nutrition

Scientists prove the human body can predict meals

Mealtime Intermittent Fasting
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A new study from the University of Surrey reveals that the human body can predict the time of regular meals and that daily blood sugar rhythms can be influenced by both the time and size of meals. Research suggests that there is a physiological drive for people to eat at certain times because their bodies have been trained to expect food.

According to a recent study from the University of Surrey, the human body has the ability to predict the time of regular meals. The research team’s findings suggest that the daily rhythms of blood glucose levels may be influenced not only by the timing of meals but also by their portion sizes.

A team of researchers from Surrey, led by Professor Jonathan Johnston, have carried out a pioneering investigation to determine whether the human circadian system is able to anticipate large meals. Circadian rhythms, which refer to the physiological changes that occur in a 24-hour cycle and are usually synchronized with environmental cues like light and dark, encompass a variety of metabolic changes.

Previous studies in this area have focused on control animals and so far it has not been determined whether human physiology can predict mealtimes and food availability.

Jonathan Johnston, professor of chronobiology and integrative physiology at the University of Surrey, said: “We are often hungry around the same time each day, but the extent to which our biology can anticipate meals is unknown. It’s possible that metabolic rhythms align with meal patterns, and meal regularity means that we eat when our bodies are best suited to deal with it.

To find out more, 24 male participants undertook an eight-day lab study with strict sleep-wake schedules, exposure to light-dark cycles, and food intake. For six days, 12 participants consumed small meals every hour throughout the waking period, with the remaining participants consuming two large meals daily (7.5 and 14.5 hours after waking).

After six days, all participants were then put on the same eating schedule for 37 hours and given small meals every hour in a procedure known to reveal internal circadian rhythms. Glucose was measured every 15 minutes during the study, and hunger levels were measured hourly during waking hours on days two, four, and six in the first stage of the study, then every hours for the last 37 hours.

By analyzing the results of the first six days of the study, the researchers found that the glucose concentration of the participants in the small meal group increased upon awakening and remained high throughout the day until decreasing after their last meal. In the large meal group, there was a similar increase in glucose concentration upon awakening, but there was a gradual decline before the first meal.

Over the past 37 hours, when both groups received the same small meals every hour, all participants showed an initial rise in glucose concentration upon waking. However, in those who had already received two large meals, blood sugar levels began to drop before the scheduled large meal (which they did not receive) while for participants who had always consumed small meals every hour, their blood sugar continued to rise as seen previously. Additionally, in the large meal group, there was an increase in hunger before projected meal times that decreased sharply after the projected meal time.

Professor Johnston added: ‘What we have discovered is that the human body is rhythmically programmed to anticipate meal times, particularly when food is not readily available. This suggests that there is a physiological drive for some people to eat at certain times because their bodies have been trained to expect food rather than just being a psychological habit.

Reference: “Human Glucose Rhythms and Subjective Hunger Anticipate Meal Timing” by Cheryl M. Isherwood, Daan R. van der Veen, Hana Hassanin, Debra J. Skene, and Jonathan D. Johnston, February 22, 2023, Current biology.
DOI: 10.1016/j.cub.2023.02.005

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