Gastric and Intestinal Satiation in Obese and Normal Weight Healthy People

• gastric emptying [ Time Frame: 240 minutes end-expiratory breath sample collection ] [ Designated as safety issue: No ]
• time needed to reach the level of satiation [ Time Frame: up to 30 min ] [ Designated as safety issue: No ]
• total calorie intake [ Time Frame: up to 30 min ] [ Designated as safety issue: No ]

The purpose of this study is to determine the reciprocal control between gastric functions and intestinal parameters in the development of satiation in obese people.

Obesity has reached pandemic proportions, obesity-associated complications are extensive and the current treatment options are limited. These facts demonstrate the need for an improved understanding of the pathogenesis of obesity. The gastrointestinal tract plays a key element in the control of satiation; discrepancies exist, however, for the role of gastric and intestinal parameters in the control of satiation in relation to body mass. To achieve a comprehensive understanding for the reciprocal control between gastric functions and intestinal parameters in the development of satiation in obese people the investigators will compare satiation parameters, gastric emptying and plasma glucagon-like peptide-1 (GLP-1), peptide tyrosine tyrosine (PYY) and ghrelin levels between normal and obese healthy volunteers.

Time needed to reach the level of satiation and total calorie intake will be measured by a standardized nutrient drink test; gastric emptying of solids by a 13C-octanoic acid breath test; and plasma GLP-1, PYY and ghrelin levels will be measured after a standardized nutrient drink.

• Dietary Supplement: ensure plus
  17 % protein, 30 % fat and 53 % carbohydrate; 1 kcal/mL
• Dietary Supplement: standardized test meal
  scrambled eggs, two slices of whole wheat bread, 200 mL of milk and labeled with 13C-octanoic acid

• Active Comparator: satiation_obese weight
  Obese subjects will receive a complex nutrient drink (Ensure Plus; 17 % protein, 30 % fat and 53 % carbohydrate, 1 kcal/mL). Nutrient intake will be stopped when subjects had reached maximal or unbearable satiation; the time needed to reach the maximal level of satiation (tmax) and the quantity of volume drunk will be recorded and calorie intake calculated.
  Intervention: Dietary Supplement: ensure plus
• Active Comparator: gastric emptying_obese weight
  Obese subjects will receive a standardized meal, consisting of two scrambled eggs (cooked with 10 g butter), placed on two slices of whole wheat bread and 200 mL of milk (in total: 468 kcal). The test meal will be labeled with 100 mg of 13C-octanoic acid for determination of gastric emptying.
  Intervention: Dietary Supplement: standardized test meal
• Placebo Comparator: gastric emptying_normal weight
  Normal weight subjects will receive a standardized meal, consisting of two scrambled eggs (cooked with 10 g butter), placed on two slices of whole wheat bread and 200 mL of milk (in total: 468 kcal). The test meal will be labeled with 100 mg of 13C-octanoic acid for determination of gastric emptying.
  Intervention: Dietary Supplement: standardized test meal
• Placebo Comparator: satiation_normal weight
  Normal weight subjects will receive a complex nutrient drink (Ensure Plus; 17 % protein, 30 % fat and 53 % carbohydrate, 1 kcal/mL). Nutrient intake will be stopped when subjects had reached maximal or unbearable satiation; the time needed to reach the maximal level of satiation (tmax) and the quantity of volume drunk will be recorded and calorie intake calculated.
  Intervention: Dietary Supplement: ensure plus
• Active Comparator: hormone profiles_obese weight
  Obese subjects will receive 500 mL of a complex nutrient drink (Ensure Plus; 17 % protein, 30 % fat and 53 % carbohydrate). At regular time intervals fasting and post-prandial blood samples will be collected.
  Intervention: Dietary Supplement: ensure plus
• Placebo Comparator: hormone profiles_normal weight
  Normal weight subjects will receive 500 mL of a complex nutrient drink (Ensure Plus; 17 % protein, 30 % fat and 53 % carbohydrate). At regular time intervals fasting and post-prandial blood samples will be collected.
  Intervention: Dietary Supplement: ensure plus

Inclusion Criteria:

• healthy subjects
• age 18-45

Exclusion Criteria:

• smoking
• substance abuse
• regular intake of medication
• medical or psychiatric illness
• gastrointestinal disorders or food allergies