Contrary to diet gurus’ insistence that a person’s metabolism can be boosted if breakfast is the biggest meal of the day, a new study suggests the timing of the highest calorie meal has no impact on the rate energy is burned.
An analysis of data from an experiment that included 30 adults revealed that people who ate a big breakfast did not burn calories any faster than those who consumed most of their calories in the evening meal, according to a study published in Cell Metabolism.
“Our work suggests that the distribution of calories throughout the day does not influence energy metabolism or weight loss,” said study coauthor Alexandra Johnstone, a professor at the Rowett Institute at the University of Aberdeen in the UK. “Eating more calories at breakfast might be beneficial to control appetite throughout the rest of the day, so you can stick to the calorie restriction without feeling hungry.”
Johnstone was not surprised by the study’s findings.
“These are the results that I expected — that weight loss would be similar, with similar energy metabolism, regardless of time of eating,” Johnstone said in an email. “This is somewhat contrary to the dogma in the traditional circadian rhythm science.”
The belief in the weight loss benefits of a big breakfast has been around for a long time, Johnstone said.
“The meme, ‘Eat like a king in the morning, a prince at noon, and a peasant at dinner’ is purported to come from a medieval philosopher and doctor, named Maimonides,” she added. “However, the science of chrono-nutrition (chrono — meaning time, thus time of eating) is a relatively young science, that relates time of day with food intake and health. Previous work suggested that eating earlier in the day enhanced weight loss, affecting energy metabolism, compared to eating later in the day.”
To take a closer look at whether eating a big breakfast could help speed weight loss, Johnstone and her colleagues recruited 16 men and 14 women who were overweight or obese and who were willing to allow what they ate to be controlled by the researchers and to allow Johnstone and her team to measure the impact of big-meal timing on metabolism.
The researchers randomly assigned the volunteers to either eat a calorie-loaded meal in the morning or in the evening for four weeks. All the meals — which contained 30% protein, 35% carbohydrate and 35% fat — were planned by the researchers.
Throughout the study, the volunteers’ total daily energy expenditure and weight were measured. After four weeks, the volunteers initially randomized to have a big breakfast were switched to have a big dinner and vice versa. When the researchers analyzed the energy expenditure and weight measurements, they found it made no difference whether the volunteers consumed a big meal in the morning or the evening.
Overall, the volunteers reported they were less hungry on the days they ate a big breakfast. On average, they lost about 7 pounds during each of the four week periods.
The control of hunger may be the one benefit to consuming a big breakfast, Johnstone said.
“Hunger is one of the main reasons that people fail to comply with a weight loss or calorie restricted diets,” she added. “If we have diet strategies that can help control hunger, then it would be beneficial in the real world. We need more work on chrono-nutrition to examine the effect of time of eating and fasting on health.”
The new study is “interesting,” said Dr. Megan Jenkins, a specialist in weight loss surgery and an associate professor of surgery at NYU Langone Health in New York.
“It highlights more than anything that if you put someone on a regimented diet — like Weight Watchers or Jenny Craig — and you stipulate that they have regular check-ins, they are more apt to follow the diet and lose weight,” Jenkins said. “The question is what happens when they come off the diet and they’re allowed eat what they want and not weigh-in multiple times a week.”
As for the hunger benefits of eating a big breakfast, that turns out to depend on the individual, Jenkins said. And that means “that the timing of the big meal has to be tailored to the individual,” she added. “If you’re a late night person, having a big dinner at 7 or 8 PM is reasonable.”
Some people, Jenkins said, are not especially hungry in the morning. “You have to understand that you should eat when you’re hungry and you don’t need to eat if you’re not hungry,” she added.