A social media trend urging people to finish dinner by 5 p.m. is getting a second look from doctors, after a randomized trial found that adults who confined their eating to an eight-hour daily window for 12 weeks kept off several more pounds a full year later, compared to those who ate on a normal schedule.
The concept of eating dinner early is not new -- the "early bird special" has been around for decades. What's changed is the volume.
Videos on the "Early Bird Dinner" trend have dominated social media in recent months, and restaurants have reported a shift toward earlier reservations. Media outlets, meanwhile, have queried whether the habit delivers sleep benefits or other health perks.
About 40% of U.S. adults have obesity, which raises the risk of Type 2 diabetes, heart disease and high blood pressure, according to the Centers for Disease Control and Prevention. For many, the "Early Bird Dinner" trend offers a low-risk experiment: an earlier plate, a calmer stomach and possibly a better night's sleep.
Researchers in Granada, Spain, randomly assigned 99 adults with overweight or obesity to one of four groups: Three limited all eating to an eight-hour window, starting early in the day, starting late, or at a time each participant picked. The fourth kept its usual schedule of 12 hours or more. Every group, including the comparison group, also went through a Mediterranean diet education program.
After 12 weeks, participants were told nothing further and went back to living normally. A year later, the early and late groups had kept off roughly 5 to 6 pounds more than the comparison group. Only the early group held onto a significant reduction in fat mass.
The early group's window is strikingly close to what the social media trend prescribes: Participants typically ate between about 9:30 a.m. and 5:15 p.m.
Doctors have cautioned against reading too much into a single trial.
"It was a pretty small study -- 99 people -- and only 65 made it to the one-year follow-up," Dr. Nishtha Modi, a board-certified internal medicine physician who focuses on obesity and wellness, told ABC News. "That's not a reason to dismiss it, but it's also not enough for me to tell everyone they need to stop eating four to five hours before bed."
The eight-hour groups also lost more fat-free mass, which includes muscle, than the comparison group, and had not fully recovered it a year later. The authors call for pairing this kind of eating plan with resistance training and enough protein.
The analysis was exploratory, run at a single site, and measured body composition with bioelectrical impedance, which is less precise than a DXA scan.
The trial was publicly funded, and the authors reported no conflicts of interest.
Modi said the problem with late eating is often what's on the plate.
"Let's be honest -- most of us aren't reaching for grilled salmon and broccoli at 10:30 p.m. We're usually eyeing chips, cookies, or whatever's left in the freezer," she said. "Eating a big meal right before bed can also make acid reflux worse and interfere with sleep quality, and if you're sleeping poorly, you're probably going to have less energy to exercise and make healthy food choices the next day. It's a vicious cycle."
Modi warned that fasting also isn't for everyone.
"People taking insulin or certain diabetes medications should talk with their healthcare provider before trying it, because fasting can increase the risk of low blood sugar," she said. "I also urge caution in older adults who may be at risk for losing muscle mass."
For those looking to make eating changes, the takeaway shouldn't be to fixate on the time on the clock, Modi said.
"Don't get so caught up chasing the 'perfect' eating schedule that you forget the basics," she said. "Eat real nutritious food, move your body in ways you enjoy, don’t overeat, and spend time with people who make you laugh."
She added, "The best diet isn't the 'perfect' one -- it's the one you can actually follow. Everyone has different jobs, social lives, and schedules. If a plan means you have to skip every birthday dinner or never meet friends for tacos again... it's probably not going to last."
Yonathan Daniel, M.D., is an internal medicine resident physician at NYU Langone Health and a member of the ABC News Medical Unit.
