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Original Investigation

Observations of a Commercial Weight Loss Program on Physical Function and Selected CVD Risk Factors

Rogers, Renee J.1; Kovacs, Sara J.2; Collins, Katherine A.1; Raybuck, Shawn1; Collins, Audrey M.1; Marcin, Marissa L.1; Foster, Gary D.3,4; Jakicic, John M.1

Author Information
Translational Journal of the ACSM: Fall 2020 - Volume 5 - Issue 12 - e000137
doi: 10.1249/TJX.0000000000000137

Abstract

INTRODUCTION

Overweight (body mass index [BMI] ≥25 kg·m−2) and obesity (BMI ≥30 kg·m−2) continue to be of significant public health concern given their high prevalence and their association with numerous negative health outcomes (1–3). There is a higher prevalence of mortality (4) and morbidity (5,6) from chronic conditions associated with overweight and obesity, and individuals with overweight or obesity have a poorer cardiometabolic profile that includes blood lipids, blood pressure, and glucose control (5). Moreover, physical function has greater impairment at higher levels of BMI (7).

Behavioral interventions focused on reducing energy intake and increasing physical activity have resulted in significant weight loss (8). This weight loss has been shown to be associated with numerous health benefits. These include favorable benefits to cardiovascular disease risk factors such as improved blood lipids, reduced resting blood pressure, improved glucose control, and others (9). When weight loss is of sufficient magnitude, it has been shown to reduce onset of cardiovascular disease (10) and type 2 diabetes (11). In addition to cardiometabolic benefits, intentional weight loss has been shown to improve physical function such as mobility through improved walking (12).

Although these findings are promising, many of these have been in response to interventions that have been developed and implemented within the context of university- or hospital-based research settings (9,11,13,14). There are, however, widely available weight loss interventions that are developed and implemented outside of these university- or hospital-based research settings and have greater reach. It is important to evaluate the effectiveness of these programs for weight loss and other health benefits. Therefore, the purpose of this study is to report on observations of a widely available program on weight loss, selective cardiometabolic risk factors, and physical function (mobility and flexibility). Moreover, this study evaluated whether the observed responses were influenced by initial level of BMI, and whether the magnitude of weight loss was associated with greater health improvement.

METHODS

A video description of selective aspects of the study purpose and methods is provided in Supplemental Digital Content 1, http://links.lww.com/TJACSM/A111.

Study Design

Data were combined from two 6-month, single arm studies that were designed to evaluate a widely available weight management program (WW, formerly Weight Watchers). The studies involved common measures of demographic characteristics, physical function, and selective cardiometabolic risk factors. In addition, both interventions were 6 months in duration and used similar participant eligibility criteria.

Participants

A combined 300 adults were enrolled into the two studies (study 1: n = 150; study 2: n = 150) that were initiated between July 2015 and March 2017. Participants were recruited using postcard mailings, which were sent by postal carrier or e-mail, and university electronic advertisements that were sent to faculty and staff. The University of Pittsburgh Institutional Review Board and Human Research Protection Office approved all research procedures. All participants provided informed consent before participating in any research-related activities.

Both studies used common inclusion and exclusion criteria. Eligible participants were 18–75 yr with a BMI between 25 and 43 kg·m−2. Participants had to be willing to enroll in a WW program that included the use of a smartphone for intervention behavior tracking, with participants not incurring a cost to enroll in the program. Exclusion criteria included the following: 1) current participant or participating in a structured weight loss program within the previous 6 months; 2) weight loss of ≥5 kg in the previous 6 months; 3) pregnancy, nursing, or planning to become pregnant in the next 9 months; 4) history of a diagnosed eating disorder; 5) an orthopedic limitation preventing participation in regular physical activity; 6) untreated thyroid disease or change in thyroid medication in the previous 6 months; 7) taking any prescription medication with known effects on appetite or weight (stable doses of selective serotonin reuptake inhibitors for 6 months were permitted); 8) diuretic use for hypertension over 1.5 mg·d−1; 9) chronic inflammatory gastrointestinal disorders; 10) previous surgical procedure for weight loss; 11) major surgery within the previous 6 months; 12) uncontrolled hypertension of >160 mm Hg (systolic) and/or >100 mm Hg (diastolic); 13) history of cardiac problems within the previous 6 months; 14) diagnosis of type 1 or type 2 diabetes; 15) presence of implanted cardiac defibrillator or pacemaker; 16) current treatment for or history of cancer within past 5 yr; 17) consuming more than 14 alcoholic drinks per week or more than 3 drinks per day; and 18) planned relocation within 9 months.

