Impact of Whey Protein Supplementation in a Weight-Loss Intervention in Rural Dwelling Adults: A Feasibility Study

Abstract

Background & Aims:

Weight loss in older adults enhances physical function, but may lead to sarcopenia and osteoporosis. Whey protein is a low cost rich source of essential amino acids, may improve physical function. We evaluated the feasibility and acceptability of consuming whey protein in the context of a weight-loss intervention in older adults with obesity.

Methods:

A 12-week pilot feasibility, non-randomized weight loss study of 28 older adults was conducted, consisting of individualized, weekly dietitian visits with twice weekly physical therapist-led group strengthening classes. Half consumed whey protein, three times weekly, following exercise. Preliminary efficacy measures of body composition, sit-to-stand, 6-minute walk and grip strength and subjective measures of self-reported health and function were also evaluated.

Results:

Of the 37 enrolled, 28 completed the study (50% in the protein group). Attendance rates for protein vs. non-protein groups were 89.9±11.1% vs. 95.6±3.4% (p=0.08). Protein consumption was high in those attending classes (90.3%) as was compliance at home (82.6%). Whey was pleasant (67.3±22.1, range 30-100, above average), had little aftertaste, and was neither salty or sticky. All were compliant (0.64±0.84, range 0-5, low = higher compliance). Both groups lost significant weight (protein vs. no protein, −3.45±2.86 vs. −5.79±3.08, p=0.47); Sit-to-stand, six-minute walk, and gait speed were no different, grip strength was improved in the protein compared to the non-protein group (−2.63 kg vs. 4.29 kg; p<0.001).

Conclusions:

Our results suggest that whey protein is a low-cost and readily available nutritional supplement that can be integrated into a weight loss intervention.

Introduction

The growing obesity epidemic affects over 40% of adults 65 years and older[1], and is associated with a higher risk of institutionalization[2], mortality[3], and costs[4]. Health promotion interventions in older adults, including weight loss, can enhance physical function and quality of life[5], but should be guided cautiously to prevent sarcopenia and osteoporosis[6] particularly in vulnerable older adults[7]. Energy deficits created by caloric reduction can lead to a downregulation of muscle protein synthesis and an increase in muscle proteolysis. This can contribute to reduced skeletal muscle mass which consequently may affect strength[8]. Sarcopenia developed during weight loss can threaten physical function and long-term health[9] but may be partially mitigated by increasing protein intake with a supplement. Additional protein may restore optimal anabolic signaling in aging.[10, 11] In addition, there may be an improvement in muscle parameters during resistance training.[12] through increased muscle protein synthesis.[13]

Whey protein, a milk-derived protein, contains essential amino acids and high quantities of branched-chain amino acids.[14] As a fast-acting protein, whey can stimulate post-prandial muscle protein synthesis more efficiently through faster digestion and quicker absorption[15] compared to casein or soy.[14] Increasing daily protein intake has been recommended for older adults, and may mitigate sarcopenia during weight-loss efforts in older adults.[16] Protein supplementation has been purported to enhance muscle mass and strength within the context of weight loss interventions.[17] It has been hypothesized that this may indeed improve physical function and preserve changes in body composition in behavior-based obesity treatments.[18]

Whey supplementation comes in tablet, liquid, or powder-based formulations. Older adults often are prescribed supplementation during unintentional weight loss or following an acute illness.[19] Palatability of supplementation is a key driver of compliance.[20] Hence, it is critical that the supplement within the context of a weight loss intervention is feasible, tolerable, and patient’s exhibit compliance prior to a large-scale clinical trial. Only then can the effectiveness of high-dose whey protein (>20g) be evaluated whether it can attenuate muscle catabolism. Our objective was: a) to ascertain the feasibility of providing whey protein supplementation during a 12-week weight loss intervention in older adults with obesity; b) determine the acceptability of consuming the supplement; and c) evaluate in an exploratory manner whether there were preliminary signals of efficacy between our comparison groups. This information can provide preliminary data prior to investing resources in conducting a large-scale trial evaluating the efficacy of such a supplement on changes in body composition or physical function observed with weight loss.

