Doctors have long advised people trying to lose weight to stop eating after the sun goes down, making lunch the day’s heartiest meal.

Now, researchers from the Universitat Oberta de Catalunya (UOC) and Columbia University can point to another major benefit of this piece of advice for metabolic health, revealing that eating at least 45 percent of your daily calories after 5 pm hinders the body’s ability to regulate blood sugar levels.

Eating later at night can drastically increase the risk of developing diabetes.

Their findings could provide some scientific validity to the intermittent fasting diet plan, which discourages eating later in the evening.

About 10 percent of Americans use intermittent fasting as a diet. Fans of this approach typically restrict daily eating to a six-hour period each day, such as 11 am to 5 pm.

And people who engage in intermittent fasting usually take in most of their calories earlier in the day.

One of the study's co-authors, Dr Diana Díaz Rizzolo, said: ‘The body's ability to metabolize glucose is limited at night, because the secretion of insulin is reduced, and our cells' sensitivity to this hormone declines due to the circadian rhythm, which is determined by a central clock in our brain that is coordinated with the hours of daylight and night.’

The study, published in Nutrition and Diabetes, included 26 people 50 to 75 years old who were overweight or had obesity and prediabetes or type 2 diabetes.

People were divided into two groups: early eaters and late eaters. They ate the same foods and the same amount of calories, just at different times of the day.

Those who ate more after 5 pm, the later eaters, had higher glucose levels after a glucose test, suggesting poorer glucose tolerance.

Intermittent fasting, meanwhile, has been shown to significantly improve the body’s ability to effectively use glucose from food and utilize insulin to manage blood sugar levels, in part because it encourages people to end their eating for the day relatively early, around 5 pm.

By limiting the eating window and extending the amount of time without food, the body can better process glucose more efficiently.

Researchers added food typically eaten late at night is more calorie-dense and often processed, ‘which may explain why late eating is associated with greater body weight and fat mass.’

Dr Díaz Rizzolo said: ‘Until now, personal decisions in nutrition have been based on two main questions: how much we eat, and what foods to choose.

‘With this study, a new factor in cardiometabolic health is beginning to become increasingly important: when we eat.’

In addition to typically eating unhealthy foods at night, late eaters have been shown to burn calories at a slower rate. Their bodies also showed signs of encouraging fat storage and reducing fat breakdown, which can lead to increased fat growth, according to a Harvard University study.

In the weeks leading up to the Harvard study, 16 overweight or obese people followed fixed sleep and eating schedules. Each participant experienced early meals and late meals, allowing the researchers to examine the effects of meal timing on the same people.

The results showed late eating decreased leptin, the hormone that signals fullness and influences appetite-regulating hormones, making participants feel hungrier over time.

These changes could potentially influence the risk of developing obesity, which is a key risk factor for type 2 diabetes.