Child obesity could be 35-40% inherited from parents irrespective of the child's country of residence according to a new international study of 100,000 children in six different countries worldwide.
Research carried out by the University of Sussex in the UK studying children in the UK, the USA, China, Indonesia, Spain and Mexico found that the more obese the child, the more their BMI was dependent on genetic inheritance from their parents.
Obesity is defined as a body mass index of over 35. A BMI of between 18.5 and 25 is considered healthy. BMI is calculated by dividing a person's weight in kilograms by their height squared in meters.
For the 100,000 children studied, around 35-40% of their BMI (defining how fat or thin they are) was found to be inherited from their parents, with 20% from the mother and 20% from the father. For the most obese children, the proportion of parental effect rose to 55-60%.
The researchers discovered a lower parental effect on BMI in the thinnest children, with 10% inherited from the mother and 10% from the father. This was closer to 30% from each parent for the fattest children. What's more, the pattern proved consistent across the countries studied, irrespective of their economic development, industrialization or type of economy.
In China, less than 1% of children and adolescents were obese in 1985. However, obesity levels reached 17% for boys and 9% for girls in 2014, echoing obesity levels in American children aged two to 18 years old (17.4%).
Beyond healthy eating and lifestyle factors which are essential in the fight against obesity the study gives important insight into how obesity can be transmitted from generation to generation.
"We found that the process of intergenerational transmission is the same across all the different countries," explains lead author Professor Peter Dolton of the University of Sussex.
Global obesity levels are rising rapidly, with around 650 million adults, or approximately 13% of the world's adult population, currently considered obese. This could rise to 20% by 2025 if the current rate of progression is maintained, according to a study published in The Lancet in April 2016. According to figures published in October 2016 by Eurostat, the statistical office of the European Union, 15.9% of Europeans are obese.
In the USA, approximately one in five pregnant women is thought to be overweight or obese.