New research shows that weight loss can be supported by switching mealtimes to a smaller window earlier in the day. It also shows that loss of weight from this form of meal schedule is likely due to reduction of appetite and hunger hormone, rather than calorie burning.
A paper featured in the Obesity journal explains a trial that demonstrates how metabolism is affected by the timing of meals.
“Eating in line with circadian rhythms by eating early in the daytime seems to reduce body weight and enhance metabolic health,” the authors write.
They add, however, that it is not clear which mechanisms might drive “these weight loss effects.”
Therefore, the new study is the “first randomized trial to determine how meal timing affects energy metabolism in 24 hours when food intake and meal frequency match.”
The researchers compared two groups of people who eat the same three meals a day for 4 days but with different timings: the time-limited early feeding schedule (eTRF) and the control schedule.
There were 11 men and women in total who completed the trial: 6 in the eTRF group and 5 in the control group. Participants had to be in good health, aged between 25 and 45 years, and bear excess weight to qualify for the trial.
Appetite suppression and appetite hormone
The eTRF party breakfast at 8:00 a.m. And at 14:00, had their last meal of the day. They then fasted the next day for about 18 hours before breakfast.
The control group also breakfasted at 8:00 a.m. but their last meal of the day was at 8:00 p.m. Therefore, they fasted for around 12 hours before breakfasting the next day.
The authors likened the control schedule “to the median reported breakfast and dinner times for American adults.”
On the fourth day, the participants completed a battery of tests to assess their metabolism in a respiratory chamber. The measurements contained burned calories, and burned fat, carbohydrates and proteins.
The participants measured various aspects of appetite — such as hunger, desire and ability to eat, and satisfaction— by showing their experience on a visual sliding scale of those scales.
The team was also able to assess levels of hunger hormones from the blood and urine samples that the participants gave in the morning and evening.
The results showed that calorie burning differed little between the groups. Those on the eTRF schedule, however, had lower levels of the hunger hormone ghrelin and showed some aspects of appetite increased.
Burned more fat
The results also indicate that over a 24-hour cycle, the eTRF community seemed to have burned more fat.
The team suggests that eating the last meal of the day in the afternoon might help the body switch from burning carbohydrates to burning fat for energy.
The researchers, however, warn that the results on fat burning are preliminary and call for a longer study to check and validate whether strategies like eTRF will help shed body fat on people.
Lead research author Courtney M. Peterson, Ph.D., an assistant professor of nutritional sciences at Birmingham University of Alabama, says previous studies could not explain whether meal scheduling techniques help people lose weight by consuming calories or reducing appetite.
Findings from animal studies seem to contradict those from human studies. Several studies based on rodents have indicated that meal timing techniques help shed weight by calorie burning while others have not found out.
Peterson and colleagues, however, point out that those earlier studies had not specifically assessed calorie burning or had other disadvantages that might have clouded results.
“We suspect that a majority of people may find meal timing strategies helpful for losing weight or to maintain their weight since these strategies naturally appear to curb appetite, which may help people eat less.”
Courtney M. Peterson, Ph.D.