Intervention

The interventions for both study 1 and study 2 were 6 months in duration and involved weekly group meetings focused on discussions around dietary change, physical activity, behavior strategies to facilitate these changes, and barriers that impede behavior change. Sessions were 30–45 min in duration and were facilitated by trained WW coaches. Sessions were held on one of four evenings per week. At the start of each session, participants had a private check-in with a WW coach. During this weekly check-in, participants had the opportunity to weigh themselves, reflect on their progress related to intake and activity goals, and set actionable next steps for the following week. The weekly group discussion began with celebrating member’s successes and problem-solving challenges over the past week. A new topic and technique focused on a skill related to weight loss, and behavior change was presented in didactic and interactive format. The session ended with coaches encouraging members to set one behavioral goal for the upcoming week, based on the weekly topic. Weekly topics were within one of the three WW program pillars that include food, physical activity, or mind-set. The investigators were not involved in the content or the delivery of any aspects of the intervention. However, a member of the research staff was onsite but not in the intervention space, which occurred in a University of Pittsburgh facility, to provide any logistical support should that be needed. Written materials were provided to supplement each weekly workshop, and participants used the WW mobile app to self-monitor diet, physical activity, and weight.

Each participant received a personalized energy deficit diet based on the WW Smartpoints™ system, which was determined by their sex, age, height, and weight calculated to create an energy deficit. SmartPoints is WW’s proprietary food system that assigns each food and drink a SmartPoints value based on the calories, saturated fat, sugar, and protein. The WW food system also guides participants toward a healthier pattern of eating, with more fruits, vegetables, lean proteins, and less saturated fat and sugar. Participants also received a personalized weekly physical activity goal, based on the WW FitPoints system, determined by their current activity level. FitPoints are earned based on the type, duration, and intensity of activity. The foundation of the physical activity recommendation is based on the 2008 Physical Activity Guidelines for Americans (the current guidelines when the interventions in this study were initiated) (15), and the WW activity system encouraged participants to regularly incorporate physical activity into their life. This also included the concept that all activity movement can contribute to energy expenditure and potential health benefits, and it encouraged participants to gradually build their activity level, try a variety of activities, and find ways of moving that they enjoy.

Although the majority of the components of the two weight loss weight loss interventions were similar, there were a few differences between the interventions. In study 1, participants utilized the WW SmartPoints™ program that assigns a point value based on calories, protein, and more unhealthy measures of saturated fat and sugar. In addition, fruits and vegetables are assigned a zero points value. By comparison, in study 2, SmartPoints™ were combined with a “special meal.” A special meal was a meal in which the participant was encouraged to eat this meal mindfully without the requirement to track the SmartPoints™ value of the meal. The special meal was earned by a participant consistently tracking their dietary intake in the WW mobile app.

Assessments

Outcome assessments were performed at baseline, 3 months, and 6 months. Assessments were conducted by research staff from the University of Pittsburgh. Again, the research staff were not involved in the delivery of the WW intervention.

Height was assessed using a wall-mounted stadiometer to the nearest 0.1 cm with duplicate measures different by ≤0.5 cm. Body weight was assessed using a calibrated digital scale to the nearest 0.1 kg with duplicate measures different by ≤0.5 kg. Weight and height were used to compute BMI (kg·m−2). Waist circumference was assessed over the skin at the level of the umbilicus and measured to the nearest 0.1 cm with duplicate measures differing by ≤1.0 cm using a Gulick tape measure. Resting blood pressure was assessed using an automated blood pressure cuff (DINAMAP V100) after a 5-min seated rest period, and heart rate was obtained by palpation of the radial pulse for 10 s.

Participants completed a 6-min walk test (16,17) performed on a designated 30-m length-walking course. The total distance walked and the mean gait speed during the 6 min walked were used for data analysis. Using a standardized script, participants were instructed to walk at a brisk pace for the duration of the 6 min. Participants were allowed to slow down, stop, or rest as necessary, but they were asked not to sit down or lean against the wall.

