The effects of whey and soy protein supplementation on appetite and dietary quality in overweight and obese college-aged individuals

Background: Over one-third of the United States population is obese. Obesity is a complicated disorder associated with many chronic diseases such as coronary artery disease, diabetes, hypertension and stroke. Many college students are overweight or obese, which may be due to lack of physical activity and unhealthy diets. Both dietary quality and satiety are important factors that may help modify obesity and associated health conditions. The impact of various interventions on these factors has not been clarified. Protein supplementation may be able to improve satiety, but research regarding improvement in diet quality in relation to this supplementation is limited. Objective: To determine the impact of an 8-week protein supplementation intervention on dietary quality and appetite by comparing groups supplemented with whey or soy protein with each other and with an assessment only control group. Methods: In a randomized, control trial with pre-post testing, subjects were randomized to one of three groups, whey protein, soy protein or non-treatment control. Experimental group subjects participated in 8 weeks of protein supplementation, and the control group received no treatment. Dietary quality and appetite were assessed at week 0 and week 8. The primary dietary quality outcome was total Alternate Healthy Eating Index (AHEI) score. The primary appetite outcomes were lab-assessed fasting hunger and satiety. Subjects assigned to the supplement groups were asked to ingest either the whey or the soy protein supplement, providing 21.5 grams of protein per day, on a daily basis for 8-weeks. All laboratory visits were conducted at the University of Rhode Island. Analysis of variance was used to compare within-group and between-group differences in dietary quality and satiety for pre and post measurements. Participants: Nine overweight and obese students (three per group) were recruited from the University of Rhode Island and surrounding areas through classroom announcements, fliers and mass emails. Results: There were no significant differences between the groups at baseline, although, based on the visual analog scales, the control group tended to have higher fasting hunger levels (control: 54.1±27.7mm, experimental: 35.5±26.1mm) and lower fasting satiety levels (control: 35.5±19.3mm, experimental: 56.0±26.5mm). The control group also had lower energy intake (control: 2428.4±1266.9kcal, experimental: 2838.3±1182.5kcal) and lower protein intake (control: 77.3±13.3g, experimental: 99.3±24.4g) based on three day food diaries, as well as higher diet quality (control: 44.0±6.6, experimental: 35.7±6.5) based on the total AHEI scores. No significant time by group or within group differences were found for AHEI scores or visual analog scales for hunger, satiety or appetite. During supplementation, the experimental groups consumed significantly more protein than the control group (experimental: 115.3±25.5 grams, control: 73.7±10.6grams, p=.033). Measures of satiety and hunger were not significantly impacted by the intervention. Conclusion: The addition of a protein supplement to the diet of overweight and obese young adults, with dietary counseling incorporated, did not improve diet quality or suppress fasting appetite. With a larger sample size, the effectiveness of this intervention may be measureable. Overall, this research gathered valuable information for use in interventions in the future.