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Should You Consider Intermittent Fasting for Good Health?

Firefighters do better when they restrict eating time. Should you consider intermittent fasting for health?

Americans love to snack. Stop to fill up your gas tank and you can purchase all sorts of treats—ice cream, popcorn, candy, crackers, cookies and nuts, just to name a few of the many enticements. Go shopping at just about any big box discount store and you will find tons of snack food just vying for your attention at the checkout counter. We stuff our mouths from morning till evening. Perhaps we would all be better off if we tried intermittent fasting instead of nonstop snacking.

What Is Intermittent Fasting?

There is no absolute definition because there are so many variations on what experts consider intermittent fasting. If you consume no food, snacks or treats for 18 hours a day, that would be one form of intermittent fasting. Another possibility would be to only eat on alternate days. Some people describe this as fasting one day and feasting the next.

Many people can’t stop eating for 24 hours. Instead, they cut back about 75% on calories during fast days. Others stop eating after 3:00 pm. Basically, they just eat breakfast and lunch and skip supper and snacks.

Some people consider intermittent fasting the 5:2 approach. They fast 2 days a week and eat normally the other 5 days.

Time Restricted Eating and Health Benefits:

There has been a lot of buzz around time-restricted eating, but studies have reached inconsistent conclusions. However, two trials reported in Cell Metabolism (Study 1 and Study 2, Oct. 4, 2022) suggest that eating breakfast, a light lunch and no supper may be especially helpful.

In one of the studies, 16 overweight people ate standardized meals early or late while researchers measured hormone levels. People who ate early reported feeling less hungry.

The authors conclude:

“Our results show that late eating consistently altered physiological functions and biological processes involved in regulation of energy intake, expenditure, and storage—each of these three in a direction favoring weight gain…Late eating caused increased hunger and an increase in the ratio of (acylated) ghrelin:leptin concentrations, even though the 24-h nutritional intake was kept identical, indicating an increased drive for energy intake.”

In other words, late-day snacking/eating increases the likelihood that you will be hungrier and gain weight.

In a second study, 137 firefighters adhered to a 10-hour window or ate throughout the day. Those practicing time-restricted eating had better blood sugar, blood pressure and blood lipid levels.

Here are the authors’ conclusions in their own words:

“We found that a 10-h TRE [time-restricted eating] intervention was feasible in firefighters on 24-h shifts. The TRE group decreased their eating window by 3–11.13 h…There was a significant reduction in body weight, BMI [body mass index], and DBP [diastolic blood pressure] in the TRE, but not in SOC [standard of care].”

If You Consider Intermittent Fasting, Is It Healthy?

Studies in rodents show that animals that are only allowed to eat during a small part of the day appear to have lower inflammation and better biomarkers for cardiovascular health. Researchers at Texas State University have found that this type of intermittent fasting can also benefit humans (Nutrition Research, Dec. 4, 2019)

The study included 22 men in a 28-day study. They were allowed to eat only during an eight hour period, such as between 9 am and 5 pm. During the other 16 hours of the day, they consumed nothing other than water. Half of the men were allowed to eat as much as they liked during this time-restricted feeding. The other half followed a calorie-controlled regimen that limited the men to the same amount of food they had eaten before the study began.

The investigators expected that if men lost weight and lowered their blood pressure, it would be due to eating fewer calories. However, they actually found that even men who consumed the same amount of calories had less body fat, lower blood pressure and better beneficial HDL cholesterol. The scientists concluded that time-restricted feeding can improve numerous markers of cardiometabolic health.

The New England Journal of Medicine (NEJM): Consider Intermittent Fasting

On December 26, 2019 the New England Journal of Medicine published a review titled:

“Effects of Intermittent Fasting on Health, Aging, and Disease” 

“Studies in animals and humans have shown that many of the health benefits of intermittent fasting are not simply the result of reduced free-radical production or weight loss. Instead, intermittent fasting elicits evolutionarily conserved, adaptive cellular responses that are integrated between and within organs in a manner that improves glucose regulation, increases stress resistance, and suppresses inflammation. During fasting, cells activate pathways that enhance intrinsic defenses against oxidative and metabolic stress and those that remove or repair damaged molecules.”

During fasting, ketone bodies are used as fuel for the body instead of glucose. Ketone bodies also affect a great many cellular functions. Not only is metabolism changed but genes are activated that may benefit brain health.

The authors of the NEJM review suggest it’s not just fewer calories that lead to health benefits:

“In humans, intermittent-fasting interventions ameliorate obesity, insulin resistance, dyslipidemia, hypertension, and inflammation. Intermittent fasting seems to confer health benefits to a greater extent than can be attributed just to a reduction in caloric intake.”

The authors conclude:

“Preclinical studies and clinical trials have shown that intermittent fasting has broad-spectrum benefits for many health conditions, such as obesity, diabetes mellitus, cardiovascular disease, cancers, and neurologic disorders.”

Could You Consider Intermittent Fasting?

Do you want to consider intermittent fasting? Here is a link to a free podcast of our one-hour interview with Dr. Jason Fung, a leading expert on this topic. You can listen to the streaming audio by clicking on the arrow inside the green circle under Dr. Fung’s photo. You can also download the free mp3 file or purchase a CD at the bottom of the page. Check out some of the comments from listeners.

Show 1143: Can You Control Your Blood Sugar by Fasting?

Share your thoughts in the comment section below. Would you ever consider intermittent fasting? If not, why not?

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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  • Vujovic N et al, "Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity." Cell Metabolism, Oct. 4, 2022. DOI:https://doi.org/10.1016/j.cmet.2022.09.007
  • Manoogian ENC et al, "Feasibility of time-restricted eating and impacts on cardiometabolic health in 24-h shift workers: The Healthy Heroes randomized control trial." Cell Metabolism, Oct. 4, 2022. DOI:https://doi.org/10.1016/j.cmet.2022.08.018
  • McAllister, M. J., et al, "Time-restricted feeding improves markers of cardiometabolic health in physically active college-age men: A 4-week randomized pre-post pilot study," Nutrition Research, Dec. 4, 2019, https://doi.org/10.1016/j.nutres.2019.12.001
  • de Cabo, R. and Mattson, M. P., "Effects of Intermittent Fasting on Health, Aging, and Disease," New England Journal of Medicine, Dec. 26, 2019, DOI: 10.1056/NEJMra1905136
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