Flexibility was assessed using the YMCA sit and reach test (18). Using a yardstick anchored to the floor, participants were asked to sit with their legs extended and feet in dorsiflexion approximately 10–12 inches apart at the heel line. Participants were instructed to slowly stretch forward as far as possible sliding overlapped hands along the yardstick while keeping the knees extended, and participants were instructed to pause briefly at their maximal stretch to ensure proper recording of the distance (cm) of the stretch. This was performed three times, with a brief rest between each trial, with the highest score of the three trials used for data analysis.

Statistical Analysis

Data were analyzed using IBM SPSS Statistics software (version 24.0.0.0). Descriptive data were analyzed to compute mean ± SD for continuous data or to determine n (%) for categorical data (Table 1). Outcome measures were analyzed using repeated-measures ANOVA to examine changes across the intervention (baseline, 3 months, and 6 months) (Table 2). Additional analyses were completed using repeated-measures ANOVA to determine whether changes in outcome measures differed by initial BMI (25.0 to <30.0 kg·m−2, 30.0 to <35.0 kg·m−2, 35.0 to <40.0 kg·m−2, and ≥40.0 kg·m−2) (Table 3). Pearson correlation coefficients were computed to examine the associations between change in weight, BMI, and waist circumference with change in physical function, resting blood pressure, and resting heart rate (Table 4). Statistical significance for all analyses was a priori defined as P < 0.05. Given the small amount of missing data, with study data available on approximately 97% of the sample at both 3 and 6 months, only completer analyses were performed.

TABLE 1 - Baseline Demographic Characteristics of Study Participants.
Variable Study Baseline Characteristics for Participants Completing Baseline Assessments Baseline Characteristics for Participants Completing
3-Month Assessments
Baseline Characteristics for Participants Completing 6-Month Assessments
Participants, n (%) Combined 300 (100%) 291 (97.0%) 290 (96.7%)
Study 1 150 (100%) 144 (96.0%) 144 (96.0%)
Study 2 150 (100%) 147 (98.0%) 146 (97.3%)
Female, n (%) Combined 271 (90.0%) 262 (90.0%) 261 (90.0%)
Study 1 138 (92.0%) 132 (91.7%) 132 (91.7%)
Study 2 133 (88.7%) 130 (88.4%) 129 (88.4%)
Age (yr) a Combined 47.3 ± 12.6 47.3 ± 12.7 47.3 ± 12.7
Study 1 47.5 ± 12.8 47.5 ± 12.8 47.5 ± 12.8
Study 2 47.0 ± 12.6 47.1 ± 12.5 47.0 ± 12.6
Weight (kg) a Combined 90.1 ± 15.6 90.2 ± 15.6 90.1 ± 15.7
Study 1 91.9 ± 14.7 92.0 ± 14.6 91.9 ± 14.7
Study 2 88.3 ± 16.5 88.4 ± 16.4 88.3 ± 16.5
BMI (kg·m−2) a Combined 33.2 ± 4.4 33.2 ± 4.4 33.2 ± 4.4
Study 1 33.8 ± 4.3 33.9 ± 4.3 33.8 ± 4.3
Study 2 32.6 ± 4.5 32.6 ± 4.5 32.6 ± 4.5
Waist circumference (cm) a Combined 103.9 ± 11.7 103.9 ± 11.8 103.8 ± 11.8
Study 1 104.7 ± 11.3 104.9 ± 11.2 104.7 ± 11.3
Study 2 103.0 ± 12.3 103.0 ± 12.3 103.0 ± 12.3
Race, n (%) Caucasian or White Combined 247 (82.3%) 240 (82.5%) 238 (82.1%)
Study 1 113 (75.3%) 109 (75.7%) 108 (78.3%)
Study 2 134 (90.5%) 131 (89.1%) 130 (89.0%)
African American or Black Combined 41 (13.7%) 39 (13.4%) 40 (13.8%)
Study 1 29 (19.3%) 27 (18.8%) 28 (20.3%)
Study 2 12 (8.1%) 12 (8.2%) 12 (8.2%)
Asian Combined 3 (1.0%) 3 (1.0%) 3 (1.0%)
Study 1 1 (0.7%) 1 (0.7%) 1 (0.7%)
Study 2 2 (1.3%) 2 (1.4%) 2 (1.4%)
American Indian or Alaskan Native Combined 1 (0.3%) 1 (0.3%) 1 (0.3%)
Study 1 1 (0.7%) 1 (0.7%) 1 (0.7%)
Study 2 0 (0%) 0 (0%) 0 (0%)
Other Combined 8 (2.7%) 8 (2.7%) 8 (2.8%)
Study 1 6 (4.0%) 6 (4.2%) 6 (4.2%)
Study 2 2 (1.3%) 2 (1.4%) 2 (1.4%)
Hispanic or Latino, n (%) Combined 6 (2.0%) 6 (2.1%) 6 (2.1%)
Study 1 4 (2.7%) 4 (2.8%) 4 (2.8%)
Study 2 2 (1.3%) 2 (1.4%) 2 (1.4%)
Demographic characteristics did not differ by study.
a Mean ± SD.

