MedicalResearch.com Interview with>
Katarina Borer, Ph.D. Professor
School of Kinesiology
The University of Michigan
Ann Arbor, MI
MedicalResearch.com: What is the background for this study?
Response: This study was part of the doctoral dissertation of Po-Ju Lin, who is now a post-doctoral fellow at the University of Rochester. With this study, we wanted to answer three questions:
(1) Is daily carbohydrate load responsible for evening glucose intolerance and post-meal insulin resistance. (Evening glucose intolerance represents well-documented higher glucose and insulin responses in the evening than in the morning when the same quantity of glucose is eaten or infused intravenously) To answer this question we offered two daily meals containing about 800 Kcal and either 30% or 60% of carbohydrates.
(2) Will exercise before the meals improve glucose tolerance (glucose clearance from the blood and insulin response) after eating? (Exercise is a well-known means of increasing glucose uptake by the muscle and of increasing muscle sensitivity to insulin action for a number of hours after exercise). To answer this question we had the subjects exercise for two hours walking on a treadmill at 45% of their maximal aerobic effort one hour before each meal.
(3) Is the upper-intestinal hormone GIP involved in any effects associated with variation in dietary carbohydrate? (GIP or glucose-dependent insulinotropic peptide, stimulates insulin secretion in advance of absorbed glucose).
MedicalResearch.com: What are the main findings?
Response: After the third meal, or 24 hours after eating low-carbohydrate diet, which happened in our study in the evening, post-meal insulin and GIP responses and insulin resistance declined by over 30%, but no such change occurred when eating 60%-carbohydrate meals. This effect was independent of pre-meal exercise. The parallel timing and magnitude of post-meal changes in GIP and insulin suggest that they reflect a delayed intestinal adaptation to low-carbohydrate diet. Pre-meal exercise made evening post-meal glucose intolerance worse.
MedicalResearch.com: What should readers take away from your report?
Response: That eating high carbohydrate diets near the upper range of recommendation by Departments of Health and Human Services and Agriculture published in 2010 (45 to 65% dietary carbohydrate) is not beneficial as far as evening post-meal insulin resistance. Reducing the daily carbohydrate load to about 100 grams in a 1,600-Kcal diet substantially improves post-meal insulin resistance by lowering the insulin response. And exercising before such meals does not have an additional beneficial effect.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: Future research should determine whether the beneficial effects of reduced carbohydrate diets work as well in the morning as in the evening; what types of carbohydrates, fats, and proteins work best in such diets; and whether exercise within an hour after lower-carbohydrate meals can improve glucose clearance and insulin responses.
MedicalResearch.com: Is there anything else you would like to add?
Response: Our diets had sugar to non-sugar ratios of 52:48 in low-carbohydrate meals, and 43:57 in high-carbohydrate meals.
MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.
Third Exposure to a Reduced Carbohydrate Meal Lowers Evening Postprandial Insulin and GIP Responses and HOMA-IR Estimate of Insulin Resistance
Po-Ju Lin,Katarina T. Borer
Published: October 31, 2016
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