There is something almost magical about the holiday period. Family meals start at an hour when on a regular day we would already be finished with dinner, kids stay up late, in the morning we wake up at a different time, travel, host, and sit for hours around the table. Holidays connect with weekends, and for several weeks the familiar routine changes repeatedly.
For us, these are the holidays. For the body, it is a change in schedule.
The body operates with the help of an internal timing system known as the biological clock. It helps coordinate between sleep and wakefulness, eating, physical activity, hormone secretion, and metabolic processes. Light and darkness are central signals for this system, but meal times and activity also help the body understand what time it is and what it is supposed to do.
When we suddenly change the hours in which we sleep, eat, and move, we change some of the regular signals the body is used to receiving. This does not mean that a single holiday meal puts us at risk, but several weeks in which every day takes place at different hours may cause fatigue, heaviness, and a feeling that the body has gone out of balance.
Not only how much you sleep, but also when
When talking about sleep, the first question is usually how many hours we slept. However, studies from recent years point out that regularity is also important: Whether we go to sleep and wake up at similar hours, or whether every day looks completely different.
A systematic review published in 2025 that included 59 studies found a link between less regular sleep and poorer health indicators. Among other things, links were found to blood pressure, insulin resistance, cardiovascular health, and symptoms of anxiety and depression. The researchers noted that alongside sleep duration and quality, its regularity should also be addressed as part of healthy sleep habits.
It is important to put the findings into proportion. The review mainly examined links between sleep patterns and health indicators, and therefore does not prove that every change in bedtime is the direct cause of the problem. One evening when we went to sleep late is not a medical event, and a night different from usual should not cause anxiety.
The difficulty begins mainly when one evening becomes a period in which you go to sleep and wake up at a different time every instance. The body is required to adapt repeatedly to changing hours of sleep, wakefulness, and activity. Even if it is impossible to maintain the regular schedule during the holidays, you can try not to get too far away from it for many days in a row.
Food has a clock too
We are used to thinking about food in terms of what we ate and how much we ate, but it turns out that when we ate is also important. Meal times are connected to the biological clock and to the way the body processes food.
Studies and reviews point to a link between late-night eating, and in particular concentrating a large part of calorie consumption in the evening and night, and poorer metabolic indicators. A scientific statement by the American Heart Association from 2025 emphasized that the health of the biological clock is affected by the timing and regularity of sleep, light exposure, meals, and physical activity. Continuous disruption of these may be related to heart health and metabolic function.
Here too, main research deals with patterns that persist over time, and not with the effect of a single holiday meal. There is no need to move family meals to the afternoon or give up favorite foods. However, you can make it a little easier on the body and not arrive at the meal after almost a whole day without food, out of the thought that you need to "save" calories for the evening.
When arriving very hungry, it is easier to eat quickly, ignore the feeling of fullness, and consume a larger amount than intended. On non-fasting days, it is better to eat light, organized meals during the day, drink water, and arrive at the table moderately hungry.
No need for a workout, just move
During holidays, our activity pattern also changes. Preparations can be exhausting, but they do not always include sufficient movement. Afterward come hours of sitting around the table, long drives, and spending time on the couch.
There is no need to squeeze a full workout between the meal and dessert. Even a short walk, playing with the kids, a family trip, or standing up from the table occasionally are preferable to long hours of continuous sitting. The goal is not to "burn" the holiday meal, but to give the body natural opportunities for movement even when the routine changes.
It is also worth remembering to drink. On a day busy with cooking, hosting, and traveling, it is easy to confuse thirst with hunger or simply forget about water. Placing a water pitcher on the table and drinking throughout the day are small actions that can help.
Medications do not go on vacation
People living with diabetes, hypertension, or cardiovascular diseases, as well as those taking medications regularly, should remember that even during holidays, treatment continues as usual.
A change in mealtime is not a reason to independently change medication times or dosage. This is especially important for those treated with insulin or other glucose-lowering drugs, as a change in meal times or fasting may require appropriate preparation.
Those planning to fast and living with a chronic disease, pregnant women, older adults, and those taking medications regularly should consult with a doctor or pharmacist in advance. Do not skip treatment, shift medication time, or change dosage without medical guidance.
It is also allowed to just enjoy
The holiday season does not need to turn into a health project. There is no need to count every bite, stress over every change in bedtime, or feel guilty because a few days went out of routine. Studies mainly deal with recurring patterns over months and years, and not with damage from a festive meal or a single late night.
The message is simple: You can celebrate, host, be hosted, and sit with the family around the table. Just keep a few familiar anchors for the body. Drink water, do not arrive at meals starving, find small opportunities for movement, and return to regular sleep hours whenever the holiday allows it.
Routine might go on vacation, but the body keeps working. It still needs sleep, movement, and fluids, and it still likes a little order. Even within the sequence of holidays, you can enjoy, rest, and spend time, without taking it completely out of rhythm.
Dr. Lee Erez is a family medicine specialist at Maccabi Healthcare Services, Northern District