When it comes to IIFYM and fiber, there is no additional math. With IIFYM and weight loss, we base everything off of the gross amount of carbohydrates, not net carbs. Losing weight is all about the gross amount of food we eat, which is why there’s no reason to subtract fiber from carbs.

So, when you get your macros from the IIFYM calculator, keep this in mind so you’re focused on only the essential aspects.

Why You Don’t Subtract Fiber with IIFYM

If your macro diet dictates that hit 150 grams of carbs and 30 grams of fiber, you do just that. At the end of the day, on your weight loss log, make sure that you have eaten 150 grams of carbs and 30 grams of fiber.

  • Not 120 carbs and 30 fiber
  • Not 180 carbs and 30 fiber

If you care about weight loss, 30 grams of your carbs should be fiber, and they still count as calories (for our example).

Should I subtract fiber from carbs?

The way your body digests your carbs is not of concern to us. The glycemic index of the carbs, nor the sugar content, nor the type of sugar is a concern. All we care about is the fiber content. So at the end of the day, just make sure that you hit your fiber and your carbs separately.

You will find, however, that since carbohydrates and fiber are connected, that this can be tricky at first. If you have a hard time getting all of your fiber in, you might want to try using a fiber supplement. Just be sure to log it, since there are calories in fiber and as you know. Calories = Fat gain if you are in a surplus!