A pilot study conducted at LSU’s Pennington Biomedical Research Center shows that eating all of your meals by mid-afternoon and fasting the rest of the day improves blood sugar control, blood pressure and oxidative stress, even when people don’t change what they eat.
“Ours is the first study in humans that shows consuming all of your calories in a six-hour period provides metabolic advantages compared to eating the exact same amount over 12 hours or more, even if you don’t lose weight,” said Dr. Eric Ravussin, associate executive director of Pennington Biomedical, director of the Nutrition Obesity Research Center, and one of the study’s co-authors.
“Our data also indicate that our feeding regimen has to be synchronized with the body’s circadian rhythm and our biological clock,” said Dr. Ravussin.
The study, published in the journal Cell Metabolism, is now available online.
Dr. Ravussin is a world-renowned expert in the conduct of translational research in obesity and type 2 diabetes. Over his more than 30-year career, he has conducted numerous clinical investigations on measures of energy expenditure, body composition, carbohydrate metabolism and biomarkers of aging in health and disease states.
Dr. Courtney Peterson, an adjunct assistant professor at Pennington Biomedical and an assistant professor at the University of Alabama at Birmingham, was the primary investigator on the study.
The research is important because it shows for the first time in humans that the benefits of intermittent fasting are not solely due to eating less. Practicing intermittent fasting has intrinsic benefits regardless of what you eat. Also, the study shows that eating early in the day may be a particularly beneficial form of intermittent fasting.
Peterson hopes that the research will also raise awareness of the role of the body’s internal biological clock — called the circadian system — in health.
“If you eat late at night, it’s bad for your metabolism,” Peterson said. “Our bodies are optimized to do certain things at certain times of the day and eating in sync with our circadian rhythms seems to improve our health in multiple ways. For instance, our body’s ability to keep our blood sugar under control is better in the morning than it is in the afternoon and the evening, so it makes sense to eat most of our food in the morning and early afternoon.”
Previous studies showed intermittent fasting improves metabolism and health. However, researchers didn’t know whether these effects are simply because people ate less and lost weight.
Peterson and her colleagues decided to conduct the first highly controlled study to determine whether the benefits of intermittent fasting are solely due to eating less. The study was also the first to test a form of intermittent fasting called early time-restricted feeding, or eTRF in humans. Early time-restricted feeding involves combining time-restricted feeding — a type of intermittent fasting where people eat in an 8-hour or shorter period each day — with eating early in the day to be in alignment with the body’s circadian rhythms in metabolism. It is tantamount to eating dinner in the mid-afternoon and then fasting for the rest of the day.
In the study, eight men with prediabetes tried following eTRF and eating at typical American meal times for five weeks each. On the eTRF schedule, the men each started breakfast between 6:30-8:30 am each morning, finished eating six hours later, and then fasted for the rest of the day — about 18 hours. Everyone finished dinner no later than 3 p.m. By contrast, on the typical American schedule, they ate their meals spread across a 12-hour period. The men ate the same foods on each schedule, and the researchers carefully monitored the men to make sure that they ate at the correct times and only ate the food that the researchers gave them.
The researchers found that eTRF improved insulin sensitivity, which reflects how quickly cells can take up blood sugar, and it also improved their pancreases’ ability to respond to rising blood sugar levels. The researchers also found that eTRF dramatically lowered the men’s blood pressure, as well as their oxidative stress levels and their appetite levels in the evening.
These findings could lead to better ways to help prevent type 2 diabetes and hypertension. In light of these promising results, Peterson said more research is needed on intermittent fasting and meal timing to find out how they affect health and to figure out what types of approaches are doable for most people.
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