Obesity and Cancer

Introduction

Obesity is a significant risk factor for various types of cancer, including breast, colorectal, endometrial, and pancreatic cancer. Excess body fat can lead to chronic inflammation, hormonal imbalances, and insulin resistance, all of which contribute to cancer development and progression. Maintaining a healthy weight through a balanced diet and regular exercise can help reduce the risk of obesity-related cancers.

Overweight and obesity may be detected using the body mass index (BMI). Adults who have a BMI between 25.0 and 29.9 are deemed overweight. An individual is considered obese if their BMI is 30.0 or over. In the United States, around two out of five persons are obese.

The calculation of BMI is the same for kids and teenagers, but the interpretation varies. It compares a child or teen’s BMI to that of others of the same age and sex. In the US, obesity affects almost one in five kids and teenagers.

Obesity: What is it?

When a person has an unhealthy distribution or quantity of body fat, they are said to be obese. Those who are overweight or obese have a higher chance of dying from all causes and are more likely to suffer from several illnesses, such as diabetes, high blood pressure, cardiovascular disease, stroke, and at least 13 different forms of cancer, than those who are of a healthy weight.

The body mass index (BMI) is a metric that researchers frequently use to assess whether a person is obese. The calculation of a person’s BMI involves dividing their weight in kilograms by their height in meters squared, which is often represented as kg/m2. For most people, body mass index (BMI) is a useful (although imperfect) indication of body fatness, and it gives a more accurate assessment of obesity than weight alone.

A BMI calculator for adults is available from the National Heart Lung and Blood Institute. For people aged 20 and up, the following are the typical weight categories based on BMI:

• Underweight below 18.5
• Healthy, 18.5 to 24.9
• Overweight, 25.0 to 29.9
• Between 30.0 and 39.9 Obese
• 40.0 or better fat vey severe

A BMI percentile calculator for kids and teenagers is available from the Centers for Disease Control and Prevention (CDC). According to the CDC’s BMI-for-age growth charts, individuals under the age of 20 who are overweight or obese may see considerable changes in their BMI as they mature.

• Age-specific BMI below the 5th percentile for a given sex: Underweight
• BMI for age that is below the 85th percentile but at or above the sex-specific 5th percentile: Healthful
• BMI for age below the 95th percentile but at or above the sex-specific 85th percentile: Overweight
• Age-for-sex BMI at or above the 95th percentile: Obesity
• A BMI that is 120% or higher above the 95th percentile for a certain sex: extreme obesity

BMI is occasionally used in conjunction with measurements that show the distribution of body fat as markers of obesity and illness risk. These measurements include waist circumference, waist-to-hip ratio (waist divided by hip), waist-to-height ratio, and fat distribution as determined by CT or PET imaging or dual-energy X-ray absorptiometry (DXA or DEXA).

These metrics are employed because of the growing understanding that fat distribution is associated with the risk of illness. The fat that surrounds internal organs, or visceral fat, appears to be more harmful in terms of disease risks than either subcutaneous fat or total fat (the layer immediately beneath the skin).

What is known about the connection between cancer and obesity?

Large cohort studies, a kind of observational research, provide almost all of the data that obesity increases the chance of developing cancer. Observational study data, however, cannot conclusively prove that obesity causes cancer. This is due to the possibility that individuals with obesity or overweight may differ from those without these illnesses in ways other than body fat and that these differences may account for their elevated risk of cancer rather than body fat.

Types of cancer linked to obesity

Obesity and excess weight are linked to a greater risk of 13 different cancer types. 40% of all cancers diagnosed in the US each year are these types of malignancies.

• Lung cancer of the esophagus.
• Breast (for women who have had menopause).
• The rectum and colon.
• The uterus.
• Gallbladder.
• Upper abdomen.
• Kidneys.
• Liver.
• Ovaries.
• Pancreas.
• Thyroid.
• A kind of brain cancer is called meningioma.
• Multiple myeloma.

How obesity and excess weight can cause cancer

Obesity and overweight can result in elevated levels of sex hormones, insulin, and insulin-like growth factors, as well as chronic inflammation. Cancer may result from these alterations. The longer a person is overweight and the more additional weight they accumulate, the higher their chance of developing cancer.

The second leading cause of cancer in the UK is being overweight or obese. Your risk of developing cancer is higher if you are overweight than if you are at a healthy weight.

It is not a given that being overweight will result in cancer. However, the more your weight and the longer you have been overweight, the greater the danger. If you are overweight, lowering your weight and preventing weight gain will help lower your chance of developing cancer.

There are several advantages to maintaining a healthy weight. These include having more vitality and a lower chance of developing diseases including joint discomfort, heart disease, and stroke.

The following can be impacted by fat cells’ signals:

• Increased amounts of growth hormones, which instruct cells to divide more often, can result from excess body fat. The development of cancer cells is increased as a result.
• When the body has a lot of fat cells, immune cells go there, causing inflammation. Cells may divide more quickly as a result of inflammation. This can raise the risk of cancer over time.
• Hormones related to sex: Following menopause, fat cells generate the hormone estrogen. Breast and womb cells may divide more often as a result of this hormone, raising the possibility of cancer.

How to reduce your risk

You can lower your risk of obesity-related cancer by eating a balanced diet and exercising often. Consult your physician if you have concerns about your weight or the weight of your kid.

How medical professionals may assist their patients in treating or preventing obesity

There are several methods by which healthcare professionals may assist patients in achieving a healthy weight. As an illustration, they can:

• Calculate the BMI, height, and weight of the patients.
• A person’s chance of developing cancer can be reduced by maintaining a healthy weight.
• Refer patients and their families to neighborhood resources that offer wholesome meals and opportunities for physical activity.
• Patients with a high body mass index who wish to reduce their weight are sent to rigorous lifestyle regimens. To lose weight, these programs assist patients in altering their diet and level of physical activity. Both the American Academy of Pediatrics and the US Preventive Services Task Force advocate for such programs for both adults and children.
• Talk about the use of drugs, surgery, and other therapies for overweight in older adults and children.

Does losing weight help those who are overweight or obese after receiving a cancer diagnosis?

Breast cancer has been the subject of the majority of research on this topic. Weight reduction therapies have been shown in several randomized clinical trials including breast cancer survivors to produce both weight loss and positive changes in biomarkers associated with the relationship between obesity and prognosis.

There is, however, limited data about whether losing weight lowers the chance of dying from or recurrence of breast cancer. An ongoing randomized phase III research, the NCI-sponsored Breast Cancer Weight Loss (BWEL) Study, is investigating the potential effects of weight loss on invasive disease-free survival and recurrence in overweight and obese women following a breast cancer diagnosis.

FAQs

References:

• Obesity and Cancer fact sheet. (2022, April 5). Cancer.gov. https://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet
• Obesity and cancer. (2025, January 14). Cancer. https://www.cdc.gov/cancer/risk-factors/obesity.html
• Cancer Research UK. (2024, December 4). How does obesity cause cancer? https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/bodyweight-and-cancer/how-does-obesity-cause-cancer