MATERIALS & METHODS

Study Design and Setting

We conducted a non-randomized study of older adults with obesity (body mass index [BMI] ≥30 kg/m²) residing in rural Northern New England. Dartmouth-Hitchcock is an academic medical center located on the New Hampshire and Vermont border, serving >1.5 million patients yearly. Study activities took place at a community-based aging center serving older adults. The study was approved by the Committee for the Protection of Human Subjects at Dartmouth College, the Dartmouth-Hitchcock Institutional Review Board, and the Institutional Review Board at the University of North Carolina at Chapel Hill, and registered on clinicaltrials.gov (NCT#03104192). Informed consent was obtained for experimentation with human subjects.

Intervention

A series of studies consisted of 6-8 participants at each time were conducted over an 18-month period. Briefly, each set of participants received a 12-week, on-site, diet and exercise intervention consisting of individual, weekly, 30-minute registered dietitian nutrition sessions, and twice-weekly, 75-minute physical therapist-based group exercise sessions based on the recommendations of the American College of Sports Medicine.[21] An individualized program consisting of resistance, flexibility and balance exercise plans were developed as previously described [22, 23]. All participants were provided a wearable fitness device (Fitbit Flex 2) and a Samsung Galaxy Tab A tablet to permit remote monitoring of their aerobic activity. Participants were evaluated weekly as to whether they completed a third session of resistance exercises weekly.

Recruitment

Participants were recruited from both primary care clinics and community settings as previously described.[22] Adults aged ≥ 65 years with a BMI ≥ 30kg/m² were eligible, but excluded if there was an electronic medical record diagnosis of dementia, uncontrolled psychiatric illness, bariatric surgery, life-threatening or end-of-life illness, participation in other weight-loss endeavors, on obesogenic medications, advanced systemic illness, or an intentional weight loss of ≥5% in the past six months. Information was also obtained from self-reported survey questionnaires. Participants required a score of ≥3 on the Callahan Cognitive questionnaire[24], and scores of ≥71.2 and ≥56.4 on the Functional Status questionnaire for basic and instrumental activities of daily living[25]. All 37 participants consented were compensated $25 for each assessment completed, of which 28 completed the intervention.

Whey Protein Supplementation

Half of the participants (n=14) were asked to consume one serving of a whey-protein based supplement (Thorne Whey Protein Isolate, Thorne Research, Dover, ID), consisting of a choice of 27g (vanilla) or 29g (chocolate) of whey, three times per week after each exercise session. The manufacturer’s label indicated 2.2g of leucine per serving. Two servings were consumed under direct supervision by the physical therapists during the in-person sessions, while the third dose was self-administered at home. The powder was constituted in 8 oz of water and consumed within 30 min of their exercise session. Participants were provided the protein on-site from the same flavored container; each was given an individual protein container for home use. Compliance was monitored using a self-report diary. No sham protein was provided to the non-protein group. The research team conducted an analysis using mass spectroscopy of the total protein and amino acid composition of all samples (MToZ-biolabs, Boston, MA). A standard protocol evaluated a branch chain amino acid analysis. [14, 26]

Study Outcomes

Our primary outcome was the feasibility and acceptability of whey protein consumption in the whey protein group. Drink characteristics of the whey supplement were rated on a 100-mm visual analogue scale[27], with anchors placed at 0 mm (not at all) and 100mm (extremely/extreme). Select questions from the Moriskey Medication Adherence Scale[28] scale were rated on a 0-5 Likert scale (low to high). Semi-structured interviews were related to the protein supplement and conducted by the lead author and coded independently by members of the team (See Supplementary Appendix #1). The purpose of these interviews was to gain insights into the consumption of the protein as part of this intervention.

