In some developed and emergingcountries more than 50% of young womenare now overweight (BMI >25-30) or obese(BMI >30). If overweight/obese mothersare breastfeeding gain weight of theirinfants is faster during the first 12 monthsthan indicated by the 50th percentile of theWHO Growth Standard. Rapid weight gainduring infancy is associated with higher riskof obesity during childhood and adult life.Maternal obesity can result in unfavorable(epigenetic) pre- and postnatal programmingof important genes of the offspring. Thiscan have lifelong consequences such asincreased risk of NCDs. It has also beenspeculated that rapid early weight gain isassociated with changes in the microbiomeof the infant and increased proteinconcentration in breast milk.Many studies indicate that infants ofobese- and non-obese mothers who werefed traditional (high protein) formulas gainweight more rapidly than breastfed infants.Those formulas are still recommended byCODEX ALIMENTARIUS. An updated metaanalysis(n=1150) now indicates that infantswho are fed a whey-based low-proteinformula (1.8g/100kcal) with an essentialamino-acid profile close to breast milk growas indicated by the WHO Growth Standard(0-4 months). A new experimental lowproteinformula (1.61-1.65g protein/100kcal)for infants between 3 and 12 months wasrecently tested in 2 randomized clinical trialsand children were followed until 2-3 years.Growth and biomarkers were comparedwith infants who were fed formulas withhigher protein concentrations and breastfedreference groups. One trial was in ageneral US population where growth ofinfants fed the low protein-formula wasnot inferior to the WHO Growth Standardand the breast-fed reference group. Thepercentage of infants who were abovethe 85th percentile of the WHO standardsduring the intervention period was lower(p 0.036) in the group fed the low-proteinformula than infants fed the control formula(2,15g protein/100kcal). The second trial(Chile) was in infants of mothers with BMI>25. Infants fed the low-protein formulagained less weight until 12 (p 0.015) and 36months (0.031) than infants fed the controlformula with 2,7g protein/100kcal, butweight gain was similar to the breast-fedreference group. In both trials, biomarkersof protein metabolism, IGF-1 and C-peptideof the infants fed the low-protein formulaswere closer to breast-fed infants than therespective biomarkers of the infants fed thehigh-protein formulas.Prevention measures of childhood andadult obesity should start during thefirst 1000 days of life. Unfavorable fetalprogramming can be prevented by weightmanagement/lifestyle change programs ofyoung women before and during pregnancy.After birth, promotion of breastfeedingbeyond 6 months is most important toprevent from excessive weight gain duringinfancy. Our studies indicate that nonbreastfedinfants fed a low-protein formula(1,8g/100kcal) until 12 months growaccording to the WHO standard. Feedinga new experimental low-protein formula(1,61-1,65g/100kcal) between 3 and 12months can help to slow down rapid weightgain during infancy in at risk infants, whichmight contribute to a reduction of obesityrisk in childhood and adult life.