TABLE 2 - Change in Outcomes by Intervention Study.
Variable n Intervention Assessment Periods P Values
Baseline 3 Months 6 Months Time Effect Study Effect Time–Study
Weight (kg) 288 Combined 90.1 ± 15.7 85.9 ± 15.6 85.1 ± 16.0 <0.001 0.002 <0.001
142 Study 1 91.9 ± 14.7 88.9 ± 15.0 89.0 ± 15.4
146 Study 2 88.3 ± 16.5 83.0 ± 15.7 81.4 ± 15.7
BMI (kg·m−2) 288 Combined 33.2 ± 4.4 31.7 ± 4.6 31.4 ± 4.7 <0.001 <0.001 <0.001
142 Study 1 33.8 ± 4.3 32.7 ± 4.5 32.7 ± 4.6
146 Study 2 32.6 ± 4.5 30.6 ± 4.4 30.0 ± 4.5
Waist circumference (cm) 288 Combined 103.8 ± 11.8 100.5 ± 11.8 99.0 ± 12.4 <0.001 0.002 <0.001
142 Study 1 104.7 ± 11.1 102.8 ± 10.8 102.3 ± 11.0
146 Study 2 103.0 ± 12.3 98.4 ± 12.3 95.8 ± 12.8
Systolic blood pressure (mm Hg) 287 Combined 123.0 ± 12.2 118.6 ± 11.7 119.7 ± 12.0 <0.001 <0.001 <0.001
141 Study 1 124.5 ± 11.9 122.7 ± 11.9 123.8 ± 12.3
146 Study 2 121.6 ± 12.3 114.7 ± 10.2 115.8 ± 10.2
Diastolic blood pressure (mm Hg) 287 Combined 71.1 ± 9.1 69.8 ± 9.1 71.1 ± 9.1 0.002 0.001 <0.001
141 Study 1 71.2 ± 9.8 71.9 ± 10.0 73.9 ± 9.2
146 Study 2 71.1 ± 8.5 67.8 ± 7.7 68.4 ± 8.2
Resting heart rate (bpm) 287 Combined 72.5 ± 10.6 68.0 ± 9.8 70.0 ± 10.7 <0.001 <0.001 0.268
141 Study 1 74.5 ± 11.2 70.3 ± 9.0 72.9 ± 10.1
146 Study 2 70.6 ± 9.6 65.8 ± 10.1 67.1 ± 10.6
Sit and reach (cm) 282 Combined 34.4 ± 11.3 37.2 ± 10.8 38.2 ± 10.8 <0.001 0.001 0.133
140 Study 1 32.1 ± 10.1 35.5 ± 9.9 35.8 ± 10.0
142 Study 2 36.6 ± 12.1 38.9 ± 11.3 40.5 ± 11.2
6-min walk distance (m) 280 Combined 511.6 ± 60.6 526.6 ± 60.8 537.0 ± 63.0 <0.001 <0.001 0.320
140 Study 1 496.6 ± 56.1 513.6 ± 55.7 520.6 ± 57.9
140 Study 2 526.6 ± 61.3 540.3 ± 63.0 553.4 ± 63.9
Gait speed (m·s−1) 280 Combined 1.42 ± 0.17 1.461 ± 0.17 1.49 ± 0.18 <0.001 <0.001 0.320
140 Study 1 1.38 ± 0.16 1.43 ± 0.15 1.45 ± 0.16
140 Study 2 1.46 ± 0.17 1.50 ± 0.17 1.54 ± 0.018

