The saying goes: “Breakfast like a king, lunch like a prince and dine like a pauper”. But in recent years, the trend for intermittent fasting has seen many of us ditch our morning meal in favour of later refuelling. Whether you’re actively trying to reduce your eating window, tend to have frantic mornings or simply don’t feel hungry in the mornings, breakfast is often the first meal to get scrapped or delayed. But while the benefits of intermittent fasting for some are undeniable (a big IF Zoe study found that it can boost mood, concentration and energy), having a morning meal can be really important. In fact, some research suggests that skipping breakfast can increase stress, spike blood sugar and reduce the efficiency of our immune system.

Aside from very simple fact that our bodies need to refuel after sleeping (it’s called break-fast for a reason), breakfast eaters are widely thought to have healthier lifestyles generally, with lower risks of chronic diseases and a greater intake of nutrients throughout the day.

Plenty of nutritional experts stress the importance of eating breakfast, including clinical nutritionist Hannah Hope. “A protein-rich breakfast is a really important start to your day,” she tells Strong Women. “A healthy breakfast will raise your energy levels, give you the energy you need if you wish to exercise, and lead to better choices around food for the rest of the day – as well as improving concentration and attention span.”

It can compromise our immune system

According to a study by the Icahn School of Medicine at Mount Sinai hospital, skipping breakfast could leave us less able to fight infections and increase our risk of heart disease. Researchers looked at mice models, feeding one group a large breakfast and the other group nothing. They discovered that being in a fasted state triggers a response in the brain that negatively affects immune cells; the fasted mice lost 90% of their white blood cells over a period of four hours. Once food was reintroduced, the fasted mice experienced a surge of immune cells back into their bloodstreams – triggering inflammation and leaving them less resistant to fighting infection. 

While it goes without saying that human trials are needed next, researchers suggested that it still provided food for thought when it comes to immunity and the gut. We already know that a whopping 80% of our immune system is located in our gut, so it makes sense that what and how we feed our microbiome might play a role in keeping us cold and flu-free.

It might exacerbate existing stress

The same mouse study found that going without breakfast elicited a stress response in the brains of the hungry mice. If you’re the kind of person who gets hangry after a few hours of not eating, you might relate. Additionally, a 2018 study of teenagers showed that those who ate a good breakfast experienced lower levels of stress and depression than those who ate a poor-quality meal in the morning. 

“Intermittent fasting using methods such as skipping breakfast can increase levels of the stress hormone, cortisol,” agrees health coach Sarah Elisabeth. “If you’re already stressed (which the majority of us are due to the demands of day-to-day life), skipping breakfast is only going to perpetuate the problem.”

Hope believes that a protein-rich breakfast can help to regulate that cortisol production, giving us a better chance of staying calm throughout the morning. “Foods with protein such as eggs, fibre-rich oats or a smoothie packed with vegetables and seeds, will set you up well for the day ahead,” she advises. “Eating a decent breakfast will boost your energy levels and leave the body better able to fight stress.”

It may have a negative impact on blood sugar levels

If you’re someone who experiences energy highs and lows throughout the day (3pm slump, anyone?), not eating breakfast could just make things worse.

“Skipping breakfast leaves you devoid of satisfaction, meaning you’ll likely reach for foods which will raise your blood sugar levels quickly,” explains Elisabeth. She also flags that the longer you delay your first meal, the more likely you are to turn to coffee as an energy aid. Intermittent fasting allows for black tea and coffee, and while neither tend to raise blood sugar, some research suggests that caffeine can impair insulin sensitivity.

Relying on sugar and caffeine to plug the gap until lunchtime isn’t going to do you many nutritional favours, so if you do find yourself reaching for the coffee machine umpteen times before midday or grabbing a quick sweet snack, you might be better off just having a proper meal. 

It can negatively affect our sleep

It might sound ridiculous, but a good night’s sleep starts with what you start the day with. Plenty of sleep experts suggest that breakfast can play a vital role in nighttime rest, including Anna McKay, founder of Zeez Sleep.

“Good sleep is the foundation of good health; without it, we can’t benefit from good food or exercise,” she says. “To sleep well, we need enough melatonin (our sleep hormone), which is made from serotonin. A morning meal rich in the amino acid tryptophan (found in eggs, chicken, fish and nuts) ensures our bodies can produce enough serotonin over the day and therefore create enough melatonin by the time we start to wind down. That’s essential for healthy sleep.”

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