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Surprising study: How extended fasting, timed meals might fight obesity

Kathleen Blanchard's picture

It might be easier than we thought to stay slim, avoid obesity, diabetes and other diseases that include cancer, by fasting every day. Salk researchers found that daily fasting, even for people who eat a high-fat diet, might help keep the pounds off and help us stay metabolically healthy too. The idea, found in mouse studies, is not to eat throughout the day ,and instead stick to regularly timed meal times when we're awake. The finding might also show how important it is to avoid trips to the refrigerator for a midnight snack, which extends fasting time.

Fasting periods help the body make ‘good’ brown fat

What the study found – in mice – is that eating throughout the day disturbs nutrient sensors and disrupts metabolic pathways.

When mice studied were limited to regularly timed meals during an 8 hours period, researchers found it boosted liver enzymes that promote brown fat – the good kind – that helps keep blood sugar levels normal. They also found that eating makes the body store fat, but within a few hours of fasting, fat-burning starts and cholesterol is broken down. Eating frequently throughout the day doesn’t seem to be beneficial to health, despite suggestions that small frequent meals can help with weight loss and prevent weight gain.

"It's a dogma that a high-fat diet leads to obesity and that we should eat frequently when we are awake," says Satchidananda Panda in a media release. Panda, who is an associate professor in the Regulatory Biology Laboratory and senior author of the paper added, "Our findings, however, suggest that regular eating times and fasting for a significant number of hours a day might be beneficial to our health.”

Two sets of mice were studied. Once group ate the human equivalent of potato chips and ice cream for all of their meals that comprised 60% of calories. Another group ate whatever and whenever they wanted; consuming half of their food at night because they are nocturnal and then they were allowed to nibble ad lib.

The Salk scientists also used two control groups of mice that consumed a controlled diet with 13% of calories from fat.

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Just like humans, mice that ate fat throughout the day and night became obese, developed high cholesterol and poor motor control, had elevated blood sugar levels and liver damage. But the mice that fasted regularly stayed healthy in every aspect and even lost weight. They also outperformed the ad lib eaters on exercise tests.

This was a surprising result," says Megumi Hatori, a postdoctoral researcher in Panda's laboratory and a first author of the study. "For the last 50 years, we have been told to reduce our calories from fat and to eat smaller meals and snacks throughout the day.”

Timing meals could undo damage from high-fat foods

Hatori adds, “We found, however, that fasting time is important. By eating in a time-restricted fashion, you can still resist the damaging effects of a high-fat diet, and we did not find any adverse effects of time-restricted eating when eating healthy food."

The study isn’t the first to show that eating frequently is suboptimal for fighting obesity. Purdue University scientists suggest from their studies that eating regularly with more protein included in a meal does more to stave off hunger and facilitate weight loss than eating throughout the day – regardless of what kind of food you’re consuming.

The finding is important because it shows we might be able to fight major diseases like diabetes, heart attack, fatty liver disease and stroke by fasting for longer intervals throughout the day and timing our meals to allow for fat burning and increased brown fat metabolism. Targeting obesity is a major concern of researchers as diabetes rates have soared and anticipated to affect 51.2 million people by the year 2025.

But the authors warn that it’s important not to start eating high fat foods until the results are studied in humans. The take home message says Dr. Panda "is that eating at regular times during the day and overnight fasting may prove to be beneficial, but, we will have to wait for human studies to prove this."

Salk Institute
May 17, 2012