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Researchers found that people who ate their main meal of the day after 3 p.m. lost less weight over 20 weeks than their "early eater" counterparts. 

You may be when -- not what -- you eat

by Kaitlyn Zufall
Jan 31, 2013

When the diet doesn’t work, it might not be what you eat, but when you eat it.

Researchers at Brigham and Women’s Hospital in Boston, working with the University of Murcia and Tufts University, found that timing could be an important factor in weight loss.

People who ate their main meal earlier in the day lost more weight than their counterparts who ate the meal later in the day, according to their study published Tuesday in the International Journal of Obesity.

“These results are interesting and suggest that people that have a certain behavioral profile, that in this case has been classified as early or late eaters, have different weight loss following a specific diet/behavior program,” noted study author José Ordovás, a professor of nutrition and genetics at Tufts in Boston.

Subjects were taken from a mixed pool of men and women who were voluntarily attending five nutrition clinics in the southeast of Spain in order to lose weight. The group was divided into “early” and “late” eaters depending on when they reported eating lunch, the main meal in the Mediterranean population.

Those who ate before 3 p.m. were classified as early eaters and those who ate after 3 p.m. were considered late eaters.

The 420 overweight and obese participants were monitored over 20 weeks. There was not a significant difference in caloric intake or physical activity reported among the two groups.

At the end of the observation period, early eaters reported an average weight loss of about 22 pounds while late eaters on average lost just under 18 pounds, even though both groups ate the same overall amounts of food.

Researchers hope to continue studying the concept of meal timing to verify their data and determine what exactly caused the results they observed.

“We need to know how, from the energy balance point of view, we can have with the same intake but different weight loss,” Ordovás stated. “This needs to be understood before people go crazy changing their meal times.”

Though the findings suggest that the time that a person eats could be a factor in weight loss, Ordovas cautions that it’s too early to draw definite conclusions.

“There are many other factors that were not measured or are difficult to measure with enough precision that could influence the outcome,” he stated. “The next obvious step should be the wise design of a study that could remove the potential and probable confounders that are present in the analysis of the published paper.”

Even the location itself could prove to be a variable.

“This is a Mediterranean population with specific habits. We don’t know how this will apply to a Northern European or a US population with a totally different life style,” Ordovás noted.

Though this is the first large-scale study to show that the timing of eating can predict the effectiveness of attempted weight loss in humans, the idea is not a new one. Previous research has shown a link between the timing of feeding and weight regulation in animals, according to the current study.

However, even if the data is confirmed, moving your main meal up a few hours may not be enough to help you drop those extra pounds.

Eating earlier has the potential to cause people to feel hungrier later in the day. This can lead to overloading and consequent weight gain, said Lara Field, a registered dietitian and the owner and founder of FEED Kids, a nutrition counseling practice.

She instead suggests pacing meals and snacks throughout the day to limit the body’s feeling of starvation, and consequent overeating.

“Having regularly scheduled breakfast, lunch and dinner is the most successful weight loss technique,” Field said. “No more than five hours between meals. Three to four hours is recommended.”