Genetic studies in I.Family
Both genes and the environment (such as diet and other lifestyle factors) act together to influence our body composition, both our overall lean and fat mass, but also where on the body the fat mass is located.
For decades we have known that the degree of adiposity (i.e. amount of fat tissue) and its distribution runs in families. However, it has not been easy to distinguish between genetic and non-genetic contributions to family similarities. At the same time, increases in average weight and rates of obesity, in particular among children in Europe, show that changes in the environment must be driving the obesity epidemic as our gene pool does not change that rapidly. Family studies have shown that some families and individuals are more susceptible to the obesogenic environment, as children from families with overweight or obese parents are more likely to become overweight or obese.
Since 2007, genetic studies of increasing size using unrelated individuals have examined genetic differences associated with BMI, regional adiposity and obesity.; these genome-wide association studies examine differences in gene variant frequencies across all genes in the human genome. In February 2015, two very large studies on BMI and regional adiposity reported in Nature the latest findings from these extensive international collaborations on the genetics of obesity. For BMI nearly 100 genetic variants are now known, of which many are active in the regulation of appetite and food intake. These genetic variants, come in at least two forms or alleles, one of which is associated with higher BMI; these can be determined in I.Family participants, which enables researchers to conduct more precise studies of which environments are most supportive for obesity prevention among those at high genetic risk of developing overweight or obesity. The so-called ”polygenic risk score”, reflecting the sum of risk alleles, is an important tool for understanding how genes and environments interact in the development of obesity.
We can also study children in I.Family who are genetically at high risk of obesity but of normal weight to see which environmental factors protect them.
Dr Jaakko Kaprio, Professor of Genetic Epidemiology Hjelt Institute, University of Helsinki