VELLORE — A 2026 longitudinal study conducted as a collaboration between the Tata Institute of Fundamental Research and Christian Medical College, Vellore, found that children in a low-income Indian cohort experienced both thinness and a nearly tripled rate of overweight or obesity between seven and nine years of age.

The study, published in The Lancet Regional Health - Southeast Asia, enrolled 251 children at birth. Of these, 205 (82%) were followed until they reached nine years old. Most children maintained a normal body mass index during their first five years of life.

At age seven, 26.3% of the children were classified as thin, while 5.2% were classified as overweight or obese. By age nine, the percentage of children classified as thin had decreased to 21.6%, but the proportion categorized as overweight or obese had risen to 14.6%. The prevalence of overweight and obesity among these children nearly tripled in the two-year period.

Dr. Beena Koshy, a researcher at Christian Medical College, Vellore, and Dr. Birsen Yilmaz of the Advanced Research Unit on Metabolism, Development and Aging at the Tata Institute of Fundamental Research, led the study. The analyses were based on a longitudinal birth cohort initially established and maintained by Dr. Koshy. Researchers also noted a strong link between low maternal BMI and low child birth weight, which correlated with children remaining thin later in childhood. Conversely, children born with normal birth weight exhibited a higher likelihood of developing obesity by the age of nine.

"Undernutrition in early life can lead to two potential trajectories. Persistence of undernutrition, besides leading to stunting, can potentially lead to defects in insulin secretion and even situations where lean individuals develop diabetes in relation to malnutrition. On the contrary, in those with overnutrition, the potential of higher body fat accumulation, coupled with a sedentary lifestyle and other environmental factors, could lead to an exponential increase in overweight and subsequently increase the risk of diabetes, hypertension and cardiovascular disease," said Nihal Thomas, a researcher at Christian Medical College, Vellore. "The public health policies that need to evolve in this regard would need a judicious blend of lifestyle interventions and the balance of dietary co-interventions that may appear to contravene, but essentially involve promoting higher-protein diets through potentially cost-effective formulations."

"Our findings suggest the importance of focusing on child growth beyond the first 1,000 days. Extending nutrition, growth monitoring, and healthy food and physical activity initiatives into the primary school years is essential because this is when children's metabolic profiles are being shaped. Acting in this window could have a major impact on preventing the progression from early growth faltering to later obesity and related metabolic disorders in adulthood," said Ullas Kolthur, a Professor at the Advanced Research Unit on Metabolism, Development and Aging at the Tata Institute of Fundamental Research.

The World Health Organization defines the double burden of malnutrition as the coexistence of undernutrition along with overweight, obesity or diet-related non-communicable diseases within individuals, households and populations.