Fasting and Blood Glucose | Jason Fung
Introduction
In this video, the speaker explains the dawn phenomenon and what happens to blood sugar levels while fasting.
Blood Glucose and Hormones
- When you're not eating, your body releases glucose for energy.
- Your body can take glycogen in the liver or body fat and turn it back into glucose or sugar and pump it back out into the blood.
- Counter regulatory hormones such as noradrenaline, sympathetic nervous system, growth hormone, and cortisol are released when you're not eating. These hormones have the effect of taking glucose that's in storage and pumping it back out into the blood during fasting.
- During fasting, there is a rise in counter regulatory hormones which causes an increase in blood glucose levels.
Dawn Phenomenon
- The dawn phenomenon happens in everybody when they are about to wake up somewhere around four o'clock five o'clock in the morning.
- The body releases a surge of counter regulatory hormones due to its circadian rhythm. It takes sugar from your storage systems pumps it out into the blood and gets you ready for the day ahead.
- People with type 2 diabetes may experience a variation of this response where their blood glucose rises very high in the morning even though they didn't eat.
Conclusion
- If you find that your blood sugar is rising when you're fasting, there's nothing wrong with you. It doesn't mean you did anything wrong.
Blood Glucose and Fasting
In this section, the speaker discusses blood glucose levels during fasting and how it affects people with diabetes.
Blood Glucose Levels During Fasting
- The body has the ability to keep blood glucose levels normal even during fasting by turning glycogen in the liver or body fat back into sugar.
- People who take no medications for diabetes should not develop low blood sugars in response to fasting. However, those taking medications need to be careful as their blood glucose can go too low.
- It is important to talk to a doctor before changing your diet if you are taking medication for diabetes. Adjustments may need to be made to avoid overmedication.
- If blood glucose tends to go too low during fasting, reducing medication is necessary. This means that diabetes is getting better.
Studies on Fasting and Blood Glucose Levels
- Studies have shown that fasting itself does not cause low blood glucose levels. Men were fasted for 30-60 days and given a large bolus of intravenous glucose, which drove their blood glucose down further. Those who were fasted did not feel any symptoms because they had a lot of ketones, which are a source of energy for the brain.
- Another study took nine people and put them on a 60-day fast. They were given intravenous insulin to drive their blood glucose down, but every single one of them didn't notice anything at all.
Conclusion
- Blood glucose usually goes down during fasting but usually stays in the normal range. If you're on medication, adjustments may need to be made. Blood glucose going up during fasting indicates that your body probably has too much glucose overall, and fasting is doing a good thing.