What we eat, but also when we eat, affects our risks of having more body fat and developing diseases. Importantly though, neither eating by the time on the clock nor by how long we eat before going to sleep seems to matter much. Rather, research using MealLogger and other revelatory technology demonstrates that eating in alignment with our internal clock, or circadian rhythm, appears to be more influential.
Researchers from Harvard Medical School and other esteemed institutions understood that eating in or out of sync with our body’s natural rhythm can promote health or disease, and set out to study meal timing differences between lean and heavier people. They monitored the habits of 106 college-aged adults for one month, and used MealLogger to efficiently and effectively study the content and timing of their meals. MealLogger, they wrote, “time-stamped the clock-time of their meal and enabled participants to leave a detailed description of the meal content (e.g., any type of salad dressing or condiments used or additives such as milk or sugar to beverages). Upon completion of each caloric entry, data were available to study staff via web access and nutrition staff followed up with participants through the mobile app within 24 h after the meal was documented if any clarification of meal composition was needed. Participants were instructed to include an object of known size within the picture to help calculate portion size and to take a second photo if the meal was not fully consumed to estimate total caloric intake. If a participant recorded ≤2 caloric events within a waking day, study staff emailed them to confirm they had not consumed any additional calories.”
Their findings were published in the journal Nutrients, which showed, for the first time, that people eat across all phases of the circadian clock, and that leaner people eat more of their calories at an earlier circadian phase than their heavier counterparts. Specifically, the heavier group ate 8% more of their calories during the evening circadian phase than the lean group did, and they also ate 13% more carbohydrates in the afternoon. These differences were only detectable however, when considering the circadian clock, not local clock time or the time when people fell asleep, underscoring the importance of circadian rhythm in diet and health. “These findings potentially highlight a therapeutic area to target to combat the rise in unhealthy body composition”, the authors concluded, and “reflect the importance of considering each individual’s circadian timing, and not just clock time, when devising therapeutic strategies that combat the timing of caloric intake.”
Reference:
McHill AW, Czeisler CA, Phillips AJK, et al. Caloric and Macronutrient Intake Differ with Circadian Phase and between Lean and Overweight Young Adults. Nutrients. 2019;11(3):587. Published 2019 Mar 11. doi:10.3390/nu11030587