A new study suggests that eating later in the day may have a direct impact on our biological weight regulation in three key ways: through the number of calories we burn; our hunger levels; and the way our bodies store fat.
With obesity affecting hundreds of millions of people worldwide, this is a valuable insight into how to reduce the risk of becoming obese in a relatively simple way – simply by eating our meals a few hours earlier.
Previous studies had already shown a link between meal timing and weight gain, but here the researchers wanted to take a closer look at that link and tease the biological reasons behind it.
“We wanted to test the mechanisms that might explain why eating late increases the risk of obesity,” says neuroscientist Frank Scheer of Brigham and Women’s Hospital in Boston.
“Previous research by us and others had shown that eating late is associated with an increased risk of obesity, increased body fat and decreased weight loss success. We wanted to understand why.”
The study was tightly controlled and included 16 participants with a body mass index (BMI) in the range of overweight or obese.
Each volunteer underwent two different experiments that lasted six days, with their sleep and food strictly controlled beforehand, and several weeks between each test.
In one experiment, participants adhered to a strict schedule of three meals a day around normal times: breakfast at 9 a.m., lunch at 1 p.m. and dinner around 6 p.m.
In the other, the three meals were pushed back (the first around 1pm and the last around 9pm) – so lunch, dinner and supper.
Through blood samples, survey questions and other measurements, the team was able to make a number of observations.
When we ate later, levels of the hormone leptin — which tells us when we’re full — were lower for 24 hours, indicating that participants may have felt hungrier. In addition, calories were burned at a slower rate.
The tests also showed that adipose tissue gene expression — which affects how the body stores fat — increased the adipogenesis process that builds up adipose tissue and decreased the lipolysis process that breaks down fat.
Here we look at a combination of physiological and molecular mechanisms that increase the risk of obesity.
“We isolated these effects by controlling for confounding variables such as caloric intake, physical activity, sleep and light exposure, but in real life, many of these factors themselves can be influenced by meal timing,” says Scheer.
Of course, obesity can lead to other health problems, including diabetes and cancer, so finding ways to stop its development would make a huge difference to the health of the world’s population.
What this study shows is that eating earlier in the day can affect three key factors in how our bodies balance energy and the subsequent risk of obesity — and it’s a change that may be easier for some people to understand. manage than to stick to a diet or exercise regimen.
In the future, the team wants to see research involving more women (in this case, only 5 out of 16 volunteers were female), as well as research analyzing how changes in bedtime in relation to eating time may also play a role in these processes.
“In larger-scale studies, where tight control of all of these factors is not feasible, we should at least consider how other behavioral and environmental variables alter these biological pathways underlying obesity risk,” Scheer says.
The research was published in cell metabolism.