If you’re ready to achieve your weight loss goals without a fad diet, flexible dieting may sound like the perfect solution. 

Allowed to eat anything? Sweet!

But…is it too good to be true? Perhaps.

While “flexible dieting” might sound like an intriguing answer to all of your dieting woes, this style of eating may do more harm than good.

What Is Flexible Dieting?

So is this really a diet? What is flexible dieting?

Flexible dieting is a style of eating – a diet – that is based on eating a specified amount of each macronutrient per day. This means that you’re “allowed” a certain number of grams of carbs, protein, and fat per day, within your framework. 

Typically, this is also paired with a calorie-restricted or calorie-controlled diet. Ruh-roh: this is a big no-no for Intuitive Eating. 

The goals of those who practice flexible dieting can be varied from seeking weight loss, gaining muscle/bodybuilding, and simply seeking overall health.

Other terms for flexible dieting?

Does a rose by any other name smell as sweet?

Is a diet by any other name still a diet?

Let’s also just first clarify that the term “flexible dieting” is typically used synonymously with the term “IIFYM” which stands for “if it fits your macros”. 

For the purposes of this blog post, flexible dieting and IIFYM are one and the same.

Flexible dieting is also known as:

• IIFYM (If it fits your macros)
• Macro dieting
• Flex dieting
• Flexible dieting method
• Flexible Dieting lifestyle (sorry Zach, it is still a diet, not a “lifestyle” even if you call it one)
• Flexi diet
• Flex plan
• Flexible eating

Some people are also combining flexible dieting with other diets or restrictions, such as vegan flex dieting or carb cycling and flex dieting. 

That’s a lot of rules about what you’re allowed to eat…does it help you to reach your goals? And what is the risk of harming yourself by following a restrictive diet? Turns out, more than you might think. We’ll get to this in a second!

How Does Flexible Dieting Work?

The big idea here is that flexible dieting is supposed to be more tolerable because you’re less restricted in your food choices, and so you can stick with it (and the possible benefits) for longer. 

Step 1: calculate your calories

Flexible dieting works by first establishing a calorie “goal’ based on your age, gender, and activity level. 

Step 2: divvy them up. 

Those calories are divided between the 3 different macronutrients: carbs (short for carbohydrates), protein, and fat. Here is the rough breakdown that is suggested for flexible dieting:

• Protein: 0.8g/lb of lean body weight
• Fat: 0.3-0.4g/lb of lean body weight
• Fiber: 20-25% of lean body weight in grams of fiber per day
• Water: 3-4L of water in addition to any other liquids you might drink
• Carbs: Your remaining calories can be made up of carbs

Additionally, Flexible Dieters have specific recommendations for water and fiber as well, which we will discuss.

Step 3: track and eat!

Within your set ranges of macros, you can essentially pick whatever you want to eat. This is where the “flexible” part comes in. You can “spend” your grams of protein on anything with protein. This can be on chicken, a protein bar, or, heck, a candy bar. 

Just like with protein, you can “spend” your carbs however you like. Carbs can be potato chips, whole grain toast, fruit, or a cupcake. The choice is yours.

But remember, flexible dieting requires you to track everything. Every meal, snack, protein shake, a glass of water, and every french fry you snag off of your BFF’s plate. That’s a lotta tracking. 

You can track with whatever app you’d like, including MyFitness Pal and My Macros. 

So, what does an Intuitive Eating dietitian think about flexible dieting? There are some pros and cons that I’d like for you to think about. 

Pros For Flexible Dieting 

As with most nutrition plans, there are some benefits to consider. 

Flexible dieting has some positive attributes to celebrate. Let’s run through those before we discuss the cons…of which there are plenty!

Does Not Demonize “Unhealthy” Foods

One of the “benefits” of the flexible dieting approach is that it does not say you’re bad for eating, say, cake. It says, you want cake? Eat the cake! 

Studies have shown us that when we restrict specific foods – like a cupcake – it’s going to lead to us going overboard and eating those foods in a binge-like style. I talked about this idea in my YouTube video on eating dessert every day and why it’s NOT a bad thing (I do it!). The same idea applies here. What you restrict, you’re going to want more and likely eat it compulsively.

Places An Emphasis On Fiber

As a registered dietitian, I can shout from the rooftops about the health benefits of fiber. Why is fiber so awesome? Let me count the ways: 

• helps to keep you feeling full longer
• lowers blood pressure
• improves cholesterol
• reduces the risk for heart disease and stroke
• improves gut health

When I did a test calculation based on the IIFYM fiber guidelines it came out to ~25g of fiber per day, which is actually pretty in line with what is recommended by health care professionals. 

