A new study by scientists from Northwestern Medicine suggests that the timing of meals in relation to sleep may be key to improving cardiovascular and metabolic health — even without changing calorie intake.

The study results were published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology.

Unlike traditional diet studies, researchers focused not so much on what people eat, but on when they eat relative to their natural circadian rhythm — the body’s biological clock that regulates sleep and wakefulness.

The study involved 39 middle-aged and older adults with overweight or obesity and an elevated risk of cardiometabolic diseases. Participants were divided into two groups: one followed their usual eating schedule, while the other extended their overnight fasting period by about two hours, stopping food intake no later than three hours before bedtime and reducing room lighting during that time.

After 7.5 weeks, participants who synchronized meal timing with sleep showed significant improvements in cardiovascular and metabolic markers compared with the control group. At night, their blood pressure declined more naturally and their heart rate slowed — changes considered signs of a healthy cardiovascular system. During the day, their blood glucose levels were more stable: the pancreas responded more efficiently to glucose, indicating tighter regulation of insulin and blood sugar.

The authors note that not only the amount of food but also its timing in relation to sleep matters for health. The idea is that the body manages metabolic processes more effectively when periods of eating and fasting are aligned with natural biological rhythms rather than working against them.

Notably, nearly 90% of participants were able to follow the new regimen, making this approach a promising, accessible, non-surgical way to improve heart health and metabolism, particularly for middle-aged and older adults.

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