You’ve probably heard that breakfast is the most important meal of the day. You’ve probably also heard that intermittent fasting, which for many means skipping traditional breakfast and having their first meal around midday, is the best approach to optimise overall metabolic health and wellbeing. 

So, which is it? Although metabolic health is influenced by many factors, nutritionally it largely comes down to three core principles. Without going down a rabbit hole, these are:

> Balancing energy intake and expenditure, often described as “calories in versus calories out”, to help maintain a healthy body weight (1)

> Consuming adequate protein to support the maintenance and growth of muscle mass, which plays a key role in blood glucose regulation and the efficient use of energy (2).

> Ensuring overall nutrient adequacy, including fibre and key micronutrients involved in energy metabolism such as B vitamins, iron, and vitamin C (3-5).

This means that intermittent fasting is not required to achieve good metabolic health. 

What matters far more is whether the meals you do eat help support these three principles. Which brings us back to breakfast, the meal that literally “breaks your fast.” Breakfast is the first opportunity you have each day to begin meeting the nutritional requirements that support muscle health, maintain energy balance, regulate appetite, and provide key nutrients that play key roles in energy metabolism. When breakfast is protein-rich, contributes appropriate energy, and provides meaningful fibre and micronutrients, it can set you up with a metabolic foundation that lasts all day. 

Want to know why? Let’s take a closer look.

#1. Your first opportunity to regulate appetite and energy intake

How many times have you eaten breakfast only to feel hungry an hour later? What about those mid-afternoon energy crashes that have you reaching for something sweet? Or the habit of arriving home from work hungry and snacking until dinner? These are classic examples of a dietary pattern that is not particularly satiating, in other words, one that lacks the key nutrients responsible for regulating appetite by increasing feelings of fullness and reducing hunger. Although hunger and fullness are feelings we might experience subjectively, they are driven by real biological and biochemical mechanisms that are directly influenced by what we eat.

These include:

• the release of satiety hormones such as GLP-1 (glucagon-like peptide 1), PYY (peptide YY), and CCK (cholecystokinin)
• physical distension of the stomach as food is consumed
• the slowing of gastric emptying, meaning food remains in the stomach for longer 

The nutrients with most meaningful roles in these processes are protein and fibre, with fat playing a supporting role by helping to delay gastric emptying (6).

Consuming sufficient protein and fibre at breakfast can help activate all three of these mechanisms. In practice, this can increase satiety for several hours, as well as reduce energy intake (how much you decide to eat) in subsequent meals (6).

Together, this means that a breakfast built around protein and fibre can support a dietary pattern that helps to prevent the overconsumption of calories and the weight gain that may follow. It also means that if your goal is weight loss, a breakfast focused on protein and fibre can provide a strong foundation for managing appetite throughout the day.

What does that look like?

Aim for a breakfast that includes:

• At least 20 g of high-quality protein (such as eggs, protein powder, and Greek yoghurt)
• Around 7-10 g of fibre (from foods such as fruit and oats) 
• A source of healthy fat (around 5-10 g from whole foods such as nuts and seeds or avocado)

Together, these building blocks help to create a breakfast that is more likely to sustain fullness, support stable energy levels, and regulate appetite across the day. Sounds like a win!

#2. Your first opportunity to support muscle maintenance and metabolic health

We often think about muscle in terms of how lean we look, how strong we are, and how much physical activity we are involved in. However, muscle is much more than aesthetics. While it is an important part of optimal athletic performance, a key - and often underappreciated - role is in metabolic health (2).

Muscle is often referred to as the “metabolic sink”, because it is responsible for disposing of a large proportion of glucose (sugars) that we consume. This is because healthy muscle is highly insulin sensitive, meaning it readily takes up glucose from the bloodstream. In simple terms, the greater amount of healthy muscle we have, the greater our ability to manage the sugars we consume in the diet.

However, we continually break down muscle protein throughout the day, with a large proportion of this occurring overnight while we sleep (8). Unless we consume sufficient amounts of protein in the diet, this ongoing breakdown will eventually lead to noticeable muscle loss (2). Since a meaningful proportion of muscle protein breakdown occurs overnight while we sleep, consuming an adequate serving of dietary protein early in the day – at breakfast – can play an important role in supporting the maintenance of healthy muscle.

So how much protein do you need?

At least 20 g of high-quality protein per meal is recommended to meaningfully support the maintenance of muscle mass, while around 30–40 g of high-quality protein can optimise this response, especially as we age (9, 10). High quality protein is found in foods such as dairy, meat, eggs, tofu, and protein powder.

 Unfortunately, many typical breakfast foods contain far less protein than this.

#3. Your first opportunity to establish stable energy

Beyond regulating appetite and supporting muscle health, breakfast is also the first opportunity each day to provide the body with the fuel it needs to function.