The general recommendations for fiber are: 

• 25g per day for women
• 38g per day for men
• or about 14g per 1,000 calories

And while fiber sure is an important part of our overall wellness and nutrition, it is possible to go overboard. I have a whole bost about that, right here: ​​Fiber: How Much Is Too Much?

Adjusting Macronutrient Intake Can Be Helpful For Certain Disease States

Consuming a certain recommendation of macronutrients has been shown to be beneficial for disease states such as diabetes, metabolic syndrome, and Parkinson’s disease. 

If you have a health condition or disease, I would always recommend working with a dietitian 1:1 who specializes in that area, not using an online calculator!

Teaches you some nutrition

While I don’t advocate for diets, there is a benefit to learning more about nutrition and how our food choices influence how we feel. One possible benefit of the flexible dieting approach is that it teaches you about the three macronutrients – you have to be savvy about nutrition to puzzle piece your meals and snacks together within the flexible dieting framework. 

This is kind of like learning how to ride your bike with training wheels. The tool might help you to learn new skills, but you shouldn’t need it forever. There are risks of constantly tracking, which we will cover in the cons section. Let’s dive in. 

Cons For Flexible Dieting

And now, I am ready to run through the negatives of flexible dieting…as an Intuitive Eating dietitian, my goal is always to arm you with balanced information so that you can make decisions that boost your health, wellness, and relationship with eating.  

Highly Restrictive

While this diet might seem to be super flexible (I mean, it’s in the freaking name!) it’s really not. The calories that they recommend are intended to promote weight loss. Let’s look at my own experience. 

I used the calculator on the IIFYM website to give me my calorie and macro goals and… well… let’s just say it was highly unrealistic. And I asked for it to MAINTAIN my weight, not give me weight loss. 

I don’t track my usual eating. But I can tell you right now I’m eating at least 500+ calories more than they told me to eat…and I’m maintaining my weight. Do we see a flaw there?! The guidance from IIFYM is far too low. 

And here’s the thing: any time you’re restricting, whether you’re counting calories, points, or macros, your mental relationship with eating shifts. Having restrictions makes you want to overeat later. 

Your body is smarter than a calculator

This is the problem with diets and online calculators, like these ones, is that we are placing our trust in a calculator more than our own bodies. We take those calculations as gospel when in reality those calculators are kinda utter bogus…they’re just estimates. 

So many things impact our calorie needs that those calculators don’t know such as:

• natural hormone shifts (hello, periods!)
• illness/infection (even if you don’t see if your body might be fighting it off!)
• physical activity (not even just working out, like, walking to the bathroom more, grocery shopping, etc. it all adds up!)
• emotional states, like experiencing stress or anxiety
• if you’re breastfeeding
• any medical conditions, such as endocrine disorders
• heck, even the climate you live in!

And besides, you’re probably not doing exactly the same amount of movement every day, so your needs are not going to be the same each and every day, either. 

Your needs vary 

There are some days that you’re far more active than others…shouldn’t your energy needs match that? And I’m not even just talking about the workouts you do. Like, do you do the same amount of hair brushing, take the same amount of bathroom trips (steps!), etc!

Diet plans like Flexible Dieting are always estimating how much energy you need and estimating how much energy you’re using as you move through your day, take a walk, and do an aerobics class.

But who knows how much energy you actually need, if you know how to listen?

Your body. 

Intuitive Eating gives you the tools to partner with your own body to provide yourself with the energy, nutrition, and satisfaction that you deserve to have with each meal and snack (no tracking needed). 

Let’s talk about tracking more, right now. 

Tracking is stressful

When you were a kid, did you ever go to a friend’s house where their parents never seemed to leave you alone to play? Like, they were always there, peeping out the windows, yelling up the stairs to check on you, or suddenly bursting into the basement just to see how things were going?

Kind of kept you on your toes, right? Or maybe even on edge? Kind of seems like there isn’t much trust between you, your friends, and their parents. 

When we are on edge and constantly feeling monitored, we are in a state of stress. Cue the cortisol: our stress hormones are going up! And you know what? Having a restriction around eating causes a state of stress. No matter how flexible Flexible Dieting seems, it is still a restriction. 

What if you’re hungry in the evening, but you’ve run out of calories for the day? Too bad – it doesn’t fit your macros. 

Being stressed can negatively impact your body in major ways, including raising your blood pressure and even causing inflammation. Stress can also impact you mentally by causing feelings of anxiety, depression, irritability, and even physical such as GI issues, skin breakouts, sleeping issues, and lowered immunity. Tracking gets in the way of building trust with your own body. And dieting – just like having those hovering parents – thwarts trust, too. 

And that’s not all: tracking, with apps such as MyFitnessPal, has been strongly associated with disordered eating. No bueno. 

