Why Flexible Dieting (IIFYM) is the Only “Diet” You’ll Never Fail

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I’m going to be honest with you. I really don’t like the word “diet”.

By it’s very nature, it implies a temporary event.

When people go on a diet, they don’t go into it thinking they’ll diet forever.

They think that they’ll do it for a while, get in amazing shape, and then that’s where their thought process ends.

They don’t think far enough ahead about what it will be like on that diet, if it’s sustainable, or if it’s even necessary to permanently modify their relationship with food to maintain a post-dieting body.

The truth is, all “diets” aren’t sustainable. It’s not that they’re not biologically sustainable, rather, they will inevitably fail for psychological reasons.

It doesn’t matter if you have superhuman willpower, whether you last a week, a month, or 4 months, at some point, you will break and fall off the “diet” bandwagon. When you do, the weight will fly back on faster than you ever thought possible.

I’m not trying to be a downer here. Far from it. Instead, i’m trying to prepare you for the realities of nearly all rigid, calorie-restricted diets.

The Number 1 Reason Why Most Diets Fail

In short, it’s because of willpower.

Willpower is the ability to resist short term temptations in order to meet long term goals.

Translated into the dieters world, that means resisting the temptation of your favourite foods, or in some cases entire food groups (on this note, PLEASE avoid any diet that recommends the exclusion of entire food groups) in order to meet your longer term health or aesthetic goals.

In theory, this is a completely achievable proposition. In practise, it’s a whole different story.

You see, psychologists specializing in willpower research have universally agreed that willpower can be thought of as a muscle. Just like muscle power, willpower is a limited resource that is capable of being depleted. You can’t do pushups forever, eventually you will fail. The same can be said for willpower.

Let’s imagine that you’re experiencing a great deal of stress at work or in your personal life. That stress, no doubt, is causing you to exercise your willpower in some way or another. Let’s say at the same time, you’re also trying to lose weight or manipulate your body composition in some way.

willpowerBecause you’re allocating some or much of your willpower towards your work or personal life, there is little leftover to be used to control your dieting (even though they’re completely unrelated tasks, interestingly). Trying to ignore distractions, control your temper or refuse seconds at mealtime all tap the same supply of willpower. Compound this over a period of days or weeks, and a snap somewhere is inevitable. Whether that may be losing your cool with a loved one, or falling completely off the diet train and gorging your face out.

This isn’t something to be ashamed of. It’s completely, totally, unabashedly human. And yet, many people often feel terrible about falling off their diet or not being able to juggle all these different aspects of their lives at once. These same people probably don’t understand the fact that willpower is like a muscle, and the best way to be successful on your diet is to use your willpower moderately, at a sustainable pace, and to not exhaust it.

The trick here is to be mindful of how your brain and body works, and to remember that in order to be successful with weight loss over the long term, you must implement changes to your eating habits that are sustainable, flexible, and at times, self-rewarding (willpower boosting).

Enter Flexible Dieting (popularly known as IIFYM, or If It Fits Your Macros).

What is Flexible Dieting?

Flexible dieting is the only diet in existence that doesn’t restrict your food choices. Under the guiding principles of this philosophy, you’re allowed to eat any food you want, whenever you want, so long as it fits within your daily macro allotment.

Everyone has a particular macro allotment that is specifically designed to achieve a body composition goal.


What are Macros?

Macros is a short term for macronutrients. Macronutrients make up the vast majority of our diet. Don’t freak out about this term, everything you eat has macronutrients in it in differing amounts. The three macronutrients are Protein, Carbohydrates, and Fats. Each of these macronutrients has their own caloric value.

1 gram of Protein = 4 calories
1 gram of Carbohydrates = 4 calories
1 gram of Fat = 9 calories

Instead of counting calories (which is what most diets have you do), flexible dieting only requires participants to count macronutrients. On other diets, you’d have to make sure you were eating 2100 calories a day, for example. With flexible dieting, you’d instead insure you were eating 160g protein, 70g fat, and 200g carbs a day (which also equals roughly 2100 calories per day).

Why Counting Macros is Better than Counting Calories

It’s true, the law of calorie balance states that in order to lose weight you have to consume fewer calories than you need each day. This is an indisputable scientific fact that has been proven over and over again. It doesn’t matter where those calories come from, a diet full of twinkles or a diet full of broccoli and lean meats, if you eat fewer calories than you burn you will lose weight.

This is proven in a rather extreme fashion by Professor Mark Haub at Kansas State University in his famous Twinkie Diet.

When talking stricly about weight loss, a calorie is a calorie and it doesn’t matter where those calories come from – so long as you’re in a calorie deficit.

However, when you try to lose weight (or gain weight for that matter) by only counting calories, you have absolutely no control over your weight loss.

You can’t dictate how much of your weight is lost from muscle, and how much is lost from fat. More often than not, a lot of weight will come from off in the form of muscle (your body prefers to use your muscles for its fuel supply over adipose tissue).

Said another way, you have no control over your body composition (your muscle to fat ratio) when you only count calories.

This is where counting macros comes in.

