Overnight fasting — how long you go without eating from your last meal (or midnight snack) of one day and your first of the next — can have a big, and positive, impact on your health. Long periods overnight without food reduce your risk of cancer and diabetes.

That's the conclusion of University of California, San Diego School of Medicine researchers who looked at the impact the timing of eating and fasting had on breast cancer risk. Previous research has shown that diabetes is a risk factor for several types of cancers and that women with type 2 diabetes have a 23% higher risk of developing breast cancer and a 38% higher risk of dying from breast cancer than their peers. This was an effort to understand that relationship better.

Each three-hour increase in nighttime fasting was associated with a 20% lower likelihood of having abnormal tests of sugar control.

The critical factor is thought to be elevated levels of blood sugar.

Data suggest that controlling blood sugar for longer periods of time reduces cancer risks. Having daily schedules with designated periods of eating followed by 12-16 hours of fasting helps accomplish this.

When periods of fasting and eating are coordinated with the body's natural circadian rhythms, the beneficial effects of blood sugar control on health are strengthened and risks of cancers and chronic disease are lowered.

Fasting has a wide range of heath benefits for both body and brain. Intermittent fasting increases the levels of antioxidant enzymes, which help repair cellular damage. Fasting has also been linked to a reduction in inflammation and the cellular processes that can trigger Alzheimer’s disease and Parkinson’s disease.

Other studies have shown that metastases in cancer cells are reduced during periods of fasting, making daily periods of prolonged overnight fasting, aimed at controlling blood glucose levels, a potentially effective and highly achievable anti cancer strategy. It is also a good way to lose weight.

The recent research studied prolonged overnight fasting and its impact on blood glucose control.

About 2200 women were questioned about their diets, eating and sleeping patterns including the time between their last food intake of the day and the first of the next morning. Length of nighttime fasting was subdivided into groups of 9.5, 12.3 and 15.1 hours. About half of the women had blood tests to measure their glucose control. Socioeconomic, other health issues, body mass index, and demographic factors were also recorded.

Each three-hour increase in nighttime fasting was associated with a 20% lower likelihood of having abnormal tests of sugar control. Specifically, for every three hours of additional fasting, the post-prandial (two hours after eating) glucose was reduced by 4%.

Post-prandial glucose is an important measure of prediabetes and diabetes. This effect was independent of the number of calories consumed or the body mass index of the woman. The improvement in glucose control with prolonged fasting was seen regardless of how much the woman had eaten during the day, prior to the fast or if she was overweight.

“The dietary advice for cancer prevention usually focuses on limiting consumption of red meat, alcohol and refined grains, while increasing plant-based foods,” co-author Ruth Patterson said in a statement. “New evidence suggests that when and how often people eat can also play a role in cancer risk.”

Because poor glucose control is associated with increased cancer risk, the researchers maintain that their findings are extremely important in the efforts to decrease the personal and public health burden of cancer. They suggest that the benefits of prolonged overnight fasts deserve more attention.

It may be time for doctors and patients to discuss the late night snack.

The study is published in Cancer Epidemiology, Biomarkers & Prevention and was presented at the American Association of Cancer Research's annual meeting in Philadelphia.