Dietary protein restriction in pregnant females reduces offspring birth weight and increases the risk of developing obesity, type 2 diabetes, and cardiovascular disease. Despite these grave consequences, few studies have addressed the effects of preconceptional maternal malnutrition. Here we investigate how a preconceptional low protein (LP) diet affects offspring body mass and insulin- regulated glucose metabolism. Ten week old female mice (C57BL/6JBom) received either a LP or isocaloric control diet (8% and 22% crude protein, respectively) for 10 weeks before conception, but were thereafter fed standard laboratory chow (22.5% crude protein) during pregnancy, lactation and offspring growth. When the offspring were 10 weeks old, they were subjected to an intraperitoneal glucose tolerance test, and sacrificed after a 5 day recovery period to determine visceral organ mass. Body mass of LP male offspring was significantly lower at weaning compared to controls. A similar, nonsignificant, tendency was observed for LP female offspring. These differences in body mass disappeared within one week after weaning, a consequence of catch-up growth in LP offspring. Glucose tolerance tests of 10 week old offspring revealed enhanced insulin sensitivity in LP offspring of both sexes. No differences were found in body mass, food intake or absolute size of visceral organs of adult offspring. Our results indicate that maternal protein restriction imposed prior to pregnancy produces effects similar to postconceptional malnutrition, namely low birth weight, catch-up growth and enhanced insulin sensitivity at young adulthood. This could imply an increased risk of offspring developing lifestyle-acquired diseases during adulthood.