Effect of Polyphenol-rich Dark Chocolate on Insulin Sensitivity in Normal Weight and Overweight Adults

Effect of Polyphenol-rich Dark Chocolate on Insulin Sensitivity in Normal Weight and Overweight Adults

Effect of Polyphenol-rich Dark Chocolate on Insulin Sensitivity in Normal Weight and Overweight Adults

The purpose of the study is to determine the effect of polyphenol-rich dark chocolate on insulin sensitivity in normal weight and overweight adults.

Polyphenols may have several favourable effects on health. Dark chocolate (DC) is one of the highest sources of polyphenols in foods. The aim of the study is to determine the effect of polyphenol-rich dark chocolate on insulin sensitivity in normal weight and overweight adults. Seventy four volunteers with no history of hypertension, cardiovascular diseases or diabetes will be recruited. Participants will randomly receive 20g daily of one of the two different types of DC: Placebo DC (low in polyphenols) or DC rich in polyphenols (500mg) for a period of four weeks. Participants will be asked to make two appointments to the university clinical lab. Anthropometric measurements (height, weight, waist circumference), blood and saliva samples will be taken during each of the 2 visits. Compliance will be tested by the measure of total polyphenols in a 24-hour urine sample in some random samples before and at the end of the intervention. To monitor any fluctuations in the participants' diet or physical activity during the study period, a three-day diet diary and a physical activity questionnaire will be collected before the start of the study and after four weeks. Data will be analysed with an ANCOVA with time (pre- and post-) and treatment (DC and placebo) as between-subject factor.

Participants will be asked to consume 20g of dark chocolate containing 500mg of polyphenols daily for a period of 4 weeks

Participants will be asked to consume 20g of dark chocolate containing little or no polyphenols for a period of 4 weeks

Insulin sensitivity will be determined by determined by HOMA-IR (Homeostasis Model of Assessment - Insulin Resistance)

Determine if the consumption of DC rich in polyphenols can induce a change in Lipid profile (TC, HDL, LDL & TG)

Determine if the consumption of DC rich in polyphenols can induce a change in BMI and Waist circumference

Determine if the consumption of DC rich in polyphenols can induce a change in salivary cortisol-to-cortisone ratio

Inclusion Criteria: Adults with no history of hypertension, diabetes and cardiovascular diseases BMI from 18-24.9 and BMI >25 Males and Females Age: 18-65 years Exclusion Criteria: Participants with cardiovascular diseases, hypertension or diabetes Smokers and heavy alcohol drinkers Participants taking any medications that affect insulin, cholesterol, triglycerides or blood pressure Participants taking dietary supplements containing high doses of antioxidants Postmenopausal women taking HRT (Hormone Replacement Therapy) Participants who recently participated or are currently on a weight management program Participants with regular consumption of cocoa or DC (> 1 serving/week)