Dolores Corella
Professor of Preventive Medicine and Public Health at the Faculty of Medicine of the University of Valencia and researcher at the CIBER Obesity and Nutrition (CIBEROBN)
The study is of very good quality. In addition to the findings in the initial population, it performs additional replication in several populations, as well as functionality studies to better characterise the mechanisms by which statistical associations are observed.
The study has a high level of scientific evidence, both epidemiologically and experimentally based on plausible biological and physiological mechanisms. The novelty is that it has phenotypically characterised the risks of individuals homozygous for a variant of the SMIM1 gene that involves a loss of functionality and is associated with lower energy expenditure and thus higher risk of obesity. The authors replicate the results in several cohorts, increasing external validity, and characterise several biochemical parameters associated with this type of obesity. They also find that the effect is higher in women than in men. This is a very important finding to better understand the genetic heterogeneity of obesity and to be able to subsequently apply prevention strategies or more personalised treatments according to genetic variations.
However, the limitation of the findings of this study is that this is a very rare genetic variant (1 in 5,000 people, according to estimates) and its contribution to common obesity is small.