"Most important meal of the day?"
The phrase "breakfast is the most important meal of the day" is often attributed to a 1917 article in Good Health magazine — which was edited by John Harvey Kellogg, a man selling cereal. The line has been repeated for over a century, largely by people selling breakfast. The science behind it is far less absolute than the slogan.
Does skipping breakfast slow your metabolism?
No. Your metabolic rate doesn't drop because you delayed your first meal by a few hours. Resting metabolic rate is primarily determined by body size, muscle mass, age, and activity — not by whether you ate at 7 AM or 11 AM. The "thermic effect of food" (the calories burned digesting) is real, but it's proportional to what you eat, not when. Eat the same food later and you get the same thermic effect later.
What about the breakfast-skipping studies?
This is where it gets nuanced. Observational studies — the kind that just watch people — often link breakfast skipping to higher body weight, heart disease, and worse metabolic markers. But observational data can't prove cause. People who skip breakfast also tend to have more erratic schedules, higher stress, and different overall eating patterns.
When researchers run randomized controlled trials — assigning people to eat or skip breakfast — the weight-loss advantage largely disappears. A 2019 meta-analysis of randomized trials found no significant difference in weight change between breakfast eaters and skippers. Total daily intake mattered; the timing of the first meal, by itself, didn't.
Who should probably eat breakfast
Skipping isn't right for everyone. People who benefit from eating earlier include:
- People with diabetes — morning glucose can be harder to manage without food, especially on certain medications.
- Athletes training early — performance and recovery suffer without fuel.
- People who overeat later — if skipping breakfast leads to a 3 PM spiral, eating earlier may help regulate the day.
- Children and teens — growing bodies and brains benefit from consistent fuel.
- Pregnant women — morning nausea and blood sugar stability often improve with early food.
Who might be fine skipping
If you're not hungry in the morning, you don't feel worse when you skip, and your total intake across the day is adequate — skipping breakfast (or eating later, as in intermittent fasting) is a legitimate choice. The key question is whether it leads to better or worse overall eating patterns for you, not whether some universal rule demands you eat at 7 AM.
What matters more than whether you eat
When you do break your fast — whenever that is — the content of that meal matters more than the clock. A breakfast of eggs, whole grain toast, and fruit is doing real work. A "breakfast" of a pastry and sweet coffee at 10 AM is not better than skipping just because it happened in the morning. What beats when.
The takeaway
- "Breakfast is most important" originated partly from cereal marketing.
- Skipping breakfast does not slow your resting metabolism.
- Randomized trials show no clear weight-loss advantage for eating breakfast.
- People with diabetes, athletes, kids, and pregnant women often do better with breakfast.
- What you eat matters more than when you first eat.