RESEARCH STARTER

Obesity-associated cancers

Obesity-associated cancers refer to the increased risk of developing various types of cancer linked to obesity, defined as having a body mass index (BMI) of 30 or higher. This health condition is prevalent across diverse populations and has reached epidemic levels, with significant rises in obesity rates over the past few decades. Research indicates a strong association between obesity and the incidence of thirteen specific cancers, including breast, colorectal, and pancreatic cancers, among others. The mechanisms behind this connection involve hormonal changes due to excess fat tissue, which can influence cell growth and survival, potentially leading to tumor development.

Preventing obesity through education on healthy eating and physical activity is crucial, as weight reduction can significantly lower cancer risk. While various studies suggest that obesity may affect cancer prognosis differently depending on the type of cancer, they highlight the importance of managing weight in cancer treatment for better outcomes. Furthermore, obesity is linked to a range of other health issues, making its management a vital public health concern. Understanding the relationship between obesity and cancer can empower individuals to make informed choices regarding their health.

Full Article

RELATED CONDITIONS: Many types of cancer

DEFINITION: Obesity is an increase in body weight through an accumulation of fat in the body such that people exceed their ideal weight (taking into account height, sex, age, and body build) by 20 percent or more; however, some resources emphasize the importance of one's body fat compared to muscle mass over a standard percentage. The National Institutes of Health defines obesity as a body mass index (BMI) of 30 and above; 40 and above is generally considered severe obesity. (A BMI of lower than 18.5 is underweight, 18.5 to 24.9 is healthy, and greater than 25.0 is overweight.) BMI, which relates a person’s height and weight, is calculated by multiplying the person’s weight in pounds by 703, then dividing that number by the person’s height in inches squared.

Another important measurement that relates to obesity is a person’s waist measurement. A non-pregnant woman with a waist measurement of more than 35 inches and a man with a measurement of more than 40 inches are considered to be at higher risk for disease. Even if a person’s BMI falls within a healthy range, the risk of developing health problems is greater if body fat is concentrated mainly in the waist area.

Obesity has long been connected with the risks of developing many disorders, including diabetes, arthritis, stroke, and respiratory and heart disease. Research has shown that obesity has a significant impact on cancer development and its prognosis after treatment. According to the International Agency for Research on Cancer, overweight and obesity are associated with thirteen cancers in particular: breast (postmenopausal), colorectal, esophageal (adenocarcinoma), gallbladder, liver, kidney, meningioma, multiple myeloma (a blood cancer), ovarian, pancreatic, stomach, thyroid, and uterine. Further research may find links to other cancers as well.

Risk factors: Obesity is primarily caused by poor diet (excessive intake of calories) and physical inactivity. Weight gain may be caused in part by the abundance of readily available high-calorie food choices and the lack of physical exertion in modern lives, psychological factors such as stress or depression, physical conditions such as hypothyroidism, and certain medications, including migraine medications and antidepressants. Research has also shown links between genetics and obesity, demonstrating an inherited predisposition in some people to gain weight more easily or have difficulty losing weight.

Etiology and the disease process: Many researchers have studied obesity and its relationship to an increased incidence of certain cancers. It is believed that fat cells in the body produce hormones and other substances that affect cell growth. People who are obese have significantly increased levels of these compounds because of the increased number of fat cells, which can have potentially influential effects on cellular growth and programmed cellular death (apoptosis), perhaps allowing damaged cells to survive and grow into tumors. The roles of estrogen, insulin, insulin-like growth factor-1, and insulin-like growth factor-binding protein-3, leptin, and cytokines, as well as other substances and growth factors, are being examined for their relationship to obesity-associated cancers.

An example of these actions by fat tissue can be found in postmenopausal breast cancer, which is known to have a higher incidence rate in women. Estrogen, which is important for the reproductive cycle, is produced by fat tissue in addition to being produced by the ovaries. After menopause, when the ovaries stop producing hormones, fat tissue becomes the most important estrogen source. In women who are obese, postmenopausal estrogen levels are 50 to 100 percent higher than in women who are not overweight or obese. As a result, estrogen-sensitive tissues in these women are overexposed to estrogen stimulation, leading to a more rapid growth of estrogen-receptor-sensitive breast tumors. Researchers believe that fat cells stimulate surges of hormones, insulin, proteins, and other substances mentioned above, which may, in turn, cause reactions that initiate uncontrollable growth among certain cell types. A 2019 study published in Current Oncology Reports found that treatments for breast cancer patients with obesity had lower efficacy rates than those for patients without obesity. It also found that obese breast cancer patients were at increased risk for local recurrence.

