Dimming the lights and avoiding food in the three hours before going to bed can have a positive effect on blood pressure, heart rhythms and blood-sugar control in adults at risk of heart disease, a new study has found.
Scientists wanted to explore whether better matching an overnight fast to a person’s natural cycle of sleeping and waking could improve heart health and overall metabolism.
Previous studies have shown that the body’s internal clock, known as the circadian rhythm, plays a key role in regulating a range of bodily processes.
Poor metabolic health has been shown to increase the risk of chronic conditions like type 2 diabetes, non-alcoholic fatty liver disease, and heart disease.
In the new study, researchers from Northwestern Medicine in the US investigated how the timing of the last meal of the day could be optimised for the best heart health and metabolism benefits.
The 7.5-week-long study compared 39 overweight people who stopped eating at least three hours before bed with those who maintained their usual eating habits.
Participants were assigned either to a group that underwent overnight fasting for 13 to 16 hours or to a control group that maintained a habitual fasting window of 11 to 13 hours.
Both these groups dimmed their lights three hours before bedtime, a measure that has previously been shown to align the body’s circadian rhythm with a more natural cycle of light and dark.
Scientists focused only on adjusting when participants ate, and not on reducing their calorie intake.
Those who adjusted the timing of their last meal saw their nighttime blood pressure and heart rate decrease significantly at night and adjust to a healthier pattern.
When given glucose, their pancreas also responded more effectively, suggesting improved insulin release and steadier blood sugar levels, scientists said.
“Timing our fasting window to work with the body’s natural wake-sleep rhythms can improve the coordination between the heart, metabolism and sleep, all of which work together to protect cardiovascular health,” explained Daniela Grimaldi, author of the study published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology.
The researchers said eating earlier and anchoring fasts to times when people are largely asleep were realistic changes that would be achievable for the group of high-risk individuals being studied – and offered a different tactic for intervention compared to dietary changes.
“It’s not only how much and what you eat, but also when you eat relative to sleep that is important for the physiological benefits of time-restricted eating,” Dr Grimaldi said.
Researchers hope to test the benefits of similar fasting approaches in larger trials.
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