If you're trying to lose weight you've probably been told not to skip breakfast, as it could make you hungrier later in the day.
But a new analysis found that people who ate breakfast regularly consumed more calories each day and those who skipped it didn't have an increased appetite later in the day.
This meant those who ate breakfast experienced no weight loss and people who skipped their morning meal also saw no weight gain, according to the research published Wednesday in the BMJ.
Public health agencies and official eating guidelines have long stressed the importance of eating breakfast to lose weight and achieve a healthy diet but "this study clearly shows that isn't a good idea," said lead author Dr Flavia Cicuttini, professor of epidemiology at Monash University in Melbourne, Australia.
Cicuttini's team pooled results from 13 clinical trials from high-income countries, mainly the United States and the UK, from the last 28 years.
The studies included people who regularly eat breakfast and non-breakfast eaters. Five trials included overweight participants, the remaining had people with any range of body weight. Some trials looked at how breakfast effected on daily energy intake and others examined the relationship between eating in the morning and changes in body weight.
The researchers found that "the people who eat breakfast tend to have on average 260 calories a day extra and they tend to be heavier," Cicuttini said, regardless of the participants being used to having regularly breakfast or not.
People that skipped breakfast were on average 0.44 kg [0.97 pounds] lighter, according to the paper.
The results suggest that eating breakfast contributes to weight gain "simply by more calorie intake," according to Cicuttini. The clinical trials show that if people are encouraged to eat breakfast, they still eat more calories than they should later in the day, she said.
However, she added the latest findings should be interpreted with caution because some of the 13 trials used in their study didn't last long and the quality of the trials varied.
"I think the key to weight loss is the number of calories you eat," said Cicuttini. People who always eat breakfast shouldn't be discouraged from doing so, she said. But, overweight people who eat breakfast should be encouraged to count the calories they consume during the morning and see how they fit in with the rest of their meals throughout the day.
The Association of UK Dietitians recommends that 20-25% of people's daily nutritional requirements should come from their breakfast.
Cicuttini told CNN the belief breakfast helps people better metabolize food and leaves them less hungry throughout the day stems from earlier observational studies, adding that it was possible that people who ate breakfast had other healthy habits, like exercising.
Previous research has shown weight loss benefits of sticking to a morning meal. One 2013 study looked at people who ate the same amount of calories, but one group consumed the bulk of the calories earlier in the day. It showed that people who ate a big breakfast lost two and a half times more weight, compared to those that ate a big dinner.
The belief that eating food during the morning means you can burn those calories off better is not supported by the data her team collected, said Cicuttini.
She stressed that people should "follow what suits their bodies best," whether that is eating breakfast every day and cutting down on calories if they want to lose weight or, if they are not hungry in the mornings, simply skipping the morning meal.
Depends on the individual
Kevin Murphy, professor of endocrinology and metabolism at Imperial College London, said in an email to CNN that the study's "analysis suggests that eating breakfast is, on average, likely to make it more difficult to lose weight, as you eat more calories during the day."
However, "in reality, whether breakfast helps or hinders your efforts to prevent weight gain or lose weight will depend on the individual, added Murphy, who was not involved in the research. "But there are certainly many people for whom eating breakfast is in fact likely to make it tougher."
Sarah Coe, a nutrition scientist at the British Nutrition Foundation, said that the evidence for the relationship between eating or skipping breakfast and weight loss "is mixed."
Coe said in an email that the "findings of this review may not fit with existing recommendations, but they reflect the current uncertainty about the relationship between eating breakfast and weight within the scientific literature."
Coe, who was not involved in the research, added that a healthy breakfast is "just one part of a healthy, balanced lifestyle." It is a good opportunity to get "important nutrients into the diet," such as fiber from whole grain breakfast cereals and calcium from dairy foods.
"For people trying to lose weight, the key to success is finding something that works for them and that they can stick to," she said.