Early breakfast may improve insulin resistance

Adults who took their first meal before 8:30 am had better insulin resistance than those who did so after 8:30 am, independent of eating duration, according to a study presented at ENDO 2021.

“We found [that] people who started eating earlier in the day had … less insulin resistance, regardless of whether they restricted their food intake to <10 hours a day or if their food intake was spread over >13 hours daily,” said lead author Dr Marriam Ali from Northwestern University in Chicago, Illinois, US.

Researchers gathered data from the National Health and Nutrition Examination Survey (2005–2012) and analysed two nonconsecutive dietary recalls, fasting glucose, and insulin from 10,575 adults (age >18 years). Participants were divided into three groups according to their eating interval duration (<10, 10–13, and >13 hours), defined as the time between the first and last eating episode. These groups were then divided into six subgroups based on their eating interval timing (eating start time before or after 8:30 am). HOMA-IR* was used to assess estimated insulin resistance. [ENDO 2021, abstract P21-34]

Individuals with an eating duration of <10, 10–13, or >13 hours had adjusted mean HOMA-IRs of 2.23, 2.20, or 1.97, respectively (p<0.05 for all), with the highest HOMA-IR (greater insulin resistance) observed among those with the shortest eating duration.

Compared with individuals who started eating after 8:30 am, those who started eating before 8:30 am had lower adjusted mean HOMA-IRs regardless of their eating duration (1.96 vs 2.28 for <10 hours, 2.13 vs 2.28 for 10–13 hours, and 1.94 vs 2.13 for >13 hours).

“All subgroups with an early eating start time [before 8:30 am] had better metabolic outcomes regardless of eating duration,” she added.

The adjusted mean fasting glucose levels were comparable between individuals who started eating before and after 8:30 am across all eating interval durations (96.3 vs 98.7 mg/dL for <10 hours, 97.3 vs 98.4 mg/dL for 10–13 hours, and 97.3 vs 99.3 mg/dL for >13 hours, respectively).

“[As] shorter eating durations … were associated with worse metabolic outcomes, except when paired with an earlier start time [eating before 8:30 am], these findings suggest that timing is more strongly associated with metabolic measures than duration and supports early eating strategies,” Ali concluded.

*HOMA-IR: Homeostatic Model Assessment of Insulin Resistance