What Happens to Your Body When You Skip Breakfast

You get up in the morning (after hitting the snooze button once or twice), make your coffee, work out, and shower before logging on for work or heading to the office. The next thing you know, it’s noon, and you haven’t eaten a thing. If that sounds familiar, you’re in good company; about 25 percent of Americans skip breakfast daily, whether because of lack of hunger, busyness, or personal preference. Some sources claim that not eating until later is beneficial (see: intermittent fasting), while others say you should eat within 30 minutes of waking up for optimal health. It begs the debated question: Is breakfast really the most important meal of the day? What does a healthy breakfast even look like? And what happens to your body when you forgo it? I asked registered dietitians to shed light on the controversial meal and explain what happens to your body when you skip breakfast. BTW, skipping breakfast here and there won’t impact the body too much. The below research is when you consistently skip breakfast.

What Actually Happens to Your Body When You Skip Breakfast?

You may have unstable blood sugar levels

Many hormones like insulin are significantly impacted by the nutrients you nourish (or don’t nourish) the body with. “Insulin, for example, regulates blood sugar levels, and a balanced breakfast helps maintain steady glucose levels, preventing the spikes and crashes that can lead to insulin resistance over time,” Cook explained. “Without a proper breakfast, blood sugar levels can drop, prompting the body to release more insulin when food is eventually consumed.” This can create a cycle of elevated insulin production, which lowers blood sugar levels, increasing the risk of developing type 2 diabetes. Based on the findings of a 2019 study, skipping breakfast just one day a week may raise the risk of developing type 2 diabetes by 6 percent.

According to another 2019 study, the subjects who skipped breakfast experienced increased blood sugar levels and poorer blood sugar control. Because you’re fasting while you’re sleeping overnight, your blood sugar levels are naturally low when you wake up. So, if you don’t restore them by eating a well-rounded breakfast, your blood sugar will continue to decrease, which can lead to unstable blood sugar levels and significant blood sugar swings.

You may have decreased energy levels and cognitive function

If you don’t feed your body with the right nutrients upon waking in the morning, you’ll continue to have low blood sugar levels, and the body will produce more insulin as a result, causing fatigue, fogginess, mood swings, and poor cognitive performance. Without the nutrients that a healthy breakfast provides, the body doesn’t get the energy it needs to function optimally, so it pulls sugar reserves from fat and muscle tissue, slowing metabolism down and decreasing energy levels. What’s more, your brain doesn’t get the essential nutrients that fuel it for concentration, memory, and problem-solving. Research confirms this: A 2021 study discovered that breakfast skipping is linked to increased fatigue, while a 2017 study found that participants who skipped or ate an unhealthy breakfast had poorer cognitive performance throughout the day.

You may experience worsened period symptoms

According to registered dietician Shannon Cook, RD, eating breakfast is vital for stabilizing hormones, as the first meal of the day sets the tone for hormonal balance and overall health. The stress hormone cortisol tends to be highest in the morning (to help us wake up), but Cook explained that skipping breakfast can elevate cortisol levels even further, leading to prolonged stress responses. Chronic elevated cortisol can disrupt the regulation of the production of reproductive hormones like estrogen and progesterone. This can lead to issues like irregular menstrual cycles, cramping, headaches, and ovulatory dysfunction. And insulin resistance (due to unstable blood sugar levels, as mentioned earlier) is the most common underlying cause of polycystic ovarian syndrome (PCOS) (about 85 percent of women with PCOS have insulin resistance).

“Estrogen and progesterone are vital for regulating the menstrual cycle, and their balance is influenced by the availability of nutrients,” Cook conveyed. “Consuming a nutritious breakfast provides essential nutrients such as vitamins, minerals, and healthy fats that support the production and regulation of these hormones, promoting a regular menstrual cycle and overall hormonal health.” In other words, a nutrient-rich breakfast helps maintain the balance of hormones by providing the body with the energy and nutrients it needs, thereby reducing stress on the body and changes in hormones.

You may feel more stressed or anxious

Skipping breakfast doesn’t just lead to a spike in cortisol and physiological stress; it can also lead to emotional stress. Unstable blood sugar levels can trigger mood swings, irritability, and higher levels of anxiety. According to Psychology Today, skipping breakfast significantly increases the probability of psychological distress in all age groups. A 2020 study in Diabetes, Metabolic Syndrome and Obesity found breakfast skipping was even linked to depression and post-traumatic stress disorder.

While skipping a single meal is unlikely to cause any harm, habitually passing on breakfast can have detrimental effects on your mood in the long run. “When persistently high, cortisol levels are associated with anxiety and depression,” registered dietician nutritionist Claire Rifkin M.S., RDN told Eating Well. “A nutritious breakfast is more than just physical fuel; it’s a critical component in maintaining mental and emotional well-being.”

You may have nutrient deficiencies

When passing on a wholesome breakfast, it can be harder to consume all the daily essential nutrients the body needs and ensure you’re reaching your nutrition goals like eating enough protein. When you skip any meal, you increase your chances of experiencing a nutrient deficiency. A 2021 study in Proceedings of the Nutrition Society showed that adults who skipped breakfast were significantly less likely to meet the daily intake requirements of multiple essential nutrients the body needs to thrive. “Breakfast is a crucial meal that can provide ⅓ of your daily protein intake and essential vitamins and minerals necessary for maintaining overall health,” Cook said. “Without breakfast, individuals miss out on an opportunity to consume key nutrients such as calcium, iron, and various vitamins that support bodily functions and hormonal balance.”

This nutritional gap can lead to deficiencies that affect everything from your energy levels and cognitive function to metabolic health and disease prevention. “Consistently skipping breakfast undermines the foundation of a balanced diet, paving the way for various health issues such as hormone disruption and undesired weight gain.” On the other hand, eating breakfast regularly ensures you’re effectively nourishing your mind and body for them to function at their best.

