Your Gut Has Jet Lag | The Angry Gut, Chapter 17

Night shift health risks

Night Shift Health Risks You Can Actually Measure

A rotating roster changes insulin, appetite and inflammation long before it changes a diagnosis. Most of that happens in markers nobody draws, on a schedule nobody writes down.

The night shift health risks that make headlines are the dramatic ones, but the changes with the strongest evidence are quieter and faster, and they show up in numbers a routine visit rarely records. Your Gut Has Jet Lag, the video for The Angry Gut by Dr. Gurpreet Singh Padda, MD, MBA, MHP, and Ami Michelle Grimes, follows an intensive care nurse whose Crohn’s flares followed her schedule changes. Your situation may be different. The questions are the same: what the schedule is doing to your body, what a standard checkup looks at, and which measurements can show what it misses.

Does night shift work cause cancer or diabetes?

Night work carries a probable-carcinogen grade, yet when researchers pooled cancer counts across more than eight million workers, colorectal and breast cancer barely moved. The grade describes what could happen. The counts describe how often it does.

The consistent signal sits in metabolism. Across 21 pooled studies, the diabetes risk attached to shift work was about 10% higher in relative terms; the excess appeared among women rather than men, and health care workers were the highest-risk occupational group. The fastest change is insulin itself. When nine normal-weight young men were held to roughly four hours of sleep for two nights, their HOMA-IR, an insulin resistance index, climbed close to 40% and fasting insulin rose 34%. Two nights. No weight change is needed for that to register in the blood, and no bathroom scale will ever see it.

Is a rotating shift worse than working permanent nights?

A permanent night schedule and a rotating one are different exposures. Among 399 nurses, rotation carried the heaviest symptom load: 81% of rotating-shift nurses reported abdominal pain, compared with 61% on permanent nights and 54% on days. A fixed night schedule is like moving to another time zone. A rotating roster is a red-eye flight every few days, and your first brain, the gut, pays for each landing.

In a laboratory study, adults pushed out of step with their body clock showed higher tumor necrosis factor and C-reactive protein, while their cortisol went down; plain sleep deprivation pushed cortisol up instead. A short night and a shifted night are separate injuries. Dose matters as well. In a 2025 synthesis of 35 studies, a single bad night did nothing measurable to inflammatory markers, while three or more nights of short sleep raised interleukin-6 and C-reactive protein. That is metaflammation built one run of nights at a time.

The schedule is rarely yours to write. Rosters follow staffing budgets, the people covering nights take the shift that is offered, and the pay differential makes a swing hard to refuse.

What does a routine checkup miss in night shift workers?

A routine checkup records weight, blood pressure and perhaps a fasting glucose. It seldom asks when you slept, and a roster almost never reaches the chart. Glucose can sit in the normal range while insulin climbs to keep it there. Appetite shifts quietly too: in 12 healthy young men, two short nights pushed the wish for dense, high-carbohydrate foods up by 33% to 45%. That craving shows up as weight months later, long after anyone could connect it to the schedule.

Timing also distorts the few numbers that are drawn. A blood test taken after one rough week is a snapshot of that week. Without the schedule written beside it, nobody reading the result can tell a run of nights from an ordinary month.

Night shift health risks that measurements can show

Measura [Cardiometabolic and Autonomic Health Analysis] does not do sleep studies. If a sleep disorder is suspected, that evaluation happens elsewhere. What Measura measures is the terrain a disordered schedule acts on, and the results go to your physician.

Laboratory panels. Fasting insulin with glucose, lipids and inflammatory markers such as C-reactive protein. Note when your last run of nights ended before the draw.
Heart rate variability. A recording of beat-to-beat changes in heart rhythm, which reflects how the autonomic nervous system, including the vagus nerve, is balancing activity and rest.
Autonomic nervous system testing. How heart rate and blood pressure respond to breathing and posture changes, which shows whether that regulation holds under a challenge.
Indirect calorimetry. Resting metabolic rate measured from the oxygen you use and the carbon dioxide you breathe out, instead of estimated from a formula.

The metabolic rate is where the non-obvious finding lives. A randomized trial coached 80 adults with overweight who habitually slept too little; they gained roughly 1.2 extra hours of sleep nightly, and their daily intake dropped by 270 kcal, while energy expenditure did not change at all. The tired body was not burning less. It was eating more. A measured resting rate helps you and your physician tell an intake problem from an expenditure problem instead of guessing. Heart rate variability has not been the outcome in the shift-work studies above; it is included as a direct measure of autonomic regulation, not as a shift-work diagnosis.

What to bring to your appointment

Write the schedule beside your symptoms: the clock times you slept, not only the number of hours.
Note the date your most recent run of nights ended.
Keep meals on consistent clock times across a rotation, since feeding rhythm carries much of the gut’s timing.
Hold a fixed sleep window on days off instead of swinging back each time.
Ask whether insulin, not only glucose, has been checked. Insulin resistance and metabolic health explains why.

If your symptoms include lightheadedness, racing heart or digestive swings, autonomic symptoms describes what those tests look at. The book companion, the deep dive on the sleep-deprived microbiome, carries every study with its limits, and the metabolic side of fat stored around the gut is in how to measure visceral fat.

Frequently asked questions

Does Measura test for shift work sleep disorder?