Incidence: According to the American Cancer Society, the risk of cancer from obesity is similar to the risk from using tobacco. Obesity affects the entire population, regardless of age, gender, race, or ethnicity. In the United States, obesity began increasing at an alarming rate in the late twentieth century. In 1980, about 15 percent of adults were obese; by 2011, that number had more than doubled to about 35 percent.

A 2013 American Journal of Public Health study found that between 1986 and 2006, overweight and obesity accounted for 5 percent of deaths among African American men, 15.6 percent among White men, 26.8 percent among African American women, and 21.7 percent among White women. According to the US Centers for Disease Control and Prevention (CDC), the prevalence of obesity increased from around 30 percent in 1999 to 2000 to 41 percent in 2017 to 2020.

Childhood obesity became a significant concern for medical experts because of the staggering number of overweight children and the projected long-term health effects. The National Cancer Institute (NCI) reported in 2017 that between 1988 and 1994, only about 10 percent of American children and youth aged two to nineteen and 56 percent of adults were obese; by 2011–14, 17 percent of children and adolescents were obese, as were 36.5 percent of adults, according to the National Health and Nutrition Examination Survey. Overweight and obesity are most common among Black and Hispanic women, with similar patterns seen for children and adolescents in these groups. According to the CDC, between 2017 and 2020, almost 13 percent of children in the US between two and five, 21 percent of children six to 11 years old, and 22 percent of adolescents between 12 and 19 years old were obese.

Studies have increasingly linked obesity and cancer. Many studies show that the greater the degree of obesity, the stronger the association with cancer. After analyzing data from 2005 to 2014, CDC and NCI scientists found that more than half of cancers in women and about one-quarter in men, or 40 percent of all cancers diagnosed in the country, were linked to overweight and obesity. Graham Colditz, a physician with the Harvard School of Public Health, estimated that 50 to 60 percent of cancer cases could be avoided if no one were overweight or obese.

Symptoms: There are no symptoms that are specific to obesity-associated cancers.

Screening and diagnosis: Screening for obesity-associated cancers includes annual physical examinations to calculate BMI and take waist measurements, as well as annual laboratory tests, such as serum lipid panel, fasting glucose level, and thyroid function tests. In addition, people can essentially screen themselves by monitoring their own weights. There are no specific tests for obesity-related cancers; testing is done when patients exhibit other symptoms. Staging is specific to the type of cancer that develops.

Treatment and therapy: Treatment for obesity-associated cancer is specific to the type of cancer. However, based on data obtained during various studies, patients must also reduce their weight to avoid the increased risk that obesity places on successful treatment. Patients must set weight-loss goals and obtain assistance from a registered dietitian or weight-loss program for in-depth counseling. Many reputable commercial and community programs exist for obesity treatment. Desirable programs should include diets that meet the United States recommended daily allowance for nutrients, exercise counseling, behavior modification, and provision for long-term maintenance.

Some experts may suggest nonpharmacologic treatment for six months and then consideration of weight-loss medication if weight loss is unsatisfactory in those with a BMI greater than 30 or a BMI greater than 27 with associated risk factors. Patients with severe obesity (BMI greater than 40) may also be considered for gastric bypass or bariatric surgery.

Prognosis, prevention, and outcomes: Long-term maintenance of weight loss is extremely difficult. If the patient is not motivated, successful weight loss is unlikely. Prevention efforts for obesity include education and the design of evidence-based programs that patients can reasonably follow. Weight reduction can have a significant impact on a person’s risk for developing obesity-associated cancers.

Though research links obesity with the propensity for various cancers, findings vary. A study published in Innovation in 2022 found that cancer patients who were overweight or mildly obese had better survival rates than patients with low or normal BMI. The study also found that it was not beneficial for patients who were overweight or mildly obese to lose weight, especially during treatments. Another study, published by the European Society for Medical Oncology, found that mortality rates in patients with cancer and obesity depended on the type of cancer the person had. For example, patients with obesity and breast cancer had a lower survival rate than other patients, but obesity acted as a protective factor in patients with gastrointestinal tumors. Another study, published in Ocular Oncology, noted a link between obesity and a lack of metastases and death in patients with uveal melanoma, demonstrating that the cancer in patients with obesity was not spreading like it was in patients who were overweight or of a healthy weight. However, it is important to note that varying research and studies do not, and sometimes cannot, account for causality. Therefore, further research is necessary to better understand BMI rates and mortality among cancer patients.


