Longer fasts might help with weight loss but Americans eat all day long

Americans eat for roughly 15 hours a day, and much of it is on the fly, says new research.

Americans eat for roughly 15 hours a day, and much of it is on the fly, says new research.

(Mike Tripp / Associated Press)
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It’s official: Americans’ 24/7 culture of work, entertainment and digital connectivity now also extends to our dietary consumption patterns, new research finds.

Americans’ erratic, round-the-clock eating patterns, suggests the new study, have probably contributed to an epidemic of obesity and Type 2 diabetes. But they can be changed, and the restoration of a longer nighttime “fast” shows promise as a means to lower weight and better health, researchers add.

In a study that detailed the consumption patterns of just over 150 nondieting, non-shift-working people in and around San Diego for three weeks, researchers at the Salk Institute in La Jolla found that a majority of people eat for stretches of 15 hours or longer most days -- and fast for fewer than nine hours a night.


We snarf a tidbit at a midmorning meeting, nibble for much of the afternoon, knock back a drink or two with dinner and keep noshing till bedtime. Fewer than a quarter of the day’s calories were consumed before noon, they discovered. And more than a third of participants’ average daily calories, the research revealed, were consumed after 6 p.m.

Despite participants’ typical claim to be consuming three meals a day, “a breakfast-lunch-dinner temporal pattern was largely absent,” the researchers wrote in an article published Thursday in the journal Cell Metabolism.

The participants ate and drank pretty much all day, researchers found. The 10% of eaters whose consumption “events” were most limited averaged 4.22 a day. The 10% who ate most frequently averaged 15.5 noshes per day. Fewer than 10% of participants went for more than 12 hours without eating.

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In fact, just over 12% of participants’ daily average intake of 1,947 calories happened after 9 p.m., the researchers found.

And generally, that final 12% of the day’s calories was extra: Computing participants’ average caloric needs for maintenance of body weight, the researchers reckoned that, typically, all calories consumed by participants after 6:36 p.m. were over and above those needed to keep their collective weight stable.


The result appears to be a formula for steady weight gain and metabolic disturbance.

In mice being fed high-fat chow, the Salk researchers’ past studies have shown that among those allowed to eat anytime, obesity was rampant. When researchers compressed the animals’ “feeding day” to eight or nine hours, those with the long fast stepped up their calorie consumption when they were allowed to eat.

Both groups of mice ended up taking in equal calories. But the fasting mice were less likely to be obese, and had lower levels of systemic inflammation, fatty liver disease, worrisome cholesterol and metabolic disturbance than those allowed to eat whenever they wanted.

Pointing to such research, the Salk researchers have suggested that a nightly fast of 10 to 12 hours might do much more than just limit the consumption of excess calories: Even without changing daily calorie intake, a lengthy nighttime fast appears to “reset” a circadian clock disturbed by 24/7 feeding and drive up the body’s ability to burn off extra calories.

While humans cannot have their chow taken away for half the day, the authors wrote, their “erratic daily rhythm of eating/fasting ... can be manipulated to obtain desirable health benefits.”

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To demonstrate those benefits, the researchers recruited eight of the study’s participants, all of whom were overweight or obese, and whose general “eating day” normally spanned more than 14 hours.


Participants in this small pilot study were shown their long and erratic patterns of daily feeding, and asked to make one change only: to limit their consumption of anything with more than five calories to a 10- to 12-hour span each day, then to fast for the remaining 12 to 14 hours.

Over 16 weeks, the study participants lost an average of just over 7 pounds. They rated their sleep satisfaction and daily energy levels as increased, along with their level of nighttime hunger.

Their consumption records suggest that not all of their weight loss was the result of a metabolic reset. Participants cut their daily calories consumed by 20% on average: Unlike rats, who compensated for fasting by eating more during their brief eating day, these participants simply did without the excess food.

It will take longer and more regulated trials to determine whether such weight loss was purely a function of reduced calorie consumption, or whether there were metabolic benefits that aided weight reduction, the authors acknowledged.

The new study deployed a smartphone app specifically designed for the research -- available here.

Researchers said the app is available to anyone willing to contribute his or her data to a Salk Institute study being conducted under customary academic strictures. After two weeks, the program generates and shares with the participant a “feedogram,” which precisely records and analyzes his or her dietary intake patterns.


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