TABLE 3 - Change in Outcomes by Baseline BMI Category and Intervention.
Variable N Baseline BMI (kg·m −2 ) Assessment Periods P Values
Baseline 3 Months 6 Months Time Effect BMI Effect Time–BMI Time–BMI–Study
Weight (kg) 80 25 to <30 76.1 ± 6.6 72.0 ± 6.7 71.4 ± 7.7 <0.001 <0.001 0.026 0.022
110 30 to <35 84.4 ± 8.6 82.7 ± 9.4 81.2 ± 10.1
74 35 to <40 102.2 ± 12.0 97.7 ± 12.0 96.5 ± 12.8
24 ≥40 116.1 ± 13.9 110.6 ± 14.4 109.4 ± 15.7
Percent weight loss (%) 80 25 to <30 5.4 ± 4.0 6.1 ± 6.4 <0.001 <0.547 0.664 0.753
110 30 to <35 4.4 ± 4.2 5.0 ± 5.9
74 35 to <40 4.3 ± 3.9 5.5 ± 6.3
24 ≥40 4.8 ± 4.0 5.9 ± 6.1
BMI (kg·m−2) 80 25 to <30 28.2 ± 1.2 26.7 ± 1.6 26.4 ± 2.2 <0.001 <0.001 0.117 0.073
110 30 to <35 32.2 ± 1.5 30.7 ± 2.1 30.5 ± 2.5
74 35 to <40 37.4 ± 1.3 35.8 ± 2.0 35.4 ± 2.6
24 ≥40 41.7 ± 0.9 39.7 ± 2.0 39.3 ± 2.7
Waist circumference (cm) 80 25 to <30 92.6 ± 6.8 89.4 ± 7.0 87.8 ± 8.1 <0.001 <0.001 0.135 0.972
110 30 to <35 102.1 ± 6.4 99.2 ± 7.1 97.9 ± 8.1
74 35 to <40 112.6 ± 8.2 108.9 ± 8.7 107.2 ± 9.2
24 ≥40 122.4 ± 9.8 117.9 ± 10.2 116.3 ± 11.2
Systolic blood pressure (mm Hg) 79 25 to <30 119.1 ± 11.8 114.6 ± 10.1 115.5 ± 9.9 <0.001 <0.001 0.508 0.185
110 30 to <35 122.7 ± 11.0 118.8 ± 11.4 120.9 ± 11.7
74 35 to <40 125.4 ± 12.6 120.7 ± 11.2 120.5 ± 10.9
24 ≥40 130.3 ± 13.1 124.5 ± 15.8 125.7 ± 18.0
Diastolic blood pressure (mm Hg) 79 25 to <30 70.7 ± 9.5 68.9 ± 9.0 69.3 ± 8.7 0.006 0.735 0.233 0.895
110 30 to <35 70.6 ± 9.1 70.5 ± 8.9 71.9 ± 8.8
74 35 to <40 72.0 ± 8.8 69.3 ± 8.8 71.1 ± 9.1
24 ≥40 72.4 ± 9.3 71.6 ± 11.3 73.4 ± 10.8
Resting heart rate (bpm) 79 25 to <30 71.1 ± 10.1 67.7 ± 11.1 69.2 ± 11.2 <0.001 0.047 0.725 0.659
110 30 to <35 71.4 ± 10.7 66.7 ± 8.8 69.6 ± 10.3
74 35 to <40 73.7 ± 10.9 68.9 ± 9.4 70.2 ± 10.4
24 ≥40 77.9 ± 8.6 72.3 ± 10.0 73.3 ± 12.1
Sit and reach (cm) 79 25 to <30 37.9 ± 11.5 40.4 ± 11.6 41.4 ± 11.5 <0.001 0.006 0.495 0.695
107 30 to <35 34.5 ± 11.5 36.7 ± 10.4 37.9 ± 10.8
73 35 to <40 32.1 ± 10.0 35.9 ± 9.4 36.6 ± 9.2
23 ≥40 29.2 ± 10.5 32.9 ± 11.1 33.3 ± 12.0
6-min walk distance (m) 77 25 to <30 528.6 ± 58.6 542.9 ± 66.3 559.5 ± 64.6 <0.001 0.002 0.417 0.698
107 30 to <35 512.0 ± 59.9 530.1 ± 55.4 538.2 ± 59.7
73 35 to <40 503.0 ± 63.0 516.2 ± 60.1 522.5 ± 61.3
23 ≥40 480.3 ± 45.8 493.2 ± 51.3 502.1 ± 52.3
Gait speed (m·s−1) 77 25 to <30 4.47 ± 0.16 1.51 ± 0.18 1.55 ± 0.18 <0.001 0.002 0.417 0.698
107 30 to <35 1.42 ± 0.17 1.47 ± 0.15 1.49 ± 0.17
73 35 to <40 1.40 ± 0.17 1.43 ± 0.17 1.45 ± 0.17
23 ≥40 1.33 ± 0.13 1.37 ± 0.14 1.39 ± 0.15

