Trainers and nutritionists may make calories seem pretty straightforward – we do! However, this isn’t exactly true all the time. One of the more confusing foods has been Fiber – how many calories does it have?
It’s a carbohydrate, so we generally say 4 calories. At the same time, we’re told we can’t digest it, so doesn’t that make it 0 calories? This article will break it down simply and answer: How many calories are in Fiber?
What Is Fiber?
Fiber is a type of carbohydrate known as a Non-Digestible Carbohydrate or NCD. These are a group of carbohydrates that are not fully digested or absorbed in the small intestine.
Now, for an NCD to be classified as dietary fiber, it must meet several requirements including: ¹
1. Chemical Definition
The NDC must consist of ≥3 monomeric units (i.e., oligo- or polysaccharides) linked by β-glycosidic bonds.
Must be non-digestible by human digestive enzymes.
2. Source
It must be either:
Intrinsic and intact in plants (e.g., in whole oats, beans, vegetables)
or
Isolated or synthetic, and added to foods.
3. Demonstrated Physiological Benefit
If it’s an added (isolated/synthetic) fiber, it must show one or more of the following clinically proven benefits:
Lowering blood glucose levels
Lowering cholesterol levels
Increasing stool bulk/laxation
Attenuating postprandial blood glucose
Increasing calcium absorption
Reducing blood pressure or body weight
These effects must be shown in well-controlled human studies (not just mechanistic or animal data).
If it meets these requirements, it will be classified as dietary fiber, such as glucomannan,
and placed on the nutrition label.
Insoluble Vs Soluble Fiber
There are two distinct types of Fiber.
Soluble FIber
Insoluble Fiber
1. Soluble Fiber is a type of Fiber that dissolves in water and forms a gel-like substance in the gut. This brings several different benefits, including.
Slows digestion → stabilizes blood sugar
Binds to cholesterol → helps lower LDL
Feeds gut bacteria → acts as a prebiotic
2. Insoluble Fiber is a type of Fiber that does not dissolve in water. It adds bulk to stool and helps move it through the digestive tract.
Prevents constipation
Promotes regularity
Supports colon health
How Many Calories Does Fiber Have?
So now let’s quickly look at the amount of calories in Fiber. Right off the bat, we’ll tell you the numbers are anything but precise.
The exact amount of calories in Fiber can vary depending on its solubility, which ranges from 0 to 2.5 calories per gram. However, to keep things simple, the FDA uses these measurements:
Insoluble Fiber – 0 calories/gram
Soluble Fiber – 2 calories/gram
However, there’s one other important point. In 2016, the FDA passed new rules concerning seven NDCs that are either synthetic or isolated in how they are labeled in terms of being dietary Fiber.²
Previously, these NCDs were labeled as having 4 calories per gram. However, they are now said to consist of 2 calories per gram. These carbohydrates consist of:
Beta-glucan soluble Fiber
Psyllium husk
Cellulose
Guar gum
Pectin
Locust bean gum
Hydroxypropylmethylcellulose
All in all, the exact amount of calories in different sources of Fiber can vary from 0 calories to 2.5 calories per gram.
Can I Eat More Fiber To Lose Weight?
Since fiber has fewer calories than other carbs and can provide other weight loss benefits, an obvious thought is to just eat a ton of fiber.
However, “You can have too much of a good thing.”
Eating too much fiber can actually cause major health issues such as;
Bloating & Gas – Excess fermentation in the colon (especially soluble fiber)
Constipation – High fiber + low fluid = bulk with no movement
Diarrhea – Sudden increase overwhelms digestion
Nutrient Malabsorption – Fiber can bind minerals like calcium, iron, and zinc
GI Discomfort – Especially for those with IBS or sensitive guts
Therefore, the general recommendation is to eat 14g per 1,000 calories. This means a 2,000-calorie diet should have 28g of dietary fiber.
So….Do You Need To Count Fiber?
So, do you need to count Fiber?
In general, simply assume 1 gram of dietary Fiber is 2 calories. This number will get you in the ballpark, and if anything, your total daily calories will only be off by around 50 calories at most – in reality, it’s not going to play a massive role.
Still, it’s interesting to know and keep in mind as you’re traveling the complicated world of nutrition.
References
U.S. Food and Drug Administration. Guidance for Industry: The Declaration of Certain Isolated or Synthetic Non‑Digestible Carbohydrates as Dietary Fiber on Nutrition and Supplement Facts Labels. Docket No. FDA‑2018‑D‑1323. Rockville, MD: U.S. Dept of Health and Human Services; June 15, 2018. https://www.fda.gov/files/food/published/Guidance-for-Industry–The-Declaration-of-Certain-Isolated-or-Synthetic-Non-Digestible-Carbohydrates-as-Dietary-Fiber-on-Nutrition-and-Supplement-Facts-Labels-PDF.pdf
Wong AW. Digesting FDA’s New Regulatory Definition of Dietary Fiber and its Impact on the US Food and Dietary Supplement Industry. RAPS. July 2018. Accessed July 2025. Available at: Digesting FDA’s New Regulatory Definition of Dietary Fiber and its Impact on the US Food and Dietary Supplement Industry https://www.raps.org/news-and-articles/news-articles/2018/7/digesting-fdas-new-regulatory-definition-of-dieta