No. Measura does not perform sleep studies, and a suspected sleep disorder is evaluated elsewhere. Measura measures the terrain a disrupted schedule acts on, including insulin and inflammatory markers, heart rate variability, autonomic regulation and resting metabolic rate, and it sends those results to your physician. See who should be tested.

Can night shifts affect heart rate variability?

Heart rate variability reflects how the autonomic nervous system regulates the heart, and that system runs on a daily rhythm. The shift-work studies with the firmest numbers measured insulin, appetite and inflammation rather than heart rate variability, so a result describes your regulation on the day of testing, not a verdict on your schedule. See what the heart rate variability number means.

Why is my blood sugar normal if night shifts cause insulin resistance?

Because glucose is the last number to move. The body holds glucose steady by releasing more insulin, so insulin resistance can climb while glucose looks fine. In nine young men, two short nights raised an insulin resistance index close to 40% within days. Asking for fasting insulin alongside glucose shows the effort, not only the result. See what insulin resistance looks like before diabetes.

Does one bad night change my lab results?

Inflammatory markers did not change measurably after a single night of short sleep in pooled experiments, but they rose after three or more nights in a row. That is why the timing of a blood draw relative to your last run of nights belongs next to the result when your physician reads it. Read about understanding your results.

Why measure metabolic rate if I work nights?

Because a formula cannot tell whether your body is burning less or taking in more. In a sleep-extension trial, adding sleep cut intake by 270 kcal a day while energy expenditure stayed the same. A measured resting rate gives your physician a real number to plan around instead of an estimate. See measured versus estimated metabolic rate.

Is working night shift bad for your health?

The clearest harm is metabolic, and it starts fast. Across 21 pooled studies, shift work carried about a 10% higher relative risk of diabetes, highest among women and health care workers. In young men held to roughly four hours of sleep for two nights, an insulin resistance index rose close to 40%. Those changes show up in blood work long before a diagnosis or a change on the scale.

How can I avoid night shift side effects?

Start with the parts of the schedule you control. Keep meals on consistent clock times across a rotation, since feeding rhythm carries much of the gut’s timing. Hold a fixed sleep window on days off instead of swinging back each time. Write down the clock times you slept and the date your last run of nights ended, and ask whether insulin, not only glucose, has been checked.

Put your schedule next to your numbers

Request metabolic, autonomic and resting metabolic rate testing so your physician can see what your schedule is doing, measured rather than assumed.

Send a message

4477 Woodson Rd, Suite 201, St. Louis, MO 63134. Monday to Friday, 9:00 a.m. to 5:00 p.m. Please do not send symptoms, diagnoses or images through a web form — a website form is not a secure medical channel. Send your name and number and we will call you back.

References

Dun, A., Zhao, X., Jin, X., Wei, T., Gao, X., Wang, Y., & Hou, H. (2020). Association between night-shift work and cancer risk: Updated systematic review and meta-analysis. Frontiers in Oncology, 10, 1006. https://doi.org/10.3389/fonc.2020.01006
Gao, Y., Gan, T., Jiang, L., Yu, L., Tang, D., Wang, Y., Li, X., & Ding, G. (2020). Association between shift work and risk of type 2 diabetes mellitus: A systematic review and dose-response meta-analysis of observational studies. Chronobiology International, 37(1), 29-46. https://doi.org/10.1080/07420528.2019.1683570
Benedict, C., Vogel, H., Jonas, W., Woting, A., Blaut, M., Schürmann, A., & Cedernaes, J. (2016). Gut microbiota and glucometabolic alterations in response to recurrent partial sleep deprivation in normal-weight young individuals. Molecular Metabolism, 5(12), 1175-1186. https://doi.org/10.1016/j.molmet.2016.10.003
Nojkov, B., Rubenstein, J. H., Chey, W. D., & Hoogerwerf, W. A. (2010). The impact of rotating shift work on the prevalence of irritable bowel syndrome in nurses. The American Journal of Gastroenterology, 105(4), 842-847. https://doi.org/10.1038/ajg.2010.48
Wright, K. P., Drake, A. L., Frey, D. J., Fleshner, M., Desouza, C. A., Gronfier, C., & Czeisler, C. A. (2015). Influence of sleep deprivation and circadian misalignment on cortisol, inflammatory markers, and cytokine balance. Brain, Behavior, and Immunity, 47, 24-34. https://doi.org/10.1016/j.bbi.2015.01.004
Ballesio, A., Fiori, V., & Lombardo, C. (2025). Effects of experimental sleep deprivation on peripheral inflammation: An updated meta-analysis of human studies. Journal of Sleep Research, 35(1), e70099. https://doi.org/10.1111/jsr.70099
Spiegel, K., Tasali, E., Penev, P., & Van Cauter, E. (2004). Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Annals of Internal Medicine, 141(11), 846-50. https://doi.org/10.7326/0003-4819-141-11-200412070-00008
Tasali, E., Wroblewski, K., Kahn, E., Kilkus, J., & Schoeller, D. A. (2022). Effect of sleep extension on objectively assessed energy intake among adults with overweight in real-life settings: A randomized clinical trial. JAMA Internal Medicine, 182(4), 365-374. https://doi.org/10.1001/jamainternmed.2021.8098