In the news: Women 50+: Lose Weight to Cut Breast Cancer Risk;
The Latest on Intermittent Fasting

Shedding Weight May Lower Breast Cancer Risk

Though being overweight or obese (a high body mass index or BMI) is an established risk factor for breast cancer in postmenopausal women, researchers have wrestled with the important question of whether losing excess weight can reverse that risk. The problem has been a lack of sufficient evidence.

Now, a new analysis (1 )of over 180,000 women from 10 prospective studies – large enough to have statistical accuracy – has shed light on that question: Can losing weight, and keeping it off, favorably impact breast cancer risk?

It appears that for women overweight and over 50, shedding weight and maintaining that loss lowers the risk of breast cancer, at least for those not on hormone therapy. And the greater the amount of maintained weight loss, the lower the risk, though even fairly modest amounts of weight loss can be of benefit. The study was published in the December issue of the Journal of the National Cancer Institute.

Researchers from the American Cancer Society, Harvard and others report that women (not using postmenopausal hormones) who sustained a loss of roughly 4.4-10 pounds had an 18% reduction in risk compared to women whose weight remained stable over about 10 years. Stable weight was defined as consistently staying within plus or minus 4.4 pounds.

Sustained weight loss of 10-20 pounds lowered the risk by 25%. Losing and keeping off 20 pounds or more decreased the risk by 32%.

Even women who lost 20 or more pounds but gained some (but not all of it) back, still lowered their risk of this cancer compared to women with stable weight.

According to the authors, the results suggest that even modest weight loss is associated with lower breast cancer risk for women 50 and older. “Breast cancer prevention may be a strong weight loss motivator for the two-thirds of American women who are overweight or obese”, they said.

What is Intermittent Fasting?

Intermittent fasting (IF) is following a dietary pattern that cycles between periods of eating and fasting. It doesn’t tell you what foods to eat, but rather when you should eat. There are different IF approaches, but most split the day or week into eating and fasting periods.

Many animal and clinical studies of time-restricted eating have shown that changing back and forth between eating and fasting triggers a metabolic switch to go from storing fat to converting fat into energy. The body switches from using glucose derived from the liver to ketones derived from fat cells. IF aids weight loss and promotes other health benefits too – perhaps even longer life.

What is the Evidence for IF Benefits?

A recent paper published in the New England Journal of Medicine reviews the effects of IF on health, aging and disease (2). The report, according to the authors, is meant to serve as a road map for doctors to guide patients who want to try IF. The review focuses on two patterns: eating between a 6-8-hour period daily and fasting the remaining16-18 hours (time-restricted eating), and fasting for two days out of the week.

The authors point to pre-clinical studies and clinical trials that suggest IF has benefits for many health conditions including obesity, heart disease, neurologic conditions and type 2 diabetes. In animals, IF improves the health span and also increases lifespan, similar to some findings of calorie restriction studies. But one problem is that trials in humans are mostly short-term, so it’s not yet known whether people can stick with IF over the long haul to gain the same longevity benefits.

Is IF for Everyone?

Probably not, since eating 3 meals daily is culturally ingrained, and some people may not be able to adhere to IF. Additionally, others with health problems should check with their physicians first for guidance. But for many, IF is a promising way of eating for health.

References

1. Teras LR, et al. Sustained weight loss and risk of breast cancer in women > 50 years: a pooled analysis of prospective data. JNCI. Epub ahead of print, Dec. 13, 2019.
2. de Cabo R and Mattson MP. Effects of intermittent fasting on health, aging, and disease. NEJM. 381:2541-51, 2019.