Link Between Overweight, Obesity, and Cancer Risk

Overweight and obesity are linked to an increased risk of developing at least 13 different types of cancer. According to data from the Centers for Disease Control and Prevention (CDC), cancers associated with overweight and obesity accounted for 40 percent of all cancers diagnosed in the United States in 2014.

The impact of these obesity-associated cancers is particularly pronounced in older populations, with approximately 2 in 3 of these cases occurring in adults between 50 and 74 years of age.

Understanding Obesity and BMI

Obesity is defined as a disease characterized by an unhealthy amount and/or distribution of body fat. To assess levels of body fat, medical professionals commonly use the body mass index (BMI), which is calculated by dividing a person’s weight in kilograms by their height in meters squared.

While BMI is a useful estimate of body fatness in populations, it is not a direct measure of body fat and cannot be used alone to indicate obesity-related disease risks in individuals.

For adults aged 20 years or older, the standard weight categories based on BMI are as follows:

• Below 18.5: Underweight
• 18.5 to 24.9: Healthy
• 25.0 to 29.9: Overweight
• 30.0 to 39.9: Obese
• 40.0 or higher: Severely obese

For children and adolescents under 20, BMI is interpreted differently because it changes significantly during growth. In these cases, BMI is compared to those of the same sex and age using CDC BMI-for-age growth charts.

Cancers Associated with Excess Weight

The CDC identifies 13 specific types of cancer associated with being overweight or having obesity. These include:

• Adenocarcinoma of the esophagus
• Breast (specifically in women who have gone through menopause)
• Colon and rectum
• Uterus
• Gallbladder
• Upper stomach
• Kidneys
• Liver
• Ovaries
• Pancreas
• Thyroid
• Meningioma (a type of brain cancer)
• Multiple myeloma

Biological Mechanisms of Cancer Risk

Overweight and obesity can lead to cancer through several biological pathways. These include the development of long-lasting inflammation and the presence of higher than normal levels of sex hormones, insulin, and insulin-like growth factor.

Research also indicates that adiponectin, an adipokine with antiproliferative properties, is low in obese individuals compared to those with a healthy weight.

The risk of developing cancer generally increases based on the amount of excess weight gained and the duration of time a person remains overweight.

Prevention and Risk Reduction

Maintaining a healthy weight is considered an important step in lowering the risk of developing obesity-associated cancers. Public health guidance suggests following a healthy eating plan and engaging in regular physical activity to reduce this risk.

Compared to people of healthy weight, those with overweight or obesity face a greater risk for various diseases beyond cancer, including stroke, cardiovascular disease, high blood pressure, and diabetes, as well as an elevated risk of death from all causes.