medwireNews: A randomized trial in The New England Journal of Medicine shows no benefit of adding time-restricted eating to 12 months of calorie reduction in people with obesity.
All trial participants restricted their daily calorie intake, to 1500–1800 kcal for men and 1200–1500 kcal for women, and were randomly assigned to consume these either within an 8-hour period or whenever they preferred.
However, the authors of a linked editorial point out that even at baseline the participants’ average habitual eating period was “relatively short,” at around 10 hours and 25 minutes.
“Hence, the effective reduction of the eating window to 8 hours in the time-restriction group was modest (approximately 2 hours),” write Blandine Laferrère (Columbia University Irving Medical Center, New York, USA) and Satchidananda Panda (Salk Institute for Biological Studies, La Jolla, California, USA).
“Persons whose habitual time period for eating is long are likely to benefit the most from time-restricted eating,” they add.
The time window for eating in the time-restricted group was 08:00 to 16:00, reflecting the Chinese trial population’s habit of eating their main meal in the middle of the day. All 139 participants were given one protein shake per day for the first 6 months and received dietary counseling for the full 12 months. Around 85% of the participants completed all 12 months, and they successfully limited themselves to the time and calorie restrictions on about 85% of days.
The average weight loss in the time-restricted and calorie-reduction groups was 8.0 and 6.3 kg, respectively, and the average 1.8 kg difference between the two groups was not statistically significant. Likewise, body fat mass was reduced by an average 5.9 and 4.5 kg, respectively, and changes in blood pressure, lipid levels, and glucose levels were also similar in the two groups. People with diabetes were excluded from this trial.
“These results indicate that caloric intake restriction explained most of the beneficial effects seen with the time-restricted–eating regimen,” say Huijie Zhang (Southern Medical University, Guangzhou, China) and co-researchers.
However, Laferrère and Panda observe that “[t]he trial was relatively small, and the results have not precluded the possibility of a clinically important benefit of the time-restricted intervention.”
And they add: “The rigorous coaching and monitoring by trial staff also leaves open the question of whether time-restricted eating is easier to adhere to than intentional calorie restriction.”
The editorialists describe time-restricted eating as “low-cost and sustainable” and say that it “may turn out to be an approach to accomplish calorie restriction and improve metabolic health without the resource-intensive approach of intentional calorie restriction.”
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N Engl J Med 2022; 386: 1495–1504
N Engl J Med 2022; 386: 1572–1573