Background: Maternal nutrition during pregnancy or lactation may affect the chance of offspring becoming obese as adults, but little is known regarding the possible role of maternal nutrition before conception. In this study, we investigate how variable protein and carbohydrate content of the diet consumed before pregnancy affects fat deposition and gut dimensions of offspring mice.Methods:Eight-week-old female mice (C57BL/6JBom) were fed isocaloric low protein (8.4% protein; LP), standard protein (21.5% protein; ST) or high protein (44.2% protein; HP) diets. After 8 weeks of feeding, females were mated and fed a standard laboratory chow diet (22.5% protein) throughout periods of mating, gestation, lactation and weaning. Offspring mice were fed the same standard diet up to 46 days of age. Then offspring were killed and measures of dissected fat deposits and of the digestive system were taken. Results: Fat deposition of the offspring was significantly affected by preconceptional maternal nutrition and the effects differed between sexes. Male offspring deposited most fat when mothers were fed the LP diet, whereas female offspring deposited most fat when mothers were fed the ST diet. The mass and length of the digestive organs were affected by preconceptional maternal nutrition. Total gut from pyloric sphincter to anus was significantly shorter and dry mass was heavier in mice whose mothers were fed LP diets compared with offspring of mothers fed ST diets or HP diets. There was no significant effect of maternal nutrition on dry mass of the stomach or ceca. Conclusion: Our study shows that preconceptional nutrition can have important influence on several body features of offspring in mice, including body composition and dimensions of the digestive system.