TABLE 4 - Association between Change in Resting Blood Pressure, Resting Heart Rate, and Physical Function with Change in Weight, BMI, and Waist Circumference.
Change Variable Correlation with Change in Weight Correlation with Percent Change in Weight Correlation with Change in BMI Correlation with Change in Waist Circumference
Weight (kg) r = 0.984 r = 0.842
P < 0.001 P < 0.001
n = 290 n = 290
BMI (kg·m−2) r = 0.984 r = 0.977 r = 0.839
P < 0.001 P < 0.001 P < 0.001
n = 290 n = 290 n = 290
Waist circumference (cm) r = 0.842 r = 0.840 r = 0.839
P < 0.001 P < 0.001 P < 0.001
n = 290 n = 290 n = 290
Systolic blood pressure (mm Hg) r = 0.295 r = 0.281 r = 0.299 r = 0.274
P < 0.001 P < 0.001 P < 0.001 P < 0.001
n = 290 n = 290 n = 290 n = 290
Diastolic blood pressure (mm Hg) r = 0.296 r = 0.284 r = 0.309 r = 0.340
P < 0.001 P < 0.001 P < 0.001 P < 0.001
n = 290 n = 290 n = 290 n = 290
Resting heart rate (bpm) r = 0.320 r = 0.305 r = 0.312 r = 0.274
P < 0.001 P < 0.001 P < 0.001 P < 0.001
n = 290 n = 290 n = 290 n = 290
Sit and reach (cm) r = 0.210 r = 0.195 r = 0.213 r = 0.197
P < 0.001 P = 0.001 P < 0.001 P = 0.001
n = 285 n = 285 n = 285 n = 285
6-min walk distance (m) r = 0.284 r = 0.309 r = 0.291 r = 0.256
P < 0.001 P < 0.001 P < 0.001 P < 0.001
n = 283 n = 283 n = 283 n = 283
Gait speed (m·s−1) r = 0.284 r = 0.309 r = 0.291 r = 0.256
P < 0.001 P < 0.001 P < 0.001 P < 0.001
n = 283 n = 283 n = 283 n = 283

RESULTS

A video description of selective aspects of the study is provided in Supplemental Digital Content 1, http://links.lww.com/TJACSM/A111.

A total of 300 subjects were recruited across the two studies, with 150 in each study. The STROBE Diagram illustrating the participant flow through recruitment, assessments, and study completion is shown in Fig. 1. Demographic characteristics of subjects were similar across the two studies (Table 1), with the majority of participants being female (90.0%) and Caucasian (82.3%). The mean age and BMI were 47.3 ± 12.6 yr and 33.2 ± 4.4 kg·m−2, respectively. Study data were available on approximately 97% of the sample at both 3 and 6 months.

Figure 1
Figure 1:
STROBE diagram of participant recruitment and retention.

Weight, BMI, and Waist Circumference

Weight, BMI, and waist circumference data are shown in Table 2. There was significant weight loss of 4.2 ± 3.7 kg (4.7% ± 4.1%) and 4.9 ± 5.7 kg (5.5% ± 6.2%) at 3 and 6 months, respectively (P < 0.001). Similar patterns were observed for reduction in both BMI and waist circumference (Table 2). Participants were categorized based on meeting one of four percent weight loss criteria at 6 months that included the following: 1) weight loss ≥10% of baseline body weight, 2) weight loss 5% to <10% of baseline body weight, 3) weight loss 0% to <5% of baseline body weight, or 4) weight gain. Of the 291 participants providing weight data at 6 months, 22.8%, 26.2%, 33.1%, and 17.9% were in these four categories of percent weight change, respectively.

