Eating late increases risk of obesity, study says

A recent study showed that eating late increased hunger, decreased calories burned, and promoted fat growth compared to earlier eating.

The study, published in the journal, Cell Metabolism, was led by Nina Vujovic, PhD, and Frank Scheer, PhD, of the Medical Chronobiology Program in the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital in Boston, Massachusetts. Vujovic, Scheer, and their team wanted to discover, when everything else was kept consistent, if timing of eating influenced weight regulation.

"Previous research by us and others had shown that late eating is associated with increased obesity risk, increased body fat, and impaired weight loss success,” said Scheer in a statement. “We wanted to understand why.”

For the investigation, researchers recruited 16 patients with a body mass index (BMI) in the overweight to obese range. In the three days leading up to the experiment, the participants followed an identical diet and meal schedule. In addition, participants were asked to maintain fixed sleep and wake schedules during the two to three weeks prior to the in-laboratory protocols.

In the lab, patients completed two different protocols, each lasting 24 hours. For the first protocol, they strictly followed an early meal schedule. For the second, participants ate the same meals as before, but they were each scheduled four hours later. Throughout the investigation, participants documented their hunger and appetite, provided frequent blood samples, and had their body temperature as well as their energy expenditure measured. In addition, to identify any molecular changes in pathways involved in adipogenesis, researchers collected biopsies of adipose tissue from a subset of patients during both protocols.

Results showed that eating later decreased levels of the hunger and appetite regulating hormones leptin and ghrelin. Leptin levels were decreased across the 24 hours when participants were eating later meals. In addition, during the later eating protocol, participants burned fat slower than when they ate earlier.

When researchers analyzed the participants’ adipose tissue, they found that gene expression indicated increased adipogenesis and decreased lipolysis, changes that can promote fat growth.

According to researchers, these findings suggest why eating late may increase risk for obesity. For future studies, the team plans to expand their research and include more participants and fewer controls to see if their results are applicable to the general population in daily life.  

"In larger scale studies, where tight control of all these factors is not feasible, we must at least consider how other behavioral and environmental variables alter these biological pathways underlying obesity risk,” said Scheer.