TUESDAY, Jan. 29 (HealthDay News) -- People who like to eat
lunch late in the afternoon may have more trouble shedding pounds
than those who dine earlier, a new study suggests.
Researchers found that of 420 people in a weight-loss program,
the late-lunch crowd lost about 25 percent less weight than those
who usually lunched before 3 p.m.
The findings, reported Jan. 29 in the
International Journal of Obesity, come with caveats. The
researchers cannot be sure that a late lunch itself thwarts
people's diets. And the study participants were from Spain, where
lunch is the biggest meal of the day.
It's not clear if the findings would translate to a country like
the United States, where most people eat a lighter lunch and save
their main meal for dinner, said senior researcher Frank Scheer, an
assistant professor of medicine at Harvard Medical School in
It is a common belief that it's better to have your big meal
earlier in the day. Scheer pointed to the popular advice to eat
breakfast like a king and dinner like a pauper. But there hasn't
been much scientific evidence that the timing of your main meal
matters in the battle of the bulge.
"This is the first large-scale, long-term study to show that it is an important factor in weight-loss success for overweight and obese individuals," Scheer said.
It's uncertain why a late lunch would be related to slower
weight loss. One possibility, though, is that at least some late
lunchers were going too long between meals, which might have
effects on metabolism.
Some studies have suggested that evenly spaced meals -- eating
every three to four hours -- are helpful in weight control, noted
Connie Diekman, director of university nutrition at Washington
University in St. Louis.
In this study, the late-lunch group was more likely to eat a
light breakfast or skip breakfast altogether. Almost 7 percent of
later lunchers did so, versus less than 3 percent of people who ate
So the findings show a "potential connection between going too
long between meals and weight gain," said Diekman, who was not
involved in the study. "But given the study design, more studies
are needed to determine if there is a cause-and-effect
The problem is that people who hold off on lunch may differ from
other dieters in many ways -- including ways that could hinder
their weight loss.
Scheer's team did account for some of those possibilities. They
found that the early- and late-lunch groups ate a similar number of
calories and burned a similar amount (based on their reported
activity levels). The two groups also averaged about the same
amount of sleep each night, which is important because sleep loss
has been linked to a higher risk of obesity and less weight-loss
Still, that's not enough to prove the late lunch caused the
slower weight loss, Scheer and Diekman pointed out.
The findings are based on 420 overweight and obese Spanish
adults who took part in a five-month weight-loss program. They were
encouraged to follow a traditional Mediterranean diet, which
includes plenty of fish, olive oil, vegetables and whole grains,
but goes light on red meat and butter.
They got no advice, however, on the timing of their meals.
In the end, the half of the group that usually ate lunch after 3
p.m. lost an average of 17 pounds. That compared with 22 pounds in
the early-lunch group.
As is typical in Spain, lunch was the biggest meal of the day.
The dieters downed 40 percent of their daily calories at lunchtime,
on average -- whether they ate early or late.
In contrast to the lunch findings, there was no evidence that
the timing of people's breakfast or dinner affected their weight
loss. (Half of the group ate their dinner after 9:30 p.m.)
So in a culture where the biggest meal of the day is dinner,
would it matter if you ate it at 9 p.m. or 6 p.m.? "It's hard to
say, based on these data," Scheer said. Further research is needed
to answer that question, he added.
For now, the current findings are in line with animal research
showing that meal timing seems to affect weight, Scheer said.
It may have to do with effects on the body's circadian rhythms,
which influence a range of functions, including the sleep-wake
cycle and metabolism. There is a "master clock" in the brain that
coordinates those rhythms, but there are also "peripheral clocks"
in tissue and cells throughout the body, Scheer explained.
In animals, unusual feeding times seem to disrupt some of those
peripheral clocks and throw them out of sync with the master clock.
In theory, that clock "decoupling" could affect weight control.
More research is still needed, though, to see whether the timing
of a person's main meal directly influences weight -- and how
important that influence really is, Scheer said.
"We need to know if this has clinical relevance," he said.
Diekman said the findings support the notion that meal timing
matters, but she agreed that the ultimate importance to weight loss
remains to be seen.
"As a registered dietitian, this study helps me feel comfortable with recommendations about the importance of meal spacing," she said. "But it does not give an answer to why or what impacts that might have on weight."
Learn more about weight-loss dieting from the
U.S. National Institutes of Health.
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