Fiber Q&A: Tanya Zuckerbrot

Thank you all for your suggestions and questions about fiber. I was able to integrate your ideas with my own and had an extremely interesting and pleasant interview with NYC dietitian, Tanya Zuckerbrot, this morning. She is the author of The F-Factor Diet and the answers she provided really helped me make sense of just why fiber is such a necessary part of a healthy diet. Read on for the full interview. I hope you’ll find it as interesting as I did!


I know it’s important to incorporate fiber into my diet every day, but I don’t really have a solid concept of exactly what ‘fiber’ is. Can you explain the science behind it?

Fiber is the indigestible part of carbohydrates. In other words, your body can’t break it down so it leaves your body. It’s very important for weight management and for the prevention of many diseases because fiber binds with cholesterol and other toxins and pulls them from your body, reducing the risk for cardiovascular disease and certain cancers. It also helps with issues such as constipation because it increases stool bulk. It is recommended that we take in 25g of fiber per day, yet 9 out of 10 Americans do not meet those goals.

What is the difference between soluble and insoluble fiber? Which one is more important? How much of each should I be getting daily?

Don’t worry about insoluble vs. soluble fiber, just focus on total dietary fiber. They both have health benefits – you can think of soluble fiber as a sponge to absorb cholesterol and other bodily toxins, and insoluble fiber as a broom that helps move things along in digestion. They’re both essential, so you don’t need to worry about how much you’re getting of each – just make sure you’re getting at least 25g of total dietary fiber.

What are some of the other benefits of fiber?

Fiber is so hot right now. The research shows us that fiber keeps you feeling full. Two-thirds of Americans are overweight, and I 100% believe one of the reasons we are so hungry and eating more is because we’ve stripped the fiber content from food. Fiber keeps you feeling full for a long period of time, which means you are less likely to need to snack or overeat at the next meal. It therefore allows you to curb consumption and, at the end of the day, the foods are nutrient dense but not calorically dense. So many diets fail because people focus on what they are cutting out. A high fiber diet is about what you’re adding in. My patients can’t believe how full they feel! At the same time, they are losing weight.

What are some sources of fiber?

You can find fiber naturally occurring in high fiber cereals, whole grains, or berries. For example, 1 cup of raspberries has 8g of fiber, and one serving of Fiber One has 14g of fiber. If you have both with some milk for breakfast, you’ve achieved 22g of fiber through breakfast alone. You can find fiber in popcorn, beans, and vegetables. There are also a lot of new products that have fiber added to them such as orange juice and yogurt.

What’s your take on these foods with added fiber? Does it actually work like real fiber found in whole grains, fruits and veggies?

Added fiber is called imulin and comes from chicory root. It’s a soluble fiber that doesn’t alter the taste or texture of food. Imulin promotes regularity just like the natural fiber you find in whole grains or fruits. And unlike taking a fiber pill, you get even more health benefits because it’s put into food, thereby enhancing the composition of a food that’s already healthy. I’m averse to supplementing your diet via pills, but with imulin, it’s being put into food so you get those other nutrients. With yogurt, for example, you are getting the added fiber, but it also contains calcium and vitamins – not just fiber. Natural fiber is obviously the best, but if you’re drinking orange juice or yogurt you might as well get fiber! If you’re going to use Splenda, use it with fiber. Why not?

What are some easy ways to incorporate more fiber into our diet? What are YOUR favorite ways to sneak fiber into your diet?

Some of my favorite sources of fiber are raspberries, popcorn, lentils, whole wheat spaghetti, pistachios, and Gnu bars. The truth is, as fiber becomes more and more popular, it’s never been easier or more delicious to meet our fiber needs. When I first started F-Factor, the choices were limited, but now no matter where you are or what your socioeconmic status is, you can eat foods with fiber.

I have to ask, is there such a thing as too much fiber?

It’s hard enough for Americans to get enough fiber in the first place! Some research has shown that around 60, 70 or 80g you may begin to leak out certain vitamins. But most Americans don’t come anywhere close to that level anyway. I eat roughly 50g of fiber every day. The key here is that if you are starting to incorporate more fiber into your diet, it should be done gradually – if you start out with no fiber and then jump into it, you’re going to have stomach complications. Introduce it slowly by eating 1 or 2 high fiber foods every day and then build upon that. Eating as much as 50g of fiber is not going to hurt you if you do it gradually and get used to it.

How can you avoid bloating after eating too much fiber?

The biggest fiber myth is that fiber bloats you. Initially, if you’re not accustomed to it, you may feel some discomfort. But it eventually passes, and you’ll have just the opposite – the flattest stomach ever and the best bowel movement in your entire life. You can maintain a healthy body weight without struggle.

I’ve heard about a ‘net carb effect’ in foods with fiber. Is it true that we do not absorb the calories from fiber in those products?

