The purpose of the main study is to determine whether the daily consumption of protein-rich meals containing high quality, lean beef products improves appetite control and cognitive function during a weight maintenance diet. The purpose of the sub-study is to determine whether the daily consumption of protein-rich meals containing the same amount of high quality, lean beef products improves appetite control and cognitive function during a modest energy restriction, weight loss diet.
Two cross-over design studies were completed in overweight, sedentary but otherwise healthy women. For study 1, 17 participants randomly consumed 4 eucaloric diets containing standard-protein (SP; 76±1g protein/d) or high-protein (HP; 126±1g protein/d) for 7 consecutive days/treatment. The SP treatments contained all plant proteins (PLANT) or a combination of beef and plant proteins (BEEF) that were evenly distributed throughout the day (EVEN). The HP treatments were also BEEF provided as EVEN or an uneven distribution (UNEVEN) pattern. For study 2, 17 participants randomly consumed 3 energy restriction (1250 kcal/d) diets containing SP-PLANT (EVEN) and SP-BEEF (EVEN) (both, 48±1g protein/d) or HP-BEEF (EVEN) (123±1g protein/d). During day 6 of each treatment (for both studies), the participants completed a 12-h controlled-feeding, clinical testing day which included repeated appetite, satiety, food cravings, and mood questionnaires; blood sampling; and cognitive function/performance testing. During day 7 of each treatment (for both studies), the participants completed a free-living, ad libitum testing day at home/work to assess ad libitum (voluntary) daily intake and food choice. Each of the 7-day dietary patterns occurred during the follicular phase of the menstrual cycle; thus, there were 2-3 week washout periods between dietary treatments.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
SINGLE
Enrollment
Diet contains all plant proteins. Meals are evenly distributed throughout the day.
Diet contains combination of beef and plant proteins. Meals are evenly distributed throughout the day.
Diet contains combination of beef and plant proteins. Meals are evenly distributed throughout the day.
Daily Energy Intake: Total Daily Intake
Energy intake during breakfast, lunch, dinner, and evening snacks of each day 7 testing day (separated by 3-4 weeks) will be measured.
Time frame: 5 months
Perceived Fullness
Questionnaires assessing fullness will be completed throughout each of the 12-hour testing days (which are separated by 3-4 weeks). The questionnaires contain validated visual analog scales (VAS) incorporating a 100 mm horizontal line rating scale for each response. The scale is 0 to 100mm. The questions are worded in the following manner "how strong is your feeling of" with anchors of "not at all" (indicated at 0 mm) to "extremely" (indicated at 100 mm). All measures are reported at area under the curve for 0 to 630 min.
Time frame: 5 months
Reaction Time as a Measure of Cognitive Performance Assessed Using the Stroop Test
Cognitive function will be assessed during each of the 12-hour testing days using CNS Vital Signs, a validated computerized assessment. This system contains a core battery of tasks. Reaction Time is the outcome of interest measured with the Stroop Test. In the first part, the words RED, YELLOW, BLUE, \& GREEN (printed in black) appear at random on the screen, \& the participant presses the space bar as soon as the test subject sees the word. In the second part, the words RED, YELLOW, BLUE, \& GREEN appear on the screen, printed in color. The participant is asked to press the space bar when the color of the word matches what the word says. In the third part, the words RED, YELLOW, BLUE, \& GREEN appear on the screen, printed in color. The participant is asked to press the space bar when the color of the word does not match what the word says. Reaction time is in milliseconds.
Time frame: 5 months
Perceived Alertness
Alertness will be assessed during each of the 12-hour testing days (which are separated by 3-4 weeks) using the Profile of Mood States 2nd Edition (POMS2) with sub-categories of perceived vigor. POM2 is a self-report measure that allows for the quick assessment of transient, fluctuating feelings, and enduring affect states. There are 35 items. Items are rated on a 5-point Likert scale ranging from 0 (not at all) to 4 (extremely). The Alertness (Vigor-Activity) scale score indicates the extent to which individual felt alert (vigorous and/or energetic); the higher are her positive feelings and/or energy, the greater is her score (i.e., a low score indicates relatively fewer positive feelings and/or low energy). Ratings on this scale yielded a T-score of 25 (95% CI =18-32), which is ranked at the 1st percentile, and falls within the Very Low score range. The T scores were then used to calculate area under the curve.
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Diet contains combination of beef and plant proteins. Meals are unevenly distributed throughout the day.
Time frame: 5 months
Perceived Hunger
Questionnaires assessing hunger will be completed throughout each of the 12-hour testing days (which are separated by 3-4 weeks). The questionnaires contain validated visual analog scales (VAS) incorporating a 100 mm horizontal line rating scale for each response. The scale is 0 to 100mm. The questions are worded in the following manner "how strong is your feeling of" with anchors of "not at all" (indicated at 0 mm) to "extremely" (indicated at 100 mm). All measures are reported at area under the curve for 0 to 630 min.
Time frame: 5 months
Perceived Prospective Food Consumption
Questionnaires assessing prospective food consumption will be completed throughout each of the 12-hour testing days (which are separated by 3-4 weeks). The questionnaires contain validated visual analog scales (VAS) incorporating a 100 mm horizontal line rating scale for each response. The scale is 0 to 100mm. The questions are worded in the following manner "how strong is your feeling of" with anchors of "not at all" (indicated at 0 mm) to "extremely" (indicated at 100 mm). All measures are reported at area under the curve for 0 to 630 min.
Time frame: 5 months
Perceived Desire to Eat
Questionnaires assessing desire to eat will be completed throughout each of the 12-hour testing days (which are separated by 3-4 weeks). The questionnaires contain validated visual analog scales (VAS) incorporating a 100 mm horizontal line rating scale for each response. The scale is 0 to 100mm. The questions are worded in the following manner "how strong is your feeling of" with anchors of "not at all" (indicated at 0 mm) to "extremely" (indicated at 100 mm). All measures are reported at area under the curve for 0 to 630 min.
Time frame: 5 months