HEALTH NEWS

Study Title:

Soluble Fiber Lowers Increase in Abdominal Fat

Study Abstract

The objective of this study was to examine whether lifestyle factors were associated with 5-year change in abdominal fat measured by computed tomography (CT) in the Insulin Resistance and Atherosclerosis (IRAS) Family Study. We obtained abdominal CT scans at baseline and at 5 years, from African Americans (AA) (N = 339) and Hispanic Americans (N = 775), aged 18–81 years. Visceral (VAT) and subcutaneous (SAT) adipose tissue was measured at the L4/L5 vertebral level. Physical activity was documented by self-report of vigorous activity and a 1-year recall instrument. Dietary intake was assessed at follow-up using a semi-quantitative food frequency questionnaire referencing the previous year. Generalized linear models, accounting for family structure, were used to assess the associations between percent change in fat accumulation and smoking, physical activity, total calories, polyunsaturated, monounsaturated, protein, and saturated fat intake, percent of calories from sweets, and soluble and insoluble fiber. Soluble fiber intake and participation in vigorous activity were inversely related to change in VAT, independent of change in BMI. For each 10 g increase in soluble fiber, rate of VAT accumulation decreased by 3.7% (P = 0.01). Soluble fiber was not associated with change in SAT (0.2%, P = 0.82). Moderately active participants had a 7.4% decrease in rate of VAT accumulation and a 3.6% decrease in rate of SAT accumulation versus less active participants (P = 0.003 and P = 0.01, respectively). Total energy expenditure was also inversely associated with accumulation of VAT. Soluble fiber intake and increased physical activity were related to decreased VAT accumulation over 5 years.

From press release:

All fat is not created equal. Unsightly as it is, subcutaneous fat, the fat right under the skin, is not as dangerous to overall health as visceral fat, the fat deep in the belly surrounding vital organs.

According to a new study by researchers at Wake Forest Baptist Medical Center, the way to zero in and reduce visceral fat is simple: eat more soluble fiber from vegetables, fruit and beans, and engage in moderate activity.

The study found that for every 10-gram increase in soluble fiber eaten per day, visceral fat was reduced by 3.7 percent over five years. In addition, increased moderate activity resulted in a 7.4 percent decrease in the rate of visceral fat accumulation over the same time period.

"We know that a higher rate of visceral fat is associated with high blood pressure, diabetes and fatty liver disease," said Kristen Hairston, M.D., assistant professor of internal medicine at Wake Forest Baptist and lead researcher on the study. "Our study found that making a few simple changes can have a big health impact."

Ten grams of soluble fiber can be achieved by eating two small apples, one cup of green peas and one-half cup of pinto beans; moderate activity means exercising vigorously for 30 minutes, two to four times a week, Hairston added.

In the longitudinal study, published in the June 16 online issue of the journal Obesity, researchers examined whether lifestyle factors, such as diet and frequency of exercise, were associated with a five-year change in abdominal fat of African Americans and Hispanic Americans, populations at a disproportionally higher risk for developing high blood pressure and diabetes and accumulating visceral fat.

At the beginning of the study, which involved 1,114 people, the participants were given a physical exam, an extensive questionnaire on lifestyle issues, and a CT scan, the only accurate way to measure how much subcutaneous and visceral fat the participants had. Five years later, the exact same process was repeated.

Researchers found that increased soluble fiber intake was associated with a decreased rate of accumulated visceral fat, but not subcutaneous fat.

"There is mounting evidence that eating more soluble fiber and increasing exercise reduces visceral or belly fat, although we still don't know how it works," Hairston said. "Although the fiber-obesity relationship has been extensively studied, the relationship between fiber and specific fat deposits has not. Our study is valuable because it provides specific information on how dietary fiber, especially soluble fiber, may affect weight accumulation through abdominal fat deposits."

Hairston's next study, expected to be in clinical trials later this summer, will examine whether increasing soluble fiber with a widely available fiber supplement will produce similar results to those obtained in this study using soluble fiber from food.

Study Information

Kristen G. Hairston, Mara Z. Vitolins, Jill M. Norris, Andrea M. Anderson, Anthony J. Hanley, Lynne E. Wagenknecht
Lifestyle Factors and 5-Year Abdominal Fat Accumulation in a Minority Cohort: The IRAS Family Study
Obesity
2011 June
Wake Forest Baptist Medical Center.