The broad field of nutrition and health is rife with myths, misconceptions and frequently posed yet seemingly fundamental questions that we intuitively feel should have simple answers. Is a calorie a calorie? Is obesity due to eating too much or doing too little?

Is breakfast actually the most important meal of the day?

When looking through the lens of insulin resistance, breakfast has often been seen as a "problem" meal that leads to the largest blood sugar spikes...especially for Type 2 diabetics. This is largely due to the typical "healthy" Western breakfast foods that are high in carbohydrates: Cereal, oatmeal, toast and fruit.

A recent study aimed to explore if eating a low-carb and high-fat meal first thing in the morning is a simple way to prevent this large insulin spike, improve glycemic control throughout the day, and reduce other diabetes complications. This is the paper Dr. Brianna Stubbs will be diving into in this episode of the Research Roundup.

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Overview & Background

Is breakfast the most important meal of the day? First, we must define both what is meant by breakfast and what is meant by important (i.e. important for what?).

Framing our question in terms of whether breakfast is the most important meal of the day also implies some inherent value in comparing breakfast with other daily eating occasions. Why should the potential benefits of breakfast and therefore our decision about breakfast consumption depend on the relative importance of lunch or dinner? For example, breakfast consumption is unlikely to be more important for our general health than physical exercise or not smoking but that does not discount that breakfast may be sufficiently important to form part of a wider healthy lifestyle. In fact, markers of a healthy lifestyle are associated with frequent breakfast consumption, which confounds interpretation of causal links between breakfast and good health.

One issue contributing to the apparently conflicting findings in this area is that there is no universally accepted definition of breakfast; and why should there be? Without thinking about this too hard, it might at first seem logical simply to define breakfast as the first meal of the day. This is then consistent with the etymology to ‘break’ the ‘fast’ and may work for some as a general description of breakfast but is logically flawed and not overly helpful as a scientific definition. Consider an individual who breaks their fast shortly after waking by ingesting energy from carbohydrate, protein and fat in the form of coffee with milk and sugar, then nothing else until early-afternoon when the same mixed-macronutrients (plus alcohol) are consumed but this time in the form of spaghetti Bolognese and wine. Opinions may now be divided about whether this person had breakfast at all and, if so, whether it was coffee and/or spaghetti and wine. Can we count a cup of coffee as a meal? Was the spaghetti consumed in the fasted-state (i.e. post-absorptive)? What if we learn that this person woke at midday?

Although the extent to which the mere association between breakfast omission and obesity has been verified can be described as gratuitous, confirmatory studies continue to emerge even today despite the stated relationship confirmed by meta-analysis. There can be little doubt, therefore, that individuals who more frequently consume breakfast tend to be leaner and that this pattern hardly varies across a diverse range of human populations. However, no matter how strong these correlations may be, they cannot be used to draw a causal inference and so cannot inform evidence-based recommendations either encouraging or discouraging breakfast for the purposes of weight-management.

Breakfast omission affects some components of energy balance much more than others. There is no evidence to suggest that breakfast consumption per se affects resting metabolic rate, or diet induced thermogenesis of subsequent meals or over the day as a whole. Evidence that breakfast affects energy intake is compelling for laboratory studies, with the majority of studies showing energetic compensation at the next meal, but not sufficient to eliminate the deficit from morning fasting. In addition, designs where afternoon/evening feeding has been allowed do not demonstrate sustained compensation for breakfast omission. Experiments outside the laboratory understandably produce more varied results, with the balance of evidence suggesting that energy intake is either lower or similar when omitting breakfast.

So - clearly there isn’t a simple answer to our initial question.. Breakfast may or may not be the most important meal of the day, but it is certainly an important meal to investigate further, and that is where we can jump into our paper for this week.

Restricting carbohydrates at breakfast is sufficient to reduce 24-hour exposure to postprandial hyperglycemia and improve glycemic variability

This paper was actually written by Professor Jonathan Little from the University of British Colombia, in one of our previous research round ups we discussed a paper he authored about the effects of ketone esters on inflammation. Prof Little is nailing some great metabolism research right now!

