce portion of organic free-range chicken breast "healthy"? Is it the fact that it contains about 20 grams of protein and very little fat or carbohydrates? Do you consider it “clean” because it came from a chicken that was free to roam the farmland during its lifetime?  

Eating mostly lean proteins, whole-grain carbohydrates, quality fat sources, fibrous vegetables, and fruit is a natural ramification of meeting proper macronutrient and micronutrient quotas. But notice the adjective “clean" isn’t being used to describe these food groups; rather, they are “nutrient-dense” foods (the opposite of "empty-calorie"). 

Now, does this mean your meal plans should consist of nothing but chicken breast, rice, and broccoli? Of course not. There is a middle-ground here if you know how to control your portion sizes. You can certainly enjoy a piece of pie or a few Oreo cookies from time to time while achieving your weight-loss goals. By the same token, you can overeat even if you eat exclusively "clean foods."

Barring specific food allergies, health conditions, or an irrational fear of certain food additives (like corn syrup), there is no credible basis for the idea that you can’t eat "junk foods" in moderation while improving your body composition and feeling your best health-wise.

Moreover, food is oftentimes a social relief. Humans have a strong emotional/psychological connection with food, so you should eat foods you like while making sure to reach your macronutrient and micronutrient needs; two things that are not mutually exclusive.  

IIFYM vs. Clean Eating: The Final Word

clean eating vs flexible dieting

To reiterate, energy balance is the most important factor for burning body fat and building muscle mass. Calories are king.

However, your food intake determines the subtypes of macronutrients (e.g. carbohydrates, protein, and fat) you consume, and that can make a big difference towards your fitness goals and sculpting the body of your dreams.

But remember, there really are no "junk foods" that you must avoid on a healthy diet. The notion that certain foods are wholly "unhealthy" while others are "healthy" is nonsensical. It's absolutely okay to eat just about any foods you want as long as you're meeting your calorie and macronutrient needs while getting a good balance of micronutrients, fiber, essential fatty acids, and quality protein throughout the day.

More simply: The dose is what makes the difference between healthy and unhealthy.

If you're currently stuck in the habitual routine of eating grilled tilapia, rice, and asparagus six times a day, it might be time to reconsider whether that's really necessary. It's one thing to be selective about the food you eat, but limiting your meal plan to a predefined list of "healthy foods" is generally not advantageous, nor is it sustainable.




Elliot Reimers, M.S.(C), CNC
Elliot Reimers, M.S.(C), CNC

Author

Elliot holds a B.S. in Biological Sciences from the University of Minnesota, as well as being a Certified Sports Nutritionist (CISSN) and Certified Nutrition Coach (CNC). He is currently pursuing a Master's of Science in Molecular Pharmacology and Toxicology at Michigan State University. Elliot began freelance writing circa 2012 and has since written 100s of articles and several eBooks pertaining to nutritional science, dietary supplements, exercise physiology, and health/wellness. Being a “science whiz,” he has a passion for helping people understand how nutrients (and other chemicals) and exercise work on a cellular and molecular level so they can make smarter choices about what they put in, and do with, their bodies. When Elliot is not busy writing or studying, you can find him pumping iron, hiking the mountains of beautiful Colorado, or perusing nutraceutical research.



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