Table 1.

The ‘2011 Scorecard’

	Supports protective effect of breastfeeding?
Type of Study	Yes	Maybe	No
Cluster randomized controlled trial of breastfeeding promotion			No effects on anthropometric outcomes at 6.5 or 11.5 years of age, but observational data within the cohort show no (or slightly +) association
Cohort studies, mostly White European descent	Three pooled meta-analyses of (dichotomous) obesity show modest associations, but limited confounder control		One individual-level meta-analysis of mean BMI shows no effect after confounding control, but limited number of studies with sufficient data
Cohort studies in developing countries and racial/ethnic minorities			Many are null, but in some misclassification of exposure may exist
Sib-pair analyses in cohort studies		Three studies suggest effect, but low power
Comparison of cohorts with different confounding structure			One study suggests that confounding explains observed associations
‘Reverse causality?’		A few studies suggest this phenomenon, but could be in opposite direction to hypothesis
Biological effects of breast milk		Conflicting data on adipokines
Biological effects of formula	RCTs of high vs low protein (+/− energy) result in more adiposity and related outcomes
Behavioural effects of nursing	Short-term studies suggest less self-regulation in bottle- vs breast-fed infants
Ecological analysis			Breastfeeding rates have gone up along with emergence of the obesity epidemic, but that does not rule out inverse individual-level effects

Summarizing evidence for and against the hypothesis that having been breastfed reduces the risk of obesity.