Bibliography

“Adult Obesity Facts.” CDC, 14 May 2024, www.cdc.gov/obesity/adult-obesity-facts/index.html. Accessed 29 Oct. 2025.

"Excess Body Weight and Cancer Risk." American Cancer Society, 3 Sept. 2025, www.cancer.org/cancer/risk-prevention/diet-physical-activity/diet-and-physical-activity/body-weight-and-cancer-risk.html. Accessed 29 Oct. 2025.

Giovannucci, Edward, and Dominique Michaud. “The Role of Obesity and Related Metabolic Disturbances in Cancers of the Colon, Prostate, and Pancreas.” Gastroenterology, vol. 132, no. 6, 2007, pp. 2208–25, doi:10.1053/j.gastro.2007.03.050. Accessed 29 Oct. 2025.

Lee, Kyuwan, et al. “The Impact of Obesity on Breast Cancer Diagnosis and Treatment.” Current Oncology Reports, vol. 21, no. 5, 2019, pp. 1–6, doi:10.1007/s11912-019-0787-1. Accessed 29 Oct. 2025.

Masters, Ryan K., et al. "The Impact of Obesity on US Mortality Levels: The Importance of Age and Cohort Factors in Population Estimates." American Journal of Public Health, vol. 103, no. 10, 2013, pp. 1895–901, doi:10.2105/AJPH.2013.301379. Accessed 29 Oct. 2025.

"Obesity and Cancer." Cancer.gov. National Cancer Institute, National Institutes of Health, 28 Jan. 2025, www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet. Accessed 29 Oct. 2025.

"Obesity and Cancer." Centers for Disease Control and Prevention, 11 June 2025, www.cdc.gov/cancer/risk-factors/obesity.html. Accessed 29 Oct. 2025.

Sabazade, Shiva, et al. "Obesity Paradox in Uveal Melanoma: High Body Mass Index Is Associated with Low Metastatic Risk." British Journal of Ophthalmology, vol. 108, 2024, pp. 578-87, bjo.bmj.com/content/108/4/578. Accessed 29 Oct. 2025.

Tu, Huakang, et al. “Body Mass Index and Survival after Cancer Diagnosis: A Pan-Cancer Cohort Study of 114 430 Patients with Cancer.” The Innovation, vol. 3, no. 6, 2022, doi:10.1016/j.xinn.2022.100344. Accessed 29 Oct. 2025.

Full Article

RELATED CONDITIONS: Many types of cancer

DEFINITION: Obesity is an increase in body weight through an accumulation of fat in the body such that people exceed their ideal weight (taking into account height, sex, age, and body build) by 20 percent or more; however, some resources emphasize the importance of one's body fat compared to muscle mass over a standard percentage. The National Institutes of Health defines obesity as a body mass index (BMI) of 30 and above; 40 and above is generally considered severe obesity. (A BMI of lower than 18.5 is underweight, 18.5 to 24.9 is healthy, and greater than 25.0 is overweight.) BMI, which relates a person’s height and weight, is calculated by multiplying the person’s weight in pounds by 703, then dividing that number by the person’s height in inches squared.

Another important measurement that relates to obesity is a person’s waist measurement. A non-pregnant woman with a waist measurement of more than 35 inches and a man with a measurement of more than 40 inches are considered to be at higher risk for disease. Even if a person’s BMI falls within a healthy range, the risk of developing health problems is greater if body fat is concentrated mainly in the waist area.

Obesity has long been connected with the risks of developing many disorders, including diabetes, arthritis, stroke, and respiratory and heart disease. Research has shown that obesity has a significant impact on cancer development and its prognosis after treatment. According to the International Agency for Research on Cancer, overweight and obesity are associated with thirteen cancers in particular: breast (postmenopausal), colorectal, esophageal (adenocarcinoma), gallbladder, liver, kidney, meningioma, multiple myeloma (a blood cancer), ovarian, pancreatic, stomach, thyroid, and uterine. Further research may find links to other cancers as well.

