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Flexible Dieting (IIFYM) | How To Follow It Properly

Flexible dieting, commonly known as If It Fits Your Macros (IIFYM), is a growing trend within the fitness industry.
IIFYM was originally started by several bodybuilders who wanted a change from the typical foods which are viewed as ‘clean’ and opted to indulge on more ‘fun’ foods.

The idea behind it is that you can achieve the same results by eating what you want (within reason) as you would sticking to a strict list of ‘clean’ or ‘bro’ foods, as long as you fulfil your daily macronutrient goals.

Opinions on Flexible Dieting

IIFYM is quite a controversial topic. Lots of nutrition experts argue that body composition and health are not correlated. This means tha580x348-mp-wk22-CG-Male-Content-June-7-Cookiet although eating what you like may give you the same visible results as eating ‘healthily’, you will not be as physically healthy and won’t function as efficiently.

Personally, I believe that flexible dieting is a great approach to nutrition, if you follow it correctly.

…This means you’re ensuring you are eating good, wholesome food as well as some of the fun stuff!


Flexible Dieting the Correct Way

The most successful followers of flexible dieting tend follow a more orthodox approach. This meaning that they aren’t consuming 100% of their daily calories from just junk food.

It is recommended that when you’re flexible dieting, you should still consume between 80-90% of your daily calories from micronutrient dense (clean) foods, whilst consuming the other 10-20% of their calories from discretionary sources i.e. treats, junk etc. For the sake of argument, I will use the figures 85% and 15%.

Say you’re eating 2500 calories per day. 2125 (85%) of these would be from micronutrient rich foods, whilst the remaining 375 (15%) can come from any other source you choose. This is especially appealing to those who have cravings for junk/sweet foods, or those who don’t want to give up a favourite food/beverage whilst reaching their goals.healthy eating iifym

I guarantee you will see fantastic results by following this approach, whist ensuring you stick to it as you aren’t cutting out your favourite foods entirely. This is a much better approach than just eating whatever you like, when you like, since it is unlikely you will see results, and if you do they will not be optimum.

Even though they are both seen to mean the same thing, I would class flexible dieting as fitting in the unhealthy foods to your diet where suitable, compared to IIFYM being where you just cram in junk food and use the term as an excuse.

Benefits of IIFYM

✓  Flexible dieting promotes you tracking your macros, which is a good habit to get into and ensures you are making the best progress possible. An easy way to track macros is by using MyFitnessPal.

✓  Following flexible dieting means you are less likely to binge on bad foods, as you are allowing yourself to consume them, within reason; therefore it is very sustainable in the long term.

✓  It allows you to be more flexible with what you eat, making the process a more enjoyable experience.

✓  It is effective and works for most people, so give it a try before you knock it.


Dis-advantages of IIFYM

✗ For most, there is no clear line between what is ‘healthy’ and fits into the ~85% or is ‘unhealthy’ and fits into the ~15%.

✗ It is often tempting to overindulge on the treats, meaning the effectiveness of the approach will be diminished.

✗ It can often be difficult to calculate and track your daily macros.


1)  Use MyFitnessPal and get familiar with it. Tracking your macros is easy once you know how, and only takes a few minutes to do. Log your foods before or after you eat them, don’t leave to long a gap though as you may forget something you ate.

2)  Invest in a food scale, meaning you can accurately weigh out your food so that you can track your macros more easily.

3)  Tweak your macros according to the results you are getting. If you aren’t losing fat at a desired rate, cut down on carbs. Likewise, if you aren’t gaining muscle as quickly as you would like, up your macros, focusing on protein – maybe add extra protein shakes for convenience!

How To Manually Calculate Your Macros


The general formula for calculating your macros manually is as follows (adapted from Dan Bolton’s formula)  :

For males: [10*weight (kg)] + [6.25*height (cm)] – [5*age (years)] +5

For females: [10*weight (kg)] + [6.25*height (cm)] – [5*age (years)] – 161

This figure will be your REE, which is the amount of calories your metabolism burns without any other exercise or energy expenditure. In order to calculate your TDEE (total daily energy expenditure) you must multiply the figures by one of the following numbers according to your daily physical activity:

Sedentary (normal daily activity with little exercise) = REE x 1.2

Light Activity (normal daily activity with moderate levels of exercise) = REE x 1.375

Moderate Activity (normal daily activity with higher levels of exercise) = REE x 1.55

Very Active (large amounts of high demanding, physical exercise daily) = REE x 1.725

You can now use this number as a rough estimate to work out your maintenance calories, i.e the amount of calories you need to eat to maintain your current body weight.

Generally, those looking to put on mass will eat ~500 calories over this figure, likewise those looking to lose weight will opt to eat ~500 calories under. Add or subtract calories from this figure depending on your goals.

✓  Protein:salmon steak

Generally, people opt to eat 1.0-1.5g of protein per lb of lean body mass. This is your total body mass – your fat weight.

Calculate this by taking your body fat percentage and input that as a percentage of your total body weight, giving you your fat weight. E.g if your body fat is 10% and you are 180 lbs, your fat weight is 18 lbs. Remember, one gram of protein contains 4 calories.

✓  Fat

Some people like to eat around 0.45g of fat per lb of lean body mass. Others opt to consume 25% of their calories from fat. Remember, one gram of fat contains 9 calories, making it more calorie dense than protein or carbohydrates.Banana smoothie

✓  Carbohydrates

Generally, the rest of your calories will be allocated towards carbohydrates. Remember, one gram of carbohydrates contains 4 calories. Using this figure you take the remaining number of calories you are left with after calculating protein and fat, and divide it by 4. This is how many carbs you should consume.

Take Home Message

Remember: this is just a rough estimate. For best results you need to adapt your macros as you go along. If they are working for you, stick to them. If you aren’t seeing results then switch them up.

If this was too confusing, there are plenty of online calculators which allow you to calculate your macros. For any further help be sure to leave a comment and with any questions you may have!






Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.



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