Obesity, Weight, and Cancer Risk

Approved by the Cancer.Net Editorial Board, 02/2019

More than two-thirds of American adults are overweight and obese, making this an important topic for people living with cancer. When a person is overweight or obese, it means that they have too much body fat in relation to lean body tissue, such as muscle.

Many factors can cause people to become obese. These include genetic, hormonal, environmental, emotional, and cultural factors. People who are overweight have a higher risk of many serious health conditions, including type-2 diabetes, high blood pressure, and heart disease. Being overweight is also associated with an increased risk of many types of cancer.

Understanding weight gain and cancer risk

Several studies have explored why being overweight or obese may increase cancer risk and growth. The possible reasons that obesity is linked with cancer include:

  • Increased levels of insulin and insulin growth factor-1 (IGF-1), which may help some cancers develop

  • Chronic, low-level inflammation, which is more common in people who are obese and is linked with an increased cancer risk

  • Higher amounts of estrogen produced by fat tissue, which can drive the development of some cancers, such as breast and endometrial cancers

  • Fat cells may effect processes that regulate cancer cell growth.

How your weight changes throughout your life may also affect your risk for cancer. Studies have shown that the following factors can affect your cancer risk:

  • High birth weight

  • Gaining weight as an adult

  • Losing and regaining weight repeatedly

Research suggests that maintaining a healthy weight is associated with a lower risk of cancer and of the cancer returning in survivors.

Types of cancer linked with an increased weight

Being overweight or obese has been linked to these cancers:

  • Breast

  • Colorectal

  • Uterine

  • Kidney

  • Head and neck

  • Esophageal

  • Pancreatic

  • Endometrium

  • Prostate

  • Gallbladder

  • Thyroid

Measuring weight gain

Obesity is often measured with body mass index (BMI) and waist measurements. BMI is the ratio of a person's weight and height. A healthy BMI is usually between 18.5 and 24.9. A BMI between 25 and 29.5 is considered overweight, while a BMI of 30 or higher is obese.

Also, people with larger waist measurements have a higher risk of various diseases, such as heart disease. A healthy waist measurement is under 40 inches for men and under 35 inches for women.

Weight management tips

To control weight gain, pay attention to what you eat and how much you exercise. You should also make healthy choices about what you eat and drink. This can be challenging because eating a high-calorie diet is typical in the United States. The reasons for this include a complete, relatively low-cost food supply and large portions. Here are some tips to help:

  • Eat more vegetables, fruits, lean protein, and whole grains. Some types of food, such as broth-based soups, also help a person feel "full" faster.

  • Avoid foods and beverages that are high in sugar, such as juice and soda.

  • Eat and drink only as many calories as you need to maintain a healthy weight and support your level of physical activity.

  • Aim for 30 to 60 minutes per day of moderate to intense physical activity on most days. But even a small increase in physical activity has benefits.

Suggestions for people who are overweight or obese

If you are currently overweight or obese, it is best to start by taking steps to lose weight through nutrition and exercise. Aim to lose 5% to 10% of your body weight as your first goal. Although this amount may seem small, research shows that even losing 5% to 10% of your weight is beneficial. Most hospitals and health care organizations have professionals such as dietitians who can provide weight management counseling and treatment.

Sometimes nutritional changes and increasing physical activity are not enough. But there are other steps you can take. The National Institutes of Health approach to obesity treatment includes:

A change in lifestyle behaviors. First, change behaviors to reduce the amount of food you eat and increase physical activity. A registered dietitian, exercise physiologist, clinical psychologist, or doctor who specializes in weight loss can help.

Behavior change support. For many, being overweight or obese is more complex than simply eating too much and exercising too little. It is important to get support when you are trying to lose weight. Most weight loss programs include sessions with a dietitian or weight loss specialist to help you make healthy lifestyle changes and stick with them over time.

Medication. Weight loss drugs are usually only recommended when a combination of diet, exercise, and behavior change support have not worked. Or, if you have other serious health conditions from being obese.

Surgery. A variety of procedures can make a person’s stomach smaller. This is called weight loss surgery or bariatric surgery. This may be an option for people with a BMI of 40 or higher. Or for those with a BMI of 35 or higher who have another serious health condition related to obesity.

Questions to ask a medical professional about weight loss

Talk with your health care team about your weight. They can provide guidance and help you find resources. Consider asking these questions:

  • Is my weight unhealthy?

  • How is my extra weight harming my health?

  • How will losing weight improve my health?

  • How much weight do I need to lose?

  • How much weight should I lose each week?

  • What programs and treatments are available to help me lose weight?

  • Can you recommend professionals who can help me develop a weight loss program?

  • Where can I find information on healthy eating?

  • Where can I find information on exercise?

Related Resources

Physical Activity and Cancer Risk

Changes People Can Make to Lower Their Cancer Risk

Food and Cancer Prevention

More Information

Academy of Nutrition and Dietetics: Your Health and Your Weight

National Cancer Institute: Obesity and Cancer Risk

Society of Gynecologic Oncology: A Patient’s Guide to Losing Weight to Reduce Your Risk of Endometrial Cancer

Managing Your Weight After a Cancer Diagnosis: A Guide for Patients and Families. Cancer.Net; Doctor-Approved Patient Information from ASCODownload ASCO’s free booklet, Managing Your Weight After a Cancer Diagnosis: A Guide for Patients and Families, as a printable PDF in English (16 pages) or Spanish (16 pages). Order printed copies of the booklet through the ASCO Store.