Not everyone is a “breakfast person”—and for metabolically healthy people, occasionally skipping the first meal of the day isn’t necessarily harmful. But for some, it may affect blood sugar and insulin regulation in ways that could contribute to short- and long-term metabolic changes.
“Breakfast” means breaking a fast. When you skip it, you’re extending the overnight fast and delaying your body’s first insulin release of the day.
To keep blood sugar levels from dropping too low, the pancreas releases a hormone called glucagon, which tells the liver to release stored glucose. “When people regularly skip breakfast, blood sugar typically stays within normal range, but the body works harder to maintain it,” Rekha Kumar, MD, MS, a physician specializing in endocrinology and metabolism and senior medical advisor at Found, told Health.
Going longer without eating also raises levels of circulating nonesterified fatty acids (NEFAs). Over time, higher NEFA levels can contribute to insulin resistance, meaning your cells don’t respond to insulin as well, said Kelly Candela, MS, RD, a registered dietitian specializing in metabolic and gut health and director of nutrition coaching at Parsley Health.
We all know what it’s like to feel a little “hangry.” The brain runs on glucose, and without it, some people may experience brain fog, irritability, trouble concentrating, or even headaches if they go too long without eating, Candela said.
When you skip breakfast, your body may start producing ketones, which burn fat for fuel instead of glucose. But ketones can also contribute to that foggy feeling, said Gillian Goddard, MD, a board-certified endocrinologist and adjunct assistant professor at NYU Grossman School of Medicine, said.
Some research suggests that skipping breakfast can lead to a higher-than-normal blood sugar rise after you eat later in the day.
“When you finally eat lunch, your body may struggle to manage glucose as efficiently,” Candela told Health. “Research shows that even after skipping breakfast once, healthy individuals can experience up to a 40% to 50% higher blood sugar rise after lunch compared to when they ate breakfast.”
Some studies have found that people who skip breakfast report feeling hungrier throughout the day. For some, that may lead to increased calorie intake, which could contribute to weight gain over time. However, research findings are mixed, and not everyone compensates by eating more.
“The first meal after a long fast tends to trigger a larger blood sugar spike and a bigger insulin response, which can also drive hunger and cravings,” Kumar said.
We usually think of circadian rhythms as controlling sleep, but they also influence blood sugar. “Fasting glucose levels are highest in the morning and fall over the course of the day, reaching their lowest levels by midafternoon,” Goddard said.
Metabolism follows a similar pattern. The body tends to be more sensitive to insulin earlier in the day, meaning it can handle glucose more efficiently. Skipping breakfast may work against that built-in timing, Candela said.
“Breakfast, or the first meal of the day, can be a powerful tool for blood sugar stability and overall metabolic health,” Candela said. “Even if you practice intermittent fasting, aligning your eating window with your body’s natural rhythms can maximize the benefits while minimizing stress on the system.”
People with metabolic conditions—such as PCOS, prediabetes, or type 2 diabetes—may experience more greater blood sugar fluctuations when they skip breakfast. In these individuals, delayed or larger glucose spikes later in the day could contribute to higher average blood sugar levels over time, Candela said.
“[For people with metabolic disorders,] I generally recommend eating breakfast consistently at a similar time each day,” Candela said. “Evidence shows that a morning meal helps prime insulin response, stabilizes glucose throughout the day, and reduces post-meal spikes.”
Hormonal shifts may also play a role. “For women navigating perimenopause or PCOS, these effects can be more pronounced,” Kumar said. “Estrogen [influences] insulin sensitivity, so as levels fluctuate or decline, the body becomes more reactive to glucose and cortisol patterns.”
If you find yourself feeling foggy, fatigued, ravenous, or exhausted in the afternoon—or if you work out intensely in the morning—skipping breakfast might not be the best choice. People with metabolic conditions may also benefit from more consistent morning meals.
To keep you satiated and your blood sugar levels steady, experts recommend building breakfasts that include a balance of:
- Protein to improve satiety, support insulin response, and reduce glucose excursions. Aim for about 25 grams.
- Healthy fats to help slow gastric emptying and blunt glucose spikes.
- Soluble fiber, like whole grains, beans, pears, apples, berries, asparagus, and root veggies, to improve insulin sensitivity and slow carb absorption
- Low-to-moderate glycemic carbs, like legumes, berries, and whole grains, in modest portions.
