Written by Kelsey Schaffstall Young MS, RDN, CDN, LDN
What is Intermittent Fasting?
Intermittent fasting has become a wildly popular weight loss method over the past few years. A new study, published in April 2022 in the New England Journal of Medicine, sheds light on this topic in an article titled, Calorie Restriction with or without Time-Restricted Eating in Weight Loss, which explored the long-term efficacy of calorie restriction and time restricted eating.
What is time-restricted eating?
Time-restricted eating is a form of intermittent fasting in which a person restricts their eating window to a certain number of hours per 24-hour period. Despite its popularity, few studies have explored the long-term efficacy of this practice.
This study was conducted in China on 139 participants between 18-75 years of age with BMIs in the range of 28-45. For 12 months, participants in both groups restricted calories – 1500-1800 calories per day for men and 1200-1500 calories per day for women. However, in the intervention group, participants also practiced time-restricted eating – only consuming their alotted calories between the hours of 8am and 4pm. The 12-month intervention period was broken into two phases. In the first 6-month phase, participants kept daily food logs and photographed their meals. They also received support from a health coach in the form of messages twice weekly and individual counseling sessions twice monthly. In the second 6-month phase, participants tracked their food less frequently – keeping written and photographic food logs only 3 days per week. They also received a bit less support with health coach messages occurring once weekly and wellness counseling sessions occurring once per month.
Group sizes were nearly equal and the study population was approximately 50% male and 50% female. The average age and weight of the participants was 32 years old and 88.kg (194 lbs), respectively. Both groups consumed similar percentages of caloric intake from fat, carbohydrates, and protein.
Mean weight loss from baseline at 12 months in the time-restriction group was −8.0 kg or 17.6 lbs. In the daily calorie restriction group, participants lost an average of −6.3 kg or 13.9 lbs with no statistically significant differences between the groups. Both groups showed similar reductions from baseline in body and visceral fat, blood pressure, glucose levels, and lipid levels.
The authors concluded that the 8-hour time restricted eating regimen did not produce any significant advantage over calorie restriction alone and caloric restriction explained most of the beneficial effects seen in the time-restricted eating group. So, what does this tell us?
Though no significant benefit was found for time-restricted eating in addition to calorie restriction, these results indicate that both interventions were similarly effective. This means
that each approach could be successful for a person who is interested in pursuing weight loss, and ultimately a person should consider which approach would be most sustainable for them. For some people, time-restricted eating could provide more structure and they may naturally eat less if they are eating during a shorter period of time each day. For others, the limited eating window might feel restrictive and interfere with important social aspects of life such as family dinners or evening social events.
Remember, this study also provided a high level of professional guidance and support over the course of a year which most likely contributed to participants success. Interestingly, despite this support, the figures in this paper show that participants did regain some weight toward the end of the 12-month intervention which is consistent with other studies on weight loss and calorie restriction.
If you are considering a change in eating habits, reach out to a Registered Dietitian who can help you make sense of the evidence and develop a lifestyle plan that will support your
1. Liu, D., Huang, Y., Huang, C., Yang, S., Wei, X., Zhang, P., … & Zhang, H. (2022). Calorie
Restriction with or without Time-Restricted Eating in Weight Loss. New England Journal
of Medicine, 386(16), 1495-1504.
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