It is well known that obesity has a significant detrimental effect on human health. It has also been known that obese people are more likely to develop diseases. Conditions that have been found to be associated with obesity include diabetes mellitus, hyperlipidemia, hypertension, coronary artery disease and artherosclerosis. Other conditions include cancers such as colorectal cancer and endometrial cancer, as well as joint problems.

Recent studies have shown that obese women are more likely to develop breast cancer and obese men are more likely to develop colorectal cancer and prostate cancer than non-obese people.

One study has shown that people have increased risk of death in proportion to the increase in BMI [weight in kg divided by the square of height in meters (kg/m2)]. For example, if a person has a BMI of 35 or higher, he or she will have an eightfold higher risk of diabetes and 50 percent higher risk of cancer. However, it is not just the degree of obesity, but also the distribution of body fat that matters. 

Obesity of the upper body, which is predominantly central obesity (also known as male-type obesity), has a higher association with diabetes mellitus and other metabolic problems than obesity of the lower body (also known as female-type obesity) where there is increased fat distribution in the hips and the thighs.

Central obesity is also associated with resistance to insulin, which in turn leads to increased atherosclerosis, which can cause coronary heart disease or stroke. Recently, it has been found that the risk factors of cardiovascular diseases, such as insulin resistance, hyperglycemia, hypertension and hyperlipidemia tend to occur in various patterns in the same person. This is known as the “metabolic syndrome.” Obesity is also associated with sleep apnea, gall stones and biliary tract diseases, osteoarthritis, menstrual irregularity, constipation, liver steatosis (fatty liver disease), delayed wound healing, peripheral circulatory problems as well as psychological illnesses.

However, a small reduction in body weight can greatly reduce the risks. Therefore, it is important to maintain a healthy weight through a controlled diet and physical exercise. Even if you have already developed complications from obesity, you can prevent new complications from developing and can start ameliorating the present complications by reducing your weight.

Children of obese parents are also often obese. This leads to the question regarding the role of genetic factors in obesity. Although the answer to this question is not clear, it can be said that the risk of developing obesity has some genetic components. Recent molecular biologic studies into obesity will hopefully produce new answers to this question.

If a genetic cause of obesity is found, it will be possible to select the group of children who are at increased risk to offer preventative treatment. It may also be possible to develop new therapies targeting the causative genes. However, it is important that even those people with a genetic susceptibility to obesity can lose weight through diet and physical exercise.

There are very limited studies in Korea concerning this issue, and the likelihood of genes playing a role in obesity has been studied in identical twins.

Studies on the concordance of obesity in identical twins (who have identical genes) in comparison with that of obesity in non-identical twins have shown that the concordance rate was higher in the identical twins. This suggests that genetic factors might be associated with the obesity besides the environmental factors. Other studies have also been done on family members. The genetic component of BMI has been reported to range between 5 and 40 percent, showing that there is at least some genetic component of obesity. Another study in adopted children and different generations of the same family has reported a genetic association of 30 percent in obesity. These studies show that there is at least some genetic component to obesity. Future studies will investigate the exact roles of these genetic factors.

By Lee Moon-kyu

The author is a doctor at the division of endocrinology and metabolism at Samsung Medical Center and a professor at Sungkyunkwan University School of Medicine. ― Ed.