Effects of a carbohydrate-restricted diet with and without supplemental soluble fiber on plasma low-density lipoprotein cholesterol and other clinical markers of cardiovascular risk

Metabolism. 2007 Jan;56(1):58-67. doi: 10.1016/j.metabol.2006.08.021.


Carbohydrate-restricted diets (CRDs) promote weight loss, reductions in plasma triacylglycerol (TAG) levels, and increases in high-density lipoprotein cholesterol (HDL-C) levels but may cause undesirable low-density lipoprotein cholesterol (LDL-C) responses in some people. The objective of the present study was to determine the effect of adding soluble fiber to a CRD on plasma LDL-C and other traditionally measured markers of cardiovascular disease. Using a parallel-arm, double-blind, placebo-controlled design, 30 overweight and obese men (body mass index, 25-35 kg/m(2)) were randomly assigned to supplement a CRD with soluble fiber (Konjac-mannan, 3g/d) (n = 15) or placebo (n = 15). Plasma lipids, anthropometrics, body composition, blood pressure, and nutrient intake were evaluated at baseline and at 6 and 12 weeks. Compliance was excellent as assessed by 7-day weighed dietary records and ketonuria. Both groups experienced decreases in (P < .01) body weight, percent body fat, systolic blood pressure, waist circumference, and plasma glucose levels. After 12 weeks, HDL-C and TAG improved significantly in the fiber (10% and -34%) and placebo (14%, -43%) groups. LDL-C decreased by 17.6% (P < .01) at week 6 and 14.1% (P < .01) at week 12 in the fiber group. Conversely, LDL-C reductions were significant in the placebo group only after 12 weeks (-6.0%, P < .05). We conclude that although clearly effective at lowering LDL-C, adding soluble fiber to a CRD during active and significant weight loss provides no additional benefits to the diet alone. Furthermore, a CRD led to clinically important positive alterations in cardiovascular disease risk factors.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Blood Glucose / metabolism
  • Blood Pressure
  • Body Composition / physiology
  • Body Weight / physiology
  • Cardiovascular Diseases / blood
  • Cardiovascular Diseases / prevention & control*
  • Cholesterol, HDL / blood
  • Cholesterol, LDL / blood*
  • Diet, Carbohydrate-Restricted / methods*
  • Dietary Fiber / administration & dosage
  • Double-Blind Method
  • Humans
  • Insulin / blood
  • Male
  • Mannans / pharmacology*
  • Middle Aged
  • Triglycerides / blood


  • Blood Glucose
  • Cholesterol, HDL
  • Cholesterol, LDL
  • Dietary Fiber
  • Insulin
  • Mannans
  • Triglycerides
  • (1-6)-alpha-glucomannan