The gut microbiome interacts with the host in the metabolic response to diet, and early microbial aberrancies may be linked to the development of obesity and metabolic disorders later in life. Probiotics have been proposed to affect metabolic programming and blood lipid levels, although studies are lacking in infants. Here, we report on the lipid profile and global metabolic response following daily feeding of probiotics during weaning. A total of 179 healthy, term infants were randomised to daily intake of cereals with (n 89) or without (n 90) the addition of Lactobacillus paracasei ssp. paracasei F19 (LF19) 108 colony-forming units per serving from 4 to 13 months of age. Weight, length and skinfold thickness were monitored. Venous blood was drawn at 5·5 and 13 months of age for analysis of the serum lipid profile. In a subsample, randomly selected from each group, GC-time-of-flight/MS was used to metabolically characterise plasma samples from thirty-seven infants. A combination of multi- and univariate analysis was applied to reveal differences related to LF19 treatment based on 228 putative metabolites, of which ninety-nine were identified or classified. We observed no effects of probiotic feeding on anthropometrics or the serum lipid profile. However, we detected significantly lower levels of palmitoleic acid (16 : 1) (P< 0·05) and significantly higher levels of putrescine (P< 0·01) in LF19-treated infants. Palmitoleic acid is a major MUFA strongly linked to visceral obesity, while putrescine is a polyamine with importance for gut integrity. Whether the observed differences will have long-term health consequences are being followed.