And you know what else is no bueno? The assumption is that anyone in a larger body is not healthy. Let’s tackle that sticky topic now. 

Lower weight doesn’t necessarily mean better health

If you follow my blog regularly you know that as an Intuitive Eating Dietitian, I don’t advocate for intentional weight loss. Dieting to lose weight does not improve your health. 

(You 100% cannot determine your health by your weight).

Instead, more and more research is helping us to understand what we’ve gotten wrong in the past. We used to believe that having a lower weight meant that we were healthier. What we’ve discovered more recently is that our health behaviors matter far more than the numbers on the scale, measuring tape, or tracking app. 

Just because someone is in a smaller body does not mean that they’re healthier than someone in a larger body. Nor can you assume that someone in a larger body is unhealthy. 

Your body has a range of weights that suits your health and wellness best: this is called your set point weight. (I have a whole blog post on what a set point weight is and why it’s backed by science). A quick rundown of set point weight is that our bodies are smart. We basically have an “internal thermostat” that tries to keep our body at a certain weight where we function well. 

You might be thinking “But, Colleen, mine is broke.. I neeeeed a diet!” and I totally understand that. But… what if…. Your thermostat was one of those fancy pants wifi ones and right now it’s just offline. We gotta hook up that wifi connection and it’ll start working again. (That metaphorical wifi connection is gettin’ you back to being an intuitive eater with no food rules!)

As we diet and restrict food, our bodies see that as danger – food is restricted – and your body is trying to protect itself. So, it increases that thermostat to pack on a few extra lbs. This extra weight is there to protect against food scarcity in the future, should it happen again.

This is why most dieters regain the weight they lost in the long run and then some. I’m talkin’ 66% of dieters regain lost weight within one year and then some. And if this is something you’re familiar with, including feelings of guilt or shame, know that it is not your lack of willpower or inability to “stick to it”, it’s biology. And, well, ya just can’t fight that!

This continual loss then re-gain is called weight cycling, which has been shown to have adverse effects on health (layman terms: it’s not healthy.) 

What HAS been shown to increase health status are health-promoting behaviors- not weight loss. One study proved that healthy behaviors such as consuming fruits & veggies, not smoking, reducing alcohol intake, and physical activity all provided a positive health impact regardless of what happened with weight.

You CAN be healthy at any size. Is everyone healthy at every size? No. 

But can you be healthy at any size? Yes. 

This is why it is so so important to find your set point weight. Does that make sense? We all have different body types and how we treat our bodies matters, not the number on the scale. If you want to dig into this topic more I highly recommend my comprehensive blog post: Can You Really Be Healthy At Every Size? (HAES Explained!). 

I get that letting go of dieting and “trusting your body” is, like, a really hard concept to wrap your mind around. So to help I made a whole e-book for you called “Intuitive Eating Sounds Great But… Won’t I Gain Weight?!”. You can snag a copy here!

Promoted by non-pros

You know what really gets me heated? People giving nutrition advice without the training to do so. As a registered dietitian, I went through years of schooling, completed a rigorous internship, passed a board exam, and now have years of experience working. 

How does that compare to someone else’s Google search or six-week online certificate? Not well, methinks. 

Exploring what eating pattern helps you to fuel and function your best is a good thing. But that does not mean you’re an expert at providing nutrition counseling to others. 

I mean, just because I brush my teeth does not mean I’m a dentist, right?

Unfortunately, a lot of the people promoting flexible dieting, be it through websites or just casually at the gym, are not trained, registered dietitians. They’re not credentialed; they’re not licensed. 

Being able to (legally, ethically) provide nutrition counseling to clients is a privilege…one that should be earned through the completion of a credentialed program. 

More Protein Is Not Always Better

When the protein breakdown was calculated it came to 2.15g/kg/day. The recommended dietary allowance (RDA) for protein is 0.8g/kg/day. The RDA is essentially how much your body needs in order for it to do its job. You can see that the flexible dieting recommendation is way above this amount.

And if you’re thinking “Well, more protein is better, especially for athletes” one landmark study found that there were no improvements in lean body mass beyond 1.6g/kg/day protein intake.

Consuming too much protein could also negatively impact bone health, renal status (our bodies’ natural detoxification!), and the possible progression of coronary artery disease.

IIFYM Is Too Low Carb

Again, with the sample calculation done the carbs amount that the IIFYM calculator provided was off. The IIFYM calculator recommended 2.6/kg which is below what the Academy Of Nutrition & Dietetics recommends for the activity level.

This to me again goes back to that restriction we talked about and quite possibly leads to overeating carbs when they’re finally consumed, such as, say, on a “cheat day”. Then again, it would likely go back to that weight cycling we talked about, which is no bueno.

