According to research1 presented at the Endocrine Society's annual meeting, March 23, 2019, intermittent fasting, where you eat all your meals for the day within a narrow window of time — in this case eight hours — drastically reduces a woman's risk of breast cancer. According to Dr. Manasi Das, a postdoctoral fellow at the University of California, San Diego, who led the research team:2

"Improving the metabolic health of postmenopausal women with obesity may mitigate their risk for breast cancer. Time-restricted eating may be more successful than calorie restriction in controlling the negative effects of obesity, due to the hunger and irritability that makes it more difficult to stick with long-term calorie restriction.

The results suggest the anti-tumor effect of time-restricted eating is at least partially due to lower levels of insulin, suggesting this intervention may be effective in breast cancer prevention and therapy.

Exploring the ability of time-restricted eating to prevent breast cancer could provide an inexpensive but effective strategy to prevent cancer impacting a wide range of patients and represents a groundbreaking advance in breast cancer research."

Link Between Insulin Resistance and Cancer Strengthens

The team conducted three separate experiments on mice whose ovaries had been removed to simulate a postmenopausal state. In the first, the mice were first fattened up with a high-fat diet, after which they were divided into two groups: One had access to food around the clock, while the other had eight-hour access to chow at night (the time of highest physical activity).

The control group consisted of lean mice given access to a low-fat diet 24 hours a day. Three weeks into the experiment, all of the animals were injected with breast cancer cells. Results showed time-restricted feeding, also known as intermittent fasting, reduced tumor growth in the obese mice to levels similar to those in the lean mice.

In the second experiment, they used mice that were genetically modified to develop breast cancer. As before, half of them had round-the-clock access to a high-fat diet while the other had access to food for eight hours. Here, they also assessed the impact of insulin by artificially raising insulin in some mice using an insulin pump, while lowering it in others using the drug diazoxide.

In the third experiment, mice fed a low-fat diet were either given insulin via an insulin pump or saline as a control, while mice on a high-fat diet were either given diazoxide to lower their insulin levels, or no drug as the control. As you'd suspect, higher insulin levels fueled tumor development, while lower levels inhibited cancer growth. As reported by the New York Post:3

"The results add to a growing body of evidence that indicates obesity and metabolic syndrome, a collection of risk factors that increase the chance of developing heart disease stroke and diabetes, are also risk factors for cancer, particularly postmenopausal breast cancer."

Indeed, other studies have found intermittent fasting is a powerful anticancer strategy, and researchers are even working on getting it approved by the U.S. Food and Drug Administration as an adjunct to cancer treatment to improve long-term survival rates.

Benefits of Intermittent Fasting

Intermittent fasting, i.e., following a meal-timing schedule where you're fasting for at least 16 hours every day and eating all of your meals within eight consecutive hours, has a long list of confirmed health benefits.

There are also other intermittent fasting plans where you dramatically cut back on your calories for a certain number of days each week, while eating normally during the remainder. The 5-to-2 intermittent fasting plan is one such example. The fasting mimicking diet, developed to match the effects of water-only fasting, is another.

Most if not all of these plans have similar benefits, which include the following. 4,5,6,7 For a rundown of the science behind some of these benefits, see Chris Kresser's article "Intermittent Fasting: The Science Behind the Trend."8