Dad’s weight before baby’s birth may influence that child’s risk of developing obesity

21 May 2025

(Hamilton, ON) New research from the CHILD Cohort Study (CHILD) and the University of Toronto shows that the offspring of fathers with obesity are more likely to follow growth trajectories that lead to their developing obesity in early childhood. This risk is found to increase when the child’s mother is also with overweight or obesity.

It is one of the first and largest studies to investigate how fathers’ body-mass-index (BMI) and weight influence their children’s BMI growth patterns through early childhood (from birth up to 5 years of age).

“These findings underscore how parents’ preconception health can shape the early development of their children,” comments first author Antonio Rossi, a graduate student in Nutritional Sciences at the University of Toronto.

“Because having obesity in early childhood often continues into adulthood and can have long-term health consequences, our results suggest that we need to offer broader health counseling to people planning to become parents; we also need to develop new interventions to optimize their health.”

Published in the International Journal of Obesity, the study analyzed data from 2,238 participants in CHILD, a pregnancy cohort study that has following the health and development of over 3,000 Canadian children from before birth through to adolescence. The researchers analyzed height and weight measurements taken from parents before their children’s birth, as well as the same measurements taken from their kids at birth, 3 months, 1 year, 3 years and 5 years of age. They used weight categorization and BMI scores based on World Health Organization (WHO) standards.

The researchers also considered various other factors—including the parents’ ages, whether there were smokers in the child’s household, the family’s socio-economic status, and the child’s level of physical activity—but did not find any of them to override the influence of parental weight when it came to the child’s growth development.

“We already knew that a mom’s weight status tended to influence her baby’s growth and risk of obesity,” observes lead author Dr. Kozeta Miliku, CHILD’s Clinical Science Officer and Assistant Professor in the Department of Nutritional Sciences at the University of Toronto, “but before this study there was a knowledge gap when it came to understanding the influence of the father’s in their child growth pattern.”

“Not only did we find that dad’s weight matters, we found that the combination of both parents being with obesity has an even bigger impact. When both the mom and dad are with obesity before the child’s birth, their child is more than four times as likely to experience rapid BMI growth gain compared to children born of parents without obesity or overweight.”

The study’s results also suggest that the influence of the father’s weight may become more pronounced as the child gets older, while the influence of the mother’s may remain relatively consistent from birth to childhood.

“Our research could lead to paradigm shifts in healthcare and public health policies, prompting the inclusion of specific preconception care guidelines for men,” Dr. Miliku comments.

“This study promotes a more inclusive approach to family health, challenging traditional views that often place the onus of intergenerational health solely on mothers. Our research encourages a societal shift towards recognizing the collective responsibility of both parents in influencing the health of future generations.”

This research was funded by a CIHR Operating Grant, the Ontario Regional Centre of the Canadian Statistical Sciences Institute, a Connaught New Investigator Award, and a University of Toronto Pathway Grant.

About Dr. Kozeta Miliku: Dr. Kozeta Miliku is an MD, PhD, Assistant Professor of Nutritional Sciences at the University of Toronto, and Department of Medicine at McMaster University. She is also the Clinical Science Officer of the CHILD Cohort Study and the EDII co-chair of the Canadian Developmental Origins of Health and Disease Society.

About the CHILD Cohort Study: Launched in 2008 by CIHR and AllerGen Inc. (a Networks of Centres of Excellence from 2004 to 2019), the CHILD Cohort Study (CHILD) is tracking nearly 3,500 Canadian infants and their families to determine the root causes of chronic diseases such as asthma, allergies and obesity. CHILD has study sites in four provinces and involves over 140 multidisciplinary researchers, students and research staff. Its national headquarters are hosted by McMaster University in Hamilton, ON.

About the Department of Nutritional Sciences, University of Toronto: The Department of Nutritional Sciences is one of the few departments of nutrition in North America to be located within a Faculty of Medicine. This, together with its close linkages with University of Toronto’s Dalla Lana School of Public Health, allows the department to fully explore the relationships between nutrition and human health and disease, and to influence clinical practice and public health programs. It also creates unique opportunities for collaboration with the highest concentration of university-affiliated hospitals, clinicians, and health researchers in North America.

For more information or to request an interview with Dr. Miliku, please contact:
Kozeta Miliku
Kozeta.miliku@utoronto.ca