Razi Berry

Two daily fasting diets, also known as time-restricted feeding diets, are effective for weight loss, according to a new study published by researchers from the University of Illinois at Chicago.

First human clinical trial to compare effects of two popular forms of time-restricted feeding on body weight and cardiometabolic risk

The study reported results from a clinical trial that compared a 4-hour time-restricted feeding diet and a 6-hour time-restricted feeding diet to a control group.

“This is the first human clinical trial to compare the effects of two popular forms of time-restricted feeding on body weight and cardiometabolic risk factors,” said Krista Varady, professor of nutrition at the UIC College of Applied Health Sciences and corresponding author of the story.

Participants in the 4 and 6-hour time-restricted feeding diet group

Participants in the 4-hour time-restricted feeding diet group were asked to eat only between the hours of 1 p.m. and 5 p.m. Participants in the 6-hour time-restricted feeding diet group were asked to eat only between the hours of 1 p.m. and 7 p.m.

Patients permitted to eat whatever they wanted in both study groups

In both the study groups, patients were allowed to eat whatever they wanted during the 4-hour or 6-hour eating period. During the fasting hours, participants were directed to only drink water or calorie-free beverages. In the control group, participants were directed to maintain their weight and not change their diet or physical activity levels.

The participants were followed for 10 weeks as weight, insulin resistance, oxidative stress, blood pressure, LDL cholesterol, HDL cholesterol, triglycerides and inflammatory markers were tracked.

The study’s findings

The study, published in Cell Metabolism, found that participants in both daily fasting groups reduced calorie intake by about 550 calories each day simply by adhering to the schedule and lost about 3% of their body weight. The researchers also found that insulin resistance and oxidative stress levels were reduced among participants in the study groups when compared with the control group. There was no effect on blood pressure, LDL cholesterol, HDL cholesterol or triglycerides.

No significant difference in weight loss or cardiometabolic risk factors for these groups

There also was no significant difference in weight loss or cardiometabolic risk factors between the 4-hour and 6-hour diet groups.

“The findings of this study are promising and reinforce what we’ve seen in other studies — fasting diets are a viable option for people who want to lose weight, especially for people who do not want to count calories or find other diets to be fatiguing,” Varady said. “It’s also telling that there was no added weight loss benefit for people who sustained a longer fast — until we have further studies that directly compare the two diets or seek to study the optimal time for fasting, these results suggest that the 6-hour fast might make sense for most people who want to pursue a daily fasting diet.”


1. Sofia Cienfuegos, Kelsey Gabel, Faiza Kalam, Mark Ezpeleta, Eric Wiseman, Vasiliki Pavlou, Shuhao Lin, Manoela Lima Oliveira, Krista A. Varady. Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metabolism, 2020; DOI: 10.1016/j.cmet.2020.06.018


Razi Berry is the founder and publisher of the journal Naturopathic Doctor News & Review, which has been in print since 2005, and the premier consumer-faced website of naturopathic medicine, NaturalPath. She is the host of The Love is Medicine Project docuseries, The Natural Cancer Prevention Summit, The Heart Revolution-Heal, Empower and Follow Your Heart, and the popular 10-week Sugar Free Summer program. From a near death experience as a young girl that healed her failing heart, to later overcoming infertility and chronic fatigue syndrome and fibromyalgia through naturopathic medicine, Razi has lived the mind/body healing paradigm. Her projects uniquely capture the tradition and philosophy of naturopathy: The healing power of nature, the vital life force in every living thing and the undeniable role that science and mind/body medicine have in creating health and overcoming dis-ease. You can follow Razi on social media: Facebook at Razi Berry, Instagram at Razi.Berry and join the Love is Medicine group to explore the convergence of love and health. Look for more, and listen to more Love is Medicine podcast episodes here.

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