Preliminary efficacy measures were based on physical function, weight and body composition measures using subjective and objective measures. Weight was measured using an A+D scale; height was assessed using a stadiometer. BMI was calculated using Quetelet’s formula. Waist circumference was measured at the level of the iliac crest using a standard tape measure. Physical function measures included gait speed, 5-times sit-to-stand test, and 6-minute walk test. A 5-m course permitted assessment of gait speed, with an acceleration/deceleration component. Three trials of grip strength in each had was measured using a JAMAR dynamometer. The maximum strength was used in the analysis. A 5-times sit-to-stand test was conducted using a standard chair with a back. Participants performed the test with their arms folded and their buttocks hitting the chair on each repetition. Surveys were administered using RedCAP with data double verified. The Patient Reported Outcome Measurement Information System (PROMIS) Global short form 10 function (physical and mental health) and the Function component of the Late-life Function and Disability Instrument were also posed to participants as in our previous studies[22, 23].

Body composition, including percent body and visceral fat, was assessed using the Seca mBCA bioelectrical impedance analyzer (Hamburg, Germany). This eight-point method uses a flow of low alternating current. Participants’ physical activity level (on 5 levels) was entered and they then stood barefoot for 20 seconds holding the hand electrodes. Appendicular lean mass (ALM) was defined as the sum of the upper and lower extremities and then normalized for both BMI and height (m²).

Statistical Analysis

A priori, we defined successful retention as a dropout rate <20%, and attendance rate of >75% of sessions as acceptable. Continuous variables are presented as means (standard deviation) or counts (percent). Paired t-tests compared pre/post characteristics within groups. We compared the pre-post change in each metric between participants in the whey protein group vs. the non-whey group using an unpaired t-test with unequal variances for continuous values, or chi-square for categorical variables. We used a mixed effects model clustering on the individual to examine the impact that protein supplementation had on the change in each metric of interest as an outcome while adjusting for baseline grip strength. The analysis was based on complete case ascertainment. A sensitivity analysis was also conducted adjusting for baseline grip strength. All quantitative analyses were conducted using R v3.6 (www.R-project.org). Interviews were transcribed using a commercial transcription service. Transcripts were read and open coding was conducted, a process of labeling portions of text to identify ideas and concepts. Codes were inductively- and deductively evaluated. A query tool retrieved text by code, which were reviewed for content, relevance and prevalence of themes. Qualitative data from the semi-structured interviews were evaluated using Dedoose. A p-value <0.05 was considered statistically significant.

RESULTS

There were 37 participants enrolled in both arms with 28 completing the study (Table 1). Other than smoking status, there were no differences in demographics between the protein vs. non-protein groups. In the protein (whey) group, our completion rate was 14/17 (82.4%). Mean attendance rates were 89.9±11.1% vs. 95.6±3.4% (p=0.08), in the protein vs. non-protein groups. Protein consumption was high in those attending classes (90.3%) as was self-report compliance of whey at home (82.6%). Eleven participants consumed chocolate whey and 6 chose vanilla whey. Mean total protein (g) in each serving was no different (9.51±1.41 vs. 9.94±0.75, p=0.70), and mean leucine concentration between chocolate and vanilla was statistically different (2.49±0.29 vs. 2.25±0.07, p=0.02). Table 2 highlights the questions on drink characteristics scale. The reconstituted whey drink was pleasant (67.3±22.1, range 30-100, interpretation of above average), had little aftertaste, and was neither salty, creamy thick, sticky or fruity. Participants exhibited good compliance with consuming the drink at home as they rated forgetting to take their whey at home as low (0.64±0.84, range 0-5, low to high). The protein was not perceived as an inconvenience to consume (0.57±1.16).

