A preliminary study in mice suggests that when a person eats, and not what a person eats, may decrease the risk of breast tumors in obese women. Researchers at the University of California San Diego investigated whether time-restricted feeding (TRF) — eating all meals and snacks within a specified period of time each day, when the individual is most active — could improve metabolic health and decrease the risk of breast cancer development and growth. In these studies, time-restricted eating had a dramatic effect, delaying the development of tumors and reducing tumor growth in obese mice, who were fed a high-fat diet, to levels seen in lean mice, researchers said. The anti-tumor effect of TRF appeared to rely, at least in part, on the lowering of insulin levels, which are typically high in obese subjects and are linked to a higher risk of cancer, the study showed. "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," said Manasi Das, PhD, the study's lead researcher, in a press release. “Improving the metabolic health of postmenopausal women with obesity may mitigate their risk for breast cancer,” Das said. The study's findings were communicated in a poster titled “Time Restricted Feeding Delays Breast Cancer Initiation and Growth in a Mouse Model of Postmenopausal Obesity” at the Endocrine Society's meeting ENDO 2019, held in March in New Orleans. Researchers noted that time-restricted feeding — a type of intermittent fasting — does not necessarily lead to weight loss. TRF does not imply any changes in the amount of calories ingested, only the tim