Gene-Environment Interactions and the Effect on Obesity Risk in LMICs: A Systematic Review

Abstract

Obesity is a term used to describe people with high body mass index (BMI) and an excess of body fat that affects their health. It is a disease that increases the chance of developing other diseases, such as heart disease or certain cancers. Obesity is a problem worldwide, however, currently, the proportion of people classified as obese is increasing quicker in low- and middle-income countries (LMICs) compared to high-income countries (HICs). Obesity is also considered an inherited condition, with genetic information playing a big role in how likely people develop it. Since 2008, a type of genetic research known as genome-wide association studies (GWAS) has been used to identify specific genes associated with obesity. These genes, also called single nucleotide polymorphisms (SNPs), vary between individual people and populations. More recent research has shown that different SNPs can interact with a person’s environment or lifestyle choices, such as their diet or levels of exercise, to either increase or decrease their risk of obesity. Like GWAS, studies investigating gene-environment interactions (GxE), have mainly been performed in HICs among European populations. However, findings from GxE research in HICs cannot be assumed to be the same in LMICs. This is because people living in LMICs have different ethnic backgrounds with different genetic information, and live in different environments with different lifestyles. At present, research analysing GxE on obesity in LMICs is limited but growing. This review discusses what research is available, and brings to light areas for improvement for future scientific studies. Three different databases, which contain millions of scientific research articles, were searched using combinations of key words such as ‘obesity’, ‘diet’ ‘LMIC’ and ‘SNP’. Search results up until November 2022 were checked and irrelevant research was excluded. From these results, eighteen research papers were considered relevant to this review. The risk of bias was assessed for all included studies, which is the risk that a scientific study may have presented misleading results due to how they designed the study or collected scientific data. Overall, 14 different SNPs were found to significantly interact with different lifestyle factors to change the likelihood of an individual being obese. However, significant interactions were not repeated across different research studies or in different populations. This review also highlighted several problems with the way current scientific studies collected lifestyle information, or how they defined or classified obesity using varied BMI cut-off values. Statistical analyses were also outdated, relied on information found in old European-based GWAS, or were weakened by small numbers of research participants. Future scientific studies in LMICs should therefore focus on improving the quality of their research, by using standardised data-collection methods, updated statistical techniques, and information from GWAS performed in populations of the same ethnicity.