Skip To Main

Fiber 101 Guide

You already know that you should be eating more fiber: After all, the carb:fiber ratio is a key component of the Calibrate food program, and the lowest ratios are achieved when fiber plays a big role. But what does that really mean, and what’s the best way to do it?

First, let’s revisit carbohydrates

In order to really understand fiber (also called dietary fiber on a nutrition label), we need to zoom back out and start with carbohydrates: Carbs are made up of a combination of starches, sugars, and fiber. In Lesson 1 of the Nutrition Basics class, you learned that sugars are the simple carbohydrates that flood your system with glucose and cause your insulin to spike. But fiber is the magical part of the equation that helps slow down your digestion and keep your blood sugar stable. That’s why we talk so much about fast-digesting carbohydrates (more sugar, less fiber) and slow-digesting carbohydrates (more fiber, less sugar). 

10:1: The magic number

As luck would have it, nutrition labels don’t just tell us how many carbohydrates a food contains, they also separate out the fiber. This allows us to understand how much fiber a food contains relative to its carbohydrate content. Even better, research has shown that there’s a pretty clear line in the sand for when the ratio of total carbs to fiber is low enough to keep your blood sugar stable and when it isn’t. That threshold ratio is 10:1—anything above that is how we separate red foods from the rest. Anything below is Calibrate-approved.

What else does fiber do?

Most people hear fiber and think constipation relief (and they’re right—fiber does an excellent job of keeping you regular, which can be especially helpful if you’re taking GLP-1s). There are two sources of fiber: Soluble fiber absorbs water from partially-digested food, slowing down digestion. Insoluble fiber doesn’t absorb water and therefore helps food move more efficiently through your body. Both types pass through our systems relatively intact, helping you feel full for longer. 

Fiber also helps feed the bacteria in your microbiome and decrease inflammation. Plus, studies have shown that people with diets higher in fiber have better control over their cholesterol, blood sugar, and blood pressure—all of which helps reduce the risk of developing heart disease. In fact, there is a nine percent lower risk of heart disease for every additional seven grams a day of total fiber you consume (that’s about the equivalent of just one large pear).

Where to find fiber

Experts recommend that adults consume between 25 and 38 grams of fiber daily, yet the average American eats only 17 grams a day. Luckily, fiber is easily (and naturally) found in a great deal of whole, plant-based foods. And it’s no coincidence that most of them are considered green on the Calibrate Food Triangle:

  • Many fruits and vegetables are great sources, especially guava, berries, artichokes, canned pumpkin, green peas, Brussels sprouts, sweet potatoes, parsnips, jicama, broccoli, turnip greens, cauliflower, kale, kohlrabi, and avocados. (Remember: Intact versions of fruits and vegetables are better sources of fiber than juices, since the juicing process strips away most of the fruits’ fibrous parts.)
  • You can also find fiber in beans and legumes like navy beans, lima beans, cannellini beans, Adzuki beans, split peas, lentils, lupini beans, mung beans, black beans, and pinto beans.
  • Seeds and nuts can also be a fantastic option; just 1 ounce of chia seeds has close to 10 grams of fiber.
  • Intact whole grains — including barley, buckwheat, steel-cut oats, millet, quinoa, sorghum, and rye berries— can also be great sources of dietary fiber (and often are what many people think of first when considering fiber). Even so, at certain times during your Calibrate year, we’ll ask you to limit your grain intake at different times since they’re higher in fast-digesting carbohydrates than other sources of fiber.

Quality is key

One last important thing to note: Many processed cereals, breads, tortillas, and granola bars may seem to be all-star sources of fiber, but most of the time these foods have added synthetic or functional fibers that are made from starches or sugars (Tip: on a nutrition label, you’ll find these synthetic fibers in the form of words like oat fiber, soluble corn fiber, guar gum, locust bean gum, cellulose, beta-glucan soluble fiber, pectin, psyllium husk, and hydroxypropylmethylcellulose). 

