- Fasting may help curb your appetite and boost fat-burning, according to new research.
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- A new study has found that a type of intermittent fasting that limits meals to early in the day could lower appetite and help the body burn fat.
- Participants who ate between 8 a.m. and 2 p.m. had lower levels of the hunger hormone ghrelin, and burned more fat than those on a normal meal schedule.
- The study’s small sample size means more research is needed to understand intermittent fasting’s potential benefits for weight loss and metabolic health.
- Visit INSIDER’s homepage for more.
Intermittent fasting is the latest in a long line of dieting trends, and new research suggests a version of the eating style that matches your meal times to your body’s natural rhythms may help you burn fat and eat less while feeling fuller.
In the study, published Wednesday in the journal Obesity, researchers tracked 11 overweight men and women, ages 20 to 45, over a four-day period on two different meal-timing plans.
One plan limited participants to eating during a six-hour period from 8 a.m to 2 p.m. This window of time was chosen because it combines two types of meal-timing strategies – fasting for at least 14 hours a day, and eating earlier to align with the circadian rhythm, or the body’s internal clock. The six-hour window is also suspected to be the smallest eating window that people can sustain long term.
The control group ate according to “typical American meal times” at approximately 8 a.m., 1 p.m., and 8 p.m. All participants tried both meal plans, in a random order, with about a month in between, and ate the same amount of food on both plans. Subjects were then tested via a variety of rigorous methods, including blood samples, urine tests, and a respiratory chamber that measures energy use, to look at how each eating schedule affected metabolism.
Read more: Everything you need to know about ‘intermittent fasting’ – the buzzy diet that won’t make you change what you eat
The researchers found that when participants fasted, they had a decreased appetite, both by self-reported surveys of how hungry they felt, and according to measurements of the body’s level of ghrelin, a hormone known to stimulate appetite. The limited meal times also prompted the body to burn more fat in a 24-hour period.
The fat-burning finding was a surprise to researchers, Courtney Peterson, co-author of the study and professor of nutrition at the University of Alabama, told INSIDER. Her research team intended to better understand why people who try intermittent fasting tend to lose weight.
“What we think this means is that when you lose weight, you burn more body fat but keep muscle mass,” she said. A follow-up study will look at this fat-burning potential, Peterson said, and more research is needed to investigate how fasting might effect muscle mass.
These results suggest intermittent fasting could work for weight loss by reducing appetite, not by burning more calories
Previous research in animals has suggested that fasting can boost metabolism and burn more daily calories, which was believed to be the reason for its weight-loss benefits. This study, however, found that one of its primary effects was a lower appetite. In conjunction with the fat-burning effect, this could be the reason for IF’s weight-loss potential.
“Maybe people think there’s some miraculous property, that it really revs up your metabolism, but we didn’t find that to be the case,” Peterson said.
More research is still needed to understand intermittent fasting’s potential benefits
Although this study did not directly measure weight loss, these results are part of a growing body of research that touts intermittent fasting as a strategy for helping people shed pounds.
The very small sample size, short time frame, and careful regulation of the study, however, means more research is necessary to better understand how intermittent fasting works in everyday life.
For instance, most people who try IF for weight loss won’t have the benefit of a team of researchers planning their meals and ensuring they eat them (and nothing else). Participants in both plans ate specially-prepared meals on days three and four of the study, calculated to meet their energy and nutritional needs based on age, gender, and weight.
“In the real world, if someone did time-restricted feeding and ate less, they might be hungrier than we found in our study,” Peterson said.
Fasting may also not be for everyone – people with a history of eating disorders or with health complications like diabetes should be wary about trying to fast for 18 hours at a time, and some fasts are more sustainable than others.
There’s more evidence that fasting may make you healthier, and it comes from studying Ramadan observers
The best and worst types of intermittent fasting, according to experts
8 reasons you should try intermittent fasting – and 8 reasons you shouldn’t
The “blue light” in light-emitting diode (LED) lighting can damage the eye’s retina and disturb natural sleep rhythms, France’s government-run health watchdog said recently.
New findings confirm earlier concerns that “exposure to an intense and powerful (LED) light is ‘photo-toxic’ and can lead to irreversible loss of retinal cells and diminished sharpness of vision,” the French Agency for Food, Environmental and Occupational Health and Safety (Anses) warned in a statement.
