"Eat a big breakfast to lose weight fast – you'll 'burn twice as many calories'," reports The Sun.
The advice to eat more at breakfast than at dinner has long been proposed to help people trying to lose weight. The idea is that calories consumed at the start of the day are more likely to be burned off than those consumed in the evening.
German researchers say they found that people do burn off more calories after breakfast than dinner. They also feel less hungry in the afternoon and evening if they have a bigger breakfast.
However, their study included just 16 people, who were all healthy young men. None of the participants were trying to lose weight and the study did not measure weight loss.
We do not know whether eating a big breakfast every day would lead to weight loss in real-world conditions, or whether the results are relevant to women or people who have health complications due to being overweight or obese. The study was also just a 3-day laboratory experiment in which men ate only set meals provided and did no physical exercise.
However, other studies have suggested that eating a healthy breakfast may help people to eat less during the rest of the day. This could help people stick to a weight loss diet, rather than skipping breakfast and eating more later because they are hungry.
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Where did the story come from?
The researchers who carried out the study were from the University of Lubeck in Germany. The study was funded by the German Research Foundation and published in the peer-reviewed Journal of Clinical Endocrinology and Metabolism on an open access basis so it is free to read online.
The report in The Sun overstated the results. The Sun report says that "The researchers claimed the hour of the day – when you eat and how frequently you eat – is more important than what you eat and how many calories you eat."
This is not true – the researchers only said that the time a meal was eaten had an effect on calories burned and appetite. They did not say that this was "more important" than what people eat or how much they eat.
The report by the Mail Online was more balanced, making it clear that a big breakfast was only helpful if balanced by a small dinner. Both news reports included photographs of a fried full English breakfast, which is high in fat and salt and not likely to be a very healthy start to the day.
What kind of research was this?
This was an experimental crossover study carried out in a laboratory.
These types of studies may be helpful to establish how the body behaves under controlled conditions. However, these studies may be of less immediate relevance in the real world.
What did the research involve?
The researchers recruited 16 men in their early 20s. The participants were all:
- a healthy weight
- free of a range of medical conditions
- not taking any kind of medicine
- not misusing drugs or alcohol
- not working shifts
The researchers said they excluded women "to avoid possible effects of the female hormone cycle on energy metabolism". If such effects exist, that means the study results do not apply to women.
The men stayed at a research centre twice, 2 weeks apart, for 3 days on each stay. On the evening of their arrival they had a standard evening meal. For the next 2 days, they had either:
- a low-calorie (11% of daily calories) breakfast, standard (20% of daily calories) lunch, high-calorie (69% of daily calories) dinner
- a high-calorie breakfast, standard lunch and low-calorie dinner
The researchers took measurements at regular intervals during the day, including before and after meals, of:
- resting energy expenditure – measured by comparing oxygen consumption and carbon dioxide production over a set period, using a hood to capture gases breathed in and out
- blood glucose
- blood insulin
- how hungry the men felt
- how much they craved sweets
The men were allowed to read, draw, watch television, play games, listen to music and spend time at a computer, but could not do any exercise.
On their second visit, the men were given the reverse to their original meals. Those who had a high-calorie breakfast and low-calorie dinner now received a low-calorie breakfast and high-calorie dinner, and vice versa.
The researchers used the difference between resting energy expenditure before and after a meal to calculate diet-induced thermogenesis (DIT), or the amount of energy used while digesting a meal. They compared DIT after high- or low-calorie meals at breakfast or dinner.
What were the basic results?
Researchers found that the men's DIT, the measure of how many calories were burned digesting a meal, was around 2.5 times higher after breakfast than after dinner. It did not make a difference whether the meal was high or low calorie.
Their blood glucose, a measure of how much sugar is in the bloodstream immediately after a meal, was 44% higher after a high-calorie dinner, compared to a high-calorie breakfast. This suggests that glucose peaks more after an evening meal than a morning meal. The difference was 17% higher after dinner when both meals were low calorie.
Their concentrations of insulin, which the body releases to help it metabolise sugar, were also 40% higher after a high-calorie dinner than after a high-calorie breakfast.
The men said they felt less hungry after dinner than after breakfast, regardless of whether dinner was high or low calorie. Compared to hunger before breakfast, hunger decreased 5 hours after a high-calorie breakfast whereas it increased 5 hours after a low-calorie breakfast.
The men said they were hungrier in the period before dinner if they had a low-calorie breakfast, compared to those who had a high-calorie breakfast. They also craved sweets during the day more if they had a low-calorie breakfast compared with a high-calorie breakfast.
How did the researchers interpret the results?
The researchers said: "Our results show that a nutritional pattern with an extensive breakfast and few calories in the evening has a favourable effect on energy as well as glucose metabolism."
They added: "An extensive breakfast should therefore be preferred over large dinner meals to reduce the risk of metabolic diseases."
Small, experimental studies such as this may help scientists establish how the body works under experimental conditions – at least in the case of the healthy young men included in the study. It is unclear whether they are relevant to the wider population.
The study is limited by its nature. It included only 16 men and tracked their consumption and resting energy expenditure over a short time period. We do not know exactly what food they ate – only the calorific value and the balance of carbohydrates, protein and fat.
The study shows us that these 16 men burned off more calories after their morning meal than their evening meal, regardless of how many calories in that meal. Because of the standardised conditions of the experiment, we do not know how the results would have been affected by doing physical exercise. The effect the different regimes had on the men's weight was not measured.
This makes it hard to know how relevant the results are to people trying to reduce their weight in the real world. People's choices about when and what they eat are affected by many things, including caring responsibilities, work schedule and the preferences of family members.
The important thing about dieting to lose weight is to find a healthy diet that ensures you are getting all the nutrients you need. It should also be something that you are able to stick to.
Many people have found the NHS weight loss guide helpful for losing weight steadily and safely.
Find out more about the NHS weight loss guide.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Mail Online, 19 February 2020
The Sun, 19 February 2020
Links to the science
The Journal of Clinical Endocrinology & Metabolism. Published online 19 February 2020