Table 1:

Study Participant Characteristics

	Protein (N=14)	No Protein (N=14)	p value
Age, years	72.9 (4.4)	73.0 (6.3)	0.94
Female Sex, %	12 (85.7)	11 (78.6)	0.62
White Race, %	14 (100.0)	14 (100.0)	1.00
Marital status, %
Single	0 (0.0)	0 (0.0)
Married	4 (28.6)	10 (71.4)
Divorced	9 (64.3)	3 (21.4)
Widowed	1 (7.1)	1 (7.1)
Insurance, %			0.44
Medicare	14 (100.0)	14 (100.0)
Private insurance	8 (57.1)	10 (71.4)
Smoking status, %			0.005
Non-smoker	6 (42.9)	13 (92.9)
Former smoker	8 (57.1)	1 (7.1)
Education, %			0.12
High school	2 (14.3)	0 (0.0)
Some college	5 (35.7)	3 (21.4)
College degree	3 (21.4)	5 (35.7)
Post-college degree	4 (28.6)	6 (42.9)
Drinks per week, %			0.54
None	6 (42.9)	7 (50.0)
1 to 5	7 (50.0)	6 (42.9)
6 to 10	0 (0.0)	1 (7.1)
11 to 15	1 (7.1)	0 (0.0)
Income, %			0.42
Less than $25,000	2 (14.3)	0 (0.0)
$25,000 to $49,999	9 (64.3)	9 (64.3)
$50,000 to $74,999	1 (7.1)	3 (21.4)
$75,000 to $99,999	1 (7.1)	1 (7.1)
$100,000 or more	1 (7.1)	1 (7.1)
Comorbidities, %
Anxiety	2 (14.3)	1 (7.1)	0.55
Coronary artery disease	1 (7.1)	2 (14.3)	0.55
COPD	1 (7.1)	0 (0.0)	0.32
Depression	3 (21.4)	3 (21.4)	1.00
Diabetes	3 (21.4)	2 (14.3)	0.63
Fibromyalgia	0 (0.0)	1 (7.1)	0.32
High cholesterol	5 (35.7)	4 (28.6)	0.69
Hypertension	7 (50.0)	7 (50.0)	1.00
Non skin cancer	1 (7.1)	0 (0.0)	0.32
Osteoarthritis	6 (42.9)	6 (42.9)	1.00
Rheumatologic disease	1 (7.1)	1 (7.1)	1.00
Sleep apnea	2 (14.3)	4 (28.6)	0.37

All variables are represented as mean (standard deviation) or counts (percent)

Abbreviations: BMI – body mass index; COPD – Chronic Obstructive Pulmonary Disease

Table 2:

Monteyne Whey Characteristics Scale

N = 14	Mean (SD)	Range	Range of Responses	Interpretation
How pleasant was the drink	67.3 (22.1)	30.0 - 100.0	Not at all, Extreme	Above Average
How much after taste did the drink have	37.3 (24.1)	4.0 - 83.0	None, a lot	Not much
How salty was the drink	11.0 (15.3)	0.0 - 54.0	Not at all, Extreme	Little
How creamy was the drink	29.1 (24.3)	0.0 - 85.0	Not at all, Extreme	Little
How thick was the drink	26.9 (22.8)	0.0 - 75.0	Not at all, Extreme	Little
How sticky was the drink	17.5 (17.7)	0.0 - 49.0	Not at all, Extreme	Little
How fruity was the drink	7.4 (10.2)	0.0 - 25.0	Not at all, Extreme	Little
How refreshing was the drink	38.0 (26.3)	0.0 - 78.0	Not at all, Extreme	Little

All values represented indicate mean (standard deviation), range, and the range of responses. The last column represents the interpretation of the scoring.

Key qualitative themes are represented in Table 3. Participants did not have any pre-conceived expectations of the suitability of the protein supplement and were unsure whether the protein helped them. It tasted better than expected and would consider using it again. All participants believed protein was critical in weight management and in preserving muscle. Reportedly, participants stated they consumed the whey on their non-person days as a result of their commitment to the study.