Risk factors: Obesity is primarily caused by poor diet (excessive intake of calories) and physical inactivity. Weight gain may be caused in part by the abundance of readily available high-calorie food choices and the lack of physical exertion in modern lives, psychological factors such as stress or depression, physical conditions such as hypothyroidism, and certain medications, including migraine medications and antidepressants. Research has also shown links between genetics and obesity, demonstrating an inherited predisposition in some people to gain weight more easily or have difficulty losing weight.

Etiology and the disease process: Many researchers have studied obesity and its relationship to an increased incidence of certain cancers. It is believed that fat cells in the body produce hormones and other substances that affect cell growth. People who are obese have significantly increased levels of these compounds because of the increased number of fat cells, which can have potentially influential effects on cellular growth and programmed cellular death (apoptosis), perhaps allowing damaged cells to survive and grow into tumors. The roles of estrogen, insulin, insulin-like growth factor-1, and insulin-like growth factor-binding protein-3, leptin, and cytokines, as well as other substances and growth factors, are being examined for their relationship to obesity-associated cancers.

An example of these actions by fat tissue can be found in postmenopausal breast cancer, which is known to have a higher incidence rate in women. Estrogen, which is important for the reproductive cycle, is produced by fat tissue in addition to being produced by the ovaries. After menopause, when the ovaries stop producing hormones, fat tissue becomes the most important estrogen source. In women who are obese, postmenopausal estrogen levels are 50 to 100 percent higher than in women who are not overweight or obese. As a result, estrogen-sensitive tissues in these women are overexposed to estrogen stimulation, leading to a more rapid growth of estrogen-receptor-sensitive breast tumors. Researchers believe that fat cells stimulate surges of hormones, insulin, proteins, and other substances mentioned above, which may, in turn, cause reactions that initiate uncontrollable growth among certain cell types. A 2019 study published in Current Oncology Reports found that treatments for breast cancer patients with obesity had lower efficacy rates than those for patients without obesity. It also found that obese breast cancer patients were at increased risk for local recurrence.

Incidence: According to the American Cancer Society, the risk of cancer from obesity is similar to the risk from using tobacco. Obesity affects the entire population, regardless of age, gender, race, or ethnicity. In the United States, obesity began increasing at an alarming rate in the late twentieth century. In 1980, about 15 percent of adults were obese; by 2011, that number had more than doubled to about 35 percent.

A 2013 American Journal of Public Health study found that between 1986 and 2006, overweight and obesity accounted for 5 percent of deaths among African American men, 15.6 percent among White men, 26.8 percent among African American women, and 21.7 percent among White women. According to the US Centers for Disease Control and Prevention (CDC), the prevalence of obesity increased from around 30 percent in 1999 to 2000 to 41 percent in 2017 to 2020.

Childhood obesity became a significant concern for medical experts because of the staggering number of overweight children and the projected long-term health effects. The National Cancer Institute (NCI) reported in 2017 that between 1988 and 1994, only about 10 percent of American children and youth aged two to nineteen and 56 percent of adults were obese; by 2011–14, 17 percent of children and adolescents were obese, as were 36.5 percent of adults, according to the National Health and Nutrition Examination Survey. Overweight and obesity are most common among Black and Hispanic women, with similar patterns seen for children and adolescents in these groups. According to the CDC, between 2017 and 2020, almost 13 percent of children in the US between two and five, 21 percent of children six to 11 years old, and 22 percent of adolescents between 12 and 19 years old were obese.

Studies have increasingly linked obesity and cancer. Many studies show that the greater the degree of obesity, the stronger the association with cancer. After analyzing data from 2005 to 2014, CDC and NCI scientists found that more than half of cancers in women and about one-quarter in men, or 40 percent of all cancers diagnosed in the country, were linked to overweight and obesity. Graham Colditz, a physician with the Harvard School of Public Health, estimated that 50 to 60 percent of cancer cases could be avoided if no one were overweight or obese.

Symptoms: There are no symptoms that are specific to obesity-associated cancers.

Screening and diagnosis: Screening for obesity-associated cancers includes annual physical examinations to calculate BMI and take waist measurements, as well as annual laboratory tests, such as serum lipid panel, fasting glucose level, and thyroid function tests. In addition, people can essentially screen themselves by monitoring their own weights. There are no specific tests for obesity-related cancers; testing is done when patients exhibit other symptoms. Staging is specific to the type of cancer that develops.

