Should You Count the Caloric Value of Fiber?

Question:

I’ve had my body fat tested via Dexascan and my metabolism calculated via a breathing test. The determination was that I should be consuming no more than 2,103 calories and no fewer than 1,700 calories daily.

I prefer to eat only 1,700 calories whenever possible — and work out (weights & cardio) a few days each week in order to create an even greater deficit. It’s my understanding that, for me, eating fewer than 1,700 calories daily can result in a “starvation response” whereby I’ll actually retain fat instead of burning it.

My Question: Since fiber isn’t used for energy or stored — but is counted as a carb worth 4 calories/gram on nutritional labels and calorie-tracking apps — should I deduct from my daily totals the caloric value of the fiber I eat in order to stay out of “starvation mode”?

For example, say I’ve eaten 1,700 calories today, but that included 35g of fiber, which equals 140 calories. That dips my actual daily calories roughly 10% — to 1,560 — and into the starvation-mode territory. Should I compensate for those “missing” fiber calories with more food, or is my logic flawed and fiber actually DOES count toward my macros/calories?

– Darin S.

Answer:

Great question, Darin! Fibers are non-digestible carbohydrates from plant sources that may be fermented in the large intestine. Considered a subset of the total carbohydrate, dietary fiber is listed under carbohydrates on a Nutrition Facts panel. It includes both soluble and insoluble fiber, as well as lignin, whether naturally occurring or added.

Yes, since fiber is not digested (thus not used for energy or stored), it’s known to have less than the 4 calories per gram than other carbohydrates do. In fact, certain fibers offer almost 0 calories, while others provide only a smidge of energy after their fermentation by colonic bacteria. The Food and Drug Administration estimates that fermentable fibers provide about 2 calories per gram. Manufacturers may subtract the insoluble fibers when calculating energy, but not soluble fiber grams. Half of your stated 140 calories calculated from the fiber may already have been considered on food labels, leaving only 70 calories or 4% of your daily target of 1,700.

My recommendation would be to not compensate for any “missing” fiber calories, as people, in general, tend to under-report food intake when tracking and diet analysis calculations are already inaccurate by 10%. Maintain your protein intake when restricting calories and I’d suggest bumping your pre- or post-exercise nutrition up by 100 calories on your workout days.

Rather than focus on fiber in calorie-counting accuracy, readers should instead focus on getting the recommended amount of fiber each day, which has recently increased. As of 2016, the FDA the daily reference value of fiber was raised from 25 grams to 28 grams.

Resource

Carbohydrate Issues: Type and Amount. ML Wheeler and FX Pi-Sunyer. Journal of the American Dietetic Association, April 2008; Suppl 1, 108(4): s34-39.

– Debbie J., MS, RD

This article should not replace any exercise program or restrictions, any dietary supplements or restrictions, or any other medical recommendations from your primary care physician. Before starting any exercise program or diet, make sure it is approved by your doctor.

Some questions have been edited for length and/or clarity.