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Flexible Dieting And IIFYM – An Ultimate Guide

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Flexible Dieting, otherwise known as IIFYM, is one of the newest and most popular dieting approaches in years!

Flexible dieting is an approach to dieting that places an emphasis on total calorie intake and specific macronutrients, two key factors in weight loss and body composition optimization.

When these are set up, there’s less specific focus on what foods ‘fit those macros’ or make up that daily intake.

The difference between IIFYM and other traditional diets is that this methodology emphasizes calories and macros rather than simply the foods you eat. This means that, as long as it fits within your calorie and macronutrient budget, consuming foods such as pizza, ice cream and pop-tarts is acceptable!

In this article, I’ll provide an ultimate guide to the major concepts of flexible dieting, the benefits, how to set it up and optimize it and, finally, describe the pros and cons.

What is Flexible Dieting And How Does It Work?

Flexible dieting or If It Fits Your Macros (IIFYM) means you focus on calories and macros then have flexibility within that to eat what you like, that is, as long as it conforms to the set daily goals.

For example, you could be prescribed 1800 calories per day with 150g carbs, 150g fat and 66g fat.

Within this, you could consume some normal healthy fats containing meat and vegetables, along with other less healthy foods, such as ice cream and candy, consumed with a protein shake.

Ultimately, as long as your daily intake of calories and all 3 macros are met each day then it allows for flexibility and variation, along with ‘processed or bad’ food when you fancy it.

Depending on how you approach this, it can either be a great tool to create a balanced dieting plan, or an excuse to binge eat on a daily basis. Like with most diets, this means it can be great for some and not so great for others.

How To Practice Flexible Dieting

Here’s a quick overview of how to start or set up a flexible dieting plan.

Step 1: Decide on Your Calories & Calorie Intake

The first step in using flexible dieting is to first determine your ideal calorie intake, based on your goals.

This step is based on the theory of energy balance, which states that in order to lose or gain weight, you’ll need to consume less or more calories, respectively, in order to lose or gain weight.

To find your maintenance calorie intake, you can use online trackers or, to get just a rough idea, you can follow this calorie guide:

Fat Loss: 11-12 x Calories per 1LB Bodyweight

Weight Maintenance: 15-16 x Calories per 1LB Bodyweight

Muscle Growth: 18-20 x Calories per 1LB Bodyweight

Step 2: Set Macronutrient Ratios

The 3 main macronutrients (protein, fat, carbs) all have a caloric content. Protein and carbohydrates account for 4 calories while fat accounts for 9.  These macros make up your total calorie intake.

Based on your requirements, you can adjust these macronutrients to fit your needs.

A typical ratio for those looking to improve body composition is 40% Protein, 30% Carbohydrates, and 30% Fat. However, this isn’t set in stone. Feel free to adjust these ratios to fit your abilities and needs. Just make sure that the total calories match your caloric needs.

Simply take your calories and divide it up based on the ratio you pick. From here, calculate the amount of carbs, protein and fat you need.

(Related: Let me personalize a diet and training plan for you here).

Step 3: Track Your Intake

Since  flexible dieting is based on calories and macros, it’s strongly advised that you begin tracking your intake using an app such as MyFitnessPal.

Doing so will ensure that you are consuming the right amount of calories and macronutrients, relative to your goal that we set at the start.

Additionally, since you’re able to eat less than optimal calorie dense foods, like pizza, without tracking, it can become quite easy to accidentally overdo it and ruin progress.

With tracking, you can fit in the odd ‘bad’ or processed food and still not mess up your long-term plan or goals. This can be great for lots of people as it lets them still enjoy a balanced life without binge eating.

