Can meal-timing strategies, such as intermittent fasting or eating earlier in the daytime, help people to lose weight by lowering appetite rather than burning more calories? The answer could be ‘yes’, if a study published in the journal Obesity, the flagship journal of The Obesity Society, is any indication. Apparently, the study is the first to show how meal timing affect 24-hour energy metabolism when food intake and meal frequency are matched.
The study showed that 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.
This will not be a surprise to Indians who are familiar with what Ayurveda prescribes—that between 10am and 2pm your agni or digestive power is at its peak. Some Indian approaches also prescribe finishing dinner before sundown.
“Coordinating meals with circadian rhythms, or your body's internal clock, may be a powerful strategy for reducing appetite and improving metabolic health,” according Eric Ravussin, PhD, one of the study's authors and associate executive director for clinical science at Louisiana State University's Pennington Biomedical Research Center in Baton Rouge.
“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,” said Courtney M Peterson, PhD, lead author of the study and an assistant professor in the Department of Nutrition Sciences at the University of Alabama.
However, the study's authors said that the results on fat-burning are preliminary. Whether these strategies help people lose body fat need to be tested and confirmed in a much longer study.
For the Alabama study, researchers recruited 11 adult men and women who were weighty, between November 2014 and August 2016, from among adults in general good health and were 20 years to 45 years old. The candidates had a body mass index (BMI) between 25kg and 35 kg/m2 (inclusive), body weight between 68kg and 100kg, regular bedtime between 9:30 pm and 12am, and for women, a regular menstrual cycle.
Participants tried two different meal-timing strategies in random order: a control schedule where participants ate three meals during a 12-hour period with breakfast at 8:00am and dinner at 8:00pm and an eTRF schedule where participants ate three meals over a six-hour period with breakfast at 8:00am and dinner at 2:00pm. 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 chamber where researchers measured how many calories, carbohydrates, fat and protein were burned. Researchers also measured the appetite levels of participants every three hours when they were awake, as well as hunger hormones in the morning and evening.
The researchers found that eTRF did lower levels of the hunger hormone. It also increased fat-burning over the 24-hour day. “By testing eTRF, we were able to kill two birds with one stone,” said Dr Peterson. The researchers were able to gain some insight into daily intermittent fasting (time-restricted-feeding), as well as meal timing strategies that involve eating earlier in the daytime to be in sync with circadian rhythms. The researchers believe that these two broader classes of meal-timing strategies may have similar benefits to eTRF.
Apparently, earlier research was not clear about whether meal-timing strategies help with weight loss by helping burn more calories or by lowering appetite. Studies in rodents suggest such strategies burn more calories; but data from human studies were conflicting. Some studies suggested meal-timing strategies increase calories burned, but other reports showed no difference. The previous studies did not directly measure how many calories people burned or were imperfect in other ways.
In this context, it is worth mentioning that there are a variety of successful time-restricted diet strategies. One of the most fascinating ones is by Bert Herring (www.bertherring.com
). He suggests extending the daily fast from whatever it is now (it may be only the time you’re asleep) to 19 hours, so you eat only between 5pm and 10pm. If you stick to this plan, your ability to turn away from food during the day increases; your appetite during the eating window decreases; and your calorie intake falls by around 500 calories a day—enough to lose about half a kilo per week.