Inquiry Annotation - Is breakfast really the most important meal of the day?
Author: Jessica Brown
(Brown, Jessica. Author. 12/1/2025).
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We’ve all heard that the advice about having a good breakfast can set us up for the day. But does that mean this meal can makes us healthier and thinner – or is it something else?
Along with old classics like "carrots give you night vision" and "Santa doesn't bring toys to misbehaving children", one of the most well-worn phrases in the arsenal of tired parents everywhere is that breakfast is the most important meal of the day. Many of us grow up believing that skipping breakfast is a dietary travesty, but the number of us who take time to eat it can vary.
Around three-quarters of Americans regularly eat breakfast, while in the UK, around 94% of adults and just 77% of adolescents will regularly eat breakfast. A study in Switzerland showed only two thirds of adults there regularly consume the meal.
When pressed for time, the morning breakfast is often the first thing to go. How many of us eat it while on the run, or gladly exchange a a bowl of cereal, a couple of slices of toast or a pastry for a few extra minutes in bed?
Yet, the clue for why breakfast is supposed to be important is in its name: we're advised to eat it to break our overnight fast.
"The body uses a lot of energy stores for growth and repair through the night," explains dietician Sarah Elder. "Eating a balanced breakfast helps to up our energy, as well as protein and calcium used throughout the night."
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But there’s widespread disagreement over whether breakfast should be deemed so important. As well as the rising popularity of fasting diets, there have been concerns around the sugar content of cereal and the food industry's involvement in pro-breakfast research – and even one claim from an academic that breakfast is "dangerous".
So what's the reality? Is breakfast a necessary start to the day… or a marketing ploy by cereal companies?
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Can skipping breakfast cause weight gain?
The most researched aspect of breakfast (and breakfast-skipping) has been its links to obesity. Scientists have different theories as to why there's a relationship between the two.
In one US study that analysed the health data of 50,000 people over seven years, researchers found that those who made breakfast the largest meal of the day were more likely to have a lower body mass index (BMI) than those who ate a large lunch or dinner. The researchers argued that breakfast helps increase satiety, reduce daily calorie intake, improve the quality of our diet – since breakfast foods are often higher in fibre and nutrients – and improve insulin sensitivity at subsequent meals, which can be a risk for diabetes.
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But as with any study of this kind, it was unclear if that was the cause – or if breakfast-skippers were just more likely to be overweight to begin with.
To find out, researchers designed a study in which 52 obese women took part in a 12-week weight loss programme. All had the same number of calories over the day, but half had breakfast, while the other half did not.
What they found was that it wasn’t breakfast itself that caused the participants to lose weight: it was changing their normal routine. The women who said before the study that they usually ate breakfast lost 8.9kg when they stopped having breakfast, compared to 6.2kg in the breakfast group. Meanwhile, those who usually skipped breakfast lost 7.7kg when they started eating it – and 6kg when they continued to skip it.
If breakfast alone isn't a guarantee of weight loss, why is there a link between obesity and skipping breakfast?
One review found "limited evidence" either for or against the argument that breakfast influences weight.
Alexandra Johnstone, professor of appetite research at the University of Aberdeen, argues that it may simply be because breakfast-skippers have been found to be less knowledgeable about nutrition and health.
"There are a lot of studies on the relationship between breakfast eating and possible health outcomes, but this may be because those who eat breakfast choose to habitually have health-enhancing behaviours such as not smoking and regular exercise," she says.
A 2020 review of 45 studies looking into the relationship between breakfast and obesity confirmed that skipping breakfast increases the risk of obesity. The same effect has been found in children.
Does it matter when we eat breakfast?
Intermittent fasting, which involves fasting overnight and into the next day, is gaining ground among those looking to lose or maintain their weight or improve their health.
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One pilot study published in 2018, for example, found that intermittent fasting improves blood sugar control and insulin sensitivity and lowers blood pressure. Eight men with pre-diabetes were assigned one of two eating schedules: either eating all their calories between 9am and 3pm, or eating the same number of calories over 12 hours. The results for the 9am-3pm group were found to be on par with medicine that lowers blood pressure, according to Courtney Peterson, the study's author and assistant professor of nutrition sciences at the University of Alabama at Birmingham.
Still, the study's small size means more research is needed on its possible long-term benefits.
If skipping breakfast (and other food outside of a restricted time slot) could potentially be good for you, does that mean breakfast could be bad for you? One academic has said so as eating early in the day causes our cortisol to peak more than it does later on. This causes the body to become resistant to insulin over time and can lead to type 2 diabetes.
But Fredrik Karpe, professor of metabolic medicine at Oxford Centre for Diabetes, Endocrinology and Metabolism, argues this isn't the case. Instead, higher levels of cortisol in the morning are just part of our body's natural rhythm.
Not only that, but breakfast is key to jumpstarting our metabolism, he says. "In order for other tissues to respond well to food intake, you need an initial trigger involving carbs responding to insulin. Breakfast is critical for this to happen," Karpe says.
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A randomised control trial found that skipping breakfast disrupted the circadian rhythms and led to larger spikes in blood glucose levels after eating. Eating breakfast, the researchers conclude, is essential for keeping our body clock running on time.
A 2023 review of Japanese adolescents found that skipping breakfast was associated with pre-diabetes – particularly among those who were overweight.
