The effect of various grades of obesity on serum fructosamine concentr
ations was studied in Type 2 diabetic (n = 105) and non-diabetic (n =
128) subjects. In obese diabetic and non-diabetic subjects (body mass
index greater-than-or-equal-to 30 kg m-2), the concentration of fructo
samine was markedly lower than that obtained for lean diabetic and non
-diabetic subjects with similar glycaemic control. Stepwise multiple-r
egression analysis showed that fructosamine was associated with glycae
mic control (as indicated by fasting plasma glucose and glycated haemo
globin), fasting triglycerides, and body mass index in both diabetic a
nd non-diabetic subjects. In vitro studies showed marked decreases in
both the extent of [C-14]-glucose incorporation into plasma proteins a
nd fructosamine production by incubated sera of obese patients whether
diabetic or non-diabetic, with obese subjects with body mass index >
40 kg m-2 exhibiting the greatest decrease. In conclusion, serum fruct
osamine concentrations are shown to decrease in obese diabetic and non
-diabetic subjects with body mass index greater-than-or-equal-to 30 kg
m-2 giving rise to the underestimation of glycaemic control as indica
ted by fructosamine measurement. A change in the glycation reaction it
self may be partly responsible for such decrease.