Data were also analyzed to examine if the magnitude of change in weight, percent weight loss, BMI, or waist circumference differed by initial BMI (Table 3). As expected, based on BMI categorization, there was a difference between the BMI categories for weight, BMI, and waist circumference (P < 0.001). The pattern of weight change differed by BMI category (P value for time–BMI effect = 0.026) with higher weight loss achieved at higher levels of baseline BMI; however, change in BMI and waist circumference did not differ by BMI category (P values for time–BMI effect = 0.117 and 0.135, respectively). Percent weight loss did not differ by baseline BMI category.

Physical Function

Data for change in measures of physical function are presented in Table 2. There were improvements in sit and reach, 6-min walk distance, and gait speed (P < 0.001) in response to the 6-month interventions. Data were also analyzed to examine if the magnitude of change in measure of physical function differed by initial BMI category (Table 3). With increasing level of baseline BMI, there was a lower score for sit and reach (P = 0.006), walking distance (P = 0.002), and gait speed (P = 0.002). However, the measures of physical function improved across the 6-month interventions, and the pattern of improvement did not differ by baseline BMI category (P values for time–BMI effect: sit and reach = 0.495, walk distance = 0.417, and gait speed = 0.417). There were significant and modest associations between change in weight and sit and reach (r = 0.210, P < 0.001), walking distance (r = 0.284, P < 0.001), and gait speed (r = 0.284, P < 0.001). Similar associations were observed for change in sit and reach, walking distance, and gait speed with change in BMI and waist circumference (see Table 4).

Resting Blood Pressure and Heart Rate

Data for change in resting blood pressure and resting heart rate are presented in Table 2. Overall, there were reductions in resting blood pressure and heart rate. Data were also analyzed to examine if the magnitude of change in resting blood pressure and heart rate differed by initial BMI category (Table 3). Resting systolic blood pressure (P < 0.001) and heart rate (P = 0.047) were greater with higher baseline BMI, but resting diastolic blood pressure did not differ by BMI category (P = 0.735). Although there was a significant reduction in resting systolic blood pressure, diastolic blood pressure, and heart rate across the interventions, the change in resting blood pressure and heart rate did not differ by baseline BMI category (P values for time–BMI effect = 0.508, 0.233, and 0.725, respectively). We also conducted analysis with participants stratified by baseline resting systolic blood pressure (<120, 120 to <140, and >140 mm Hg) and by baseline resting diastolic blood pressure (<80 and >80 mm Hg), with results showing a greater reduction for both outcomes with higher baseline values (data not shown).

Associations between change in resting blood pressure and heart rate with change in weight, BMI, and waist circumference are presented in Table 4. There were significant and modest associations between change in weight and change in systolic blood pressure (r = 0.295, P < 0.001), diastolic blood pressure (r = 0.296, P < 0.001), and heart rate (r = 0.320, P < 0.001). Similar associations were observed for resting systolic blood pressure, diastolic blood pressure, and heart rate with change in BMI and waist circumference (see Table 4).

DISCUSSION

The 2013 clinical guidelines outline components of a behavioral intervention to elicit weight loss; however, the majority of studies contributing to the scientific evidence base were conducted in university- or hospital-based settings (5). The reach of commercial weight loss programs is likely greater than specialty clinics, and the programs have been shown to be effective for weight loss compared with control or education alone conditions (19). However, few studies of commercial programs report results beyond the effects on weight and some cardiovascular disease risk factors (e.g., blood pressure and serum values). This study reports on observations from a widely available weight management program (WW) primarily on change in physical function, with resting blood pressure and heart rate also being examined. Results showed that participants in this program had a mean weight loss of 4.9% across the 6-month interventions, and there were also concomitant reductions in BMI and waist circumference. The magnitude of weight loss observed is within the range (3.6%–7.3%) of that observed in other 6-month clinical trials of the WW program (20–22). Although weight loss interventions conducted within university-based research settings produce greater weight losses (approximately 8%–10% over 6 months) (8), they may also do so with higher cost that more broadly available commercial programs due to smaller group sizes and specialized providers (23). Of importance, the reductions in body weight observed in this study may have been sufficient to confer improvements in functional outcomes, resting blood pressure, and resting heart rate.

