Obesity is a result of chronic energy imbalance in an individual. People who intake more calories than how much their bodies require for metabolic reactions get obese. During the Coronavirus pandemic, and in recent decades, people have been open to “obesogenic” environments, which expose people to high calorie foods while limiting physical activity. This is considered as an important public health problem since it increases the risk of developing coronary heart disease and other serious diseases. However, even though people are exposed to such an environment, the negative impact on certain individuals is not as bad as others. Some scientists believe that this due to genetic factors and is the fact that obesity is closely related to genetics true?
There was a key study held in England, 1990 which compared the body mass index (BMI) of twins reared in different environments and this study clearly indicates that inherited factors have high correlation with obesity. Scientists have studied samples of 93 identical twins reared apart, 154 pairs of identical twins reared together, 208 pairs of fraternal twins reared together, and 218 pairs of fraternal twins reared together. Heights and weights were reported by the twins themselves through questionnaires and it was found that the correlation coefficients of the values for BMI of identical twins reared apart were 0.70 for men and 0.66 for women. Since identical twins have the exact same phenotypes and genotypes, they are seen as the most direct estimates of relative importance of genetic influence on BMI, and it was clear that childhood environment did not contribute to the similarity of BMI of twins later in life.
Then what genes are the causes of obesity? The most commonly known gene is MC4R, which encodes the melanocortin 4 receptor. Changes in MC4R genes affect children, making them to feel extremely hungry and become obese due to overeating(hyperphagia). Also, in a study held by genome-wide association, more than 50 genes were known to be associated with obesity but with minor effects.
The genes being the basis for the signals and responses that guide food intake, affects the brain, and the brain regulates food intake by responding to signals to transmit hormones such as leptin, insulin, and ghrelin. The brain also instructs the body to eat or reduce energy use, or do the opposite. So the genes can be seen as the ultimate source for signaling energy intake and energy use. Below is a table showing other various genes related to obesity.
Therefore it can be concluded that genetics and obesity have a high correlation. Even though the effect might seem minor to some individuals, to a certain extent, people are affected by the genes carried on from their ancestors. This foundation could then be applied in our daily life and help one to recognize that one is more prone to obesity, making them able to control their diet and exercise regularly.