Obesity – What Are The Causes And Risk Factors?

Obesity is a condition that results from an environment with readily available food, including food of high energy density, and decreasing physical activity. Overweight and obesity are assessed in adults by calculating the body mass index ( BMI – weight in kilograms divided by the square of the height in metres). Obesity is defined as a BMI of 30 or more. Normal range the BMI is between 18.5 to 24.99. Underweight the BMI is less than 18.5. If the BMI is greater than 25, it is classified as overweight. The BMI is useful in all patients except those at the extremes of age and the very fit and muscular. It gives a good approximation of the body’s adiposity.

Causes and Risk Factors

The causes of and risk factors for obesity are many, with most patients having a combination of reasons that contribute to their obesity problem.


There are many studies indicating that inherited genetic variation is an important risk factor for obesity, with evidence indicating that total body fatness and fat distribution are influenced by genetic factors. Genetic factors may contribute to some 25 to 70% of cases of obesity.


Diet — diets high in fat and energy are associated with increased weight. We are consuming more energy each day and it is interesting to note that this increase in daily energy intake is greater in children and adolescents.

Lifestyle and Activity — Sedentary lifestyle, lack of physical activity and decreased regular exercises all contribute to decreased caloric burning and therefore increased weight gain. We are all becoming less active and that children and adolescents spend many more hours in sedentary leisure activities such as television and computer games than in active leisure pursuits

Psychological — Binge eating disorders or disturbances in mood, such as depression, may contribute to the obesity. These disorders are more common in the more severely obese. Yet, in the majority of cases no significant differences in mood can be found in those who have obesity compared with people of normal weight

Medical condition — It can contribute to weight gain. Some illness such as acromegaly, cushing’s syndrome, hypogonadism and hypothyroidism can cause insidious weight gain. Some medications such as amitriptyline which are used for the treament of depression and steroids can increase body weight. Others include beta blockers, antiepileptics, sulfonylureas, insulin and antipsychotics. Obesity is a risk factor for several medical conditions and is a significant cause of morbidity and mortality in our society. Some of the high risks medical conditions include diabetes, insulin resistance, hypertension,sleep apnoea, dyslipidaemia and gallbladder disease.

Finally, with modest reduction in weight of 5% to 10 % have been shown to modify risk factors for medical conditions such as diabetes, hypertension and hyperlipidaemia.