The agency recommended in a 400-page report that the maximum limit for acute exposure be revised, even if such levels are rarely met in home or work environments. The report distinguished between acute exposure of high-intensity LED light, and “chronic exposure” to lower intensity sources.
While less dangerous, even chronic exposure can “accelerate the ageing of retinal tissue, contributing to a decline in visual acuity and certain degenerative diseases such as age-related macular degeneration,” the agency concluded.
Long-lasting, energy efficient and inexpensive, LED technology has gobbled up half of the general lighting market in a decade, and will top 60% by the end of next year, according to industry projections.
LED uses only a fifth of the electricity needed for an incandescent bulb of comparable brightness. The world’s leading LED light-bulb makers are GE Lighting, Osram and Philips.
The basic technology for producing a white light combines a short wavelength LED such as blue or ultraviolet with a yellow phosphor coating. The whiter or “colder” the light, the greater the proportion of blue in the spectrum.
While LED screens on mobile devices do not affect eye health, they do disturb your body’s rhythms and sleep patterns when used in the dark.
LEDs are used for home and street lighting, as well as in offices and industry. It is also increasingly found in auto headlights, torches and some toys.
LED mobile phone, tablet and laptop screens do not pose a risk of eye damage because their luminosity is very low compared to other types of lighting, said Francine Behar-Cohen, an ophthalmologist and head of the expert group that conducted the review.
But these back-lit devices – especially when they are used at night or in a dark setting – can “disturb biological rhythms, and thus, sleep patterns,” the agency cautioned.
Because the crystalline lens in their eyes are not fully formed, children and adolescents are particularly susceptible to such disruptions, the Anses report noted.
Interfering with the body’s circadian rhythm is also known to aggravate metabolic disorders such as diabetes, cardiovascular disease and some forms of cancer, noted Dina Attia, a researcher and project manager at Anses.
In addition, a stroboscopic effect in some LED lights – provoked by tiny fluctuations in electric current – can induce “headaches, visual fatigue and a higher risk of accidents,” the report said.
For domestic lighting, Anses recommended buying “warm white” LED lighting, limiting exposure to LED sources with a high concentration of blue light, and avoiding LED screens before bedtime.
The agency also said that manufacturers should “limit the luminous intensity of vehicle headlights”, some of which are too bright. Finally, the agency cast doubt on the efficacy of some “anti-blue light” filters and sunglasses. – AFP Relaxnews
Next time you stagger into a Waffle House in the wee hours of the morning and order the Texas sausage egg & cheese melt (1,040 calories), consider this new research finding: At roughly that hour, the most basic operations of the human body throttle back their caloric needs by about 10%, compared to the rate at which they will burn calories in late afternoon or early evening.
Maybe you’d prefer to come back around dinner time.
This pattern of calorie use doesn’t significantly vary based on whether you’re the waitress working the graveyard shift or a 9-to-5’er stopping in for breakfast after eight hours of shut-eye, the researchers found.
Humans’ “resting energy expenditure” – the body’s use of calories to power such basic functions as respiration, brain activity and fluid circulation – follows a predictable cycle that waxes as the day progresses and wanes as night sets in.
The study, published in the journal Current Biology, offers further evidence that circadian rhythms dictate not just when we feel the urge to sleep, but also how complex mechanisms like metabolism operate across a 24-hour period.
It may help explain why people who keep irregular sleep schedules, including swing shift workers, have higher rates of obesity and are more likely to develop metabolic abnormalities such as type 2 diabetes.
And it demonstrates that whether we hear it or not, our body’s clock is always ticking, locating us in our daily cycle with uncanny precision.
At “hour zero” – roughly corresponding to somewhere between 4am and 5am – our core body temperature dips to its lowest point and our idling fuel use reaches its nadir.
From that point, at first quickly and then a bit more slowly, the body’s “resting energy expenditure” rises until the late afternoon/early evening.
After reaching its peak at roughly 5pm, the number of calories we burn while at rest plummets steadily for about 12 hours.
And then, just as surely as day follows night, we start again.
These new findings are a reminder that no matter how 24/7 our schedules have become, our bodies were built for a slower, simpler world in which humans moved around all day in search of food, ate while the sun was up, and slept when the sky was dark.
