Origins of adult obesity found in early childhood

The Raine Study has provided important data for a major international study that has found body mass index (BMI) in babies, children and adults is influenced by different genetic factors that change as we age.

The study, led by scientists at Imperial College London, the University of Surrey, and the University of Oulu, Finland, discovered that BMI in babies was influenced by a distinct set of genetic variations that played little role in determining weight in later life.

They found, however, that some genetic variants associated with adult BMI start playing a role during childhood from around the age of four to seven years old – suggesting that the origins of obesity in adults may lie in this critical stage of childhood.

The study, published in Science Advances, raises hopes that it may be possible to intervene at this early age to help to prevent unhealthy weight trajectories in later life.

Study co-author Emeritus Professor Lawrence Beilin, senior honorary research fellow in UWA’s Medical School, said the Raine Study was one of world’s most successful multi-generational pregnancy cohort studies.

“The data that we’ve been able to collect from all those Western Australians who are part of the Raine Study is so important because it’s being used by researchers around the world to better understand and improve our health and quality of life,” Professor Beilin said.

Senior author Professor Marjo-Riitta Jarvelin, from Imperial College London’s School of Public Health, said the study showed that nearly 100 genetic variations, which increased a person’s risk of obesity in adulthood, seemed to start taking effect at an important stage of childhood development, from around the age of four.

“Environmental factors like the food we eat and our lifestyle have more and more impact on obesity development as we age,” Professor Jarvelin said. “These external factors seem to unmask gradually the genetic contributors to obesity that we have from early life, programming development towards an unhealthy direction.

“We have shown that the origins of adult obesity lie in early childhood, and that there are clear windows across the life course which should be better considered in obesity prevention.”

The research was conducted as part of the Early Growth Genetics Consortium, which combines data from multiple genome-wide association studies to identify genetic variants implicated in human development.

In total, they analysed measures such as BMI and growth rates from two weeks to 13 years of age of more than 22,000 children and compared these to variations in their genetic make-up. This enabled the researchers to identify common genetic variants associated with the peaks and troughs in BMI and their timings in childhood.

BMI (an indicator of body fat) does not follow a linear path through a person’s life, but instead has three distinct periods of change. After birth, BMI rises rapidly until the age of nine months, where it peaks before declining again until the age of five to six years old, known as ‘adiposity rebound point’. BMI then steadily increases until early adulthood.

Previous studies have suggested that adiposity rebound is a key period for determining obesity in later life and the results from the new research now help to explain those findings.

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