We’re often told that breakfast is an essential part of a healthy diet, especially if you are watching your weight. Some schools run breakfast to ensure that as many pupils as possible eat this all-important first meal of the day. But not everyone can stomach an early morning meal. In Europe and US between 10% and 30% of people skip breakfast, with teenage girls most likely to give it a miss, saying they’ve not got time, don’t feel hungry or that they’re on a diet.

Missing breakfast for dietary reasons runs counter to a great deal of advice. The logic goes that missing an early morning meal will leave you hungry for the rest of the day, tempting you to snack on high-calorie foods, and resulting in weight gain.

It’s a plausible theory, until you look for evidence that people who skip breakfast consume any more calories than anyone else. The impact skipping breakfast has on weight is harder to study systematically than you might expect. The first problem is how to define that first meal of the day. How much food counts as a real breakfast? Do you have to eat it seven days a week to be defined as a breakfast-eater? And how early in the day does it need to be eaten? For example, when the US Department of Agriculture conducted a systematic review on the topic they found that most studies defined breakfast as food eaten before ten in the morning. Anyone who ate at 10.05 was considered to have skipped breakfast, which could skew the results.

Another difficulty is that what is eaten for breakfast varies from country to country. In Scandinavia it might include smoked fish, in Germany cold meats, and in the UK boxed cereals, which can often contain more sugar and salt than people realise (the Consensus Action on Salt and Health group says some cereals are saltier than seawater). This makes the impact of eating breakfast more difficult to study on a global level because the nutritional benefits will depend on what you include in the meal.

But if we stick to looking at calories consumed, there have been many attempts to study the impact of eating breakfast on a person’s weight. A review of studies conducted before 2004 found that on the whole breakfast-skippers do not consume more calories during the rest of the day to compensate. People who ate breakfast tended to have a diet that was more nutritionally balanced, but it wasn’t more calorific. The findings on weight are a little more complex. Four studies found that children who didn’t eat breakfast had on average a higher body mass index, but another three studies found it made no difference. The advantage of those first four studies was that they had taken more trouble to control for factors which might skew the results. So the evidence begins to tip slightly towards a link between missing breakfast and increased weight.

To muddy the waters, a US review in 2011 cited five studies that found an association between breakfast-skipping and weight gain: three that found it made no difference, and one which found the opposite – that amongst overweight children, the breakfast-eaters weighed even more. And to confuse the issue even more, a meta-analysis which pooled the results of nineteen studies conducted in Asian and Pacific regions found a relationship between increased weight and missing breakfast. A European systematic review had similar findings, but one study found the relationship between breakfast-skipping and weight only existed for boys.

Does size matter?

What happens when you turn the question round? Seven studies found that overweight children are more likely to skip breakfast. But this highlights the problem with these studies – they are cross-sectional. They take a snapshot in time. They don’t prove causation. We can’t know which came first – the excess weight or the breakfast-skipping. Perhaps these children are missing breakfast because they are already overweight and are trying to eat less.

The alternative is to study people for a long period of time, and the first longitudinal study on this topic was done in 2003. When the study researchers took a snapshot in time they found that children who skipped breakfast weighed more on average. But when they followed the same children for three years the heavier children who missed breakfast actually lost weight over time.

So we’re left with a situation where many studies, but by no means all, find that children who miss breakfast are more likely to be overweight. However, we can’t be sure whether their diet or missing breakfast is making them overweight. If missing breakfast is contributing to their weight gain then it’s not clear why, because they don’t consume more calories overall.

If it’s not about total calories consumed, could the timing of meals have an effect? Are three smaller meals better than two larger ones? Very few randomised controlled trials have been done on this topic, but there was one carried out in 1992 on adults. Obese women were given diet plans in which everyone ate the same total number of calories in a day – half had three smaller meals a day, while the other half missed breakfast, but had lunch, followed by a larger supper later on. These results really are fascinating. Those who were accustomed to skipping breakfast lost more weight if they were put in the group who ate breakfast, while the people used to regularly eating an early morning meal lost more weight if they skipped breakfast. In other words, a change in their normal routine helped them to lose weight. So maybe the lesson of that study is that you should simply do something different. At the University of Hertfordshire in the UK psychologists have developed and researched a weight loss programme based on just this premise.

It is a confusing picture, which is why a new paper just published on dieting myths includes skipping breakfast as one of the diet presumptions that have not been proven. If you choose a single study you can prove your argument either way. So when it comes to weight the jury is out,

But there could be other benefits of eating breakfast. Randomised controlled trials in rural Jamaica and Peru showed improved grades in children who ate breakfast at school. These might not generalise to everywhere because they might well have been nutritionally-deprived beforehand, so breakfast might have made more difference there than in well-nourished children.

So, to the acid question: should you eat breakfast or not if you want to lose weight? People who eat breakfast do tend to have a more balanced diet overall, but if you are only interested in the weight aspect, then until more randomised controlled trials have been done, it comes down to personal preference. Some of us simply can’t face the idea of an early breakfast. If that’s you, you can blame your chronotype – new research has found that evening types just don’t feel hungry early in the mornings. In that case, until some really good randomised controlled trials prove otherwise, perhaps the answer is to follow your stomach, not fight it.

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