A new study has observed that time-restricted feeding, or intermittent fasting as it is now commonly known, improves insulin levels and reduces tumour growth in mice with obesity-driven post-menopausal breast cancer.
The study, conducted by researchers at the University of California (UC), San Diego School of Medicine, Moores Cancer Center and Veterans Affairs San Diego Healthcare System (VASDHS), has been published in the journal Nature Communications. It observes that tumour growth was driven and accelerated by elevated insulin levels in the mice, and lowering the mice’s insulin levels, while improving their metabolic health, had an anti-tumour effect.
“Time-restricted eating has a positive effect on metabolic health and does not trigger the hunger and irritability that is associated with long-term fasting or calorie restriction,” said Dr Manasi Das, post-doctoral fellow at UC San Diego. “Through its beneficial metabolic effects, time-restricted eating may also provide an inexpensive, easy to adopt but effective strategy to prevent and inhibit breast cancer without requiring a change in diet or physical activity.”
The study reports that being overweight or obese increases the risk of developing at least 13 types of cancer. Although more research is necessary, obesity also seems to disrupt circadian rhythms which control the body’s internal clocks. A disruption in these rhythms can change how the body responds to insulin which helps in regulating blood sugar levels. Such changes can, in turn, cause a person to become insulin tolerant or develop metabolic syndrome both of which may increase the risk of developing chronic diseases such as cancer.
Recent research suggests that disruptions in the circadian rhythm also appear to promote tumour growth by interfering with the cell cycle and activity of cells that suppress tumour growth. Previous research in mice has found that eating a high-fat diet on a time-restricted feeding schedule seems to reduce or reverse negative health complications related to obesity.
Time-restricted feeding (in animals) or time-restricted eating (in humans), is a type of intermittent fasting where food intake is restricted to a specific number of hours per day in line with circadian rhythms. Often, this means that food is consumed only for six to12 hours per day during the times a person is usually most active.
In this study, the researchers were attempting to investigate whether time-restricted feeding would impact growth and development of tumours and reduce the risk of breast cancer metastasising to the lungs in mice with obesity-driven breast cancer. For this purpose, they caused female mice to develop hormonal conditions similar to those which women experience following menopause.
The researchers gave two groups of mice unrestricted access to high-fat foods for 10 weeks before the trial to make them obese. While another control group of mice was given normal food throughout this period. Once the trial began, one group of mice continued to have unrestricted access to high-fat foods, while the control group still had unrestricted access to normal food. The final group of mice, who were fed on a time-restricted feeding schedule, had access to high-fat foods only for eight hours during the night, as mice are naturally most active during this period.
In a separate part of the study, researchers also tested to see whether time-restricted feeding reduced tumour growth and spread in the mice, with obesity, that were injected with breast cancer cells or induced tumour.
The researchers observe that time-restricted feeding seems to reduce obesity enhanced breast cancer tumour growth without reducing calorie intake. It also appeared to reduce the risk of developing breast cancer, as well as the risk of its spreading to the lungs. These results are likely due to the fact that time-restricted feeding improved circadian disruptions and metabolic problems associated with obesity.
“We were able to increase insulin sensitivity, reduce hyperinsulinemia, restore circadian rhythms, and reduce tumor growth by simply modifying when and for how long mice had access to food,” said senior author Dr Nicholas Webster, a professor at UC San Diego and senior research scientist at VASDHS.
“Our data suggests that a person may benefit from simply timing their meals differently to prevent breast cancer rather than changing what they eat,” said Dr Das.
The team now feels that they need to confirm their findings on a larger scale and also in humans. They will also need to figure out how time-restricted feeding impacts men, as well as other types of cancer.
Following an eating schedule of this manner does not involve reducing food intake or making dietary restrictions and, hence, this dietary method can be beneficial to many people, since usually people cannot commit to major lifestyle and dietary changes, or are not able to follow them strictly.
