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Study of In Vivo Glucose Metabolism in High-fat Diet-fed Mice Using Oral Glucose Tolerance Test OGTT and Insulin Tolerance Test ITT
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Prolonged Glycemic Adaptation Following Transition From a Low- to High-Carbohydrate Diet: A Randomized Controlled
Lisa T Jansen1, Nianlan Yang2, Julia M W Wong1
1New Balance Foundation Obesity Prevention Center, Boston Children's Hospital and Harvard Medical School, Boston, MA.
Diabetes Care
|February 2, 2022
Summary
Transitioning to a high-carbohydrate diet after a very-low-carbohydrate diet takes many weeks for glucose levels to stabilize. This impacts the accuracy of diabetes tests and macronutrient trial interpretations.
Area of Science:
- Endocrinology
- Metabolic Science
- Nutritional Science
Background:
- A 3-day high-carbohydrate diet (≥150 g/day) is recommended before an oral glucose tolerance test (OGTT) for diabetes diagnosis.
- The physiological adaptation period from very-low-carbohydrate (VLC) to high-carbohydrate diets is not well-defined.
Purpose of the Study:
- To evaluate the time course of glycemic changes after switching from a VLC diet to high-carbohydrate diets.
- To assess the impact of dietary carbohydrate transition on glucose tolerance test results.
Main Methods:
- Participants (BMI ≥27 kg/m2) were assigned to VLC, high-starch (HC-Starch), or high-sugar (HC-Sugar) isoenergetic diets for 10 weeks after a run-in VLC phase.
- Continuous glucose monitoring (CGM) was used throughout the trial, with OGTTs performed at the start and end.
Main Results:
- Glucose metrics continued to improve in HC-Starch and HC-Sugar groups for up to 9 weeks, unlike the VLC group.
- The proportion of participants with abnormal glucose tolerance decreased significantly in both high-carbohydrate groups post-intervention.
- Fasting and 2-h glucose levels showed significant decreases in HC-Starch and HC-Sugar groups over time.
Conclusions:
- Physiological adaptation to high-carbohydrate diets from VLC diets can take several weeks.
- The findings have implications for the accuracy of diabetes diagnostic tests and the interpretation of macronutrient studies.
- Periodic deviations from VLC diets require careful consideration of adaptation periods for accurate health assessments.
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