1. The Purpose of the Test: To See the Usual Response
The purpose of the Oral Glucose Tolerance Test (OGTT) is to see how efficiently our body, while maintaining its ‘usual’ dietary habits, copes when a large amount of glucose (75g) is suddenly introduced. Therefore, if you eat an extreme or unusual diet for a few days before the test, the results can be distorted and may not accurately reflect your body’s actual condition.
2. Why You Shouldn’t Reduce Carb Intake
If you severely restrict carbohydrate intake for several days before the test, your body adapts to a ‘low-carb state.’
– Insufficient Insulin Secretion Preparation: The pancreas is prepared to secrete insulin based on the usual amount of incoming carbohydrates. If very few carbs are consumed for several days, the pancreas’s insulin response can become temporarily sluggish.
– Causing a ‘False Positive’ Result: In this sluggish state, if you suddenly drink the high-concentration glucose solution, the pancreas may not be able to secrete enough insulin in time, leading to a blood sugar reading that is much higher than your actual state. In other words, a ‘false positive’ error can occur, where the test result looks like diabetes even though you don’t actually have it.
3. The Correct Way to Prepare for the Test
For accurate test results, most medical institutions provide the following instructions:
– For 3 days before the test: Maintain normal activities and a diet containing at least 150g of carbohydrates per day.
– After dinner the night before the test: Fast for at least 8 hours (water is allowed).
– On the morning of the test: Refrain from smoking and rest until the test is complete.
Summary: To get accurate OGTT results, it is important not to reduce carbohydrate intake for a few days before the test, but rather to eat a sufficient amount as usual, so that your body is tested under its normal conditions.
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