Background and objective:The suckling period is a critical phase of development, in which maternal overnutrition may program the susceptibility of developing chronic diseases and disorders, such as obesity and metabolic alterations, in adult life. Here, we questioned whether the consumption of a cafeteria diet throughout lactation in rats affects the macronutrient composition of milk and whether it results in permanent metabolic effects in the offspring.Methods:Nursing rats were fed a control diet or a cafeteria diet during lactation. Milk was obtained at different time points of lactation. Offspring (males and females) were weaned onto a control diet until the age of 6 months. Circulating parameters were measured under ad libitum feeding and under 12-h fasting conditions at weaning and at 3 and 6 months of age. An oral glucose tolerance test (OGTT) was performed at 3 and 6 months of age.Results:Rats fed a cafeteria diet during lactation consumed an unbalanced diet, with lower protein and higher fat content versus controls, which was reflected in the composition of the milk. The offspring of rats fed a cafeteria diet during lactation showed lower body weight and lower lean mass, but greater fat accumulation, compared with controls. They also displayed hyperleptinaemia, altered lipid profile and impaired response to an OGTT.Conclusion:Maternal consumption of a cafeteria diet throughout lactation in rats produces lasting effects in the metabolic health of their offspring, which are not associated with a higher body weight but with a greater fat accumulation, similarly to the thin-outside-fat-inside phenotype.