Bethany writes: “Have you heard of this new approach to flexible dieting called IIFYM, which stands for If It Fits Your Macros? A lot of people seem to be doing it and I'm interested in what this is all about.”
Yup, this is a thing! There’s an IIFYM website, mobile apps and community forums. You can get ebooks and meal plans and pay for IIFYM coaching sessions. It seems to be particularly popular with the body-building crowd. But there’s nothing particularly new or revolutionary about this approach.
How Does IIFYM Work?
It starts the way most weight management plans start: You decide how many calories you should be eating, based on your personal statistics (such as your age, height, current weight and activity level) and what you’re trying to accomplish (that is: lose, gain, or maintain).
Then you decide what percentage of those calories should come from carbs, fats, and proteins. Again, this is based on your goals. If you’re trying to “bulk up” with a lot of muscle for example, your protein percentage is higher. If you’re trying to slim down, your carbohydrate percentage is lower.
Although it may seem as if these percentages are highly scientific and precise, they’re not. Virtually every dietary philosophy takes some sort of stand on what percentage of your calories each of the three macronutrients should contribute—and they certainly don’t all come up with the same answer. That’s because the various answers are all derived from a pretty shaggy mix of scientific data, speculation, philosophical commitments, and wishful thinking.
Eat Whatever You Want?
One you have your macro prescription, you’re ready to start your IIFYM diet. And the rules are simple: You can eat whatever you want as long as it fits your macros. My macro prescription, for example, allots me 60 grams of fat. According to the IIFYM principles, the source of the fat doesn’t matter, as long as I don’t go over 60 grams of fat. If I want to get it all from heavy cream, that’s perfectly fine.
Likewise, I can eat my entire 250 grams worth of carbohydrates in the form of Swedish fish if I want to. The source of the carbohydrates doesn’t matter as long as I don’t go over my allowance. You get the idea.
This strategy is also referred to as “flexible dieting” because you can eat whatever you want. In practice, however, IIFYM dieting is not all that carefree. You have to carefully weigh and measure everything you eat and log it into a diet tracker that counts carbs, fats, and proteins. And even though no foods are off limits, it’s still going to take a fair amount of planning to hit your macros every day.
Does Flexible Dieting Work?
Can you lose weight or gain muscle with this approach? Possibly. By following your macro prescription, you’ll be eating a certain number of calories every day. If that number of calories is low enough, you’ll lose weight—at least at first. You’d also be getting a reasonably balanced proportion of fats, carbs, and protein. That’s certainly better than nothing. But only slightly.
See also: Are Some Calories More Fattening Than Others?
Better than nothing. But only slightly.
I think the quality of your food choices does matter, both in terms of weight management and overall health. A serving of whole grains may have the same number of calories and carbs as a Coke, but it will have very different effects on your blood sugar and appetite. Olive oil provides nutritional benefits that you don’t get from heavy cream. Protein from fish does a lot more for your health than protein from hot dogs. I think it’s ridiculous to suggest that macronutrients are the only aspect of a food that matters.
Of course, the IIFYM approach can also be used with a little more common sense. You could choose more nutritious foods, or foods that fill you up for fewer calories—as well as some treats. You could decide, for example, that as long as you’ve eaten five servings of vegetables and gotten at least 25 grams of fiber, you can spend the rest of your carbs on Swedish fish if you want. Maybe one day you'll treat yourself to as much full-fat Haagen-Daaz as your macros will allow—just not every day.
But once we’ve injected a little common sense into the IIFYM equation, it starts to looks a lot like any other healthy eating strategy that involves balancing and moderating your food intake—except that it may be unnecessarily rigid. Here are some less cumbersome ways to accomplish the same thing:
How to Lose Weight Without Dieting
Can You Lose Weight Without Counting Calories?
Have any of you experimented with the IIFYM diet? I’d like to hear what it was like for you. What did you find to be the main pros and cons? Did you feel that the nutritional quality of your diet improved or suffered? Did you lose weight? Was it something that you found sustainable? Post your comments below or on the Nutrition Diva Facebook page.