Are There Benefits to Time-Restricted Eating?
Previously in this space, I’ve reported on quite a few studies looking at the idea of time-restricted eating (ie, intermittent fasting) as a weight loss strategy. So far, the evidence shows that there's no significant difference in the amount of weight lost between cutting calories overall vs intermittent fasting.1 Worse yet, those practicing intermittent fasting lost both muscle mass and body fat while those cutting calories lost mostly body fat.
But what if you did both?
The Research
Researchers at Southern Medical University in Guangzhou, China, teamed up with colleagues at Tulane University School of Public Health and Tropical Medicine to design a study to compare the effects of cutting calories vs restricting when one eats to cut calories.1
The team in China recruited 118 men and women with clinical obesity to participate in their 12-month program. The men were instructed to consume 1500-1800 calories per day and the women were to consume 1200-1500 calories per day. All participants were to consume approximately 40-55% of their calories from carbohydrates, 15-20% from protein, and 20-30% of calories from dietary fat.
To help the participants stick to their caloric goals, they were provided with a daily protein shake for the first 6 months and received diet counseling throughout the study.
The participants were randomly assigned to a time-restricted-eating group (only consuming calories between 8 AM and 4 PM local time) or the control group (no time restriction).
To make sure they were complying with the study's requirements, for the first 6 months of the study, the participants kept a daily food diary, photographed everything they ate with a time stamp through a special app, and had individual meetings with a health coach every 2 weeks.
During the last 6 months of the study, the participants kept a food diary and photographed their food 3 days per week and met with a health coach once a month.
At the close of the study, the authors compared not only the amount of weight the participants in each group lost, but also measured body fat and lean mass, comparing the measures to readings taken at the start of the study.
The Results
There were no clinically significant differences between the 2 groups: the time-restricted-eating group lost an average of 8 kg (about 17.6 lbs) while the control group lost an average of 6.3 kg (about 13.9 lbs).
Similarly, those on the time-restricted diet lost about 5.9 kg of body fat (about 13 lbs) while the control group lost 4.5 kg body fat (9.9 lbs). Changes in blood pressures, fasting glucose levels, and cholesterol scores were also similar between the 2 groups.
The Bottom Line
The authors conclude, "our data suggest that caloric intake restriction explained most of the beneficial effects of a time-restricted eating regimen." That is, the results for both groups were likely due to cutting calories, not limiting when they ate.
Reference:
- Liu D, Huang Y, Huang C, et al. Calorie restriction with or without time-restricted eating in weight lost. N Engl J Med. Published online April 21, 2022. doi:10.1056/NEJMoa2114833
Dr. Gourmet is the definitive health and nutrition web resource for both physicians and patients with evidence-based resources including special diets for coumadin users, patients with GERD/acid reflux, celiac disease, type 2 diabetes, low sodium diets (1500 mg/d), and lactose intolerance.
Timothy S. Harlan, MD, FACP, CCMS, is a practicing, board-certified Internist. He is currently an Associate Professor of Medicine at George Washington University and Director of the GW Culinary Medicine Program.
Health meets Food: the Culinary Medicine Curriculum, is an innovative program teaching medical students about diet and lifestyle that bridges the gap between the basic sciences, clinical medicine, the community, and culinary education. Medical students work side-by-side in the kitchen with culinary students to teach each other, and most importantly, teach the community and patients how to return to their kitchens and transform their health.
He served as Associate Dean for Clinical Services at Tulane University School of Medicine and is the founder and Senior Advisor of the Goldring Center for Culinary Medicine, the first of its kind teaching kitchen operated by a medical school.
Dr Harlan attended medical school at Emory University School of Medicine in Atlanta, Georgia, and pursued his residency at Emory University School of Medicine Affiliated Hospitals in Atlanta, GA.