Effect of Soy Protein and Polydextrose on Food Intake in Young Chinese Adult Males

The primary hypothesis of this study is that the higher concentration of soy protein intake will increase satiety and decrease the energy intake at the subsequent meal.

The secondary hypothesis is that the synergistic effect of soy protein and polydextrose will further increase satiety and reduce energy intake at the subsequent meal.

The third hypothesis is that the ingestion of protein and polydextrose will differentially impact on satiety-related metabolism, i.e. blood glucose, insulin, urea, plasma amino acids, gut hormones and gastric emptying.

Soy foods have been part of Asian food systems for millennia. In the past decades, both soy proteins and polydextrose have been widely used in a variety of food products. Helping consumers to feel less hungry is an approach to weight management because it has the potential to decrease inter-meal hunger and hence reduce overall energy intake. Considering the possible satiety effect of soy protein and polydextrose, inclusion of these molecules in the diet could therefore potentially reduce the energy intake and assist with weight management in order to attenuate the rise in obesity incidence globally. The study will provide data for the first time on how soy protein and soluble fiber impact on satiety and acute energy intake in those of Chinese ethnic origin. The research sets out to determine the effect of soy protein and polydextrose on satiety and food intake in Asians. It specifically attempts to comprehend the physiological mechanisms involving blood glucose, insulin, urea, plasma amino acids, gut hormones and the rate of gastric emptying of soy protein and polydextrose on appetite ratings, satiety and subsequent food intake. The study will recruit healthy young Chinese male, who will return for four test sessions on non-consecutive days. At each session, the subjects will be given a standard breakfast, followed 180 min later by a soybean curd preload and a buffet lunch 90 min after the preload. Four preloads will be tested: (1) low protein, (2) high protein, (3) low protein with polydextrose, and (4) high protein with polydextrose. Each soybean curd preload will be tested once by each subject. Blood samples from cannulated veins and fingerpricks will be collected before the preload, 15, 30, 45, 60, 75 and 90 min after the preload for the analysis of glucose, insulin, urea, plasma amino acids, and gut hormones. At the same time points as when blood samples collected, gastric emptying measurements will be carried out using ultrasound. Subjective motivational ratings for hunger, fullness, desire to eat and prospective food consumption will be measured by the use of visual analogue scales (VAS).

Inclusion Criteria:

• Males
• Chinese ethnicity
• Age between 21-40 years
• Body mass index (BMI) between 18-24 kg/m2
• Healthy
• Normal blood pressure (120/80 mm Hg)
• Fasting blood glucose < 6 mmol/L

Exclusion Criteria:

• Having eating disorders or conscious restriction of food intake
• Partaking in sports at the competitive and endurance levelsHaving allergies/ intolerances to the foods presented in the study
• Having metabolic diseases (diabetes, hypertension and the metabolic syndrome) or chronic gastrointestinal disorders
• Having regime diets (for medical or aesthetic reasons)
• Having medical conditions requiring prescription medication and taking medications known to affect appetite (steroids, sulphonylureas, antihistamines, antidepressants, amphetamines, hypoglycaemic agents and hormones).
• Smoking