Table 3:

Select Quotations of The Whey Protein Supplement

Domain/ Theme	Representative Quote
Expectations of Protein Consumption	"Yes, it did because I used to take them on and off before and it does fill me up and when I'm on the run, it works out great."
	"I kind of thought maybe they would help. I wanted to see, and see if I noticed any difference. But of course it's hard to tell when you're increasing your exercise and doing other things, what's really helping. But it didn't hurt me any."
Characteristics of Whey Protein	"I thought it was great, the flavor of both. I had chocolate but I had tried the vanilla, they were both good. As long as it's cold and well-mixed I didn't find a problem with it whatsoever."
	"At first, I thought it tasted horrible. But then, I also discovered that you have to stir it quite a bit to get it so you don't have those little lumpy things. But once you got used to remembering that you had to take it each time after you exercise, it was okay."
Importance of Protein in Health	"I think some of them are helpful. In particular, when I wasn't eating as well as I am now. I think they were good, to make up for things that I wasn't getting.
	"Well I know that it's extremely important and it tells in the individual diet how much protein we should get per day. I've truly stuck with the plan too and done everything I should."

Table 4 reflects that both groups lost a significant amount of weight over time (protein vs. no protein, −3.45±2.86 vs. −5.79±3.08, p=0.47); however, those in the protein group lost less weight. No differences were observed in waist circumference. Neither group lost significant appendicular lean mass. In protein participants, there were no changes in body or visceral fat mass; between groups, this was statistically different. While both groups improved their sit-to-stand times, six-minute walk, and gait speed, grip strength was significantly improved in those consuming whey as compared to the non-protein group (−2.63 kg vs. 4.29 kg; p<0.001). Pre/post subjective measures of health and function improved in both groups, but no different from each other. We found minimal differences after adjusting for baseline grip strength.

Table 4:

Preliminary Efficacy of Functional and Body Composition Changes

	Protein (n=14)				No Protein (n=14)				Group	Adjusted
	Baseline	Week 12	Difference	p value	Baseline	Week 12	Difference	p value	p-value	p-value*
Anthropometrics
Weight, kg	98.0 (21.9)	94.6 (22.3)	−3.45 (2.86)	<0.001	98.7 (16.4)	92.9 (16.9)	−5.79 (3.08)	<0.001	0.047	0.047
Body Mass Index, kg/m2	37.6 (6.9)	36.3 (7.1)	−1.36 (1.09)	<0.001	36.6 (5.5)	34.5 (5.9)	−2.15 (1.18)	<0.001	0.075	0.08
Waist circumference, cm	124.3 (45.9)	109.5 (14.5)	−14.8 (45.5)	0.25	115.8 (10.4)	109.3 (10.3)	−6.45 (6.25)	0.002	0.030	0.03
Waist to hip ratio	0.88 (0.08)	0.89 (0.07)	0.02 (0.07)	0.42	0.92 (0.08)	0.92 (0.06)	−0.00 (0.04)	0.86	0.44	0.23
Body Composition
Appendicular lean mass, kg	12.4 (4.2)	12.1 (4.0)	−0.35 (0.64)	0.06	13.3 (2.8)	13.1 (2.9)	−0.17 (0.57)	0.30	0.44	0.44
Appendicular lean mass:height, kg/m2	4.69 (1.18)	4.57 (1.13)	−0.13 (0.24)	0.06	4.91 (0.87)	4.85 (0.88)	−0.06 (0.22)	0.30	0.47	0.46
Percent body fat, %	50.4 (5.1)	50.0 (5.0)	−0.46 (2.07)	0.42	46.9 (6.20)	45.0 (7.0)	−1.94 (1.62)	<0.001	0.046	0.045
Visceral Fat Mass, mL	3.99 (1.90)	3.96 (2.13)	−0.02 (0.81)	0.92	4.68 (1.55)	3.66 (1.51)	−1.02 (0.98)	0.002	0.007	0.007
Objective Measures
Sit to stand, seconds	10.39 (2.59)	7.78 (1.98)	−2.61 (2.18)	<0.001	9.14 (3.01)	7.63 (2.42)	−1.51 (1.72)	0.006	0.15	0.15
Grip strength, kg	17.9 (6.0)	22.2 (6.8)	4.29 (3.43)	<0.001	25.0 (8.7)	22.4 (7.7)	−2.63 (5.16)	0.08	<0.001	-
6-minute Walk Test, m	374.5 (89.8)	418.7 (74.5)	31.8 (27.8)	0.001	437.2 (79.7)	476.5 (93.3)	39.3 (51.6)	0.01	0.65	0.71
Gait speed, m/s	0.99 (0.23)	1.04 (0.27)	0.05 (0.21)	0.37	1.28 (0.15)	1.38 (0.20)	0.10 (0.15)	0.03	0.54	0.53
Subjective Functional Measures
PROMIS
Mental	49.3 (8.8)	53.4 (9.4)	3.48 (5.20)	0.03	49.6 (8.6)	56.0 (8.2)	6.41 (5.88)	0.001	0.18	0.20
Physical	46.6 (6.3)	49.3 (7.5)	2.27 (3.62)	0.04	50.8 (6.0)	57.2 (5.9)	6.44 (5.29)	<0.001	0.03	0.03
Late-Life Function & Disability Index
Total function score	59.4 (5.6)	62.1 (5.7)	2.72 (2.98)	0.005	62.9 (9.9)	69.0 (11.8)	6.13 (8.38)	0.02	0.17	0.16
Upper extremity domain score	79.5 (9.0)	79.4 (11.3)	−0.13 (6.78)	0.95	79.7 (12.6)	83.3 (11.7)	3.57 (11.98)	0.28	0.33	0.32
Basic lower extremity domain score	74.0 (13.3)	77.7 (11.0)	3.74 (10.73)	0.22	75.4 (14.4)	83.1 (15.0)	7.72 (9.73)	0.01	0.31	0.31

