Chemical and enzymatic interesterification are used to create spreadable fats. However, a comparison between the two processes in terms of their acute metabolic effects has not yet been investigated. A randomised crossover study in obese (plasma TAG > 1.69 mmol/L, and BMI > 30 (BMI = kg/m(2)) or waist circumference > 102 cm, n = 11, age = 59.3 +/- 1.8 years) and non-obese (plasma triacylglycerol (TAG) < 1.69 mmol/L, and BMI < 30 or waist circumference < 102 cm, n = 10, age = 55.8 +/- 2.2 years) men was undertaken to compare the effects of chemical versus enzymatic interesterification on postprandial risk factors for type 2 diabetes (T2D) and cardiovascular disease (CVD). TAG, cholesterol, glucose, insulin and free fatty acid concentrations were measured for 6 h following consumption of 1 g fat/kg body mass of non-interesterified (NIE), chemically interesterified (CIE), enzymatically interesterified (EIE) stearic acid-rich fat spread or no fat, each with 50 g available carbohydrate from white bread. Interesterification did not affect postprandial glucose, insulin, free fatty acids or cholesterol (P > 0.05). Following ingestion of NIE, increases in serum oleic acid were observed, whereas both oleic and stearic acids were increased with CIE and EIE (P < 0.05). While postprandial TAG concentrations in non-obese subjects were not affected by fat treatment (P > 0.05), obese subjects had an 85% increase in TAGs with CIE versus NIE (P < 0.05). The differences in TAG response between non-obese and obese subjects suggest that interesterification may affect healthy individuals differently compared to those already at risk for T2D and/or CVD.