After an overnight fast (which occurs naturally while you sleep) the readily available energy stores of the body (liver glycogen) are relatively depleted (11)

This means that consuming an appropriate amount of energy at breakfast helps replenish these stores and supports both physical and cognitive activity throughout the morning.

However, the type of energy provided also matters. When meals are built primarily around refined carbohydrates (e.g., white toast and jam), the result can be rapid rises and falls in blood glucose (12), leading to energy fluctuations later in the morning that often have people reaching for more refined carbohydrates. In contrast, a breakfast that provides energy from a combination of whole-food carbohydrates, protein, and healthy fats tends to support more stable metabolic energy (12).

Carbohydrates provide the body’s most readily available fuel (12), particularly for the brain and working muscles. Choosing minimally processed sources such as fruit, oats, and other whole grains helps deliver this energy alongside fibre and micronutrients.

Then we have fat, which slows digestion and contributes to a more gradual release of energy from a meal (6, 12). Including healthy fats from foods such as nuts, seeds, avocado, and whole dairy can help to support energy availability in a more sustained way.

Together, these nutrients help create a breakfast that not only satisfies hunger but also provide both immediate and sustained energy (calories) to support steady metabolic function throughout the morning and into the day.

How many calories should we be aiming for?

Research has shown that consuming an adequate amount of energy at breakfast plays a key role in managing appetite throughout the day (6). So, while the absolute number will depend on many factors, such as activity level and type of work, aiming for around 400-500 calories is a good starting point for many people.

The goal, however, is not simply to consume calories, but to consume nutrient-dense calories (13). Nutrient density refers to the level of vitamins, minerals, fibre, and other beneficial compounds provided per calorie of food (13). Choosing whole foods such as fruit, oats, dairy, eggs, nuts, seeds, and whole grains helps ensure that the energy consumed at breakfast also contributes meaningfully to the macro- and micro-nutrients required for metabolism to function efficiently.

In other words, breakfast is not just about energy. It is about the quality of that energy.

4. Your first opportunity to maximise micronutrient intake

We have talked a lot about macronutrients – mainly protein, fibre, and fat – but micronutrients also deserve a mention here. In fact, adequate micronutrient intake is essential for metabolic health, because the biochemical pathways that regulate metabolism depend on them (3-5). While micronutrients play a relatively limited role in appetite regulation, they are intimately involved in many of the biochemical processes that support metabolic health, including blood glucose regulation and the maintenance of muscle tissue.

There are 26 essential micronutrients and all of them are important for health, but if we are talking specifically about energy metabolism, bodyweight, blood sugar, and muscle then our closest friends are B vitamins, vitamin C, vitamin D, iron, magnesium, calcium, potassium, and zinc (3-5).

• The B vitamins, iron, and magnesium are central to energy metabolism within the mitochondria, where carbohydrates, fats, and proteins are ultimately converted into ATP (adenosine triphosphate), the body’s usable energy currency.
• Other micronutrients, including potassium, calcium, zinc, and vitamin D, contribute to processes that influence blood glucose regulation, muscle function, and insulin signalling.
• Meanwhile, vitamin C supports fat metabolism through its role in carnitine synthesis and helps protect metabolic tissues through its antioxidant activity.

To put things simply, while macronutrients such as protein, fibre, and fat influence appetite and energy intake, micronutrients support the biochemical processes that allow metabolism to function efficiently in the first place. This means that making sure we achieve an adequate intake of these nutrients is extremely important for our overall metabolic health.

The table below summarises the roles of each micronutrient and the key food sources (3-5). Common breakfast foods providing metabolism-supporting micronutrients include dairy, eggs, fortified cereals, nuts and seeds, and fruit.

 

Micronutrient	Key Metabolic Roles	Common Food Sources
B Vitamins (B1, B2, B3, B5, B6, B12)	Cofactors in carbohydrate, fat, and protein metabolism Essential for mitochondrial energy production and ATP generation	Whole grains, meat, dairy, eggs, legumes, leafy greens
Iron	Required for oxygen transport (haemoglobin) and mitochondrial energy metabolism Supports aerobic energy production	Red meat, poultry, fish, legumes, spinach, fortified cereals
Magnesium	Required for over 300 enzymatic reactions Involved in ATP production, glucose metabolism, insulin signalling, and muscle function	Nuts, seeds, whole grains, legumes, dark leafy greens
Potassium	Important for cellular function, muscle contraction, and glucose uptake into cells Helps regulate fluid balance and metabolic processes	Fruits (especially bananas), vegetables, potatoes, legumes, dairy
Calcium	Essential for muscle contraction, cellular signalling, and metabolic regulation	Dairy products, fortified plant milks, leafy greens, tofu
Zinc	Supports insulin synthesis and secretion, protein synthesis, and tissue repair	Meat, shellfish, dairy, whole grains, nuts, seeds
Vitamin C	Required for carnitine synthesis (important for fat metabolism) Acts as an antioxidant protecting metabolic tissues	Citrus fruits, berries, kiwifruit, capsicum, broccoli
Vitamin D	Supports muscle function, insulin sensitivity, and overall metabolic health	Sunlight exposure, fatty fish, eggs, fortified foods

 

 

If this all feels a bit overwhelming, rest assured, as now we are going to answer the question:

 

è When we put all of this together, what does a metabolically supportive breakfast actually look like?

