Based on international surveys during the past forty years, the prevalence of overweight or obesity in children has accelerated in most global regions [1
]. Latest available estimates from 34 member countries within the Organization for Economic Cooperation and Development indicate that among school age children, 21% of girls and 23% of boys are overweight [2
]. However, children are affected with excess weight at ages before they enter school. Worldwide, an estimated twenty-two million children ≤5 years of age were overweight in 2007 [3
] and at present, approximately 10–20% of infants and toddlers in the United States (US) are overweight [4
], (≥85th body mass index (BMI) percentile for age), values similar to those reported for young children in multiple countries [5
]. Equally concerning is the finding that nearly 10% of infants and toddlers, from birth—2 years are also obese, at or above the 95th percentile of the weight for recumbent length growth charts [4
]. More than half the overweight children from one longitudinal study became overweight before age 2, and 25% were overweight by 5 months of age [10
Many overweight infants remain overweight into their childhood years, and childhood obesity has long been known as a strong predictor of adult obesity [11
]. Recent results from a retrospective medical-chart review of 257 children demonstrated that an increased BMI, as early as 2 weeks of age, was associated with a significant increased risk of overweight at 6, 12, 36, and 60 months [12
]. Similarly, reports of overweight at 6–18 months of age being strongly predictive of weight in preschool years are becoming more often documented [13
]. Longitudinal data from 762 infants and children (age 0–18 years) indicated that body weight as early as 2 years of age begins a positive tracking period for adult overweight; weight status from 2–6 years was the most critical growth period for prediction and realization of adult overweight [16
]. An overweight child at age 2–4 years has a 5-fold increased risk of being overweight at age 12, compared to children not overweight during their preschool years. Although limited longitudinal data are available to categorize the proportion of overweight infants that remain overweight throughout life, infant weight status is predictive of BMI or measures of obesity during the adolescent and early adult years [15
]. The earlier a child becomes overweight, and the longer excess weight is maintained, the greater the risk that the child's overweight will follow into adulthood.
Interventions to successfully reduce rates of overweight in very young populations are emerging areas of research, but have yet to be given adequate attention. Critical periods for establishing dietary intake patterns, eating habits, and food preferences begin in infancy, and although inconsistent, may be set as early as 2 years of age [22
]. As the infant progresses to table foods, the family diet exerts a strong influence on food consumption [24
] consistent with a general adoption of the eating practices of the family.
Parental feeding practices, if not causative for weight status in young children, are strongly associated with body weight and healthy food choices throughout childhood [25
]. Research suggests that interventions to adjust food composition or caloric intake and increase physical activity, especially after infancy, have a small impact on children's weight or measures of adiposity [26
] and have been inadequate in curtailing the increased prevalence of overweight affecting young children. Obesity prevention efforts that begin during the school age years offer an approach that is insufficient in addressing the epidemic. Twenty percent of U.S. preschool age children are already overweight [4
], a finding that may be mirrored among other young children throughout the world [1
The primary objective of this narrative review is to discuss risk factors associated with early childhood overweight, with emphasis on current evidence that supports specific modifiable risk factors for obesity prevention within very young children. A review of the available, but few, interventions designed to prevent overweight and obesity within the infant age population is included. It is hoped that this review will contribute to the development of future strategies, policy, and practices consistent with the public health need for an early life obesity prevention plan.