THURSDAY, Dec. 13 (HealthDay News) -- When it comes to eating
pasta, bread and potatoes, timing could be everything.
Israeli researchers found in a small study that saving most
carbohydrates for dinnertime may help keep people from feeling
hungry the following day, supporting weight-loss efforts for those
who are obese.
The study authors were curious after reading research on Muslims
during Ramadan, an annual month of religious fasting. During this
period, Muslims fast during the day and then eat a
high-carbohydrate evening meal.
Previous studies have found that the concentration of
carbohydrates consumed at the end of the day modifies the typical
day-night pattern of leptin, a hormone responsible for satiety, or
feeling full. Muslims are better able to adhere to their daytime
fast by pushing most carbohydrates to dinner, the study authors
"We believe low leptin levels during daytime are remnants of evolution when prehistoric man had to wake up and look for food," explained Zecharia Madar, professor emeritus at the Institute of Biochemistry, Food Science and Nutrition at Hebrew University in Tel Aviv. "Today, as food is highly available, this mechanism is unnecessary, and an easy way to obesity."
The researchers were also interested in the hormone ghrelin and
the protein adiponectin. Ghrelin is produced in the stomach and
usually increases before meals to stimulate eating. Considered the
"hunger hormone," it seems to work against dieters because it tends
to peak after 1 p.m. (causing afternoon snacking) and is at its
lowest level during the night. Adiponectin plays a role in the
development of insulin resistance -- which can be a forerunner to
diabetes -- and hardening of the arteries.
The research was published in two parts, in the October 2011
Obesityand in the August online issue of
Nutrition, Metabolism & Cardiovascular Diseases.
The study involved 63 male and female police officers aged 25 to
55, who had a body mass index -- a measure of body fat based on
height and weight -- greater than 30, which is considered
Participants were randomly assigned to one of two weight-loss
diets. One held most of the carbohydrates until dinner and the
other distributed carbohydrates evenly throughout the day. None of
the participants had been diagnosed with a disease or were
pregnant, and none had been on a diet regimen for at least a year
before the study.
After 180 days on the diets, the researchers found that those on
the dinnertime carbohydrate diet had hormonal changes that reduced
hunger. They also showed improvements in weight, waist
circumference and body fat, and better blood sugar and fat
Might the special carbohydrate diet offer benefits for people of
normal weight? Madar said he doesn't know. "It would have been
interesting to find out if our diet would be a good choice for
normal-weight subjects with high glucose and pathological lipid
profiles," he said.
But experts urged caution in interpreting the study.
"We know for sure that leptin and ghrelin play roles in satiety, but the research doesn't completely demonstrate in a free-living population how you change these hormones and what is the impact," said Connie Diekman, director of university nutrition at Washington University in St. Louis.
Diekman also was concerned that at the study's start there was a
weight difference between the two groups of participants, which she
said could contribute to the difference in final results. In
addition, she said, there were notable average differences in waist
circumference between the two groups.
Amy Jamieson-Petonic, program manager at Cleveland Clinic
Wellness, said she wonders about the effect of night-shift work,
because the participants were all police, and sleep issues related
to shift work have been associated with weight problems. "We don't
know what kind of sleep problems these people were having," she
Jamieson-Petonic also questioned whether the lab data for the
research was complete enough to make a reliable conclusion. Of the
63 participants, lab results were reported for only 39
For most people, the toughest issue in dieting is maintaining
weight loss over time. Jamieson-Petonic said the fact that the data
for this study was reported after just six months fails to prove
the diet is effective. "The challenge is keeping the weight off,"
she said. "I'd love to see these people one year out, or 18 months
out. That's the challenge my clients have. And I'd also like to see
the lab values after a year."
For her part, Diekman said it's clearly too soon for people to
switch to a dinnertime carbohydrate diet. "From my perspective,
measuring calories in and calories expended gives most people the
most benefit based on what we know now."
To learn more about healthy eating, visit the
U.S. Centers for Disease Control and
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