A metabolically supportive breakfast = Protein-rich + fibre-rich + adequate energy + nutrient-dense.

That means:

1. At least 20 g but optimally 30-40 g high quality protein
2. Around 7-10 g dietary fibre
3. Around 400-500 calories (for many people)
4. Whole food carbohydrate and fat sources to deliver nutrient density, particularly essential micronutrients

A Tale of Two Breakfasts

Consider two common breakfast options.

Breakfast 1: Toast and Coffee

• 2 slices white toast with butter and jam
• Coffee with a good splash of whole milk

Approximate nutrition:

• Protein: ~8 g low quality protein from wheat + ~3.5 g high quality protein from milk
• Fibre: ~3-4 g
• Calories: ~400 kcal

While this breakfast provides adequate energy (calories), it contributes very little protein, a low amount of fibre, and relatively few micronutrients.

It won’t be satiating, meaning that a person will feel hungry quite soon after eating it.

It does not support healthy muscle mass and the metabolic benefits this provides.

It does not set a person up for metabolic health over the course of the day.

Breakfast 2: A Protein-Rich Breakfast

Example:

• 150 g Greek yoghurt
• ½ cup blueberries
• ~10 almonds
• 1/3 cup rolled oats
• Coffee with a good splash of whole milk

Approximate nutrition:

• Protein: ~17.5 g high quality protein from Greek yoghurt and milk +15 g lower quality protein from rolled oats and almonds
• Fibre: ~11 g from rolled oats and blueberries
• Calories: ~400-450 kcal

This meal provides meaningful levels of protein, fibre, and micronutrients, helping support satiety, muscle maintenance, and metabolic stability.

Breakfast isn’t automatically the most important meal of the day. That all depends on who you are and how you live. But if you are looking for ways to make a meaningful difference to your metabolic health, then breakfast is the first opportunity each day to do this.

Perhaps you are struggling with constant appetite, or energy dips (especially mid-afternoon), or brain fog, or even poor sleep. All of these are impacted by the ability of our body to regulate blood sugar and energy production in an optimal way.

Breakfast may not automatically be the most important meal of the day, but it is the first opportunity you have to shape your metabolism for everything that follows.

 

References

1.             Hall KD, Heymsfield SB, Kemnitz JW, Klein S, Schoeller DA, Speakman JR. Energy balance and its components: implications for body weight regulation. Am J Clin Nutr. 2012;95(4):989-94.

2.             Wolfe RR. The underappreciated role of muscle in health and disease. Am J Clin Nutr. 2006;84(3):475-82.

3.             National Academies Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: The National Academies; 2006.

4.             Australia New Zealand Food Standards Code. Schedule 4. Nutrition, health and related claims 2017 [Available from: https://www.legislation.gov.au/F2015L00474/latest/text.

5.             Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes. Canberra: National Health and Medical Resarch Council; 2005.

6.             Xia P, Li B, Yu Y, Yu W, Youssef M, Hou T, et al. Dietary strategies for appetite regulation: satiety and obesity management. Food & Function. 2025;16(13):5202-18.

7.             Merz KE, Thurmond DC. Role of Skeletal Muscle in Insulin Resistance and Glucose Uptake. Compr Physiol. 2020;10(3):785-809.

8.             Starck CS, Wolfe RR, Moughan PJ. A Factorial Model of the Minimum Metabolic Demand for Protein and Indispensable Amino Acids in Young Adult Males: Implications for Current Recommendations. J Nutr. 2026;156(4):101417.

9.             Schoenfeld BJ, Aragon AA. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. J Int Soc Sports Nutr. 2018;15:10.

10.          Layman DK. Impacts of protein quantity and distribution on body composition. Front Nutr. 2024;11:1388986.

11.          Iwayama K, Onishi T, Maruyama K, Takahashi H. Diurnal variation in the glycogen content of the human liver using (13) C MRS. NMR Biomed. 2020;33(6):e4289.

12.          Blaak EE, Antoine JM, Benton D, Björck I, Bozzetto L, Brouns F, et al. Impact of postprandial glycaemia on health and prevention of disease. Obes Rev. 2012;13(10):923-84.

13.          Drewnowski A, Fulgoni VL, III. Nutrient density: principles and evaluation tools. The American Journal of Clinical Nutrition. 2014;99(5):1223S-8S.