Peterson says those who skip breakfast can be divided into those who either skip breakfast and eat dinner at a normal time – getting the benefits of intermittent fasting, if not breakfast – or those who skip breakfast and eat dinner late.
While it seems breakfast is the most important meal of the day, it might actually be dinner – Courtney Peterson
"For those who eat dinner later, their risk of obesity, diabetes and cardiovascular disease goes through the roof. While it seems breakfast is the most important meal of the day, it might actually be dinner," Peterson says. "Our blood sugar control is best early in the day. When we eat dinner late, that’s when we're most vulnerable because our blood sugar is worst. There’s more research to do, but I’m confident you shouldn’t skip breakfast and have dinner late."
She says we should think of our circadian rhythm as an orchestra.
"There are two parts of our circadian clock. There's the master clock in the brain, which we should think of as analogous to a conductor of an orchestra, and the other half is in every organ, which has a separate clock," she says.
And that "orchestra" is set by two outside factors: bright light exposure and our eating schedule.
"If you're eating when you're not getting bright light exposure, the clocks that control metabolism are in different time zones, creating conflicting signals as to whether to rev up or down."
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It's like two halves of an orchestra playing different songs, Peterson explains, and this is why eating late impairs blood sugar and blood pressure levels.
Researchers from the University of Surrey and University of Aberdeen have looked into the mechanisms behind how the time we eat influences body weight. Findings published in 2022 suggest that a bigger breakfast and smaller dinner is beneficial to weight control, as a bigger breakfast led to a smaller appetite for the rest of the day.
The health benefits of eating breakfast
Breakfast has been found to affect more than just weight. Skipping breakfast has been associated with a 27% increased risk of heart disease, a 21% higher risk of type 2 diabetes in men, and a 20% higher risk of type 2 diabetes in women.
This may be because skipping breakfast affects glucose and lipid control, and insulin levels, say researchers behind a 2023 study on fasting and diabetes. They tracked the diets of more than 100,000 people over an average of seven years, and found that the risk of developing the disease was significantly higher among the participants who regularly ate breakfast after 9am, compared to those who ate it before 8am.
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One reason for some of the health benefits associated with eating breakfast – at least in the Western world – may be its nutritional value, partly because some cereals are fortified with vitamins. In one study on the breakfast habits of more than 8,000 people in the UK, researchers found that people who consumed breakfast regularly had a higher overall micronutrient intake, partly driven by current UK fortification of vitamins in breakfast cereals, bread and spreads, the researchers say. There have been similar findings in Australia, Brazil, Canada, Indonesia and the US.
Breakfast is also associated with improved brain function, including concentration and language. A review of 54 studies found that eating breakfast can improve memory, though the effects on other brain functions were inconclusive. However, one of the review’s researchers, Mary Beth Spitznagel, a clinical psychologist at Kent State University in Ohio, says there is "reasonable" evidence breakfast does improve concentration – there just needs to be more research.
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"Looking at studies that tested concentration, the number of studies showing a benefit was exactly the same as the number that found no benefit," says Spitznagel. "And no studies found that eating breakfast was bad for concentration."
What's most important, some argue, is less whether we eat breakfast but what we eat when we do.
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High-protein breakfasts have been found to be particularly effective in reducing food cravings and consumption later in the day, according to research by the Australian Commonwealth Scientific and Industrial Research Organisation.
While cereal remains a firm favourite among breakfast consumers in the UK and US, a 2020 Action on Sugar survey of 120 breakfast cereals found that a third were high in sugar, and only three cereals were low in sugar.
But some research suggests if we're going to eat sugary foods, it's best to do it early. One study found that changing levels of the appetite hormone leptin in the body throughout the day coincide with having our lowest threshold for sweet food in a morning, while scientists from Tel Aviv University have found that hunger is best regulated in the morning. They recruited 200 obese adults to take part in a 16-week-long diet, where half added dessert to their breakfast, and half didn’t. Those who added dessert lost an average of 40lbs (18kg) more – however, the study was unable to show the long-term effects.
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A review of 54 studies found that there is no consensus yet on what type of breakfast is healthier and it concluded that the type of breakfast doesn't matter as much as simply eating something.
Another factor to consider is where you eat breakfast. A 2022 study looking at the breakfast habits of almost 4,000 young people found that those who eat breakfast out of the home were more likely to have psychosocial behavioural problems than those who eat breakfast at home. One reason for this, the researchers say, is that the social context of having breakfast as a family may be linked to having a more nutritious breakfast.
Final take
While there's no conclusive evidence on exactly what we should be eating and when, the consensus is that we should listen to our own bodies and eat when we're hungry.
Breakfast is most important for people who are hungry when they wake up – Alexandra Johnstone
"Breakfast is most important for people who are hungry when they wake up," Johnstone says.
For instance, research shows that those with pre-diabetes and diabetes may find they have better concentration after a lower-GI breakfast such as porridge, which is broken down more slowly and causes a more gradual rise in blood sugar levels.
Everybody starts the day differently – and those individual differences, particularly in glucose function, need to be researched more closely, Spitznagel says.
In the end, the key may be to be mindful of not over-emphasising any single meal, but rather looking at how we eat all day long.
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"A balanced breakfast is really helpful, but getting regular meals throughout the day is more important to leave blood sugar stable throughout the day, which helps control weight and hunger levels," says Elder.
"Breakfast isn’t the only meal we should be getting right."
*This article was originally published on 27 November 2018. It was updated on 16 July 2025 to include recent research.
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