<qa>  What is the cross-over within parallel design?This is a cross-over within parallel design. Parallel groups will receive Gelesis200 either 2 times or 3 times in one day before meals. Within the parallel groups, subjects will cross-over to 4 arms: A Gelesis200 10 min before meals, B Gelesis200 30 min before meals, C Placebo 10 min before meals, D Placebo 30 min before meals. Postprandial glucose, insulin and subjective appetite ratings will also be measured. 