When you count macros, you’re counting calories (remember, we know how many calories each of the macronutrients contains), but you’re also counting the amount of protein, carbohydrates, and fats that enter your body. By ensuring a minimum amount of protein and fat intake on a daily basis, you can maintain the maximum amount of muscle and cause your body to eat up a greater proportion of fat tissue.

When it comes to dictating body composition during weight loss or weight gaining, a calorie is no longer a calorie.

If aesthetics and body composition are important to you, strongly consider counting macros. You will be truly shocked at how quickly you can get into shape when compared to just counting calories alone.

If you are looking for a good calculator to determine your daily macro requirements, I recommend this one: Macro Calculator

Why Flexible Dieting is So Effective

Body composition is affected by macronutrient ratios only, not by the nutritional content of the food.

Said another way, as long as you hit your macronutrient ratios on a daily basis, the foods you eat will not negatively affect your body composition. It doesn’t matter if your carbs come from white rice, bread or pasta, or solely from broccoli and yams, so long as you hit your desired macronutrient numbers, your resulting body composition will be exactly the same.

This allows you a significant degree of flexibility in your diet to include small portions of your favourite foods, treats, a beer at the end of the day or to be able to snack at your friends party. Not only that, but you can do these things completely without guilt – something that often causes people to fall off their diet.

Flexible dieting allows you to significantly reduce the amount of willpower it takes to stay on your “diet”. This one reason is what makes flexible dieting a superior dietary approach to anything else out there today. Flexible dieting reduces boredom, is totally sustainable, and last but not least; extraordinarily effective.

So I Can Stuff Your Face With Twinkies All day Long and Still Get Ripped?

Not exactly. In theory, flexible dieting allows you to eat anything you want. However, to reach each macronutrient allotment on a daily basis, you’ll soon find that you have to eat a diet which minimizes a lot of calorie-dense, high fat foods.

In practise, your diet will consist of lots of fruits, vegetables, and protein. This will allow you to have a small treat on a daily basis of your choosing, but don’t think it will allow you to eat a McDonalds meal and not have to drastically accommodate for it the rest of the day.

For example, let’s say your daily macronutrient goal is 160P, 65F, and 220C. You go to McDonalds and order a Big Mac meal. Let’s break down the macronutrients:

big mac lego meal

Big Mac: 24P, 29F, 44C

Medium Fries: 4P, 17F, 66C

Medium Coke: 0 P, 0F, 56C

Total Nutritional Content: 28P, 46F, 166C

Your protein total is relatively small, which is fine. It allows plenty of room to get protein from other sources during the day. However, you’ve used up over two-thirds of your daily allotment of fat and carbohydrates in ONE meal.

That drastically reduces the amount AND types of food you can eat the rest of the day. It makes it really difficult to hit your remaining macros properly. Trust me. You’ll end up starving because the quantity of food in your McDonalds meal is quite small for the amount of macros that it uses up. The total volume of food that you'll eat that day is minuscule, and that's very unsustainable. The solution is to eat foods with higher satiety values.


Let’s compare our McDonalds Big Mac meal to this:

a typical flexible dieting meal

Total Nutritional content: 60p, 10F, 70C

This food is higher in fiber and much lower in caloric density, meaning it’s more filling, while also taking up less of your daily macronutrient allotment. You could still fit in a filling and nutritious shake, a sandwich, a pile of almonds, a protein bar, and a small bowl of ice cream or some chocolate that day and hit your daily macro allotment.

In fact, that’s very similar to what I eat on a daily basis, even while in a calorie deficit and cutting. The best part? I’m full all the time and I’m never hungry, and I ALWAYS have a treat of my choice – recharging my willpower for the next day.

Flexible dieting is the only way of eating I recommend and is by far the most effective way to get in peak shape.


– Willpower is like a muscle, you have a finite amount of it at any one time.
– When you use too much of it in any aspect of your life (work, personal, etc), it becomes easy to fall off your diet.
– Flexible Dieting allows you to eat anything you want, as long as if fits within your daily macronutrient allotment.
– Psychological research proves that this flexibility increases willpower, allowing you to sustain your diet indefinitely.
– Flexible dieting is the only method of eating I recommend when it comes to getting in shape.


1. Baumeister, R., & Tierney, J. (2011) Willpower: Rediscovering the Greatest Human Strength. New York: Penguin Press.

2. Duckworth, A. (2011). The significance of self-control. Proceedings of the National Academy of Sciences, 108, 2639-2640.

3. Duckworth, A., & Seligman, M. (2005). Self-discipline outdoes IQ in predicting academic performance in adolescents. Psychological Science, 16, 939-944.

4. Moffitt, T., et al. (2011). A gradient of childhood self-control predicts health, wealth, and public safety. Proceedings of the National Academy of Sciences, 108, 2693-2698.

5. Tangney, J., Baumeister, R., & Boone, A.L. (2004). High self-control predicts good adjustment, less pathology, better grades, and interpersonal success. Journal of Personality, 72, 271-324.

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  • I am curious what that form of diet does in relation to cheat day scheduling or metabolic drop at caloric deficits.

    • Diets have surprisingly little to do with your basal metabolic rate. Studies show that you’d have to not eat for approximately 3 days before you’d a see a significant drop in your metabolism and even then it isn’t as large as you’d think (around 15%). And cheat days are absolutely recommend and beneficial.