Today, our appetites and the all-night availability of tempting food may induce us to eat well after sundown. And our jobs may demand that we sleep during the day and wait tables, care for patients or drive trucks through the night.
But our bodies still adhere to their ancient, inflexible clocks.
The study’s findings also come with an implicit warning: When we disregard the biological rhythms that rule our bodies, we do so at our peril.
Resting energy expenditure accounts for the majority of the minimum calories we burn in a day. Just to spend a day eating, sleeping and breathing uses up 60% to 70% of our “resting energy expenditure”.
So a serious mismatch in the time when calories are consumed and the time when most of them are burned could prompt the body to make decisions – like storing calories as fat – that aren’t necessarily healthy.
The study adds to a growing body of evidence suggesting that a good 12-hour fast, when aligned with darkness and our bodies’ nocturnal response, may be a way to prevent or reverse obesity.
In lab animals and a growing number of people, Salk Institute researcher Satchin Panda has demonstrated the impact of dietary obedience to our circadian rhythms.
Others have demonstrated the power of timing by showing how readily it can be disrupted.
People who keep irregular sleep schedules, including swing shift workers, have higher rates of obesity and are more likely to develop metabolic abnormalities such as type 2 diabetes. — AFP
In a 2014 study, 14 lean, healthy adults agreed to turn their days upside-down over a six-day period. Fed a diet sufficient to maintain their weight, the subjects quickly adapted by turning their thermostats down.
Compared to the baseline readings taken upon their arrival (when they were awake by day and asleep eight hours at night), the subjects burned 52 fewer calories on day two of their swing-shift schedule, and 59 fewer calories on day three of that schedule.
Do that for a couple of days and you might feel a little off. Do it for months, years or a lifetime, and the result could be too much stored fat and metabolic processes that go haywire.
“One take-away is indeed that for optimal health, including metabolic health, it’s best for us to have a regular schedule seven days a week – getting up and going to bed at the same time and eating our meals at the same time,” said senior author Jeanne F. Duffy, a neuroscientist and sleep specialist at Brigham & Women’s Hospital in Boston, United States.
“We have these powerful clocks in ourselves and they’re prepared to deal with certain events – eating and sleeping – at particular times everyday. So we want them to be optimally prepared for that.”
To get to these findings, the researchers had to coax seven people to spend three weeks sequestered in windowless rooms without clocks, cellphones or internet service.
In what is called a “forced desynchrony protocol”, the researchers extended the subjects’ days by four hours.
All got a minimum of eight hours in bed at the end of their extended day, but then woke up and marched through an 18-hour period of artificial “daylight” before being allowed to sleep again.
At first, they seemed to race to keep up with this odd clock. But after three weeks of such discombobulation, subjects essentially come to rely on their own internal clocks to set the duration of their days and separate their days from nights.
The individual rhythms that each subject fell back into did not show that much variation: Without alarm clocks or other cues, they eventually found their way back to a cycle of sleeping and waking that hovered closely around 24 hours, Duffy said.
By the end of week one, the patterns in their hour-by-hour resting energy expenditure had become clear: In a span of time ranging from 23 to 24.5 hours, subjects who were disconnected from day and night cues showed patterns of resting energy use that were remarkably similar, and that followed the same daytime rise and nighttime decline.
These patterns remained unchanged until the end of week three.
Along with that were similar patterns of “macronutrient utilisation”. Subjects burned the most carbohydrates early in their waking day. Carbohydrate use then declined steadily, with a small jump in the middle of the night.
The burning of fat was lowest in the morning, peaked in early evening, and declined from there.
“We were impressed by the fact that these patterns were so similar between individuals,” Duffy said. “That told us this was something real.”
The number of calories we burn – or store as fat – is likely influenced not just by our size, what we eat and the amount of exercise we get, she said. The timing of our eating matters too.
When we sleep late on weekends, hopscotch across time zones, or work on schedules that have us up all night then back on the day-shift, “we’re disrupting our clocks and making our metabolisms inefficient, and in the long term, that will lead to disease,” she said.
“Staying on the same schedule is the best way to prevent that.” – Los Angeles Times/Tribune News Service