All values represented are means (Standard deviations). Baseline and week 12 aggregate scores are represented with the intra-group differences (and corresponding p-values using a paired t-test). Group p-value represents the differences between Protein and non-Protein groups.

Abbreviations: PROMIS: Patient Reported Outcomes Measurement Information Systems.

^*Adjusted for baseline grip strength

DISCUSSION

This study evaluating whey protein supplementation demonstrated its feasibility and acceptability. Using quantitative and qualitative data, we confirmed in a sample of 14 participants, that this supplement can be integrated in future health service interventions. Importantly, we also demonstrated preliminary efficacy of physical function measures.

Our data provides formative information to set the stage for a future trial. First, we had minimal number of dropouts in our protein cohort; this suggests that the supplement would not impact our approach and that interventionists could potentially focus on delivering a weight loss intervention rather than focusing on its palatability. Hence, we feel confident that we can proceed with a larger scale trial. Second, we have documented patient acceptability using standardized scales. Third, while whey protein supplementation physiologically is suggestive of maintaining muscle mass and strength in older adults, our results demonstrate a maintenance of appendicular lean mass. These findings approximated those found by others; however, whey was administered in exercise-only studies (following exercise) but had a higher protein dose (40g/day)[29] or only on exercise days[30] (e.g, three times weekly). Fourth, the added caloric intake from whey protein may blunt the degree of weight loss; it is unclear whether protein impacts satiety or meal consumption. Such findings need to be confirmed in larger scale studies.

A major concern at the beginning of the study was whether protein supplementation would be acceptable to participants. Our results suggest excellent compliance and tolerability which is similar to what was observed by others[27, 31]. Palatability is a key component for any type of intervention in that unpalatable items will lead to non-compliance. Our quantitative data also confirmed the quantitative findings. We believe that future studies should be generally confident of its acceptability.

Previous studies have demonstrated that multicomponent interventions consisting of caloric restriction and resistance/aerobic exercises have led to significant weight loss.[32, 33] The addition of whey protein in our study led to less weight loss and minimal changes in body or visceral fat. A number of reasons could explain these findings. First, the duration of treatment was short. Studies whose duration is three months have shown fewer changes in body composition[34]. Other studies last up to six months that demonstrated maintained muscle mass with accompanied improvements in muscle protein synthesis and muscle quality in the vastis lateralis[35], or reductions in intramuscular fat.[36] Second, it is unclear whether the functional status of our study population may have impacted our results. While we did not specifically incorporate the Short Physical Performance Battery as an outcome measure, our participants had a rather high level of physical function. Other authors have evaluated the impact of protein supplementation on higher risk, and more functionally impaired participants[37, 38]; yet these authors found conflicting findings on physical function using protein. Yet, our findings did not change after adjusting for baseline grip strength. Third, this was a pilot study that was not powered to evaluate the effect of our efficacy outcomes, and only a fully powered randomized controlled trial could evaluate such. Last, while not a randomized trial, our results also corroborated a study demonstrating the limited impact of protein consumption with exercise.[39]

