What fasting during the night shift actually changes
The clearest direct comparison comes from a randomized crossover trial in 10 male police officers who worked night shifts. They spent two nights either fasting, eating a standardized 678-calorie meal at about 2 a.m., or sleeping at night. The morning after, fasting during the shift was associated with lower insulin levels and a lower HOMA-IR score, a common measure of insulin resistance, compared with eating at night [1]. In practical terms, the body needed less insulin to handle the same blood sugar, which is generally a good sign for metabolic health.
That same trial found a trade-off: after fasting through the night shift, participants ate more at a test meal in the early morning and consumed more energy and macronutrients over the next day, especially protein and fat [1]. So fasting changed the next day's eating behavior even as it improved the morning insulin picture. The study was small and included only male police officers, so the size and generality of the effect are uncertain.
Not all night meals are equal: the role of meal quality
A second randomized crossover trial in female nurses working night shifts compared fasting with eating one or three meals during the shift, and varied the meals' glycemic index, a measure of how quickly a food raises blood sugar. Eating one high-glycemic-index meal increased glucose variability both during the night shift and the following morning, while one or three low-glycemic-index meals did not raise most glucose-control or variability measures [4]. The number of meals eaten did not matter once glycemic index was taken into account.
Crucially, the glucose profile after a single low-glycemic-index meal was not different from the profile after no meal at all [4]. That suggests the answer to whether avoiding food helps depends on what the alternative is: skipping a high-glycemic-index night meal appears beneficial for glucose control, but skipping a low-glycemic-index meal may offer little additional glucose advantage.
Why nighttime eating may work against blood sugar control
Night shift work disrupts the body's circadian rhythms, the internal clocks that influence how the body handles food and glucose. A narrative review of circadian-aligned time-restricted eating argues that restoring alignment between feeding and fasting cycles and biological rhythms may improve glycemic control, and that early-day eating appears most physiologically advantageous, though schedules adapted to night-shift patterns may still yield meaningful improvements [3]. This is a plausible biological rationale rather than proof that fasting during night shifts is the best strategy; the review itself notes that evidence is limited by small samples and heterogeneous protocols.
Separately, a trial of timed light therapy in rotating night shift workers found that light therapy improved glucose tolerance and blood pressure, with the glucose improvement paralleled by reduced catecholamine levels [2]. That study did not test meal timing, so it does not directly answer the fasting question, but it reinforces that circadian disruption affects glucose regulation through pathways beyond diet alone.
What we still don't know, and what it means for a night-shift worker
The direct evidence is still thin. One trial was small and limited to male police officers [1], another to female nurses [4], and a third is only a protocol for a future laboratory study in simulated night shifts, so it has not yet produced results [5]. The review calls for larger, tailored clinical trials to establish feasibility and long-term efficacy [3]. Adherence is also a practical concern: fasting during night shifts may be difficult to sustain, as the nurse trial itself acknowledged [4].
For now, the evidence suggests that if you eat during a night shift, choosing a low-glycemic-index meal may keep glucose responses close to what you would see if you fasted, while a high-glycemic-index meal clearly worsens glucose control [4]. Fasting may lower morning insulin and insulin resistance [1], but it may also lead to compensatory overeating later [1]. The best choice likely depends on the person, the type of night work, and what foods are available.
Sources used in this answer
Influence of fasting during the night shift on next day eating behavior, hunger, and glucose and insulin levels: a randomized, three‐condition, crossover trial
In a small randomized crossover trial of male police officers, fasting during night shifts led to lower morning insulin and HOMA-IR compared with eating a standardized night meal, but also to higher subsequent food intake.
Light therapy improves diurnal blood pressure control in night shift workers via reduction of catecholamines: the EuRhythDia study
Timed light therapy improved glucose tolerance and diurnal blood pressure in rotating night shift workers, with effects paralleled by reduced catecholamine levels, but the study did not test meal timing.
Circadian-Aligned Time-Restricted Eating for Night Shift Workers with Type 2 Diabetes: A Targeted Public Health Approach.
A narrative review suggests circadian-aligned time-restricted eating may improve glycemic control in night shift workers with or at risk of type 2 diabetes, while noting limited and heterogeneous evidence.
The Effect of Meal Glycemic Index and Meal Frequency on Glycemic Control and Variability in Female Nurses Working Night Shifts: A Two-Arm Randomized Cross-Over Trial
In female night-shift nurses, one high-glycemic-index night meal increased glucose variability, whereas one or three low-glycemic-index meals did not raise most glucose metrics, and a single low-glycemic-index meal produced glucose profiles similar to no meal.
The effects of fasting compared to eating a meal or snack during simulated night shift on changes in metabolism associated with circadian misalignment: a protocol and methods paper
A protocol paper describes a planned laboratory study comparing no meal, a meal, or a snack during simulated night shifts on glucose, insulin, and free fatty acid responses, but does not yet report results.