Dieters who ate early lunches tended to lose more weight than those who had their midday meal on the later side, in a new Spanish study.
The finding doesn't prove bumping up your lunch hour will help you shed those extra pounds. But it's possible eating times play a role in how the body regulates weight, researchers said.
"We should now seriously start to consider the timing of food - not just what we eat, but also when we eat," said senior author Dr. Frank Scheer, from Brigham and Women's Hospital and Harvard Medical School in Boston.
His team's research included 420 people attending nutrition clinics in southeast Spain. Along with attending regular group therapy sessions with nutrition and exercise counseling, dieters measured, weighed and recorded their food and reported on their daily physical activity.
Study participants were on a Mediterranean diet, in which about 40% of each day's calories are consumed at lunch. About half of people said they ate lunch before 3:00 p.m. and half after.
Over 20 weeks of counseling, early and late lunchers ate a similar amount of food, based on their food journals, and burned a similar amount of calories through daily activities.
However, early eaters lost an average of 22 pounds - just over 11% of their starting weight - and late eaters dropped 17 pounds, or 9% of their initial weight.
The timing of breakfast or dinner wasn't linked to participants' ultimate weight loss, according to findings published in the International Journal of Obesity.
One limitation of the study is that the researchers didn't assign people randomly to eat early or late - so it's possible there were other underlying differences between dieters with different mealtimes. Certain gene variants that have been linked to obesity were more common in late lunchers, for example.
Dr. Yunsheng Ma, a nutrition researcher from the University of Massachusetts Medical School in Worcester, said people who eat later may have extra food in their stomach when they go to sleep - which could mean more of it isn't burned and ends up being stored as fat.
"One of the other aspects to this is, what we know is glucose tolerance for example - how well you can deal with sugar in your food - your body is better able to cope with that in the morning than in the evening," Dr. Scheer told Reuters Health.
How often people eat during the day and whether they bring food from home or eat out may also contribute to weight loss, added Dr. Ma, who wasn't involved in the new research.
He said any implications of late eating could be exacerbated among Americans.
"The pattern of consumption of meals is very different in the U.S.," and problematic, Dr. Ma told Reuters Health. Many people skip breakfast or lunch - then end up overdoing it on calories at dinner.
Scheer said in the U.S., where dinner is typically the biggest meal, researchers would expect people who eat later dinners to have more trouble losing weight based on his team's findings.
Regardless of exact meal times, Dr. Ma said it's important for people to spread their calories out throughout the day.
"Have a good breakfast and a good lunch, and at dinner, people should eat lightly," he advised.
By Genevra Pittman