Skip to content

One Major Side Effect of Not Eating Breakfast, Says Science

The surprising reason it really is the most important meal of the day. 
FACT CHECKED BY Kiersten Hickman

From bad time-management skills to intermittent fasting rules, there are lots of reasons you might end up skipping breakfast. And no, coffee doesn't count—especially if it's one of these sugar-laden coffee drinks. Whatever the cause, you might want to start making room for a morning meal. Why? Breakfast sets the tone for the rest of your day.

"A balanced breakfast helps you feel energized, mentally sharp, and improves your chances of making healthier food choices throughout the day," says Mary Stewart, RD, LD, founder of Cultivate Nutrition.

When you don't eat breakfast, you lose out on vital nutrients, which tanks your blood sugar and creates a ripple effect of issues. One of the biggest side effects being that it stalls your metabolism. That's right. Research has found that people who eat breakfast—even a big one—burn twice as many calories.

36 Worst Breakfast Foods on the Planet

Skipping breakfast means skipping fuel for your metabolism.

"Breakfast literally means 'breaking the fast' and jump-starting your engine and metabolism," says Laura Burak, MS, RD, author of Slim Down with Smoothies. If you don't give your engine the fuel it needs to get going, it'll be hard to go very far.

That fuel includes "your daily fiber and protein needs, which are critical to optimizing your health," says Stewart. "Fiber intake is inversely associated with body weight and composition."

Even if you do eat breakfast, it's likely you're not getting enough fiber; it's estimated that 95% of American adults aren't meeting the recommended intake of fiber per day.

Protein is "essential for proper muscle mass and has the greatest thermic effect of food— meaning it will help boost your metabolism and aid in weight loss," explains Stewart.

9 Warning Signs You're Not Eating Enough Fiber

When you don't get that morning nourishment it can cause "your metabolism to slow down and your blood sugar to drop," says Stewart. "In fact, one recent study concluded the prevalence of abnormal metabolic outcomes (abdominal circumference, blood pressure, glucose, triglycerides, and HDL) was higher among those who did not consume breakfast on a regular basis."

Skipping breakfast could lead to stronger cravings later.

You're also likely to have more cravings. When your blood sugar gets off to a rocky start it ends up overcompensating and "[making up] for calories later in the day, which usually results in raiding the pantry in the afternoon when your body and mind signal that you need to eat stat in order to bring your blood sugar back up," says Burak.

Familiar with that hangry feeling? It's "simply your body doing its job," says Burak. By "eating a larger breakfast and lunch with plenty of satiating protein you keep your blood sugar stable, prevent cravings and frequent hunger, and help with weight management," says Burak.

Does it matter when you eat breakfast?

When you eat breakfast doesn't require a hard and fast rule, but Stewart says the sweet spot is allowing 12 to 14 hours between dinner and breakfast the next morning because it's a more natural fast, gives your body a break from food (read: no late-night noshing) and allows you to "experience the health benefits of fasting without the potential negative effects of extended fasting."

If you need inspiration for your first meal of the day, check out these healthy breakfast foods dietitians say you should be eating.

Get even more healthy tips straight to your inbox by signing up for our newsletter! After, read these next:

Caitlin Kilgore
Caitlin is a freelance health and wellness writer who is always in search of science-backed tips to living a healthy and balanced life. Read more about Caitlin