To understand the relationship between obesity and cancer, at first, you have to know what obesity is. The condition, in which there is an unhealthy amount and/or distribution of body fat in a person’s body, is called obesity. A scale known as the body mass index (BMI) is commonly used by researchers to measure obesity. A person’s weight (in kilograms) is divided by their height (in meters) squared to calculate BMI. For most people, BMI is a fairly good (although indirect) indicator of body fatness. Sometimes, along with BMI, other measurements reflecting the distribution of body fat are increasingly being used as indicators of obesity and disease risks. Waist circumference and the waist-to-hip ratio (the waist circumference divided by the hip circumference) are included in these measurements.
Those who are overweight or obese are at greater risk for many diseases compared with people of normal weight. Diabetes, high blood pressure, cardiovascular disease, stroke and many cancers are some of these diseases. An increased death rate is also associated with extreme or severe obesity. Most of the excess deaths are caused by heart disease, cancer and diabetes.
Large cohort studies, a type of observational study, is the source of nearly all of the evidence linking obesity to cancer risk. However, it cannot be definitively established by the data from observational studies that obesity causes cancer and these studies can be difficult to interpret. There are also other differences between obese or overweight people from lean people than differences in terms of the body fat. It is possible that the different cancer risk of obese or overweight people can be explained by these differences rather than the body fat. If you want to know a detailed description of this matter, a cancer specialist can tell you that.
However, there is consistent evidence despite the limitations of the study designs that increased risks of a number of cancers are associated with higher amounts of body fat. These cancers include: