Effect of Polyphenol-rich Dark Chocolate on Body Weight in Overweight and Obese Adults: A Pilot Study

Polyphenols are phytochemicals widely available in plants, and may have several favourable effects on health. Dark chocolate (DC) is one of the highest sources of polyphenols in foods. Animal and in vitro studies have demonstrated that cocoa and dark chocolate may exert anti-obesity effects mainly due to the polyphenol effect on glucose and fatty acid metabolism. Human studies have showed that regular chocolate eaters have a lower body weight compared to non regular eaters, and that DC promotes satiety and reduces cravings. The aim of this pilot study is to investigate the effect of polyphenol-rich DC on body weight in the overweight and obese adult population, when incorporated into a non-restricted diet. Twenty-eight apparently healthy volunteers 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 twelve weeks. Participants will be asked to make three appointments and one follow-up appointment to the university clinical lab. Anthropometric measurements (height, weight, waist circumference, body fat percentage) will be taken during each visit. Compliance will be defined by the intake of 85 % or more of the chocolate weekly, and will be tested by the measure of total polyphenols in a 24-hour urine sample before, during 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, a Food Frequency questionnaire assessment for polyphenol intake and a physical activity questionnaire will be collected before the start of the study and every four weeks. A follow-up appointment (four weeks after the end of intervention) will check if any differences in anthropometric measures have been maintained. Data will be analysed with an ANCOVA with time (pre- and post-) and treatment (DC and placebo) as between-subject factor. This study will have novel findings and will be the basis for a future larger trial.