Christine Pelkman, PhD

Transcription

1 Christine Pelkman, PhD Dr. Pelkman is a graduate faculty member in Nutrition, and Director of the Nutrition and Health Research Laboratory at the University of Buffalo. She completed her doctoral and postdoctoral work at the Pennsylvania State University in the areas of energy regulation, obesity and nutritional factors in cardiovascular disease risk. Her research focuses on the metabolic effects of high-glycemic diets. Specifically, she is interested in understanding the acute and chronic effects of dietary-induced high blood glucose on body weight regulation and risk for cardiovascular disease and diabetes. She is also interested in how reproductive hormones affect these same parameters.

2 Effects of Low-Glycemic Carbohydrates on Satiety Christine Pelkman, Ph.D. University at Buffalo Oct 25,

3 Friday, Oct 13 Oct 25,

4 Outline Effects of food on food intake Satiety / Satiation Carbohydrate metabolism Glycemic Index / Glycemic Load Potential mechanisms to affect satiety Experimental evidence Oct 25,

5 Food Intake Regulation Oct 25,

6 Satiation: Processes that terminate a meal (meal size) Satiety: Processes that determine the length of the intermeal interval or size of next meal J.E. Blundell, 1996 Oct 25, pp

7 Carbohydrates - Classification Chemical Structure Amylose: unbranched Amylopectin: highly branched Oct 25,

8 Glycemic Response High-GI foods: More free glucose More amylopectin Finely milled, mashed, etc Outer kernal removed Low-GI foods: Less glucose, more lactose, fructose or sucrose More amylose Coarse milling Outer kernal intact Retrograde or resistant starch The more quickly a food is absorbed and converted into glucose; the higher the blood sugar after a meal Oct 25,

9 The Glycemic Index The Glycemic Load Jenkins 1981 Compares the 2-hr 2 blood sugar response (relative to glucose) 50 g of available CHO Considers the amount of CHO in a serving GL = GI X avail CHO/ Glucose, GI score = 100 Lentils, GI score = 40 Oct 25,

10 GL useful to quantify glycemic response to foods and meals Oct 25,

11 The Glucostatic Theory and GI Mayer 1953 Rate of glucose utilization sensed in CNS Campfield & Smith (Physiol Physiol Rev 2003) Transient declines in blood glucose initiate meal requests in animal and human studies Glycemic Index and Satiety Consider postprandial time course Oct 25,

12 High versus Low Glycemic responses following a meal High-glycemic CHO: Higher blood glucose levels (by definition) Rapid due to faster absorption (Jenkins) Jenkins et al. American Journal of Clinical Nutrition, Vol. 76, 2002 Oct 25,

13 Short-term term postprandial effects High blood glucose higher satiety Anderson, et al. Crossover study in lean men 5 Drinks (75 g CHO) that varied in GI Pizza lunch 1 hour after test drink 14% Oct 25,

14 Longer-term postprandial effects N= 14 overweight women BMI kg/m years of age Rapid versus Slow ingestion of glucose with a meal; to mimic high and low glycemic meals. Oct 25,

15 Study Conditions Fast with the meal Slow 20 min intervals Oct 25,

16 Glucose (mg/dl) Slow Fast High-GI: earlier return :00 am B 30 min 1 hr 2 hr 3 hr L 4.5 hr 12:00 pm 5 hr 6 hr 7 hr 5:00 pm 8 hr 9 hr of hunger 100 Slow Fast Appetite Score * * * * 0 B L Oct 25, Time (hours)

17 Insulin Infusion Experiment 16 lean men, double-blind, crossover study Oct 25,

18 2.5 mmol/l = 45 mg/dl 16% Oct 25,

19 Conclusions Dynamic changes in glycemia after a meal Influence hunger and food intake Earlier return to hunger with High-GI meals More rapid fall in blood glucose Low-GI meals may prolong satiety Prevention Adherence with reduced-calorie calorie diet Oct 25,