By Aria Bendix -
NBC News
New research suggests there may be an ideal window of time to eat during the day.
Eating meals early can be beneficial for weight loss, and keeping meals within 10 hours helps improve blood sugar and cholesterol levels, according to two studies published Tuesday in the scientific journal
Cell Metabolism
.
The first research found that eating later in the day made people hungrier over a 24-hour period than when they ate the same meals earlier in the day.
Eating later also caused the study participants to burn calories at a slower rate, and their adipose tissue appeared to store more calories with a later eating schedule than with an earlier one.
Overall, the study suggests that eating later may increase a person's risk of obesity.
The second study, conducted among a group of firefighters, found that eating meals within a 10-hour window reduced "bad cholesterol" particles, suggesting a possible reduction in heart disease risk factors.
That feeding window also improved blood pressure and blood sugar levels among firefighters with underlying health conditions such as diabetes, high blood pressure and high cholesterol.
New research suggests there may be an ideal window of time to eat during the day.Getty Images
The two studies add to existing evidence that there may be optimal times to start and stop eating, according to Courtney Peterson, an associate professor of nutritional sciences at the University of Alabama at Birmingham, who was not involved in either study. two studies.
"We have a kind of internal biological clock that makes us do different things better at different times of the day. It seems that the best time for most people's metabolism is mid to late morning," Peterson added.
Previous research has found that circadian rhythms (the body's internal clock that helps regulate sleep and wakefulness) can influence people's appetite, metabolism, and blood sugar levels.
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Satchidananda Panda, a co-author of the firefighter study and a professor at the Salk Institute, added that a 10-hour window appears to be a factor because the severe restrictions that characterize many intermittent fasting diets are difficult to maintain.
"When we think about six or eight hours, you might see a benefit, but people might not keep it for very long," Panda added.
Eating late could 'tip the scales' toward weight gain
The first of two new studies involved 16 people who were overweight or obese.
They tested two different dietary regimens for one day each.
First, some of the participants started eating an hour after their normal waking time, while the rest waited to start eating until about five hours after waking up.
The two groups then changed times at a later date.
According to Frank Scheer, lead author of the study, the meals they ate were identical and the amount of calories and nutrients were constant at both times.
The researchers measured the hormone levels of the participants and found that eating late decreased levels of leptin (a hormone that helps you feel full) by 16% on average.
Eating late also doubled the odds that people would feel hungry.
People reported their level of appetite 18 times throughout the day.
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In addition, the researchers found that those who ate late had a greater desire to eat starchy and salty foods, as well as meat, dairy and vegetables.
According to Scheer, this could be because people want more energy-dense foods when they're hungrier.
The study also found consistent changes in fat tissue associated with the late-eating regimen, suggesting a higher chance of developing new fat cells and a lower chance of burning fat.
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Ultimately, the results showed that late eaters burned about 60 fewer calories a day than early eaters, though Peterson pointed out that this was "equivalent to eating half an apple more a day, so it's not that big of a change."
Although a study published last month in the same journal found that people didn't burn more calories by eating a large breakfast and a light dinner, Peterson said the two studies measured a different set of outcomes.
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“The body processes calories differently when you eat late in the day.
This tips the scales in favor of weight gain and fat gain," Peterson said, adding, "We can get pretty clear recommendations from this study that people shouldn't skip breakfast."
Scheer added that more research is needed before he feels comfortable making any recommendations.
A 10-hour window could reduce risk factors
In the second study, 137 firefighters from San Diego, California, followed a Mediterranean diet rich in fruits, vegetables, fish, and olive oil for 12 weeks.
Seventy firefighters ate within a 10-hour window, while the rest generally ate for more than 13 hours.
The firefighters logged their meals on an app and brought wearable devices to help researchers monitor their blood sugar levels.
Most participants in the 10-hour group ate between 8 or 9 a.m. and 6 or 7 p.m. (although they occasionally fell outside that window, stretching over an 11- or 12-hour period).
Among healthy firefighters, the time restriction showed "favorable effects that should translate into less plaque buildup in the arteries and less cardiovascular disease," Peterson reported.
Firefighters in that group also reported a better quality of life.
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Among firefighters with preexisting risk factors for heart disease, time-restricted feeding lowered blood pressure and blood sugar levels.
"There's been a lot of evidence that time-restricted eating improves blood sugar and blood pressure control, but this is the first study to really test it on a large scale in people who work shifts," Peterson said.
Panda added that previous research in animals has shown that during periods of fasting, "organs get a bit of a break from digesting food so they can divert their energy toward cell repair."
A period of fasting also appears to allow the breakdown of accumulated toxins, Panda added.
And Peterson added that during fasts, the body can get rid of sodium, which in turn lowers blood pressure.
He said he wouldn't be surprised if, in the next five to 10 years, there are national recommendations on eating windows or meal times in the United States.
