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It is not so rare for people to experience tiredness after consuming sugary foods. Most often people feel cravings for sugar and feel like sugar helps them to boost the mood and feel more alert. However, in some people sugar intake causes the quite opposite results and makes them feel fatigue. There are many of reasons for fatigue after eating sugar. For most of the people this is just an occasional experience, but if it happens regularly and if a person feels extreme tiredness, it is advisable to get examined by a doctor.


The common prejudice claims that sugar provides instant energy to the body. However, the truth is absolutely different. When a person eats sugar the blood sugar levels rise and force pancreas to produce insulin in order to maintain homeostasis or balanced levels of blood sugar. This results in rapid decrease in blood sugar levels and person starts to feel tired. This is perfectly normal and the unpleasant fatigue diminishes as soon as the blood sugar levels normalize again.

Imbalance of Serotonin

Serotonin is a brain chemical that transmits the signals from one region of brain to another, mediating a great number of vital body functions. The rising blood sugar levels in some persons may cause a protein building block known as tryptophan to proceeds in the direction of brain. Tryptophan joins hydroxylase in the brain to structure serotonin and any imbalance in serotonin can make a person feel tired after eating sugary foods.

Reactive Hypoglycemia

Persons that feel fatigue after eating sugar may also suffer from reactive hypoglycemia, a condition that strikes both diabetic and non-diabetic patients. In these cases, persons also feel other symptoms such as heart palpitations, nervousness, dizziness, light-headedness, headaches, sweating, insomnia, and panic attacks. What happens in these cases is that the person’s pancreas releases surplus insulin in the blood stream causing the sudden fall in blood sugar levels that leads to exhaustion and tiredness.


Before people develop type 2 diabetes they have so called "pre-diabetes", a condition in which blood glucose levels that are higher than normal but not yet high enough to be diagnosed as diabetes. This may also be the reason of feeling fatigue after eating sugar. In pre-diabetes conditions, pancreas fails to produce sufficient levels of insulin or body doesn’t utilize the produced insulin in a proper way. Home glucose test is pretty confident way to determine if one goes trough pre-diabetes stage. The proper diagnosis is crucial because pre-diabetes can be cured quite easily by reducing body weight, refraining from sweets and foods rich in carbohydrates. Overlooked pre-diabetes will, unfortunately, lead to type 2 diabetes.

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