INTRODUCTION
Dietary fiber may play a role in obesity prevention
- more satiating due to their relatively low energy density and palatability
- soluble fiber increases the viscosity of diets and slows down the digestion
- to provide a mechanical barrier to the enzymatic digestion of other macronutrients
- to reduce postprandial blood glucose response
aim: The association of total dietary fiber, cereal fiber, and fruit and vegetable fiber with changes in weight and waist circumference
SUBJECTS AND METHODS
Participants
- A part of the DiOGenes (Diet, Obesity, and Genes) project, a multidisciplinary European project targeting obesity
- The European Prospective Investigation into Cancer and Nutrition (EPIC) study: Florence, Italy; Norfolk, United Kingdom; Amsterdam, Maastricht, and Doetinchem, Netherlands; Potsdam, Germany; and Copenhagen and Aarhus, Denmark
- 89,432 European participants, aged 20–78 y, who were free of cancer, cardiovascular disease, and diabetes at baseline
- Prospective cohort study: followed for an average of 6.5 y
Dietary assessments
- Country-specific validated country-specific food-frequency questionnaires: twelve 24-h diet recalls (Italy, Germany, and Netherlands), 16 d of weighed records (United Kingdom), or 7 d of weighed diet records (2 times) (Denmark)
- The enzymatic-gravimetric method adopted by the Association of Official Analytical Chemists (AOAC)
- United Kingdom: nonstarch polysaccharides (by multiplying 1.28 and by subtracting 0.02) using the Englyst method
- Total dietary fiber: all foods and beverages
- The weighted average of the dietary glycemic index (GI) values of carbohydrate-containing foods consumed daily
- A linear calibration was performed with the use of a single 24-h dietary recall from a stratified random sample (n = 6790) of the total EPIC participants
Anthropometric measurements
- Body weight and waist circumference
- Doetinchem (Netherlands) and Norfolk (United Kingdom): by trained technicians according to the same protocols
- Other participants: self-reported
- Florence (IT-Flo, n = 8266), Norfolk (UK-Nor, n = 12,031), Amsterdam and Maastricht (NL-AmMa, n = 6226), Doetinchem (NL-Doe, n = 3964), Potsdam (GER-Pot, n = 14,746), and Copenhagen and Aarhus (DK-CopAa, n = 33,804)
Other covariates
- Demographic information
- age
- sex
- educational level: primary school or less, technical-professional school, secondary school, university, or unknown
- physical activity: inactive, moderately inactive, moderately active, active, or unknown
- smoking: stable smoking, start smoking, quit smoking, not smoking, or unknown
- menopausal status
- use of hormone replacement therapy
- Health status: the presence of CVD, cancer, and type 2 diabetes
- weight (kg), height (cm), and waist circumference, alcohol intake (non-drinker, 0.1–4.9 g/d, 4.9–15 g/d, 15–30 g/d, 30–60 g/d, .60 g/d), GI, and the intake of protein, fat, and carbohydrate
Statistical methods
Center-specific analyses were conducted, after which random-effect meta-analyses were performed to detect heterogeneity among study centers ($I^2$) and to calculate pooled estimates
- to allow for heterogeneity not only in the effect of the exposure but also in the influence of the confounders
- to estimate the extent of heterogeneity and leads to a natural presentation of the results on a forest plot
Sensitivity analyses: uncalibrated dietary variables, anthropometrics correcting for clothing and self-reporting, and by excluding those participants who developed cancer, type 2 diabetes, or CVD during follow-up
RESULTS
The total fiber was inversely associated with subsequent weight and waist circumference change. Fruit and vegetable fiber was not associated with weight change but had a similar association with waist circumference change when compared with intake of total dietary fiber and cereal fiber
DISCUSSION
Strengths
- The large sample size and the large variation of fiber intake among participants from 5 different European countries
- To standardize the measurements across all EPIC centers
Limitations
- The difference in methodologies used to collect anthropometric data at follow-up
- Dietary information was collected only once at baseline
Benefit weight control
- High-fiber diets are more satiating and can lead to a reduced energy intake
- Fiber can limit the access of other nutrients to digestive enzymes
- Increasing fiber intake can improve insulin sensitivity and stimulate fat oxidation
Distinguishing the effects of fiber from different sources on weight and waist circumference gain is potentially important for formulating public health guidelines. Epidemiologic studies, in contrast, show that cereal fiber, and principally insoluble fiber, appear to offer protection from CVD and diabetes.
A higher intake of fiber, especially of cereal fiber, is beneficial for preventing (abdominal) obesity.
