Dietary fiber: A ‘magic bullet’ for healthy weight management

If I had to name one single food constituent that is most helpful for weight management, it would be dietary fiber. It just has so many benefits and strangely has been researched much less for its weight management benefits than many other dietary factors, but the science is all positive and just keeps getting stronger and stronger.


Fiber is Filling

My favorite fiber benefit is that it is filling… because nobody wants to walk around feeling hungry when they are trying to lose weight, and research from my laboratory has shown that weight loss success is strongly linked to fiber intake: the more fiber, the more weight disappears!


The Types of Fiber

Of course, not all fibers are equal, and I’m taking here first and foremost about the ‘insoluble’ fibers found in wheat, corn and other similar grains.

There are two different basic types of fiber: 

Soluble fibers are ones that dissolve easily to form a gel, and are generally “fermentable” which simply means they feed the good bacteria in your large intestine. .

Insoluble fibers do not dissolve and are generally inert, providing bulk without fermentation.

My favorite diet tool are the insoluble fibers that don’t get fermented in the large intestines because they don’t provoke gas and bloating in those who have that susceptibility. The ‘soluble’ fibers found in fruit, vegetables and grains like oats and barley are also good, too, but too much, especially if you increase your intake very rapidly, can lead to intestinal discomfort, which nobody enjoys. We do recommend soluble fiber, but if you are just starting with fiber, increase your soluble fiber sources slowly, and make sure you get lots of liquids with either form of fiber you eat.


Fiber for Hunger Control

Fiber also has another benefit for reducing cravings, because feeling full helps reduce temptation. What I mean is that increasing fiber is one of the best ways to way to prepare to lose weight, since it helps you feel full and satisfied. We recommend at least two days of higher fiber before starting the iDiet weight loss program, because it is remarkable how that reduces temptation and makes embarking on weight loss seem like a small step rather than something that is overwhelming.

It can be as easy as a bowl of one-half cup of high fiber cereal with 30-calorie almond milk or skim dairy milk twice a day for two days. Or if you want to make my easy iDiet Brownie Bites recipe at the end of this blog, you can enjoy your fiber in an indulgent-but-healthy form!


Fiber for Fat Loss

Yet another benefit of fiber for weight management identified by my research lab at Tufts University is that it increases metabolic rate and energy (calories) lost in stool, because the fiber sweeps some undigested nutrients down the intestine, prevention absorption. Just increasing fiber to the recommended intakes in the USDA’s My Plate guidelines [ https://www.myplate.gov/eat-healthy/what-is-myplate] compared to a typical unhealthy low-fiber American diet increased energy losses by these two routes by nearly 100 kcal a day. You can think of that as either 700 extra calories of fat lost per week… or 100 calories of additional food you can enjoy each day for the same weight loss you would have without the fiber 


Fiber for Health

Fiber also has lots of great health benefits too, via increasing the number of helpful microbes in the large intestine. People who consistently eat a diet with plenty of fiber and not too many highly process foods have a complex colony of healthier microbes that help protect against diabetes, hypertension, chronic constipation and a host of other ‘noncommunicable diseases’ that are unfortunately all too common today.

Almost everyone will achieve health benefits from extra fiber! So look to see where you can conveniently add more to your day. Though if you have any concerns about adding more fiber, or different forms of fiber to your diet, we encourage you to consult with your doctor first before changing your diet.

Dr Susan Roberts’ Raw Brownie Bites Recipe

8 servings

This recipe calls for several ingredients, but all are things we use in the regular iDiet menu plans so nothing goes to waste!


1 ¼ cups All Bran Original cereal (or see this fiber cereal blog post for alternatives)
2 tsp nut butter of your choice (peanut, cashew, almond, etc)
1/3 cup unsweetened dutch-process cocoa
½ cup plus 1 T 30-calorie unsweetened almond milk
¼ cup plain fat-free Greek-style yogurt
2 tsp chia seeds
Non-calorie sweetener of your choice such as stevia: 8 packages or to taste


Mix together the cereal and almond milk and allow to stand for about 15 minutes until they can be mashed with a fork to mix well.
Add all the remaining ingredients except the chia seeds and mash together.
You should have a stiff but slightly sticky mass (add a little more almond milk if too stuff).
Mix in the chia seeds and divide into 8 pieces. Roll each one into a round in your hand.
At this point your raw brownie bites are ready and deliciously filling – they freeze well wrapped in saran wrap — which is a great tip to prevent over-eating: Keep them in the freezer and only defrost what you need.

Nutrition Facts per 1 brownie bite
57 calories, 3 grams protein, 6 grams fat, 29 grams total carbohydrate, 12 grams fiber

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