A new study shows that eating later in the day can directly affect our biological weight regulation in three main ways: through the number of calories we burn; our hunger levels. and how our bodies store fat.
With obesity now affecting hundreds of millions of people worldwide, this is a valuable insight into how the risk of becoming obese could be reduced in a relatively simple way – just by eating our meals a few hours earlier.
Previous studies had already identified a link between meal timing and weight gain, but here the researchers wanted to examine this link more closely, as well as explore the biological reasons behind it.
“We wanted to test the mechanisms that might explain why delayed eating increases the risk of obesity,” says neuroscientist Frank Scheer, of Brigham and Women’s Hospital in Boston.
“Previous research by us and others has shown that delayed eating is associated with increased risk of obesity, increased body fat, and decreased weight loss success. We wanted to understand why.”
The research was strictly controlled and involved 16 participants with a body mass index (BMI) in the overweight or obese range.
Each volunteer went through two different six-day experiments, with sleeping and eating strictly controlled in advance, and several weeks between each test.
In one experiment, participants followed a strict schedule of three meals a day at regular times—breakfast at 9 a.m., lunch at 1 p.m. and dinner around 6 p.m.
In the other, the three meals were moved 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 over 24 hours, indicating that participants may have felt hungrier. In addition, calories were burned at a slower rate.
The tests also showed that expression of the adipose tissue gene – which affects how the body stores fat – increased the process of lipogenesis that builds adipose tissue and decreased the process of lipolysis that breaks down fat.
Here, we examine a combination of physiological and molecular mechanisms that increase obesity risk.
“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 can be affected by the timing of meals,” says Scheer.
Of course obesity can lead to other health problems, including diabetes and cancer, so finding ways to stop its growth 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 subsequent obesity risk – and it’s a change that may be easier for some people to make. managed by following a diet or exercise program.
In the future, the team wants to see research that includes more women (only 5 of the 16 volunteers were women in this case), as well as research that analyzes how changes in bedtime relative to eating time may also affect these procedures.
“In larger-scale studies, where rigorous control of all these factors is not feasible, we must at least examine how other behavioral and environmental variables alter these biological pathways that underlie obesity risk,” says Scheer.
The research has been published in Cellular Metabolism.