Empowering Healthy Kids Blog

Researchers in the UK have found a strong link between childhood obesity and genetics:

more than three quarters of the difference between children’s waistlines, with lifestyle factors such as diet and exercise playing a much smaller role.

Lead author of the study, Dr. Jane Wardle:

Weight gain in a child is unlikely to be the fault of the parents and is more likely to be due to the child’s genetic susceptibility.

The study was conducted using a twin study and drew the following conclusions:

The researchers found that, overall, the twins’ heights and weights were greater than the 1990 averages, though BMI was similar. Waist circumferences were substantially higher than in populations in 1990, particularly in girls. They also found that identical twins were more likely than non-identical twins to have similar BMI and waist circumference measurements, suggesting a genetic component to these characteristics.

Using the modelling method, the researchers conclude that variation in BMI scores is 77 per cent heritable, while variation in waist circumference is 76 per cent heritable. They also found that the “shared-environment” had little effect on BMI and waist circumference (10 per cent each).

One problem that I find with these studies is that it shows correlation but not causation, but the researchers discuss such criticisms:

• Firstly, the common finding that the shared environment has little effect. In studies of obesity, this is surprising considering the fact that many models suggest that the environment is “the root cause of obesity”. They say that this finding suggests caution when assuming that if all parents followed “current child-feeding recommendations, the obesity problem would be solved”.
• Secondly, twin studies assume that identical and non-identical twins share the same environment (in the uterus and in the family). There is discussion in the scientific literature about whether this is an accurate assumption, however the researchers here say that the effect is small and “it would not materially change the conclusion”.
• Thirdly, such studies do not identify genes responsible for traits or behaviours. No major genes that cause obesity have been identified and obesity is likely to be due to the influences of many different genes, affecting appetite as well as how fat is stored. 

Until such time as the boffins find a “fat” gene can we understand the cause of obesity an, hopefully, from that finding the best ways to combat it. What this study also means is that parents who are overweight and obese must not abandon their and their children’s efforts to lead an active and healthy lifestyle. It just means they have to work a little harder at it.