You may have a harder time managing weight

People who regularly consume breakfast tend to have a healthier body weight. “Without breakfast, individuals may experience increased hunger later in the day, leading to overeating and a higher caloric intake, which can contribute to weight gain,” Cook said. This pattern of irregular eating can disrupt metabolic processes and make weight management more challenging. However, a 2018 study in Current Developments in Nutrition demonstrated that consistently eating a high-protein breakfast can support nutrient intake and help regulate appetite and weight.

Cook explained that eating breakfast helps regulate the appetite-regulating hormones like ghrelin (signals hunger, tends to rise before meals and decrease after eating) and leptin (signals satiety, works to suppress hunger), reducing the chance of overeating later in the day and aiding in weight management. A consistent morning meal can also prevent the late-night snacking that often follows when you’re not adequately feeding your body during the day. “A balanced breakfast sets a stable foundation for appetite regularity and consistent healthy eating throughout the day,” Rifkin said. So eating that avocado-and-egg toast translates to keeping a balanced metabolism, being more in tune with your hunger cues, and overall maintaining a healthy weight.

… Or you may have an easier time losing weight

On the other hand, there’s the argument that deliberately fasting (abstaining from food and drinks for a designated period) can help with weight loss because the body looks for other ways to generate energy and eventually burns fatty acids from stored fat for energy. The body goes into ketosis (a metabolic state where your body burns stored fat for energy instead of glucose from carbohydrates) about eight hours after your last meal or snack. The 16/8 method of intermittent fasting, which involves eating within an eight-hour window and fasting the remaining 16 hours of the day, often involves skipping breakfast. Studies have found that intermittent fasting helps with weight loss and reducing inflammation, while renowned women’s health expert and best-selling author Dr. Mindy Pelz, MD, recommends fasting for weight loss.

The research does show promising results. However, the imbalanced hunger hormones and blood sugar levels throughout the day may sabotage weight loss goals, so whether or not skipping breakfast is beneficial for or hinders weight management depends on each person, their goals, and if they have a reproductive cycle (avoid fasting the week before your period, which can have an opposite effect). Always discuss with your doctor what is right for you and listen to your body; if you’re experiencing fatigue, brain fog, or hunger cues, eat a nourishing meal or snack. While breakfast skipping may help you lose minimal weight in the short term, some experts say the practice is not sustainable and has the potential to backfire.

Tips for Building an Ideal Healthy Breakfast

Aim for 30 grams of protein (before caffeine or carbohydrates)

Cook recommended starting with 30 grams of protein to create the foundation of a meal that is both nutritionally-dense and sustaining. Prioritizing protein (think: eggs, Greek yogurt, cottage cheese, lean meats, or plant-based options like tofu and legumes) supports muscle repair and growth, enhances gut health, and maintains steady energy levels. When you wake up and drink coffee on an empty stomach or eat something high in sugar and carbohydrates like a bagel or cereal, it causes a large spike in cortisol (due to caffeine) and insulin (from sugar or simple carbohydrates).

Fill your plate with protein, fiber, and fat

Rifkin suggested the power trio of protein, fiber, and fat for a well-rounded breakfast. “This combination is your secret to energizing and keeping your blood sugar happy.” Complementing your choice of protein with fiber (i.e., vegetables, fruits, whole grains) and healthy fats (i.e., avocado, flaxseed, nuts) will ensure a gradual and sustained release of energy throughout the morning. “By combining protein, vegetables, and healthy fats, you create a meal that sets a positive tone for the day, enhances energy levels, supports digestive health with fiber, and provides a solid nutritional foundation to tackle your daily activities with energy and focus,” Cook agreed.

Stick with a savory breakfast

Breakfast is often synonymous with pancakes, cereals, and pastries—the usual sugary suspects laden with added sugar and void of nutrients. While they may be quick and easy, they’re likely to cause a surge in insulin production, leading to a drop in blood sugar levels and a sugar crash. “It’s important to avoid added sugars, as they can lead to rapid spikes and crashes in your blood sugar levels, which often result in mid-morning fatigue and cravings,” Cook said.

So, what does a healthy breakfast look like? Cook offered this suggestion: an omelet made from eggs or egg whites, filled with vegetables such as spinach, bell peppers, and tomatoes, with a serving of whole-grain toast or a small bowl of oatmeal. If you have a sweet tooth first thing in the morning, try a smoothie or smoothie bowl with Greek yogurt, berries, spinach or kale, chia or hemp seeds, a nut butter, and your choice of milk, or chia pudding made with chia seeds, kefir (a fermented milk drink similar to yogurt), berries, and nuts or nut butter.

So, Is Breakfast Really the Most Important Meal of the Day?

The experts I spoke with agreed that breakfast may not be the most important meal (all meals are important). But breaking your fast in the morning (hence the name “breakfast”) with a healthy meal provides the body with the nutrients it needs to help kickstart metabolism, replenish blood sugar needed for the muscles and brain to function optimally, and keep hormones balanced so you can feel and function at your best both mentally and physically (and research supports that).

But if you don’t have an appetite in the morning, listening and honoring your body’s hunger cues and ensuring you’re nourishing your body sufficiently throughout the day might work best for you. If you continually skip a morning meal, consider speaking to a registered dietitian to ensure you’re fueling your body with the proper daily nutrient intake.

Please consult a doctor or a mental health professional before beginning or stopping any treatments, supplements, or medications. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical or mental health condition. Never disregard professional medical advice or delay in seeking it because of something you have read in this article.

What Actually Happens to Your Body When You Skip Breakfast