Fake Fiber Doesn’t Keep you Full

A new study published in the Journal of the Academy of Nutrition and Dietetics recently took a look at the effect of functional fibers on satiety.

Evidence is amassing about the effect of increased fiber intake on satiety (the feeling of fullness). But whether or not these effects are realized from functional (added) fibers as well as they are from intact fibers remains to be seen.

The researchers from the University of Minnesota examined four different types of functional (fermentable) fibers that are commonly found added to foods and beverages that are traditionally low in fiber (hence, the “fake” fiber moniker):

  • Oligofructose
  • Inulin
  • Soluble corn fiber
  • Resistant wheat starch

They recruited 22 women aged 18-40 with a BMI between 18-29, from the low end of healthy weight to overweight BMI categories.

The participants were fed chocolate crisp bars with 10 g of their assigned fiber with a no-fiber bar acting as a control. Participants were then routinely administered a questionnaire asking details about feeling of fullness and were subject to breath analysis tests to determine rates of fermentation.

By analyzing hydrogen breath excretion, the researchers found that oligofructose, inulin and soluble corn fiber were fermented in the colon, whereas resistant wheat starch was not. They were unable to determine any variation in the level of fullness based on different fiber bar consumption, stating that, “No differences were found in subjective satiety during the morning or food intake at lunch or over 24 hours.”

In their comments, the researchers also note that:

  • The most gas and bloating occurred with the oligofructose bar
  • Chronic consumption of fermentable fibers may be required to provide satiety benefits
  • Variations in physical characteristics and how types of fiber are processed in and interact with the human GI tract influence physiologic effects
  • One fiber type may not elicit the physiologic effects of another, such as inducing a feeling of satiety
  • It is difficult to assign specific effects to single food ingredients that may or may not act differently depending on food structure and interactions within that food matrix

Although the study sample size was small, it does drive home the idea that all fibers are not created equal.

Your best bet? Stick to foods that are naturally high in fiber – like whole grains, fruits, vegetables and legumes – and don’t bank on fake fibers to keep you feeling full.