If it fits your macros. The IIFYM diet explained

If it fits your macros. The IIFYM diet explained

What’s the Deal with IIFYM?

Many personal trainers and fitness professionals talk about IIFYM but does it really mean you can eat whatever you want? Sometimes known as ‘The Pop Tart Diet’ or the diet that lets you get lean whilst eating cheeseburgers, IIFYM sounds promising…does it really work?

IIFYM stands for If It Fits Your Macros. It focuses on your protein, carbohydrate and fat sources (also known as micronutrients or macros). You work out what percentage of each macro your diet should contain, and eat accordingly. 

Most trainers recommend starting with 40% carbs, 40% protein and 20% fat. Those behind IIFYM suggest this is the best place to start for muscle growth, fat burning and keeping your energy levels high.

Providing you hit your chosen percentages, you can theoretically eat ‘anything’.

How to calculate your Macros?

The first step in IIFYM is calculating your body’s energy use. This is how you work out your ideal calorie intake. From there, fit your macro percentages in. The amount of calories you burn, simply by breathing and other basic functions is known as your basal metabolic rate (BMR). Once you’ve found your BMR (which you can do here) you can then adjust it down to achieve weight loss or up if you’re looking for muscle gain.

Once you have your calorie target and you have your macros set, all you need to do is fill in the gaps. If hot buttered toast fits your macros, you can eat it. If a spinach salad fits, you eat that. Of course you’ll soon see that your macros won’t allow for a high fat or high sugar diet and then the beauty of IIFYM comes into play.

The ratios for your macros can be adjusted in an instant to suit your specific requirements. You may from the 40/40/20 approach doesn’t have the desired effect and you may choose to reduce your carbs or increase your protein to start getting the results you’re looking for.

IIFYM is often heralded as the ultimate flexible dieting approach but it only works if you’re exacting and truly stick like glue to your pre-set macros.

The Author

Jessica Ambrose

Jessica is a fitness writer who loves long distance running, yoga, strength training and healthy eating.


Sean S.
14 March 2017

Sean S.

I like the fact you can adjust the recommended amounts of protein etc according to how much you exercise. When I reckon I need to lose a bit of weight I just reduce the carbs and eat them early in the day, and up the protein/fat ratio.

Michael A.
12 March 2017

Michael A.

Hi Claire, it's a lot simpler than it sounds, and easier than counting calories, which people did for years. Don't know it til you've tried it!

Claire H.
11 March 2017

Claire H.

I'm surprised I've never heard of this, though it sounds a bit too technical for me to bother with. Really, who wants to micro-manage their eating this much?

Paula C.
9 March 2017

Paula C.

My partner has been doing this for over a year and he says it's changed his life. it seems very flexible and it's made him try different foods she used to shy away from, like pork scratchings!

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