Updated 8:47 AM EST, Fri, Mar 05, 2021

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Eating Late at Night can Cause Weight Gain and Other Health Problems

Not healthy

Late night snacking.

New findings suggest eating late at night could be more dangerous to one's health than previously thought.

 Compared to eating earlier in the day, prolonged delayed eating until late at night can increase weight, insulin and cholesterol levels. It can also negatively affect fat metabolism and hormonal markers implicated in heart disease, diabetes and other health problems, according to research from the Perelman School of Medicine at the University of Pennsylvania.

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The findings offer the first experimental evidence of the metabolic consequences of consistent delayed eating compared to daytime eating.

"We know from our sleep loss studies that when you're sleep deprived, it negatively affects weight and metabolism in part due to late-night eating," said Namni Goel, PhD, a research associate professor of psychology in Psychiatry in the division of Sleep and Chronobiology, and lead author of the ongoing study.

"But now these early findings, which control for sleep, give a more comprehensive picture of the benefits of eating earlier in the day.

"Eating later can promote a negative profile of weight, energy, and hormone markers -- such as higher glucose and insulin, which are implicated in diabetes, and cholesterol and triglycerides, which are linked with cardiovascular problems and other health conditions."

In the study, nine healthy weight adults underwent two conditions, one of daytime eating (i.e., three meals and two snacks between 8 a.m. and 7 p.m.) for eight weeks and another of delayed eating (i.e., three meals and two snacks eating from noon to 11 p.m.) for eight weeks.

The sleep period was held constant, between 11 p.m. to 9 a.m.

Participants visited Penn's Center for Human Phenomic Science to get metabolic measures and blood drawn at the beginning, after the first eating condition, after the two-week washout, and after the second eating condition.

This allowed the team to measure changes in weight, metabolism and energy used, and made sure the two week washout allowed all measures to return to baseline before the next condition.

The team found that when participants ate later, compared to the daytime condition, weight increased.

Respiratory quotient also rose during the delayed eating condition, indicating later eating led to metabolizing fewer lipids and more carbohydrates.

Respiratory quotient is the ratio of carbon dioxide produced by the body to oxygen consumed by the body that indicates which macronutrients are being metabolized.

Researchers also found that a series of other measures reflecting negative metabolic profiles increased in the delayed condition, including insulin, fasting glucose, cholesterol, and triglyceride levels.

The study also suggests that eating earlier may help prevent overeating in the evening and at night. As sleep-wake cycles were constant, melatonin levels remained constant in both groups.

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