Sugary or highly refined cereals

Despite their sweet, crunchy flavor and widespread availability at breakfast tables, most sugary cereals will not keep you satisfied for long. They're often high in sugar and low in protein, which means they'll spike your blood sugar levels quickly. When the blood-sugar-lowering hormone insulin kicks in, this might cause irritation and hunger.

Similarly, even unsweetened cereals like corn or bran flakes are low in protein, with just 2 grams per cup (25 grams) and 4 grams per cup (45 grams), respectively. So, while they have less added sugar, they aren't the healthiest way to start the day. Even more natural-looking alternatives, such as granola, are frequently high in added sugars, which have been linked to obesity, type 2 diabetes, and heart disease. For these reasons, while sugary or other highly refined cereals may be OK as a once-in-a-while treat, they are not the ideal choice for a regular breakfast.