Example Flexible Dieting Day

Meal 1:

  • 3 Eggs
  • 1 Avocado
  • Whey Protein Shake with Milk

Meal 2:

  • Lean Chicken Breast
  • 1 Cup White or Brown Rice
  • Mixed Vegetables
  • 8 oz. Water

Meal 3:

  • Bone in Pork Chop
  • Mashed Sweet Potato
  • Grilled Asparagus
  • 12 oz. Milk

Meal 4 (The ‘Flexible’ Part)

  • Whey Protein Shake
  • 2 Cups Ice Cream of Choice
  • 3 Tbsp. Chocolate Toppings of Choice

Nighttime Snack:

  • 1 Cup Cottage Cheese
  • 1 Cup Blackberries
  • 1 Stevia / Sugar Free Sweetener

As you can see above, this is a great example of how flexible dieting should actually be designed.

The majority of the example meals place an emphasis on the standard lean meats and vegetables, rich in protein and fiber. Towards the end of the night, having a dessert such as ice cream is totally acceptable as long as there are extra calories left over.

You’ll also note the addition of a protein shake, which I recommend as I believe protein at each meal to be a key strategy in overall health and physique enhancement.

So you see, it’s not 4 meals of junk food or anything crazy. This is how flexible dieting or IIFYM is supposed to be performed!

Common Misconceptions About Flexible Dieting

Undoubtedly you’ve heard many people who practice flexible dieting boasting of the typical foods they get to eat while using this method of dieting.

Unfortunately, individuals posting pictures of pizza and pop tarts give outsiders the impression that the diet is comprised solely of junk. This simply is not, or at least should not, be the case.

The thing about flexible dieting is that it’s not a free-for-all to consume junk all the time; however some people have made it look this way.

The use of flexible dieting will, or at least should, still require placing the major emphasis on healthy, single ingredient, foods rich in protein and fiber, such as lean meats and vegetables.

Therefore, I usually advise people to still focus on key principles, i.e. allocate around 80% of their intake on good choices such as healthy whole foods. After this, there is a small and sensible window per day or week for less optimal processed / “junk” food.


Is Flexible Dieting Right For You?

Using flexible dieting is entirely an individual choice.

Many people, including myself, find flexible dieting to be an approach that is sustainable and actually helps me get the results I desire, while being busy with travelling and maintaining an enjoyable social life.

However, sometimes diligently tracking intake can be quite a large, (& daunting), task for many, although it just takes 5-10 minutes per day once you are used to it.

Additionally, allowing the consumption of less than optimal foods can pose risks for those who can’t control themselves. This is where I certainly don’t recommend IIFYM. For some people, it’s normally best to just eliminate certain foods entirely rather than trying to eat small amounts of them.

So, if you can’t stop at 1 slice of pizza, 1 scoop of ice cream or 1 segment of chocolate or candy, then IIFYM may not the best solution for you.

As with any diet, attempt to understand the fundamentals as described above and assess whether or not it will be a good fit your goals, habits and personality. After that, you can test it for 2-4 weeks. If you love it, great; however, if you struggle daily and often overeat, then it may be best to try another plan such as carb cycling.

IIFYM / Flexible Dieting – The Ultimate Guide

Flexible Dieting or IIFYM is a dieting approach that places an emphasis on total calorie intake and macronutrient ratios, allowing users flexibility within that.

While eating foods such as pizza and pop tarts is certainly acceptable, (as long as they fit within calorie and macronutrient allocations and are consumed in sensible amounts), the main focus should still always be on healthy foods such as meat, vegetables, grains, etc.

If, after understanding the fundamentals and considering them suitable to help you live a flexible lifestyle, you might just find that flexible dieting is the diet you’ve been waiting for.

Learn more about 5 of the most popular diets to compare and see which is best for you.


About the author

Rudy Mawer, MSc, CISSN

Rudy has a 1st class BSc in Exercise, Nutrition & Health and a Masters in Exercise & Nutrition Science from the University of Tampa. Rudy currently works as a Human Performance Researcher, Sports Nutritionist and Physique Coach. Over 7 years he has helped over 500 people around the world achieve long last physique transformations.

He now works closely with a variety of professional athletes and teams, including the NBA, USA Athletics, World Triathlon Gold Medalists, Hollywood Celebrities and IFBB Pro Bodybuilders. If you would like to get in contact or work with Rudy please contact him on social media.

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