Researchers have discovered that intermittent fasting or eating earlier in the daytime appear to help people lose weight by lowering appetite instead of calorie-burning, according to a study from the University of Alabama at Birmingham.
This study is the first to show how meal timing affects 24-hour energy metabolism when food intake and meal frequency are matched.
Coordinating meals with circadian rhythms, or your body's internal clock, may be a powerful strategy for reducing appetite and improving metabolic health, the researchers said.
Meal timing strategies may also help people burn more fat during a 24-hour period.
Early Time-Restricted Feeding (eTRF) -- a form of daily intermittent fasting where dinner is eaten in the afternoon -- helped to improve people's ability to switch between burning carbohydrates for energy to burning fat for energy, an aspect of metabolism known as metabolic flexibility. Whether these strategies help people lose body fat, however, need to be tested and confirmed in a much longer study.
About the study
The researchers enrolled 11 overweight men and women who each tried two different meal timing strategies in random order:
1) A control schedule where participants ate three meals during a 12-hour period with breakfast at 8:00 a.m. and dinner at 8:00 p.m. and,
2) An eTRF schedule where participants ate three meals over a six-hour period with breakfast at 8:00 a.m. and dinner at 2:00 p.m.
The same amounts and types of foods were consumed on both schedules. Fasting periods for the control schedule included 12 hours per day, while the eTRF schedule involved fasting for 18 hours per day.
Study participants followed the different schedules for four days in a row.
On the fourth day, researchers measured the metabolism of participants by placing them in a respiratory chamber (a room-like device) where researchers measured how many calories, carbohydrates, fat and protein were burned.
Researchers also measured the appetite levels of participants every three hours while they were awake, as well as hunger hormones in the morning and evening.
Time-restricted eating reduce hunger hormone levels
Although eTRF did not significantly affect how many calories participants burned, the researchers found that eTRF did lower levels of the hunger hormone ghrelin and improved some aspects of appetite. It also increased fat-burning over the 24-hour day.
This study sheds more light on how patterns of eating, not just what you eat, may be important for achieving a healthy weight.
Source: Obesity, July 24, 2019.
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