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Updated: Aug 13, 2026

Study of In Vivo Glucose Metabolism in High-fat Diet-fed Mice Using Oral Glucose Tolerance Test (OGTT) and Insulin Tolerance Test (ITT)
Published on: January 7, 2018
Mechanism of glucose intolerance during fasting: differences between lean and obese subjects
Fasting significantly worsens glucose tolerance in both lean and obese individuals, but the effect is more pronounced in lean subjects. Lean individuals also experience delayed insulin response after fasting.
Area of Science:
- Metabolism and Endocrinology
- Human Physiology
Background:
- Fasting is a common practice with significant metabolic implications.
- Understanding how fasting affects glucose regulation in different body compositions is crucial.
Purpose of the Study:
- To investigate the impact of a 6-day fast on glucose tolerance and insulin sensitivity in lean versus obese non-diabetic subjects.
- To compare the metabolic responses to fasting between lean and obese individuals.
Main Methods:
- Oral glucose tolerance tests (OGTT) and insulin tolerance tests (ITT) were conducted on lean and obese subjects before and after a 6-day fast.
- Measurements included blood glucose, insulin, glucagon, growth hormone, free fatty acids, and ketone bodies.
Main Results:
- Glucose tolerance deteriorated in both groups after fasting, with a more significant decline observed in lean subjects.
- Fasting led to a delayed insulin elevation post-glucose load in lean individuals, but not in obese individuals.
- Fasting increased levels of glucagon, growth hormone, free fatty acids, and ketone bodies more in lean than in obese subjects.
- Lean subjects showed a decreased blood glucose response to insulin after fasting, while obese subjects showed no change.
Conclusions:
- Fasting has a more pronounced effect on insulin release and insulin sensitivity in lean individuals compared to obese individuals.
- Lean individuals experience a greater deterioration of glucose tolerance during fasting due to these altered metabolic responses.
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