Our intervention findings did not find any significant changes between groups over time between protein vs. non-protein groups on key measures of 5-times sit-to-stand, 6-minute walk and gait speed. The protein group had improvements in grip strength, but this was not evident in the non-protein group. The minimal differences in body composition between remained, even after we conducted a sensitivity analysis adjusted for baseline grip strength. These results suggest that the increase in strength at follow-up may be due more to gains in neuromuscular function as a result of the upper body exercises. Another possibility may have been the small statistically significant differences observed in leucine composition (0.24 g) amongst the different flavors provided; whether this is clinically significant is unclear. Importantly, other amino acids may have contributed to the differences in overall protein composition, but future studies are needed to confirm such findings. While we adhered to the Office of Dietary Supplement Product Integrity guide, the protein composition is standardized to what is available commercially. A recent systematic review and perspective statement by the Obesity Society in fact highlighted product integrity concerns among the manufacturer’s claims [40,41]. Our findings may also provide additional insights in the timing of protein supplementation since we provided this following exercise. Whether consumption at other times and/or with increased amount, concentration and/or frequency require further examination.

In our study, we increased the protein allowance to 1.0–1.5 g/kg/day or a minimum of 20% of total caloric intake.[19] Older adults are at risk of developing anabolic resistance due to reduced post-prandial amino acid availability, muscle perfusion, and uptake, and digestive capacity from splanchnic sequestration of amino acids[20]. The lower degree of weight loss in the whey group suggested that caloric restriction may need to be even further limited than previously expected, despite structured meal plans and instructions to reduce caloric (mainly fat) intake on the days that they consumed the supplement.

This study had a number of limitations. First, it was non-randomized. While we compared the baseline characteristics of the two cohorts, unknown confounders may impact our primary and secondary outcomes. Second, this was a small study of 14 participants in each cohorts. Only larger, adequately powered studies could better evaluate efficacy of protein supplementation. Third, our cohort was homogeneous and the effects of protein supplementation may differ depending on ethnic and racial cohorts. Fourth, while we used commercially available standardized methods to evaluate the protein composition as a quality control measure, we did find some differences in leucine composition. Last, the study failed to evaluate perceived strength or measure lower extremity strength; hence, we were unable to mitigate the discrepancy between observed and subjective changes in strength itself. Since supplements are not regulated by the Food and Drug Administration, we could consider the protein itself as a pragmatic, commercially available product, and understand that there may be limitations in its response or action.

Implications and Future Directions

Strategies to optimize protein anabolism during weight loss are needed to prevent negative changes in body composition[5, 6]. Our findings provide feasibility, acceptability and preliminary effectiveness data to conduct a large scale, adequately powered, randomized controlled trial comparing the effectiveness of a whey protein supplement within the context of a weight loss intervention in older adults. In such a trial, we would need to better oversee caloric restriction in the protein supplement group, extend the duration of the trial, and consider varying the protein supplement administration. If caloric intake was truly an issue, varying the administration schedule (e.g., twice weekly), timing (before exercise vs. after exercise), or amount (1/2 a serving vs. a full serving) could be considered. Importantly, whey did not have a negative impact on any of our subjective functional measures, nor on appendicular lean mass. Furthermore, emerging data suggests that lean mass is less important than loss of muscle strength and hence our findings confirm this potential finding.

ABBREVIATIONS

BMI

body mass index

PROMIS

Patient Reported Outcome Measurement Information System