What’s IIFYM…otherwise known as Flexible Dieting?

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smiling blonde woman holding an apple and a cupcake in front of blackboard

Flexible dieting means that apples AND cupcakes are allowed.

The internet has a way of making concepts that have been around for a long time seem new. This appears to be the case with Flexible Dieting, otherwise known as If It Fits Your Macros (IIFYM). The concept’s popularity seems to be associated with bodybuilders, and there’s a lot of them online bragging about how they eat pop tarts and chicken wings. This appears to be the antithesis of the standard bodybuilding contest prep diet of:

  • chicken breasts
  • tilapia
  • asparagus, broccoli, and other steamed low-carb veggies
  • oatmeal
  • broccoli
  • sweet potatoes
  • rice cakes
  • egg whites
  • protein shakes

If you can eat nothing but those foods (ideally without any sauces or condiments) for months on end, good for you! Flexible dieting means that you don’t have to.

Figuring out your Macros

You first need to determine how many calories you need. This is an estimate based on predictive equations like Mifflin-St. Jeor or Harris-Benedict. The equations take your gender, height, weight, and activity level to predict how many calories you’re burning in a day. It’s obviously just an estimate, but it’s a good place to start.

Now you need to figure out your ideal macros (carbs, protein, fat). If you look at Canada’s Food Guide (which I only do when I’m writing blogs like this because otherwise I find it fairly useless) then the recommendations for adults are:

Carbs 45-65%

Protein 10-35%

Fat 20-35%

I think it’s a rare person who does well on 65% carbs and as little as 10% protein, but I’m sure they do exist. With IIFYM, you figure out how much protein per lb of body weight you want to consume (0.7-1.2 is often suggested) and how much fat (03.-0.45) and then fill in the rest with carbs. Where you fit with protein and fat is based on age, gender, preference, training need, and goals.

Don’t Forget the Fibre!

This is an important part of IIFYM, and is part of the reason that it’s hard to eat Pop Tarts all day long and still hit your macros. You need to consume enough fibre in relation to your carb intake, generally about 25-60g a day. More is not better. Taking in too much fibre can decrease your absorption of some vitamins and minerals.

Why Flexible Dieting encourages Clean Eating

Now let’s say that you have a total calorie goal of 2000 calories per day, with 45% carbs, 30% protein, and 25% fat, with 35g of fibre. Try to do this by eating cheeseburgers all day, let’s say 6 of them at a total of about 1800 calories. Your carbs work out right at 45%, fat is 34%, and protein 21%, but your fibre is only 12g. So now you have 200 calories, none of which can be carbs, that need to have 23g of fibre. No chance!

Could you have one cheeseburger a day and still make it all work out? Probably, but it depends on your calorie and macro goals. Then the rest of your diet will inevitably be “clean” foods like lean chicken breasts and asparagus because it’s tough to meet your protein and fibre goals otherwise. Most people will still need to incorporate a lot of standard bodybuilding favourites to meet their macros and calorie intake.

Will it Work for You?

It might. Can you be bothered to track your food intake every day?

If not, IIFYM will be tedious for you and you’ll give up. If you’re a male bodybuilder whose size and activity level warrants taking in about 5000-6000 calories a day, Flexible Dieting can be a whole lot of fun! It’s a little trickier for the rest of us. IIFYM can get you away from the starve/binge cycle that clean eating often leads to. After all, most clean eating advocates usually have a cheat meal or day once a week anyway.

There’s nothing particular new about IIFYM. It’s just a version of calorie counting that also takes macros and fibre into account. If you’ve tried The Zone (40/30/30) or some other calorie counting method you’ve done a less specific version of Flexible Dieting.

IIFYM physique competitors are an enthusiastic group. After years of clean eating they’re excited to be able to have their favourite “cheat” foods on a regular basis.

Maybe their system will be right for you.

It just might be worth a try.

Ivana Chapman 

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Ivana Chapman

Ivana Chapman

Ivana Chapman BSc BA CSCS is a Canadian fitness and nutrition coach, happy wife, and mom to an energetic 5-year-old boy. She is a writer, published fitness model, speaker, 3rd Dan black belt in Shotokan Karate, former World Cup Karate Champion, one-time marathoner, and CBBF National level Natural Bikini competitor. She loves weight training and chocolate, not always in that order of preference.
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