This is the science on how fiber leads to weight loss. When you eat carbohydrates, whether it’s fruit, milk, yogurt, or starches, they contain carbs. Carbohydrates and sugars get converted into glucose, which gets stored in the body as glycogen. Glucose is energy for your body – in other words, if your body is a car, you have to fill that tank up with gas [glucose]. If you fill up the car with too much gas, it will overflow, just like your body. When you eat carbs, the glycogen is stored in your liver or your muscles, so you actually have two gas tanks. If you were to overfill both of those tanks, your body would say that the extra carbs should be converted into something else in case a famine occurs, so it gets stored as body fat.

The deal with net carbs is that if you have a slice of white bread vs. whole wheat:

White bread = 15g – 0g fiber = 15g net carbs

Whole wheat bread = 15 – 5g fiber = 10g net carbs

We subtract the fiber grams because it is not digested, so the net carb is what’s leftover that gets converted into glucose. That net is the glucose that is stored as glycogen. You want to eat foods with fiber so there is less overall net carbs. So if there are two yogurts and one has 21g carbs and no fiber, and the other contains fiber, you’ll want to choose the one with fiber because it will leave you with less carbs and less chance of weight gain.

Is there an ideal ‘net carb’ range for everyone?

The difference is in muscle mass. The more muscle you have, the more room you have for carbs. So if we’re using the car analogy again, it is possible that you can make that tank bigger. Men have more muscle and can therefore store more carbs than women. Women also tend to focus a lot on cardio, but if you devote time to strength training as well, you’ll be able to handle more carbs.

We’ve talked about the link between fiber and weight loss. What if a person is looking to gain weight?

If a person looking to gain weight is taking in a lot of fiber, I can understand why they might not see results. If he or she is feeling so full because of the fiber, he or she may not be getting enough calories in because foods with a lot of fiber tend to have less calories. But I would say it’s important to keep the fiber in your diet because you don’t want to cut out the benefits you get from it. Instead, I would focus on adding healthy fats such as avocado, olive oil, and nuts. They help to add in calories, but you don’t want to take the fiber out because foods that contain fiber are so healthy.

What are some of the basic aspects of The F-Factor Diet? How has it been successful?

I didn’t start my career with the intention of making a diet – my job was to help diabetic patients control their sugar levels and I also worked with cardiovascular patients. In working with them and their diets, I discovered that not only were they getting healthier – they all lost weight, too. I looked at the common denominators between both groups and realized they all had high fiber in their diets. That’s when it occurred to me that someone can lose weight without hunger. The more fiber in the food, the fuller you feel, so the less likely you are to overeat. But you actually take in fewer calories, so you’re feeling full and losing weight. And as more and more companies add fiber to their foods, it’s never been easier. I always say that I don’t like to dictate, I like to educate. So I show people why they should add more fiber to their diet.

Anything else that we haven’t covered that you feel is important?

I recommend visiting Fiber One’s Fiber Friend Face Off. It’s an interactive game online where you go up against a challenger and pick five foods to see if you can meet the 25g of fiber goal per day. It teaches you what foods contain fiber and what don’t in a fun way. You can also enter to win coupons and prizes.

I also recommend that my patients use a journal to keep track  of their fiber intake. People want to lose weight but they want to do it the healthy way. Introducing fiber will help, and you’re eating real foods so it’s not restrictive. You also don’t have to have a lot of money. Just make simple substitutions: if you eat a piece of fruit, instead of a melon get more fiber from an apple, and if you have rice, make it brown instead of white. Being overweight increases the risk for morbidity. Adding fiber is one of the easiest things you can do to feel healthy.


Thank you so much to Tanya Zuckerbrot for provided such thorough and insightful answers. I learned a lot and I hope that my readers did, too!

{ 2 comments… read them below or add one }

1 matt March 28, 2009 at 11:13 am

This blog’s great!! Thanks :).


2 sngglebnny June 27, 2009 at 4:43 pm

Is there a difference between fiber in foods and fiber in drink mixes? I have problems with weight gain and constipation because my digestive system is unusually slow. Doctors bounce between telling me to include more fiber in my diet and drink more water.

For over three years, I drink mostly water anyways and have tried several fiber combinations. Juice or a sugary drink is a treat that I might have with a meal as often as once a week, but I can go without for quite a while. I have tried fiber supplements, powders, and drink mixes. I have also tried fiber bars, wafers, and high fiber foods in general.

My body does not seem to recognize the fiber in the food, and in order to get the 25g out of food fiber you’ve got to eat a lot of it. In turn, you are eating a lot of everything else that comes with it. The supplemental fiber seems to work great but only work for a few weeks. Extended use brings gas, bloating, and constipation.

I have found one drink mix that I like, All Bran Fiber Drink Mix in Pink Lemonade. In the past two months, I have and am still having wonderful results. Which leads me to ask is there a difference between all of these fibers?


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