The Consumption of Beef on Appetite and Cognitive Function

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.

Eligibility Criteria:
Inclusion Criteria:

* Women
* Ages: 18-52 y
* BMI: 25-32 kg/m2
* No metabolic, hormonal, and/or neural conditions/diseases that influence metabolism, appetite, or cognition
* No blood donations to American Red Cross within past 6 months
* No medication that would influence directly appetite or cognition
* No change in any medications (over the past 3 months)
* Non-smoking (for the past year)
* Not pregnant within the past 6 months (or planning to become pregnant during study)
* Have not given birth and/or lactating within the past 6 months
* Normal menstrual cycles between 26-32 days in duration; 5 menstrual cycles within the past 6 months; or able to provide documentation of oral/hormonal contraceptive use which contains low-dose estrogen/progesterone to maintain continuous levels throughout the 28-day cycle (i.e., no placebos)
* Not clinically diagnosed with an eating disorder
* No weight loss/gain (≥10 lb. in the past 6 months)
* No past history of surgical interventions for the treatment of obesity
* No allergies and/or aversions to the study foods, particularly beef
* Consumes ≤ 800 mg caffeine/day
* Of this, ≤260 mg caffeine is consumed prior to lunch (\~12 oz. Starbucks coffee)
* Not currently and/or previously on a specific diet including high protein, vegan, vegetarian, etc.
* Willing and able to consume all study foods
* Habitually consumes breakfast, lunch, and dinner \>4 days/week
* No history of drug abuse or alcohol abuse (i.e., \>14 drinks/week; 1 drink=12 oz. beer; 5 oz. wine; 1.5 oz. liquor)
* Displays a score of \<4 on the Three Factor Eating Habits Questionnaire (TFEQ)
* Conventional (typical) and consistent sleep patterns
* awake hours somewhere between 5 am - 11 pm with no afternoon naps
* rates quality of sleep as Fairly to Very Good on the Pittsburg Sleep Quality Index (PSQI)
* averages ≥ 6 sleep hours/night over the past month
* Displays a Profile of Mood State 2nd Edition (POMS2; 60-item) Depression-Dejection Scale score within 1.5 SD of the age, gender, and racial-specific normative mean (Nyenhuis et al., 1999; Petterson K et al., 2006)
* Obtained a "Yes" on the validity indicator and displayed a score of \>70 (\>2%) on the CNS Vital Signs Battery
* Sedentary (i.e., limited purposeful physical activity)
* Willing and able to maintain current inactivity patterns throughout the study
* Willing and able to follow all study procedures
* Generally healthy, as assessed from the medical history questionnaire

Exclusion Criteria:

* Men
* Ages: \<18 or \>52 y
* BMI: \<25 or \>32 kg/m2
* Any metabolic, hormonal, and/or neural conditions/diseases that influence metabolism, appetite, or cognition
* Have donated blood to American Red Cross within past 6 months
* Medication that would influence directly appetite or cognition
* Change in medications (over the past 3 months)
* Have smoked in the past year
* Pregnant within the past 6 months (or planning to become pregnant during study)
* Have given birth and/or lactating within the past 6 months
* Abnormal menstrual cycles \[not between 26-32 days in duration; or not 5-6 menstrual cycles within the past 6 months; or not able to provide documentation of oral/hormonal contraceptive use which contains low-dose estrogen/progesterone to maintain continuous levels throughout the 28-day cycle (i.e., no placebos)\]
* Clinically diagnosed with an eating disorder
* Weight loss/gain (≥10 lb. in the past 6 months)
* Past history of surgical interventions for the treatment of obesity
* Allergies and/or aversions to the study foods, particularly beef
* Consumes \> 800 mg caffeine/day
* Or, of caffeine consumed, \>260 mg caffeine is consumed prior to lunch (\~12 oz. Starbucks coffee)
* Currently and/or previously on a specific diet including high protein, vegan, vegetarian, etc.
* Unwilling and/or unable to consume all study foods
* Habitually consumes breakfast, lunch, and dinner \<4 days/week
* History of drug abuse or alcohol abuse (i.e., \>14 drinks/week; 1 drink=12 oz. beer; 5 oz. wine; 1.5 oz. liquor)
* Displays a score of \>4 on the Three Factor Eating Habits Questionnaire (TFEQ)
* Unconventional (atypical) and/or inconsistent sleep patterns
* awake hours not somewhere between 5 am - 11 pm and/or afternoon naps
* does not rate quality of sleep as Fairly to Very Good on the Pittsburg Sleep Quality Index (PSQI)
* averages \< 6 sleep hours/night over the past month
* Does not display a Profile of Mood State 2nd Edition (POMS2; 60-item) Depression-Dejection Scale score within 1.5 SD of the age, gender, and racial-specific normative mean (Nyenhuis et al., 1999; Petterson K et al., 2006)
* Did not obtain a "Yes" on the validity indicator and/or did not display a score of \>70 (\>2%) on the CNS Vital Signs Battery
* Not sedentary (i.e., purposeful physical activity)
* Unwilling and/or unable to maintain current inactivity patterns throughout the study
* Unwilling and/or unable to follow all study procedures
* Not generally healthy, as assessed from the medical history questionnaire