Obesity continues to be a major health problem throughout the world. Globally, over one billion people are obese. Obesity carries huge health risks and is associated with an increased chance of developing over 60 diseases, including cardiovascular diseases, type two diabetes and cancer. In a recent study, Brigham and Women’s Hospital researchers were able to shed some light on why eating late increases obesity risk, pinpointing for the first time a few of the specific mechanisms involved.

Study Focusus on Mechanisms Behind Obesity

While this was a small study, it was also a tightly structured study, allowing for a tight focus on specific mechanisms that may have a role in the seemingly intractable health issue of obesity. As noted by the researchers, the more common means of dealing with obesity – reducing calorie intake, increasing physical activity to burn more calories or some combination of the two – frequently are less successful than hoped for, yielding weight loss that is slow to materialize and doesn’t last over the long-term. The researchers explain that this is because there are numerous other factors involved. Prior research demonstrates that obesity actually causes changes to the metabolic system that can lead to dysregulation, impairing its overall functioning.

So, in order to successfully isolate some of the mechanisms linking late eating to an increased risk of becoming obese, the study had to be rigorously controlled. While eating late or at night has been long associated with weight gain and more difficulty losing weight, scientist are still working on gaining a deeper understanding of the mechanisms involved.

For this study, the researchers looked at how the timing of food intake may influence obesity risk. After all, this is a readily adjustable factor well within the grasp of most people and something that could have real practical value for people dealing with this health issue.

The study involved 16 overweight or obese people, as determined by body mass index (BMI). Their ages fell between 25 and 59 years and the group included 11 males and five females. Five African-American people, three Asian people and one Hispanic person were included in the group of 16 participants. All were, aside from their weight, in generally good health with consistent levels of physical activity and all routinely ate breakfast. None of the participants engaged in shift work during the year before the study. Perimenopausal women were not included in the study. The participation of the women in the group was scheduled to avoid hormone surges that could skew study results.

For the study, participants spent nine days on site at the Brigham and Women’s Hospital Center for Clinical Investigation on two separate occasions, separated by three to twelve weeks. Each participant engaged in two weeks of preparation prior to their first on-site laboratory stay, keeping a consistent, monitored sleep-wake cycle. In the three days prior to the lab visit, they were required to keep a strict and identical diet; both in terms of content and timing.

While on site, the study participants did not have phones, internet access, radios or visitors. Light and temperature were tightly controlled and there was no exercise. They were fed a strict diet, with some on an early eating schedule and others on a late eating schedule. Those on the early schedule ate 60 minutes after they woke up, then again 250 minutes later, followed by a third meal 250 minutes after that.

Those eating on the late schedule had each meal four hours later than did the early eating group. Each meal took no more than half of an hour to consume. Hunger and appetite perceptions were recorded 18 times a day during the testing period. Hunger and satiety regulating hormones were tested hourly on test days and core body temperature was continuously monitored.

How Eating Late Increases Obesity Risk

According to the results of the study, meal timing does matter. Eating late does impact specific mechanisms and processes that, when disrupted, can increase the risk of obesity. Those eating on the late meal schedule were twice as likely to be hungry as those on the early schedule. They also had a higher desire to eat meat and starchy foods and had higher scores for how much they would like to eat.

Their appetite regulating hormones confirmed their perception of hunger, with a 34 percent increase in the ghrelin-to-leptin ratio during the hours they were awake. Ghrelin, often called the hunger hormone, increases the drive to eat, whereas leptin, known by many as the satiety hormone, tells you that you’ve had enough. When that ghrelin-leptin mechanism is disrupted, so too is appetite regulation, setting the stage for over-consumption of calories. Late eaters also had lower core body temperatures as well as lower rates of energy expenditure, meaning fewer calories burned. Instead, they were more likely to store those calories as fat.

Eat Earlier for Easier Weight Management

This detailed study just confirms that consuming the bulk of your calories earlier in the day, when you are more active, is more in line with your circadian rhythm, with how your body is meant to work, and can make weight management easier. This is practical knowledge that anyone can use to optimize their metabolism for optimal weight loss and overall health.