Relationship Between Sleep and Meal Timing with Glycemia Parameters in Individuals with Obesity Participating in a Randomized Time-Restricted Eating Study.
In individuals with obesity, morning and evening fasting intervals relative to sleep were differentially associated with glycemic control, highlighting the relevance of eating and sleep timing to glycemic parameters and informing eating window selection for individuals practicing TRE.
Key Findings
Results
Each hour increase in the Awake-AM meal interval (time from waking to first meal) was associated with lower overnight average glucose levels.
Overnight glucose was defined as average glucose between 1 AM and 5 AM.
The association persisted after adjustment for baseline sleep duration, HbA1c, and randomization assignment.
This finding was observed across all three dietary intervention groups: TRE, CR, and UE.
Participants were aged 18-65 years with obesity enrolled in a 12-week randomized intervention.
Results
Each hour increase in the Awake-AM meal interval was associated with lower glycemic variability.
Glycemic variability was measured using continuous glucose monitoring (CGM) assessed over two weeks at baseline and end-intervention.
The association remained after adjustment for baseline sleep duration, HbA1c, and randomization assignment.
Mixed effects models were used to examine associations between CGM outcomes and the Awake-AM meal interval.
Results
Each hour increase in the Awake-AM meal interval was associated with lower percentage of time with glucose above 180 mg/dL.
Time above 180 mg/dL is a standard CGM metric reflecting hyperglycemia burden.
The association persisted after adjustment for baseline sleep duration, HbA1c, and randomization assignment.
This finding was identified through mixed effects models in the secondary analysis.
Results
Each hour increase in the Awake-AM meal interval was associated with greater percentage of time with glucose below 70 mg/dL.
Time below 70 mg/dL reflects hypoglycemic episodes or lower glucose excursions.
This is the only glycemic parameter where the Awake-AM meal interval was associated with an increase rather than a decrease.
The association persisted after adjustment for baseline sleep duration, HbA1c, and randomization assignment.
Results
Each hour increase in the PM meal-Sleep interval (time from last meal to sleep onset) was associated with lower overnight average glucose.
Overnight glucose was defined as average glucose between 1 AM and 5 AM.
This association persisted after adjustment for baseline sleep duration, HbA1c, and randomization assignment.
The PM meal-Sleep interval was one of two meal-to-sleep timing intervals examined in the study.
Unlike the Awake-AM meal interval, the PM meal-Sleep interval was associated only with overnight glucose and not with glycemic variability or time above/below glucose thresholds.
Results
Morning and evening fasting intervals relative to sleep were differentially associated with glycemic control in individuals with obesity.
The Awake-AM meal interval was associated with four CGM outcomes: overnight glucose, glycemic variability, %time >180 mg/dL, and %time <70 mg/dL.
The PM meal-Sleep interval was associated with only one CGM outcome: overnight average glucose.
Both intervals showed independent associations with overnight glucose after accounting for baseline confounders.
The study involved a 12-week randomized trial with three arms: TRE (8-hour eating window), CR (15% caloric reduction), and UE (unrestricted eating).
Methods
The study used a randomized design with three dietary interventions to examine meal and sleep timing associations with glycemia in individuals with obesity.
Participants aged 18-65 years with obesity were randomized to TRE (8-hour eating window), CR (15% reduction in daily caloric intake), or UE (usual eating habits).
CGM and actigraphy were assessed over two weeks at both baseline and end-intervention (12 weeks).
This report is a secondary analysis of the randomized trial.
Mixed effects models were used to examine associations between CGM outcomes and meal-sleep timing intervals.
Background
Circadian misalignment, including mistimed sleep or eating, is associated with altered glucose metabolism, motivating the examination of eating window timing in TRE.
The importance of eating window timing for time-restricted eating is increasingly recognized.
This study sought to address whether the timing of meals relative to sleep—both in the morning and evening—matters for glycemic outcomes.
The study framed meal-to-sleep intervals as proxies for circadian alignment of eating behavior.
What This Means
This research suggests that not just when you eat during the day, but specifically how you time your meals relative to your sleep, matters for blood sugar control in people with obesity. The study followed participants across three dietary approaches—time-restricted eating (eating within an 8-hour window), calorie restriction, and unrestricted eating—and tracked their blood sugar continuously and their sleep patterns over two weeks. Researchers found that waiting longer after waking up before eating the first meal of the day was linked to lower overnight blood sugar, less blood sugar variability, and less time spent with very high blood sugar. Similarly, eating the last meal of the day farther from bedtime was linked to lower overnight blood sugar levels.
These associations held up even after accounting for differences in sleep duration, baseline blood sugar levels (HbA1c), and which dietary intervention participants were assigned to. Interestingly, morning and evening meal timing relative to sleep had somewhat different effects: the morning fasting interval (from waking to first meal) was linked to more glycemic outcomes, while the evening interval (from last meal to sleep) was specifically linked to overnight glucose levels.
This research suggests that the timing of the eating window—not just its duration—may be an important factor in how well time-restricted eating or other dietary approaches improve blood sugar control. For people with obesity who are considering time-restricted eating, these findings indicate that aligning eating patterns with the body's natural daily rhythms (eating later in the morning and earlier in the evening relative to sleep) may provide additional metabolic benefits, though further research is needed to confirm cause-and-effect relationships.
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Reutrakul S, Simon S, Wang Q, Manoogian E, Panda S, Ryu S, et al.. (2026). Relationship Between Sleep and Meal Timing with Glycemia Parameters in Individuals with Obesity Participating in a Randomized Time-Restricted Eating Study.. Nutrients. https://doi.org/10.3390/nu18111824