0606 GMT November 20, 2019
The research, presented at the American Heart Association's Scientific Sessions annual meeting, found that eating more later in the evening was associated with an increased risk of heart disease, livescience.com reported.
People in the US now have a ‘delayed lifestyle’ — they go to sleep later at night and get fewer hours of sleep, said lead study author Nour Makarem, a postdoctoral fellow in cardiology at Columbia University Vagelos College of Physicians and Surgeons. And with that delayed lifestyle, you also see higher rates of late-night eating, she said.
Makarem and her colleagues thought that this meal timing may play a role in the rise in rates of obesity, high blood pressure and diabetes seen in recent years.
So, they set out to see if that's the case. In the study, the researchers used a database called the Hispanic Community Health Study/Study of Latinos to look at information on more than 12,700 Hispanic and Latino adults ages 18 to 76.
(Though the study only looked at one specific population in the US, the Hispanic and Latino population, "we do expect to see similar associations in other populations in the US," Makarem told Live Science. Indeed, several studies conducted abroad have shown that meal timing may be associated with developing risk factors for heart disease, she added.)
In the study, the team looked at data from two separate days in which participants reported their eating habits, and compared this information to measurements such as blood pressure and blood sugar.
They found that over half of the people in the study consumed 30 percent or more of their daily calories after 6 p.m. Those participants had higher levels of fasting blood sugar (a measure of the amount of sugar in the blood when someone hasn't eaten in hours), higher levels of insulin (the hormone that regulates the amount of sugar in the blood), higher levels of HOMA-IR (a marker of resistance to insulin) and higher blood pressure than participants who reported eating less than 30 percent of their daily calories after 6 p.m.
A high fasting blood sugar level can be considered a sign of prediabetes, according to the Mayo Clinic. (Prediabetes means that a person's blood sugar levels are abnormally high, but not high enough to be considered diabetes.) Indeed, the researchers found that those who consumed 30 percent or more of their daily calories after 6 p.m. were 19 percent more likely to develop prediabetes than those who ate more earlier in the day. Seventy percent of people with prediabetes go on to develop type 2 diabetes, which is a risk factor for heart disease, Makarem noted. [Where Is Heart Disease Risk Highest and Lowest? (Maps)]
Those same participants were also 23 percent more likely to develop hypertension, compared with people who ate more earlier the day. These associations were especially common in women, Makarem added.
The study only found an association between meal timing and a person's risk of certain medical problems; it didn't prove cause-and-effect.
However, Makarem said that one possible explanation for the link is that problems can arise when our body clocks aren't synced to our environment. Almost every cell in our body can tell time, and they run on a roughly 24-hour cycle. A small part of the brain called the suprachiasmatic nucleus serves as the body's master clock, receiving external light cues (ideally from the sun) and sets the rest of the clocks in our cells accordingly, telling us when to wake up, sleep and eat, Makarem said.
"These clocks are regulated by bright-light exposure but also by behaviors, particularly food signals," Makarem said. So, when we eat at unconventional times — for example, by consuming more calories in the evening — the body's clocks can become misaligned with the master clock, leading to problems in metabolism and increasing the risk for chronic diseases such as diabetes, hypertension and heart disease, she said.
"The evidence is fairly consistent that eating more, later in the day, seems to be worse metabolically," said Kristen Knutson, an associate professor of neurology and preventative medicine at Northwestern University Feinberg School of Medicine who was not involved with the research, but attended Makarem's talk today. These problems arise because "you're not eating at the time that's optimal for your circadian system," she told Live Science.