The Impact of Timing of Introduction of Solids on Infant Body Mass Index.
To evaluate the associations between breastfeeding duration, age at solids introduction, and their interaction in relation to infant (age 9-15 months) above normal body mass index (BMI).



Cross-sectional, population-based study with 3153 infants from Melbourne (2007-2011). Above normal BMI (z score > 2, equivalent to >97.7th percentile) defined using the World Health Organization standard.



Both longer duration of full and any (full or partial) breastfeeding were associated with lower odds of above normal BMI (eg, aOR, 0.37 [95% CI, 0.22-0.60] for full breastfeeding 4-5 months versus 0-1 months). Compared with introduction of solids at 5-6 months, both early and delayed introduction were associated with increased odds of above normal BMI (aOR for 4 months, 1.75 [95% CI, 1.10-2.80] and for ≥7 months, 2.64 [95% CI, 1.26-5.54] versus 6 months). Such associations differ by breastfeeding status at 4 months (interaction P = .08). Early introduction of solids was associated with increased odds of above normal BMI in both infants fully or partially breastfed for ≥4 months (aOR, 3.66; 95% CI, 1.41-9.51) and those breastfed for <4 months (aOR, 3.11; 95% CI, 1.39-6.97). Introduction of solids at ≥7 months was associated with increased odds of above normal BMI (aOR, 5.79; 95% CI, 1.91-17.49) among infants breastfed for <4 months only.



Introduction of solids at 5-6 months, compared with either early or delayed introduction, is associated with decreased odds of above normal BMI at 1 year of age, regardless of infants' breastfeeding status at 4 months. These results may have implications for public health guidelines with regard to recommendations about the optimal timing of the introduction of solid foods in infancy.
Environmental and Genetic Epidemiology Research Group, Murdoch Childrens Research Institute (MCRI), Royal Children's Hospital, Melbourne, Victoria, Australia; Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia.
Cong
C
Sun
Monash University, Melbourne, Victoria, Australia.
Rebecca J
RJ
Foskey
Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia; Centre for Food and Allergy Research, MCRI, Royal Children's Hospital, Melbourne, Victoria, Australia; Department of Allergy and Immunology, Royal Children's Hospital, Melbourne, Victoria, Australia; Institute of Inflammation and Repair, University of Manchester, Manchester, UK. Electronic address: katie.allen@rch.org.au.
Katrina J
KJ
Allen
Centre for Epidemiology and Biostatistics, School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia.
Shyamali C
SC
Dharmage
Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia; Centre for Food and Allergy Research, MCRI, Royal Children's Hospital, Melbourne, Victoria, Australia.
Jennifer J
JJ
Koplin
Environmental and Genetic Epidemiology Research Group, Murdoch Childrens Research Institute (MCRI), Royal Children's Hospital, Melbourne, Victoria, Australia; Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia.
Anne-Louise
AL
Ponsonby
Centre for Epidemiology and Biostatistics, School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia.
Adrian J
AJ
Lowe
Centre for Epidemiology and Biostatistics, School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia.
Melanie C
MC
Matheson
Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia; Department of Allergy and Immunology, Royal Children's Hospital, Melbourne, Victoria, Australia; Allergy and Immune Disorders, MCRI, Royal Children's Hospital, Melbourne, Victoria, Australia.
Mimi L K
ML
Tang
Centre for Epidemiology and Biostatistics, School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia.
Lyle
L
Gurrin
Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia; Centre for Community Child Health, MCRI, Royal Children's Hospital, Melbourne, Victoria, Australia.
Melissa
M
Wake
Department of Pediatrics, University of Melbourne, Melbourne, Victoria, Australia; Centre for Hormone Research, MCRI, Royal Children's Hospital, Melbourne, Victoria, Australia; Department of Endocrinology and Diabetes, Royal Children's Hospital, Melbourne, Victoria, Australia.
Matthew
M
Sabin
D000367:Age Factors; D015992:Body Mass Index; D001942:Breast Feeding; D003430:Cross-Sectional Studies; D005248:Feeding Methods; D005260:Female; D005502:Food; D006801:Humans; D007223:Infant; D008297:Male; D013997:Time Factors
childhood obesity; childhood overweight; early life nutrition; infant; population-based studies