Abstract: ObjectiveTo explore the association between breastfeeding and obesity,overweight and prov ide scientific evidence for the prevention.MethodsEighthundreds adults aged 35~45 years old were sampled in Harbin randomly.Data were collected by questionnaires and physical exam.Body mass index(BMI)was used as the diagnosis standard of obesity and over weight.ResultsAdult's obesity rate of NBF(not breastfeeding)group,mixed breastfeeding group and pure breastfeeding group was 21.21%,12.08%,11.31%,respectively,without statistical difference(χ²=5.287,P=0.071).Overweight rate of the three groups was 45.45%,37.68%,28.89%,respectively with statistical difference(χ²=10.482,P=0.005).Overweight rate of NBF group was higher than that of pure breastfeeding group(χ²=7.493,P<0.05).The differences of obesity rate and overweight rate between NBF and breastfeeding group all had statistical significance(P<0.05),but there was no dose response relation between pure breastfeeding time and adult obesity rate and overweight rate.Among various influence factors,breastfeeding was a protective one to reduce adult obesity with a decreased risk of 0.816.Birth weight,mother BMI and energy intake increased the risk of obesity by 1.516,1.922 and 1.738 times,respectively.ConclusionBreastfeeding have some influence on preventing adult from obesity and overweight,rational breastfeeding should be strongly recommended.