What happens when you eat pastries for breakfast?

Eating pastries in the morning can provide a quick energy boost, but it may also cause blood sugar spikes, fatigue, and increase the risk of obesity and type 2 diabetes.

Breakfast is the most important meal of the day, helping to kickstart metabolism and fuel the brain and body. According to Dr. Trần Thị Trà Phương, Department of Nutrition and Dietetics, Tâm Anh General Hospital (Hanoi), the average adult needs around 400–500 calories for breakfast. However, the quality of calories matters more than the number itself.

Although pastries are convenient, they come with several health risks. Dr. Phương notes that most baked goods such as croissants, muffins, and butter cakes contain high amounts of refined sugar, simple carbohydrates, and saturated fats. These ingredients provide quick energy but lack essential nutrients like protein, fiber, vitamins, and minerals.

Effects on blood sugar and metabolism

Having pastries for breakfast can make you feel hungry again sooner, increase food cravings, and lead to higher calorie intake throughout the day — contributing to weight gain and obesity. Foods with a high glycemic index cause rapid insulin fluctuations, leaving you fatigued and less productive. Over time, this can reduce insulin sensitivity, leading to insulin resistance and an increased risk of type 2 diabetes.

Eating sugary and high-fat foods like pastries in the morning can also raise visceral fat levels, increase “bad” LDL cholesterol, reduce “good” HDL cholesterol, and disrupt blood sugar regulation — all of which elevate the risk of metabolic and cardiovascular diseases.

The World Health Organization (WHO) recommends that free sugar intake should not exceed 10% of total daily energy, ideally under 5% (about 25 g or 6 teaspoons per day for adults). A single slice of cream cake or sponge cake may already exceed this limit.

Negative effects on digestion and immunity

Many pastries are made with margarine, reused frying oil, or hydrogenated oils like palm or refined soybean oil to prolong shelf life. Consuming these fats can disrupt gut bacteria balance, causing bloating and indigestion.

Pastries containing high-fructose corn syrup promote the growth of harmful gut bacteria, leading to digestive issues. Refined starches also harm the gut microbiome, triggering inflammation in the body. Eating only pastries for breakfast may deprive your body of key micronutrients such as vitamins C, D, zinc, and iron, weakening the immune system and reducing resistance to illness.

Reduced concentration and mental performance

A sugar-rich diet overstimulates neurons that regulate mood, motivation, and memory. Excess sugar interferes with chromium absorption, decreases insulin sensitivity, and hinders tryptophan transport to the brain — reducing serotonin production, which can worsen anxiety, depression, and cognitive function.

Unstable blood sugar levels over time damage brain blood vessels, reducing oxygen supply and altering gut bacteria linked to cognitive development. This can lead to memory decline and poor focus. Although the effects vary by individual and sugar intake, regularly eating pastries for breakfast increases these risks.

Healthier breakfast recommendations

According to the National Institute of Nutrition (Vietnam), an ideal breakfast should account for 20–25% of daily energy intake and include a balance of complex carbohydrates, protein, healthy fats, vitamins, and minerals.

If you enjoy pastries in the morning, control your portion size and pair them with other nutrient-dense foods. Choose pastries made with whole-grain flour, oats, chia seeds, almonds, or walnuts to boost fiber and healthy fat intake. Combine them with protein-rich foods such as plain Greek yogurt, boiled eggs, or low-fat cheese to extend satiety and stabilize blood sugar.

Add fresh fruits, especially those with a low glycemic index like strawberries, apples, or kiwis for extra vitamins, antioxidants, and fiber. A balanced breakfast might include whole-grain toast with nut butter, a boiled egg, a banana, and a glass of unsweetened plant-based milk — a nutritious and energizing start to the day.