- Being overweight or obese is a risk factor for several types of cancer. Although a higher weight may not necessarily cause cancer, maintaining a healthy weight is thought to be associated with a lower risk of many chronic diseases.
- Many resources are available to help you maintain a healthy weight, including doctors and dietitians.
- Talk with your doctor about developing an appropriate weight control plan for you.
More than two-thirds of American adults are overweight or obese (substantially or extremely overweight). 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 cause people to become overweight or obese, including genetic, hormonal, environmental, emotional, and cultural factors. People who are overweight or obese have a higher risk of many serious health conditions, including type II diabetes, high blood pressure, and heart disease. Being overweight or obese is also associated with an increased risk of cancer.
Understanding weight gain and cancer risk
Several studies have explored why being overweight or obese may increase cancer risk and growth. People who are obese have more fat tissue that can produce hormones, such as insulin or estrogen, which may cause cancer cells to grow.
How your weight changes throughout your life may also affect your risk for cancer. Although more research is needed, studies have shown that the following factors can affect your cancer risk of cancer:
- High birth weight is associated with higher cancer risk.
- Weight gain during adulthood is consistently associated with an increased risk for several types of cancer.
- Weight cycling (losing and regaining weight repeatedly) may also be a risk factor.
Research suggests that maintaining a healthy weight is associated with a lower risk of cancer and a lower risk of cancer recurrence (when cancer comes back after treatment) in cancer survivors.
Types of cancer linked to overweight or obesity
Some types of cancer appear to be closely linked to weight, although this association has not been proven for all cancers. Some cancers in which overweight has been found to be consistently associated with increased risk are:
- Breast (in women who have been through menopause)
- Colon and rectum
- Endometrium (lining of the uterus)
Although more evidence is needed, being overweight has been associated with other cancers:
- Non-Hodgkin lymphoma
- Multiple myeloma
Measuring weight gain
Obesity is often measured with body mass index (BMI), the ratio of a person's weight and height, and waist measurements. A normal BMI is 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. In addition, people with larger waist measurements have a higher risk of various diseases, such as heart disease. A normal waist measurement is under 40 inches for men and under 35 inches for women.
Weight loss and weight management tips
To control weight gain, it is important to be aware of what you eat and how much you exercise and to 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 today. The reasons for this include a plentiful, 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.
- Limit 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.
- Increase levels of physical activity. Most people should aim for 30 to 60 minutes per day of moderate-to-intense exercise on most days. However, 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. Most hospitals and health-care organizations have professionals on staff that can provide weight management treatment. For instance, individualized counseling provided by a dietitian can help people lose weight and provide support.
If nutritional changes and increasing physical activity aren’t enough, there are other steps you can take. The National Institutes of Health approach to obesity treatment includes:
A change in lifestyle behaviors. Behaviors that both reduce the amount of food eaten and increase physical activity should be changed before other weight loss treatments are considered. A registered dietitian, exercise physiologist, clinical psychologist, or doctor who specializes in weight loss can help.
Medications. The use of drugs can help a person lose weight if changing diet and increasing exercise do not work.
Surgery. This may be an option for patients who are severely obese and have not lost weight with other approaches.
Questions to ask a medical professional about weight loss:
- Am I at an unhealthy weight?
- How is my excess 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 that can help me develop a weight loss program?
- Where can I find information on healthy eating?
- Where can I find information on exercise?
Academy of Nutrition and Dietetics (formerly American Dietetic Association): Healthy Weight 
Centers for Disease Control and Prevention: Overweight and Obesity 
National Cancer Institute: Obesity and Cancer Risk 
National Heart, Lung, and Blood Institute: Obesity and Physical Activity