While the quality of this fiber can still be solid, it can’t make up for the other ingredients that can cause damage to your metabolic system. Let’s think about Fruit Loops for a minute: Each cup has around three grams of fiber and a carb:fiber ratio of around 8:1. But you already know that sugary cereal isn’t supportive of your metabolic health: The bulk of its fiber content comes from added synthetic fibers and, like most ultra-processed foods, it’s also packed with added sugars and harmful additives like red 40 and yellow 5.

Oftentimes throughout the Calibrate curriculum, you’ll find that we recommend pairing fiber-free foods, like a sweetened mug of tea, with a fiber-rich snack to help slow down your body’s absorption of the sugar. You might be thinking, well, how is that any different than eating fiber-fortified Fruit Loops? Or pairing a plate of mac and cheese or a piece of chocolate cake with a spoonful of metamucil?

First off, dosage is important here: When you’re adding sugar to food or drinks yourself, stick to ½ teaspoon or less. Secondly, if you find yourself getting caught up trying to “game” the system, zoom back out and remember your year-long food pillar goal. Yes, the objective is to keep your insulin levels from spiking, but it's also to give your body the building blocks it needs to support you (we’re talking fiber, protein, and healthy fats, yes—but also vitamins, nutrients, and antioxidants). You won’t find any of those in a fortified sugary cereal or a metamucil-assisted meal. That’s why studies have shown that people who have obesity are often malnourished: Processed foods are lacking in true nutrition.

Instead, it’s much more delicious (and nourishing) to eat the foods you know your body needs the majority of the time, and occasionally enjoy a meal that feels indulgent without the need for a “hack.”

Easy ways to boost your fiber intake

The options for adding fiber to your daily routine are endless. Some of our favorites include:

  • Start your day strong. Instead of sugary cereals, opt for oats: A cup of rolled oats has eight grams of fiber and a cup of steel-cut oats has a whopping 16 grams. Plus, they’re a great blank canvas for berries, chia seeds, apples, almonds, and other fiber-filled foods. 
  • Power up your smoothies. Why should fruit have all the fun? Amp up the fiber content by tossing in a spoonful of chia or flax seeds, a sprinkle of nuts (cashews are great for adding a creamy texture), one or two dates for sweetness, or even a handful of spinach or frozen cauliflower (it’s virtually impossible to taste!).
  • Snack smarter. Pair an afternoon cup of tea with something that’s packed with fiber, like popcorn or crunchy chickpeas. Or, satisfy midday hunger with hummus and carrots or mashed avocado. 
  • Lean on beans and legumes. Replace some of the ground meat in chilis, burgers, Sloppy Joes, or even burritos with canned or presoaked beans or lentils. Add lentils to your homemade spaghetti sauce or make a bolognese with kidney beans. These are budget-friendly ways to bulk up dishes and amp up the fiber content, but are barely distinguishable taste-wise. 
  • Up your garnish game. Nuts and seeds can add both crunch and fiber to soups, stews, and salads. Sprinkle a handful of chopped pecans onto a bowl of butternut squash soup or top your salads with pomegranate arils.
  • Switch up your sides. Add variety to your dinner routine by swapping in different ancient grains to pair with your proteins and veggies. Serve quinoa, buckwheat, and fonio as you would rice—cooked, fluffed, and lightly seasoned. Try making a “risotto” with farro or pearl barley. Combine cooked bulgur with tomatoes, cucumbers, scallions, lemon juice, and herbs, then chill to make tabbouleh. For a quick-and-hearty side salad, toss cooked sorghum or freekeh with greens and dressing. 
  • Make sweet swaps. Craving something sweet? Consider snacking on fresh guava or mangoes. Or try baked apples or pears sprinkled with cinnamon.

And remember to take your time! Add fiber into your routine gradually to prevent bloating, abdominal pain, cramping, and/or gas. Whenever you’re working to increase your fiber consumption, Increase the amount of fluids you drink as well. Water will help to ensure that the extra fiber passes through your system smoothly, so you can focus on the positive side effects of fiber-packed foods.