Treatment and therapy: Treatment for obesity-associated cancer is specific to the type of cancer. However, based on data obtained during various studies, patients must also reduce their weight to avoid the increased risk that obesity places on successful treatment. Patients must set weight-loss goals and obtain assistance from a registered dietitian or weight-loss program for in-depth counseling. Many reputable commercial and community programs exist for obesity treatment. Desirable programs should include diets that meet the United States recommended daily allowance for nutrients, exercise counseling, behavior modification, and provision for long-term maintenance.

Some experts may suggest nonpharmacologic treatment for six months and then consideration of weight-loss medication if weight loss is unsatisfactory in those with a BMI greater than 30 or a BMI greater than 27 with associated risk factors. Patients with severe obesity (BMI greater than 40) may also be considered for gastric bypass or bariatric surgery.

Prognosis, prevention, and outcomes: Long-term maintenance of weight loss is extremely difficult. If the patient is not motivated, successful weight loss is unlikely. Prevention efforts for obesity include education and the design of evidence-based programs that patients can reasonably follow. Weight reduction can have a significant impact on a person’s risk for developing obesity-associated cancers.

Though research links obesity with the propensity for various cancers, findings vary. A study published in Innovation in 2022 found that cancer patients who were overweight or mildly obese had better survival rates than patients with low or normal BMI. The study also found that it was not beneficial for patients who were overweight or mildly obese to lose weight, especially during treatments. Another study, published by the European Society for Medical Oncology, found that mortality rates in patients with cancer and obesity depended on the type of cancer the person had. For example, patients with obesity and breast cancer had a lower survival rate than other patients, but obesity acted as a protective factor in patients with gastrointestinal tumors. Another study, published in Ocular Oncology, noted a link between obesity and a lack of metastases and death in patients with uveal melanoma, demonstrating that the cancer in patients with obesity was not spreading like it was in patients who were overweight or of a healthy weight. However, it is important to note that varying research and studies do not, and sometimes cannot, account for causality. Therefore, further research is necessary to better understand BMI rates and mortality among cancer patients.


Bibliography

“Adult Obesity Facts.” CDC, 14 May 2024, www.cdc.gov/obesity/adult-obesity-facts/index.html. Accessed 29 Oct. 2025.

"Excess Body Weight and Cancer Risk." American Cancer Society, 3 Sept. 2025, www.cancer.org/cancer/risk-prevention/diet-physical-activity/diet-and-physical-activity/body-weight-and-cancer-risk.html. Accessed 29 Oct. 2025.

Giovannucci, Edward, and Dominique Michaud. “The Role of Obesity and Related Metabolic Disturbances in Cancers of the Colon, Prostate, and Pancreas.” Gastroenterology, vol. 132, no. 6, 2007, pp. 2208–25, doi:10.1053/j.gastro.2007.03.050. Accessed 29 Oct. 2025.

Lee, Kyuwan, et al. “The Impact of Obesity on Breast Cancer Diagnosis and Treatment.” Current Oncology Reports, vol. 21, no. 5, 2019, pp. 1–6, doi:10.1007/s11912-019-0787-1. Accessed 29 Oct. 2025.

Masters, Ryan K., et al. "The Impact of Obesity on US Mortality Levels: The Importance of Age and Cohort Factors in Population Estimates." American Journal of Public Health, vol. 103, no. 10, 2013, pp. 1895–901, doi:10.2105/AJPH.2013.301379. Accessed 29 Oct. 2025.

"Obesity and Cancer." Cancer.gov. National Cancer Institute, National Institutes of Health, 28 Jan. 2025, www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet. Accessed 29 Oct. 2025.

"Obesity and Cancer." Centers for Disease Control and Prevention, 11 June 2025, www.cdc.gov/cancer/risk-factors/obesity.html. Accessed 29 Oct. 2025.

Sabazade, Shiva, et al. "Obesity Paradox in Uveal Melanoma: High Body Mass Index Is Associated with Low Metastatic Risk." British Journal of Ophthalmology, vol. 108, 2024, pp. 578-87, bjo.bmj.com/content/108/4/578. Accessed 29 Oct. 2025.

Tu, Huakang, et al. “Body Mass Index and Survival after Cancer Diagnosis: A Pan-Cancer Cohort Study of 114 430 Patients with Cancer.” The Innovation, vol. 3, no. 6, 2022, doi:10.1016/j.xinn.2022.100344. Accessed 29 Oct. 2025.

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