How Researchers are Using Zero to Improve the Health of Firefighters

Written and medically reviewed by Rich LaFountain, PhD

By: Rich LaFountain

This may come as a surprise, but firefighters have surprisingly high disease, obesity, and mortality risk. You’d think such a high-intensity job would require extreme physical fitness, and the truth is, it does! But the very nature of firefighting – its unpredictability – makes it tough to maintain optimal health. Just think of how difficult it would be to keep a consistent meal, sleep, and workout schedule when your shift is 24 hours long and you could be disrupted by an emergency at any minute. 

An enterprising team of researchers, aware of this catch-22, decided to see if creating a rhythm around eating might help alleviate some of these health concerns. Specifically, they decided to test whether Intermittent Fasting can help firefighters take charge of their health. And it makes sense–in other healthy populations, this same research group has shown that time restricted feeding (TRF) helps improve circadian alignment, body composition, and markers of metabolic health, all of which would benefit the health of first responders. 

Nothing is more exciting to the Zero team than seeing people dig deep into the research with fasting to unearth measurable benefits. Naturally, we were ecstatic to see several high-impact article publications using Zero to support research aimed at improving firefighter health and performance. 

So let’s dig into what this recent line of research shows. Dr. Hunter Waldman, now at University of North Alabama, describes a perfect storm of high stress and metabolic dysregulation for many first-responders. 

Firefighters must sleep and eat when their jobs allow it, so the patterns are rarely reliable or consistent. Common health struggles in firefighters including metabolic syndrome and coronary disease have been linked to irregular eating habits and poor sleep

In late 2019, Doctor Waldman first debuted a mechanistic review that detailed how TRF was a new approach to help improve cardiometabolic health in high-stress occupations by reducing a myriad of risk factors including obesity, insulin sensitivity, inflammation, cholesterol synthesis, and oxidative damage

Less than one year later, Dr. Matthew McAllister reported data in firefighters that showed six weeks of 14:10 TRF with Zero in resistance trained firefighters improved markers of metabolism (25%) and oxidative stress (31%). It seems TRF is a strategy that could offer a simple, yet effective, method for firefighters to take back some control of their feeding-fasting cycle by resetting and synchronizing their metabolic “clock” which is important to health, safety, and professional longevity. 

Firefighters, in particular, are subjected to unique stressors that make metabolic health much more precarious to build and maintain especially over the course of a decades-long career. 

High heat, smoke, and equipment load are just a few of the factors that elevate oxidative stress and cardiovascular disease risk for these particular first responders. Research suggests that demands of emergency duties are the primary cause of coronary heart disease fatalities in firefighters. Emergency alarms can elevate heart rate 30 or more beats en route on the firetruck. Additionally, firefighters sustain near-maximal heart rates during fire suppression, search, and rescue activities.

So the stressors are pretty great. And the job doesn’t lend itself to healthy eating habits or solid sleep routines, both of which might help keep heart rate and stress response within a healthy range.

Overweight and obesity prevalence in firefighters (79%) exceeds the national average for all other adults. For this group as a whole, physical demands of the job don’t align with fitness level. Poor physical fitness and obesity then go on to increase injury and disability risk.

That’s where Andrew Gonzalez decided to focus his investigation. Gonzalez suggests that firefighters require advanced training and diet programs to counteract occupational hazards. Can 14:10 TRF help enhance a firefighter’s response to physical training? In other words, can TRF be an effective advanced diet tool to help firefighters stay in shape to meet the fitness demands of the job and mitigate some of the mortality risk?

Gonzalez et al. evaluated firefighters completing  7 weeks of 14:10 TRF with Zero and the results were promising! They showed that 14:10 TRF contributed to increased exercise efficiency as firefighters were able to make more energy per unit oxygen. Increases in energy efficiency can help firefighters extend safe working times during fire suppression, particularly when breathing from oxygen tanks which are limited in volume. 

In a separate, similar, study, McAllister evaluated how TRF might help firefighters deal with exertional stress. 

In order to test this, participants completed a 14:10 TRF protocol with Zero for 8 weeks. The firefighters were asked to complete several real-world emergency activities in a laboratory-based “Firegrounds test.” Heart rate was increased to 97% of age-predicted maximum during the test which lasted approximately 8 minutes (which is a VERY long time to sustain that intensity!). Following 8 weeks of TRF, time to completion of the Firegrounds test was roughly equal, but markers of inflammation (IL-6, IL-1β) and stress response (cortisol) were reduced. This study suggests that 8 weeks of TRF may help firefighters manage extraordinary stress associated with strenuous and/or dangerous emergency calls without hindering their performance!


Firefighters struggle to control and maintain healthy habits due to extraordinary job demands. Adherence to TRF using Zero was very high in healthy young firefighters. The researchers reported participants voluntarily fasted while being both off, and on-duty, even though TRF was not required while on-duty! Interestingly, firefighters opted to fast an additional hour when asked to complete 14:10 TRF; the average fast duration was 15 hours. Zero makes fasting more accessible and supports TRF as an important metabolic tool to help improve circadian biology, boost energy efficiency, and decrease health risk in firefighters.

About the Author: Rich LaFountain

Rich LaFountain is a science writer with a passion for exploring human health through lifestyle inputs, nutrition, and exercise. Rich completed his Bachelor of Science in Biology at The College at Brockport. He received his Master’s and Doctorate degrees in Kinesiology from The Ohio State University. He is fascinated by the manipulation of dietary patterns including fasting, macronutrient composition, and calorie restriction for targeted individualized outcomes in human health and performance.

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Rich LaFountain, PhD
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