Plasma β-hydroxybutyrate concentrations were measured in the offspring of rats that were fed either a control (20% protein) diet or low-protein (8% protein) diet during pregnancy and lactation. Low-protein offspring had significantly lower plasma β-hydroxybutyrate compared with controls in the fed state ( P < .04) and after fasting for 24 hours ( P < .001) and 48 hours ( P < .04). There were no differences in blood glucose, acetoacetate, plasma glucagon, cholesterol, or glycerol between control and low-protein offspring. However, plasma nonesterified fatty acids (NEFAs) were significantly higher in low-protein offspring in the fed state ( P < .05). In contrast, plasma triglycerides and insulin were significantly lower in low-protein offspring compared with controls when fed ( P < .001) and after a 24-hour fast ( P < .001). These results suggest that poor maternal and early postnatal nutrition can have long-term effects on ketone body metabolism in the offspring during adulthood. This apparent ketosis resistance is similar to that observed in some forms of human diabetes.