Now- diabetics typically experience a large blood sugar spike following a breakfast conforming to traditional ‘nutritional guidelines.’ This is due to the combination of a more pronounced insulin resistance in the morning in people with diabetes and because typical ‘healthy’ Western breakfast foods -- cereal, oatmeal, toast and fruit -- are high in carbohydrates.

Breakfast, is consistently a "problem" meal that leads to the largest blood sugar spikes for people with type 2 diabetes. This paper aimed to explore if eating a low-carb and high-fat meal first thing in the morning is a simple way to prevent this large spike, improve glycemic control throughout the day, and perhaps also reduce other diabetes complications.

Study participants, with well-controlled type 2 diabetes, completed two experimental feeding days. On one day, they ate an omelette for breakfast and on another day, they ate oatmeal and some fruit. The two breakfast meals were matched in calories, all that was different was the macronutrient split. An identical lunch and dinner were provided on both days. A continuous glucose monitor -- a small device that attaches to your abdomen or forearm and measures glucose every five minutes -- was used to measure blood sugar fluctuations across the entire day. Participants also reported ratings of hunger, fullness and their desire to eat something sweet or savory.

The results of the study confirmed the hypothesis that determined that consuming a very low-carbohydrate high-fat breakfast completely prevented the blood sugar spike after breakfast. Importantly, this had enough of an effect to lower overall glucose exposure and improve the stability of glucose readings for the next 24 hours, which is a key finding as there was speculation if the insulin or glucose responses to food later in the day might have been adversely affected by lowering insulin at breakfast. This paper confirmed these fears were unfounded- whilst cereals are often lauded as the breakfast of champions, the results of this paper suggest people with Type 2 Diabetes should be reaching for something else. Listeners of this podcast are unlikely to be surprised by the finding that a high-fat, low-carb breakfast (more on the ‘keto’ end of the spectrum) can with blood glucose control throughout the day.

In an interview, Prof Little explained "We expected that limiting carbohydrates to less than 10 per cent at breakfast would help prevent the spike after this meal," he says. "But we were a bit surprised that this had enough of an effect and that the overall glucose control and stability were improved.” Why is this so important you might ask- we know that large swings in blood sugar are damaging to our blood vessels, eyes, and kidneys. The inclusion of a very low-carbohydrate high-fat breakfast meal in T2D patients may be a practical and easy way to target the large morning glucose spike and reduce associated complications.

Another interesting aspect of the research, participants noted that pre-meal hunger and their cravings for sweet foods later in the day tended to be lower if they ate the low-carb breakfast.

The results of this study suggest potential benefits of altering macronutrient distribution throughout the day so that carbohydrates are restricted at breakfast with a balanced lunch and dinner rather than consuming an even distribution and moderate amount of carbohydrates throughout the day. I think this is a super empowering finding- so many people are put off keto or low carb eating as it is portrayed as all or nothing- and going all in is a big commitment! What these results show is that you might be able to move the needle on your metabolic health even just by making a change to your macros at breakfast time.

Now- a few small points to note with the study- the use of CGMs makes the most practical sense for this type of study design to avoid repeated blood sampling, but these devices aren’t as accurate as lab grade analytical equipment for measuring glucose. In my view, this wouldn’t affect the results too much though!

Another point is that this paper was just an acute, one-off experiment, so it's not clear if eating a low carb breakfast every day would provide more stable blood glucose over the long term, should any adaptations occur to compensate. And also these results don’t show if this degree of reduction in insulin and glucose exposure would meaningfully affect the clinical complications of diabetes- that is assumed based on our broader understanding of metabolism.

Lastly, this experiment was done in people living with diabetes- it's not clear from these results that healthy people would have the same response. However, I think it's not too far fetched to suggest that healthy people would also have less of a glucose spike after an omelette compared to oatmeal!


My key takeaway here is that whatever change you can make to your diet to cut out big glucose spikes- its all a step in the right direction. Whether or not breakfast is the MOST important meal of the day- you can’t get away from the fact that what we eat and is an important choice and the sum of those choices, every meal and every day combine to help define our health.

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