Late-night eating raises risk of obesity

By Mark Waghorn via SWNS

Eating late at night raises the risk of obesity, according to new research from Boston.

It can reduce the burning of calories and increase hunger leading to weight gain.

Lab experiments found meals just before bedtime have profound effects on appetite-regulating hormones leptin and ghrelin.

Health experts have warned against the dangers of midnight snacking for years. The findings shed fresh light on why it can lead to chronic diseases.

Senior author Professor Frank Scheer, of Brigham and Women's Hospital, Boston, said: "We wanted to test the mechanisms that may explain why late eating increases obesity risk.

"Previous research by us and others had shown that late eating is associated with increased obesity risk, increased body fat, and impaired weight loss success. We wanted to understand why."

More than two billion adults worldwide are overweight or obese, making diabetes, cancer, cardiovascular disease and other life-threatening conditions more likely.

The study found dining at 10 pm instead of 6 pm or late eating simultaneously affected the three main players in body weight regulation.

They are energy expenditure, regulation of food consumption and chemical changes in fat tissue.

The first author Dr. Nina Vujovic said: "In this study, we asked, 'Does the time that we eat matter when everything else is kept consistent? And we found eating four hours later makes a significant difference for our hunger levels, the way we burn calories after we eat, and the way we store fat."

Obesity afflicts more than four in ten people in the US. Britain has been dubbed the 'Fat Man of Europe', with two in three overweight.

The results published in the journal Cell Metabolism have particular implications for shift workers.

Levels of the hormone leptin, which signals satiety, were decreased across 24 hours in late compared to early eating conditions.

When participants ate later, they also burned calories at a slower rate and stored more fat.

Importantly, the discoveries combine physiological and molecular mechanisms underlying the link between late-night eating and obesity.

They are consistent with a large body of evidence suggesting it increases one's risk and explain how this might occur.

Prof Scheer said: "This study shows the impact of late versus early eating. Here, we isolated these effects by controlling for confounding variables like caloric intake, physical activity, sleep and light exposure.

"But in real life, many of these factors may themselves be influenced by meal timing. In larger scale studies, where tight control of all these factors is not feasible, we must at least consider how other behavioral and environmental variables alter these biological pathways underlying obesity risk."

The team recruited 16 patients with a body mass index (BMI) in the overweight or obese range.

They completed two protocols - one with an early meal and the other with the same about four hours later in the day.

For two to three weeks prior to testing, fixed sleep and wake schedules were maintained.

In the final three days before, the participants strictly followed identical diets and meal schedules at home.

In the lab, they regularly documented their hunger and appetite, provided frequent small blood samples throughout the day and had body temperature and energy expenditure measured.

Biopsies of adipose tissue were collected from a subset during both protocols to analyze how eating time affected molecular pathways involved in adipogenesis, or how the body stores fat.

The randomized crossover study tightly controlled for behavioral and environmental factors such as physical activity, posture, sleep and light exposure.

It enabled the investigators to detect changes to the different control systems involved in energy balance, a marker of how our bodies use the food we consume.

In future studies, Prof Scheer and colleagues aim to recruit more women. The study cohort included only five female participants.

It was set up to control for the menstrual phase, reducing confounding but making recruiting women more difficult.

Going forward, they are also interested in better understanding the effects of the relationship between meal time and bedtime on energy balance.

Previous research has found eating late at night increases blood sugar levels, raising the risk of type 2 diabetes, the form linked to obesity.

It can cause symptoms like excessive thirst, needing to pee a lot and tiredness. It can also lead to serious eye heart and nerve problems.

Another study found consuming all your calories before 3 pm each day results in superior weight loss when compared to a normal eating period.

It improves insulin sensitivity that controls fat metabolism, lowers blood pressure and slashes cravings for sweet foods in the evening, said the researchers.