What are the effects of not eating breakfast?

October 30, 2025 •

4 min read

According to a study published in the Journal of the American College of Cardiology, regularly skipping breakfast is associated with an increased risk of cardiovascular disease. The effects of not eating breakfast extend far beyond a growling stomach, influencing your physical and mental health in significant ways.

Quick Summary

Regularly missing the morning meal can lead to weight gain, metabolic dysfunction, increased risk of heart disease and diabetes, poor cognitive function, and mood swings. This habit negatively impacts overall health.

Key Points

Metabolism slows: Skipping breakfast sends your body a starvation signal, which can slow down your metabolism and lead to weight gain over time.
Cognitive impairment: The brain needs glucose to function, and skipping the first meal can lead to poor concentration, memory issues, and brain fog.
Increased disease risk: Long-term breakfast skipping is linked to a higher risk of developing type 2 diabetes, heart disease, and atherosclerosis.
Mood instability: Blood sugar fluctuations can cause irritability, fatigue, and mood swings. Studies show a connection to increased stress and depression.
Nutrient shortfalls: Breakfast is an important source of key nutrients like fiber, calcium, and B vitamins. Skipping it can result in significant nutrient deficiencies.
Overeating later: Skipping the morning meal often causes intense hunger that can lead to overeating or choosing unhealthy, high-calorie snacks later in the day.
Impact on children: For school-aged children, a nutritious breakfast is vital for academic success, including better alertness and improved school performance.

The Ripple Effect on Your Metabolism and Weight

Contrary to popular belief, skipping breakfast is often counterproductive for weight management and can disrupt your body's metabolic processes. When you forgo your morning meal, your body enters an extended fasting state, which can lead to metabolic fluctuations. Research consistently links habitual breakfast skipping to a higher body mass index (BMI) and an increased prevalence of obesity. This is primarily because of the hormonal and behavioral changes that follow.

How your body responds to skipping breakfast

Slower Metabolism: When you don't eat, your body perceives a period of starvation and slows down its metabolic rate to conserve energy. Eating breakfast, conversely, signals that a new day of energy expenditure has begun, helping to kickstart your metabolism.
Overeating Later: Prolonged fasting often leads to intense hunger and cravings for high-calorie, high-sugar, and high-fat foods later in the day, causing you to consume more calories than you would have with a balanced breakfast.
Insulin Resistance: Skipping breakfast can impair the body's insulin sensitivity. One study found that overweight women skipping breakfast experienced acute insulin resistance after lunch, with significantly higher insulin and glucose levels compared to days they ate breakfast. This can increase the risk of type 2 diabetes.

Impact on Cognitive Function and Mental Health

The brain runs on glucose, and an overnight fast significantly depletes these stores. A nutritious breakfast replenishes these glucose levels, providing the fuel needed for optimal cognitive performance throughout the morning.

Brain and mood consequences

Reduced Cognitive Performance: Studies have shown a clear link between skipping breakfast and reduced cognitive function, including memory, attention, and problem-solving abilities, particularly in children and older adults.
Mood Swings and Irritability: Blood sugar drops caused by not eating can lead to the classic 'hangry' feeling, characterized by irritability, fatigue, and difficulty concentrating.
Increased Stress and Depression: Research suggests that skipping breakfast can elevate cortisol, the body's stress hormone. Consistent skipping has been associated with higher levels of perceived stress and an increased risk of depression and anxiety.

Long-Term Risks for Cardiovascular Health and Chronic Disease

The metabolic and dietary changes from consistently skipping breakfast contribute to serious long-term health risks, including cardiovascular disease and diabetes.

Evidence-based risks

Heart Attack and Disease: A study from the Harvard School of Public Health found that men who regularly skipped breakfast had a 27% higher risk of heart attack or death from coronary heart disease.
Atherosclerosis: Research has associated skipping breakfast with an increased risk of atherosclerosis, or the hardening and narrowing of arteries, a precursor to heart disease.
Poor Glycemic Control: For those with type 2 diabetes, skipping breakfast is independently associated with worse glycemic control and greater blood glucose variability throughout the day.

Nutrient Deficiencies and Dietary Habits

Breakfast is a prime opportunity to consume essential vitamins, minerals, and fiber. Those who skip it often miss out on crucial nutrients.

Inadequate Nutrient Intake: Breakfast skippers typically have lower daily intakes of protein, fiber, calcium, iron, and several vitamins (A, C, and B12), leading to potential deficiencies over time.
Unhealthy Snack Choices: Due to increased hunger, skippers are more likely to reach for less nutritious, high-sugar snacks during the day, further exacerbating poor nutritional intake.

Short-Term vs. Long-Term Effects of Skipping Breakfast

Understanding the progression of effects can highlight the importance of the habit.


Effect	Short-Term Outcome	Long-Term Outcome
Energy/Mood	Irritability, fatigue, low concentration, 'hangry' feelings	Increased risk of depression, anxiety, and overall mood disorders
Weight Management	Intense hunger, increased cravings for unhealthy foods	Higher BMI, increased risk of obesity
Blood Sugar	Blood glucose dips and spikes, insulin release disruption	Increased insulin resistance, higher risk of type 2 diabetes
Nutrient Intake	Lower daily intake of key vitamins and minerals	Chronic nutrient deficiencies, weakened immune system
Heart Health	Increased risk factors like high blood pressure and cholesterol	Higher risk of heart attack, coronary heart disease, and atherosclerosis

Conclusion: Prioritizing Your Morning Meal

While some may view breakfast as an expendable meal for saving time or calories, the scientific evidence consistently points toward significant negative health consequences. From metabolic disturbances and weight gain to impaired cognitive performance, mood instability, and heightened risk for chronic diseases like diabetes and heart disease, the body pays a price for skipping the morning meal. Prioritizing a balanced breakfast provides the sustained energy and essential nutrients needed for physical and mental well-being throughout the day. Starting your day with a nutritious breakfast is one of the simplest and most effective ways to invest in your long-term health.

For more information on nutrition and metabolism, you can explore resources from reliable institutions such as the Harvard T.H. Chan School of Public Health.

Frequently Asked Questions

Yes, studies show people who skip breakfast tend to have a higher BMI. It can disrupt metabolism and lead to increased hunger and overeating later, contributing to weight gain.

Skipping breakfast can cause blood sugar drops, leading to irritability, mood swings, and fatigue. Research has linked it to higher levels of stress and a higher risk of depression.

Multiple studies indicate that skipping breakfast is associated with an increased risk of heart disease and atherosclerosis (hardening of the arteries).

Yes, your brain needs a steady supply of glucose for optimal function. Skipping breakfast can impair cognitive functions like memory, concentration, and problem-solving, especially in the morning.

Skipping breakfast has been linked to insulin resistance and higher blood sugar levels after meals, which increases the risk of developing type 2 diabetes over time.

Breakfast skippers often consume less protein, fiber, and important vitamins and minerals like calcium, iron, and B vitamins, potentially leading to long-term nutrient deficiencies.

Common reasons include a lack of time, not feeling hungry in the morning, dietary habits like late-night eating, or attempts at weight loss.

Yes. What you eat is as important as eating at all. A balanced breakfast with protein and fiber provides sustained energy, whereas a high-sugar meal can lead to energy crashes.