After four weeks the glucomannan group had a substantial decrease in cholesterol levels of 20.9mg/dl whereas the cholesterol levels of the placebo group increased by 5.9mg/dl.
(International Journal of Obesity, 1984, Effect of Glucomannan on obese patients; A clinical study)

A study of the soluble fibre Konjac glucomannan on serum cholesterol concentration was investigated in 63 healthy men who were encouraged not to change their usual diet or lifestyle. The findings showed that Glucomannan fibre reduced total cholesterol concentrations by 10%, LDL cholesterol by 7.2%, triglycerides by 23% and systolic blood pressure by 2.5%.
(American Journal of Clinical Nutrition, 1995, Effects of short term ingestion of Konjac glucomannan on serum cholesterol in healthy men)

A literature search of different research studies carried out on the effects of glucomannan fibre was analysed in order to reach an average finding conclusion of the 14 studies. All findings were compared to reach an average finding and concluded that the use of glucomannan significantly lowered total cholesterol, LDL cholesterol, tryglycerides and body weight.
(Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure:systematic review and meta-analysis, 2008, American Journal of Clinical Nutrition)

In a study run over 4 weeks, to evaluate the benefits of glucomannan on glycemic and lipid controls in Type 2 Diabetic patients, there were significant findings.
It concluded that in type 2 diabetes, glucomannan ingestion reduced the rise of blood glucose without significantly affecting insulin levels. Long term supplement of glucomannan to the regular diabetic regimen lessened post challenge glucose levels and impeded the rise of LDL cholesterol. Glucomannan may be beneficial to the glycemia and lipid controls in Type 2 Diabetes.
(J Med Assoc Thai, 2007, Glycemic and Lipid Response to Glucomannan in Thais with Type 2 Diabetes Mellitus)

In a study aimed at evaluating, in type 2 Diabetic subjects, the glycaemic and insulinemic increments after a standard breakfast with glucomannanos enriched biscuits and with common slices of toast with the same amounts of carbohydrates and calories. The results show a reduction in glycaemic increments after breakfast with the glucomannanos biscuits. The decreased insulin secretion and the reduction of insulin can longer preserve the functional reserve of beta-cells of the pancreas.
(Pub Med. Gove, 1992, Dietary fibre in the dietetic therapy of diabetes mellitus. Experimental data with purified glucomannans)

In a study which aimed to investigate the effect of supplementing a high carbohydrate diet with fibre from Konjac-mannan on metabolic control in subjects with the insulin resistance syndrome had notable results. It concluded that a diet rich in high viscosity Konjac-mannon improves glycemic control and lipid profile, suggesting a therapeutic potential in the treatment of the insulin resistance syndrome.
(American Diabetes Association, 2000, Beneficial effects of viscous dietary fibre from Konjac-mannan in subjects with the insulin resistance syndrome: results of a controlled metabolic trial)