According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), more than 2 in 3 adults are considered to be overweight or obese.

One in 20 adults have extreme obesity, the NIDDK report, and one third of adolescents are either overweight or obese.

Overweight and obesity are considered risk factors for type 2 diabetes, heart disease, high blood pressure, fatty liver disease, as well as several types of cancer.

A new study looked at what effects eating dinner, or skipping it altogether, might have on body fat. The study examined the impact of early time restricted feeding (eTRF) schedules on overweight adults.
Time-restricted feeding has shown promise in rodents

eTRF is an eating schedule that involves eating in a short period of time, usually less than 9 hours, followed by a period of fasting of 15 hours or more.

Previous studies tested eTRF on rodents. The studies revealed that a restricted feeding schedule counters weight gain and increases energy expenditure.

Studies in rodents showed that eTRF also decreases fat mass, as well as lowering the risk of chronic diseases.

A recent study on mice found that time-restricted feeding (TRF), where food access was limited to 9-12 hours, is an effective intervention against obesity.

Without any calorie restriction, a TRF pattern can work against high-fat, high-fructose, and high-sucrose diets.

TRF also had a positive therapeutic effect against several metabolic diseases. It stabilized and finally reversed the progression of metabolic diseases in mice with pre-existing obesity and type 2 diabetes.

The effect eTRF has on the energy metabolism is connected with the body's circadian rhythm. The metabolism works at its best in the morning, so eating more in the morning can have positive effects on one's health.
Assessing eTRF in humans

Courtney Peterson, Ph.D, from the University of Alabama at Birmingham, and colleagues thought of examining the effects eTRF has on humans. This is the first time such an eTRF study was performed.

The study looked at the connection between eTRF and energy expenditure, macronutrient oxidation, and appetite. For good weight management, the energy intake has to match energy expenditure. In addition, the intake of macronutrients must match macronutrients oxidation.

Macronutrients are nutrients that the body needs to consume in large amounts in order to stay healthy. Macronutrients include carbohydrates, protein, and fats.

The study recruited 11 overweight adults with no chronic illnesses, aged between 20-45. For a week, participants kept a regular sleep pattern. Half of the participants kept an 8 a.m.-8 p.m. eating schedule, whereas the other half ate between 8 a.m. - 2 p.m. and then did not eat anything until 8 a.m. the next day.

In the interest of objectivity, participants tried both eating schedules and consumed the same number of calories on both eating schedules.

On the last day of the trial, participants ate three identical meals while undergoing 24-hour metabolic testing. Their appetite was also measured with the help of a visual analog scale.
Hunger swings, energy metabolism improved with eTRF

The study did not find any connection between eTRF and energy expenditure. Participants who were under an eTRF schedule did not burn more calories.

However, researchers found higher levels of fat oxidations at night during eTRF, along with increased protein oxidation. They also noticed a decrease in hunger swings during the day, as well as positive changes in energy metabolism. Therefore, eTRF may positively impact body composition.

It also improved metabolic flexibility, which is the body's ability to switch between burning carbs and fats.

"These preliminary findings suggest for the first time in humans what we've seen in animal models - that the timing of eating during the day does have an impact on our metabolism," says Prof. Dale Schoeller, a spokesperson for The Obesity Society.
Time-restricted feeding and weight loss

The study - presented at The Obesity Society Annual Meeting at ObesityWeek 2016 in New Orleans, LA - indicates that eTRF might help with weight loss.

"Eating only during a much smaller window of time than people are typically used to may help with weight loss," says Peterson, who led the study.

    "We found that eating between 8 a.m. and 2 p.m. followed by an 18-hour daily fast kept appetite levels more even throughout the day, in comparison to eating between 8 a.m. and 8 p.m., which is what the median American does."

    Courtney Peterson

Diminished daily hunger swings and higher metabolic flexibility, which were noticed in the study, might help with losing weight. However, researchers point out that this preliminary study is not enough to determine whether eTRF actually helps adults lose weight.

"With additional research on early-time restricted feeding on humans, we can create a more complete picture of whether this innovative method can best help prevent and treat obesity," says Prof. Schoeller.