The role of genetics in BMI

Genetics play a role in your body mass composition. In the following sections, we discuss what the body mass index (BMI) is and its intersection with genetics, examples of genetics influencing BMI, and conclude with some implications.

Body mass index (BMI) is a measure of body fat based on your weight and height. It is calculated by dividing your weight in kilograms by the square of their height in meters. The resulting number is then used to categorize individuals into different weight categories, such as underweight, normal weight, overweight, and obese.

Research has shown that genetics plays a significant role in determining your BMI. Studies have found that up to 70% of the variation in BMI can be attributed to genetic factors. There are several genetic variants that have been identified to influence BMI, including the FTO gene and the MC4R gene. However, it is important to note that BMI is a complex trait that is influenced by both genetic and environmental factors. Gene-environment interactions can also play a role in determining your BMI.

Let’s explore genetic inheritance, genetic variance, and interactions between genes and your environment.

Studies have shown that genetics plays a significant role in determining your BMI. The heritability of BMI is estimated to be between 30% and 80% However, the heritability of BMI varies across the range of BMI, with genetic effects being stronger at higher BMI values. It is important to note that heritability estimates are population-specific and can vary depending on the population studied.

Several genetic variants have been identified to influence BMI. The most well-known genetic variants are the FTO gene and the MC4R gene. The FTO gene is associated with an increased risk of obesity and has been shown to influence food intake and energy expenditure. The MC4R gene is also associated with an increased risk of obesity and is involved in the regulation of appetite and energy balance. Other genetic variants that have been identified to influence BMI include the TMEM18 gene, the GNPDA2 gene, and the BDNF gene.

It is important to understand that BMI is a simplified measurement that is influenced by both genetic and environmental factors. Gene-environment interactions can also play a role in determining your BMI. For example, studies have shown that the effect of the FTO gene on BMI is stronger in individuals who have a sedentary lifestyle. Similarly, the effect of the MC4R gene on BMI is stronger in individuals who consume a high-fat diet.

A variety of family studies have been conducted to try to determine how much of a role genetics play in body mass composition. Family studies have shown that there is a strong familial aggregation of BMI, indicating that genetic factors play a significant role in determining BMI. For example, studies have shown that the risk of obesity is higher in individuals who have a family history of obesity. Family studies have also been used to estimate the heritability of BMI, which is the proportion of the variation in BMI that can be attributed to genetic factors. These studies have estimated the heritability of BMI to be between 30% and 80%.

Twin studies have also been used to estimate the heritability of BMI. These studies involve comparing the similarity of BMI between monozygotic (identical) twins, who share 100% of their genes, and dizygotic (fraternal) twins, who share on average 50% of their genes. Twin studies have estimated the heritability of BMI to be between 40% and 70%.

Adoption studies have been used to investigate the role of genetics and environment in determining BMI. These studies involve comparing the BMI of adopted children with that of their biological and adoptive parents. Adoption studies have shown that the BMI of adopted children is more strongly correlated with the BMI of their biological parents than with the BMI of their adoptive parents, indicating that genetic factors play a significant role in determining BMI.

The HUNT study, a longitudinal study that following individuals in Norway for approximately 20 years, found that:

Obesity increased in Norway starting between the mid-1980s and mid-1990s and, compared with older birth cohorts, those born after 1970 had a substantially higher BMI already in young adulthood. BMI differed substantially between the highest and lowest fifths of genetic susceptibility for all ages at each decade, and the difference increased gradually from the 1960s to the 2000s.

The study concludes that:

This study provides evidence that genetically predisposed people are at greater risk for higher BMI and that genetic predisposition interacts with the obesogenic environment resulting in higher BMI, as observed between the mid-1980s and mid-2000s. Regardless, BMI has increased for both genetically predisposed and non-predisposed people, implying that the environment remains the main contributor.

Further research is needed to better understand the complex interplay between genetics and environment in determining BMI. For example, future studies could investigate the specific environmental factors that interact with genetic variants to influence BMI. Additionally, research could focus on developing personalized interventions that take into account an individual’s genetic risk for obesity. Such interventions could include personalized dietary and exercise plans that are tailored to an individual’s genetic profile.