For those who return home from work and pour a glass of wine or stick a biscuit, this news could make them feel less guilty.
The early evening is the time of day when we burn more calories, one study found.
Assuming that someone maintains a regular schedule, late afternoon and early evening is the time when their metabolic rate is higher. At this point, we burn five extra calories all at once or about half a gram of fat.
Researchers have discovered when people burn more calories by keeping 10 people in a lab for 37 days without clocks and moving some of their four-hour sleep hours.
The early evening is the time of day when we burn more calories, one study found
No matter what time people ate or slept, they burned most of the calories when their biological clock reached late afternoon and evening.
For most people, the first biological evening and early evening are the same thing.
But experts warn that people who do not follow a regular routine may lose the benefits by making their biological "evening" so that they arrive overnight.
The researchers also found that people burned less calories during their late biological night, typically between 4:00 and 6:00.
This means that people who are late, like shift workers, could get fat by eating at that time.
Dr Jeanne Duffy, co-author of the Brigham and Women's Hospital study, said: "We found that people's metabolic rates are all synchronized similarly to their daily schedules.
HOW MANY CALORIES DO I NEED EVERY DAY?
The basic amount of calories that an average adult needs per day is 2,000 kcal for women or 2,500 kcal for men.
This is based on the amount of energy the body needs to perform basic functions and to walk and work during the day.
People who do a lot of exercise need to eat more calories to feed their efforts, and young people and children also burn more energy.
If you eat more calories than you burn in a day, you will become more fat.
Eating less calories than those burned will make you lose weight.
Foods that are processed and have high levels of carbohydrates, sugars and salt have a higher calorie count of fresh fruit and vegetables.
Examples of caloric counts include:
- A Mac Mac McDonald's contains 508 kcal
- A two-finger KitKat contains 106 kcal
- A banana contains 95 kcal
- An apple contains 47 kcal
"So they burned most of the calories in the late organic afternoon and early in the evening and less during the late organic night.
"This shows the importance of being awake when most of the calories are burned and asleep when the metabolic rate is lower.
"But it's not just shiftworkers who interrupt their natural biological clock, because someone who stays up late to finish a project or gets up to the airport can end up doing the same thing."
The study participants had no idea what time it was, without watches, windows or telephones allowed.
In the tests, three maintained a normal routine, while another seven people had their bedtime four hours later each night to monitor their body's internal clock.
By taking only the biological clock, people burned 10% more calories in the late afternoon organic and early evening than late at night.
Dr. Kirsi-Marja Zitting, principal author of the study, said: "The fact that at one hour of the day did the same thing burning so much more calories than doing the same thing in another hour of the day surprised us ".
On the results, published in the journal Current Biology, dr. Duffy said, "It's not just what we eat, but when we eat and rest, it impacts how much energy we burn or store as fat.
"The regularity of habits such as eating and sleeping is very important for general health."