Women now have a reason to lose weight that’s more important than looking good in their bathing suit this season. A new study, presented at the American Society of Clinical Oncology's annual meeting, reveals that by losing just five to 10 percent of body weight through diet and exercise, postmenopausal women can cut the risk of breast cancer in half. Women who lost the same amount of weight through diet alone didn’t have the same benefits.

Fat increases blood levels and hormones that are linked with breast cancer, such as estradiol and testosterone. One in eight women will be diagnosed with breast cancer at some point in their lifetime, and the chances of that happening increases with age and weight. Exercise yields stronger results for decreasing the risk of breast cancer because it offers the additional benefits of preserving lean body mass, while decreasing fat.

“Women who have high levels [of these hormones] have at least twice the risk of getting breast cancer compared with women who have very low levels,” said Dr. Anne McTiernan, the study's co-author and director of the Prevention Center at Fred Hutchinson Cancer Research Center. 

Researchers tracked the weight loss through diet and exercise of 439 overweight and obese postmenopausal women who were given one of the four following weight-loss programs:

  1. Reduced-calorie diet: 1,200 to 2,000 calories (depending on their weight).
  2. Exercise alone: Moderate to vigorous activity for 45 minutes, five times a week
  3. Diet and exercise: A combination of reduced-calorie diet and exercise.
  4. Maintain usual lifestyle: The study’s control.

After one year, the women who dieted lost on average five percent of their body weight, which is equivalent to 9 lbs. if you weigh 180 lbs., for example. As a result, their estradiol levels dropped by 30 percent, which gave them a 22 percent lower risk of breast cancer. Any reduction in breast cancer risk is notably significant. However, when they did a combination of diet and exercise they lost more than 10 percent of their body weight and decreased their risk by 50 percent.

"Exercise is the preferred weight loss strategy to decrease breast cancer risk," said Anne Maria May, the study’s lead researcher from the University Medical Center Utrecht, in the Netherlands.

The key is reducing the cancer-connected hormones by losing fat. Studies have shown that women who have high levels of estradiol, a version of estrogen, double their risk of breast cancer, according to Susan G. Komen Foundation, a breast cancer awareness organization. Because there are typically higher levels of estrogen in postmenopausal women than other female age group, their risk is higher. Another risk factor for breast cancer is having higher levels of sex hormones such as testosterone.

Exercise can reduce those risks, as researchers also found a reduced risk for those who only exercised and didn’t diet. The research concluded that aside from using exercise to reduce sex hormones, it may also be its power to reduce inflammation and lower insulin levels that has shown to be effective.

“It’s never too late to start,” McTiernan said. “Women can make simple lifestyle changes to reduce calories, increase physical activity, and lose about one to two pounds a week.” 

 

Source: May AM, McTiernan A. American Society of Clinical Oncology Annual Meeting. 2014.