BETA-CELL DETERIORATION DETERMINES THE ONSET AND RATE OF PROGRESSION OF SECONDARY DIETARY FAILURE IN TYPE-2 DIABETES-MELLITUS - THE 10-YEARFOLLOW-UP OF THE BELFAST DIET STUDY

Secondary failure of plasma glucose control following initial successf ul response to diet therapy may be due to dietary indiscretion, or to progression of the intrinsic diabetic condition. We report a 10-year p rospective natural history study of 432 newly diagnosed diabetic patie nts aged 10-69 years undertaken to assess the effect of intensive diet ary management, where patients were transferred to insulin, or oral hy poglycaemic therapy (tolbutamide, metformin) by predetermined criteria of weight and plasma glucose. Secondary failure to diet therapy occur red in 41 patients in years 2-4, 67 patients in years 5-7, and 51 pati ents in years 8-10; 173 patients remained on diet alone until death or the end of the study. Continuation on diet alone was associated with a lower ongoing fasting plasma glucose, greater beta-cell function ass essed by an oral glucose tolerance test at 6 months, and increasing ag e. The rate of rise of fasting plasma glucose was inversely related to the duration of successful dietary therapy, but mean weight remained constant in all groups while on diet alone. The ongoing fall in beta-c ell function assessed by HOMA modelling closely mirrored the progressi ve rise in fasting plasma glucose: there was no change in mean insulin sensitivity in any of the groups. (C) 1998 John Wiley & Sons, Ltd.