A new study from Northwestern Medicine examines how aligning meal times with the body’s sleep-wake cycle may boost heart and metabolic health, especially for middle-aged and older adults at greater risk for disease. This research may be helpful as primary care providers (PCPs) work with patients in managing blood sugar and cardiovascular health. Medscape consulted with three experts for viewpoints and clinical commentary.
Breaking Down the Data
Time-restricted eating is increasingly popular, as data showed it can boost cardiometabolic health and be as effective as calorie restriction. However, most research looks at fasting duration rather than its alignment with sleep, which is crucial for metabolism. The Northwestern study suggested that using sleep as a reference point for time-restricted eating could be an easier, nondrug approach to boost cardiometabolic health, especially in middle-aged and older adults at greater risk for these diseases.
How Sleep and Cardiometabolic Health Intersect
Clinical data continues to reveal how the integrity of both sleep and the circadian rhythm is essential for cardiometabolic health.
“At night, during sleep, the cardiovascular system is downregulated, with overall decreases in blood pressure and heart rate,” said Naima Covassin, PhD, a Mayo Clinic faculty, cardiovascular medicine researcher in Rochester, Minnesota. “Lipolysis (fat mobilization) increases, while insulin secretion decreases. When we adjust meal timing to more closely match the body’s natural sleep and wake cycle, we promote circadian rhythm synchronization.” This, in turn, facilitates the circadian control of these biological processes, she said.
Melatonin, an important circadian synchronizer, may be involved.
“Melatonin levels are low during the day and begin to increase, on average, a couple of hours before bedtime,” Covassin said. Previous studies, including research from Harvard, have shown that late-night eating disrupts the melatonin rhythm and this contributes to altered metabolism, including impaired glucose tolerance, she noted.
The effects observed in the present study may be especially evident in middle-aged and older adults because, with aging, the circadian rhythm weakens and sleep becomes more disrupted, Covassin said.
“While this occurs physiologically, due to biological changes associated with aging itself, health conditions common with advanced age may also contribute to sleep and circadian rhythm disturbances,” she said.
Key Points: Patients Who Practice Intermittent Fasting
Intermittent fasting refers to various diets that cycle between eating and fasting periods. The most common intermittent fasting diets include the alternate day fasting (fast day alternating with feast days); the 5:2 diet (5 days of eating and 2 days of fasting per week), and time-restricted eating.
Time-restricted eating limits food intake to a set window, typically 4-10 hours each day. Some evidence from clinical trials suggests that time-restricted eating regimens with early eating windows may lead to greater metabolic improvements compared to those with late eating windows, particularly with respect to glycemic parameters, Covassin said.
“Insulin sensitivity exhibits also a similar day-night pattern,” Covassin said. “This may be worth considering, for instance, if someone is interested in attaining better blood sugar control.”
When individuals select time-restricted eating windows according to their own preferences, they seem to experience similarly positive health effects, she also said.
Moreover, the Mayo Clinic researcher affirmed the study adds to this literature by showing that self-selected eating windows that are aligned with individual’s habitual bedtimes, with extended overnight fasting, improve blood pressure and heart rate as well as blood sugar control.
Circadian Rhythm: Sleep, Digestion, and Blood Sugar Markers
Most molecular, physiologic, and behavioral processes oscillate across the 24 hours following a circadian pattern, and virtually every cell has a circadian clock, said Covassin.
“These peripheral clocks are synchronized within each organ and tissue and also by the central clock, which is located in the suprachiasmatic nucleus of the hypothalamus. The central clock receives light information from the retina and entrains biological and behavioral rhythms to the external 24-hour light-dark cycle,” she said.
Circadian synchrony is achieved and maintained through the rhythmic release of multiple hormones, such as melatonin and cortisol, and through neuronal signals, including those from the autonomic nervous system. And peripheral clocks are also responsive to behavioral timing cues, like the feeding-fasting cycle, said Covassin.
Study Participants Ate Earlier. How PCPs Can Apply Findings
In your practice, consider using these guidelines in care management, provided by Jennifer L. Martin, PhD, professor in the Herbert Wertheim College of Medicine at Florida International University in Miami, who is also a spokesperson for the American Academy of Sleep Medicine.
This strategy may be particularly relevant for patients with cardiometabolic risk factors such as obesity, prediabetes, metabolic syndrome, or hypertension. “However, clinicians should individualize recommendations,” Martin said.
Patients who have a history of hypoglycemia, individuals taking medications that require regular food intake, pregnant patients, or those with a history of disordered eating may not be appropriate candidates for extended fasting approaches, Martin emphasized.
PCP Conversations: Drawbacks of Late-Night Eating
Advising how late-night eating can contribute to a variety of undesirable symptoms and health outcomes is warranted.
“Digestion and metabolism slow down during sleep, so eating late at night may cause heartburn, indigestion, and bloating,” said Brianne Thornton, MS, RDN, program manager, Lifestyle Medicine, UW Health in Madison, Wisconsin.
In addition, sharing how sleep quality may be poor due to having trouble falling asleep, feeling restless, or having disrupted sleep due to increased urination, she said.
“Eating late at night can also cause elevated blood sugar and may alter our hunger and satiety hormones. For these reasons, it’s ideal to finish eating at least 3 hours before you go to bed,” said Thornton.
Considerations for Shift Workers
Shift workers should finish eating ≥ 3 hours before bed for the same reasons, affirmed Thornton. “In addition, shift workers should focus on good sleep hygiene to support quality sleep when their sleep cycles aren’t aligned with a natural circadian rhythm.”
Per Thornton, directives include:
- Prioritize a consistent sleep schedule and a relaxing routine to wind down ≥ 30 minutes before bed.
- Avoid screens ≥ 1 hour before bed.
- Ensure the bedroom is dark, quiet, and cool.
- Limit naps to 30 minutes or less and managing stress can also support restful sleep.
As an RD, she also suggests the importance of advising patients to balance food groups and nutrients at that meal. “Having adequate protein and fiber, as well as healthy fats, can increase satiety and make it easier to avoid late night snacking,” stated Thornton. “Additionally, it can be helpful to understand triggers for late night snacking, such as boredom, stress, or sadness, and how to effectively manage emotions.”
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