Are carb cravings making you feel outta control? You’re going to want to check out this post: ​​Not The Enemy: Understanding Carb Cravings. You’ll be relieved once you read it!

That’s Just Too Much Water

The IIFYM diet recommends consuming 3-4 liters of water in addition to your normal liquids. So, 3-4 liters on top of things like your morning cups of coffee, an afternoon cup of tea, etc.

Fluid needs vary, but typically it’s:

• 11.5 cups per day for women 
• 15.5 cups per day for men 

BUT, you also get water from foods – such as fruit and veggies –  which is said to be about 20% of your fluid needs. This brings the recommendation of what you actually need to drink down to 

• 9 cups per day for women 
• 12.5 cups per day for men

Let’s do some math: There are ~4.2 cups in a liter, so Flexible Dieting recommends that you drink 16.1-20.3 cups of water, on top of tea and coffee. That’s a lot. 

I’m not saying you’re going to cause harm with this amount, but it’s likely more than you need. 

My fear with this is that you are essentially tricking your stomach into thinking it’s full when it isn’t. And there is a difference between having a full stomach and being satisfied. 

No matter how much water you put in your body, if you’re not providing it with the nutrients it truly needs you’re going to be driven to eat more food as a result. And, well, that just wouldn’t be comfortable.

And can we talk about how many trips to the bathroom you’re going to be making? No thanks!

All Calories Are Not The Same

The old idea of calories in, calories out is bogus. Even within macronutrient categories, 1+1 does not always = 2. For instance, potato chips do not offer the same nutrition as a sweet potato.

I’m totally not hating on potato chips by any means. But, my guess is that you’ll feel much more full and satisfied for longer after eating a sweet potato. Further, your body is going to get a lot more nutrients from the sweet potato like vitamin A, vitamin C, and fiber.

What I fear happening here is that “entitlement eating” will happen. Meaning, “Oh, I can eat potato chips for all of my carbs?! I’m going to do it!” You’re almost acting as a rebel to healthy eating, vs. really understanding what makes your body feel good and what doesn’t.

When I’m teaching my clients how to live with no food rules it’s SUPER important to make sure they understand how different foods make them feel. Yes, you CAN eat potato chips all day every day, but do you want to? Would that feel good? This is how intuitive eaters actually wind up with a “healthier” diet overall than dieters! Yep. You read that right.

May Lead To Malnutrition & Nutritional Deficiencies

Going along that same line, Flexible Dieting, where you’re only focused on total calories and those macros may cause you to develop nutritional deficiencies. The IIFYM plan does state to take a multivitamin, but as a registered dietitian, I always recommend food first, not supplements. When a diet tells you to lean on a pill for your nutrient needs, that should be a HUGE red flag.

There was a super interesting study done assessing the nutritional status of macro counting bodybuilders and there were multiple nutritional deficiencies found such as vitamins A, D, E, potassium, fiber, and, in the women, iron. This seemed to be exacerbated in the women, which I also find very interesting and to me makes total sense. Men and women truly are different beasts and I think this also speaks to the pressure that is placed on women to be “perfect” by society.

Bottom Line For The Flexible Dieting Approach

I think we can agree: the cons outweigh the pros for flexible dieting and IIFYM. 

Personally, I do not advocate for tracking or counting anything in one’s diet. This has tendencies to lead to disordered eating and eating disorders, no matter how innocently it starts. If you’re curious about your own eating habits and if they “count” as healthy eating…or dieting…I invite you to take my Food Rules Quiz. In 60 seconds, I’ll provide you with the answer.

No matter what, we can’t trick our own biology. We cannot lower our bodies’ set point weight beyond where they want to be based on a variety of factors including our genetics, no matter what a tracker or diet promises. Yes, this can be very tough to hear, that some people will live in larger bodies their entire lives, but that doesn’t mean you can’t live a healthy and happy one. We need a total overhaul of the thin ideal if you ask me.

I DO think it is important to think about macronutrients as you make your food choices, however. I live by a stance of using gentle nutrition (I have an entire blog post explaining this). It’s totally okay to say “Hey, these potato chips aren’t going to keep me satisfied for long, let me pick the sweet potato with some almond butter drizzled on it”. BUT, here is the kicker, you shouldn’t be so wrapped up in nutrition that you’d feel guilty/stressed/anxious if only the potato chips were available. I teach more about this and guide you to this point in The SociEATy.

I hope this blog post was super helpful in showing you the pros and cons of Flexible Dieting and the IIFYM lifestyle and giving you the knowledge to make an educated decision about your eating style!

Leave a comment with your thoughts and pin this article to your Pinterest board to share with others!

XOXO

-Colleen