Although it has been demonstrated that adults with greater levels of obesity have poorer physical functioning (7,24) these outcomes have not been evaluated in commercial programs. One aspect of physical function that was improved was low back and hip flexibility as measured by the sit and reach test. This improvement may need to be interpreted with caution given that the intervention did not necessarily target these specific parameters. Rather, one potential explanation for this improvement may be the reduction in waist circumference, which may allow for greater mobility of the trunk and hips. Regardless of the mechanism by which low back and hip flexibility improved, this improvement may facilitate engagement in activities of daily living in adults, such as bending over to tie shoes, picking items off the floor, and others that may affect quality of life.

There was also significant improvement in 6-min walk distance and gait speed across the 6-month intervention. At baseline, participants walked approximately 512 m in 6 min (1.42 m·s−1), which is comparable with that reported by Larsson et al. (17) and Hergenroeder et al. (7) in observational samples of patients with overweight and obesity. Hergenroeder and colleagues (7) also demonstrated significant differences in gait speed by weight class with those at a higher BMI walking at a slower gait speed, and this current study demonstrated a similar pattern of results at baseline. Although the improvement in distance traveled during the 6-min walk improved across all BMI strata in this study, those individuals with the lowest BMI at baseline had the greatest function both before and after weight loss compared with those individuals at higher levels of BMI. However, the mean improvement in walking distance observed after 6 months of treatment was approximately 20–30 m, which is less than the suggested clinically meaningful threshold of an 80-m improvement in walking distance (17). Moreover, this is less than the improvement observed in studies that have elicited greater weight loss than what was observed in this study (25), and these studies have also suggested that other factors such as pain may contribute to walking distance during the 6-min walk test (25). Other studies have also demonstrated that exercise contributes to 6-min walk performance in adults with obesity (26). Thus, potentially targeting this aspect of physical function, eliciting greater weight loss, placing an increased focused on exercise, and incorporating pain management within the context of a clinical weight loss program may be necessary to elicit greater functional improvements.

There are a number of strengths of this study. This includes the relatively large sample (N = 300) and high retention rate (96.7%) at 6 months. The intervention was delivered independent of the research staff, and the research staff conducted the evaluation of this commercial program, which allowed for an independent evaluation of this program. In addition, this study includes measures of physical function, which are unique outcomes within the context of a commercial weight loss program.

There were also limitations to this study. Two studies of a commercial weight loss program were combined for the analyses presented, and differences in weight loss between these studies were observed, which may have influenced the findings presented. However, given that neither of these studies used a randomized design, it is possible that any differences observed between these two studies were by chance rather than representing a true statistical difference, and this warrants consideration. The lack of a control or comparison group may limit the ability of these findings to provide definitive results. The commercial weight loss program was also offered to all participants free of charge, which may have influenced the recruitment of participants, and the characteristics of participants in this study may not fully reflect the participant characteristics of individuals who typically enroll in this commercial weight management program. This study also recruited primarily Caucasian women, which may limit the generalizability of these findings to individuals of a different sex, race, or ethnicity. The observations in this study are limited to individuals within a BMI range of 25 to 43 kg·m−2 based on inclusion criteria. The intervention was also 6 months in duration, and therefore it is unclear how longer duration exposure to the intervention may influence weight loss and other health-related benefits. The intervention includes a proprietary smartphone App developed by WW, and data on the use of this App the information collected within it were not made available to the researchers. Moreover, additional measures of diet and nutrition, physical activity, or other behavioral factors that may have influenced the weight loss observed were not included in this study. Future studies of commercial programs may need to consider these limitations in their design and implementation.

An interesting observation is that approximately 18% of the sample providing data at 6 months demonstrated weight gain compared with their baseline weight. By comparison, based on the examination of unpublished data from our laboratory in which 340 adults engaged in a recently completed in-person group-based behavioral weight loss intervention, similar to the type of intervention implemented in this study, we observed that approximately 5% of the sample gained weight at 6 months. If we were to assume that the 43 participants who initiated the intervention but did not provide weight data at 6 months gained weight, this would increase to 16%. This demonstrates that not all individuals will lose weight in response to these behavioral programs, whether they are delivered through a commercial program or a university-based research program, and therefore will not experience the potential health benefits of weight loss. It is important to understand this lack of weight loss to understand reasons for this lack of reason and to identify individuals who may not benefit from these programs.

In summary, the unique findings of this study are that there were significant improvements observed in measures of physical function in participants in a widely available commercial weight loss program, which may positively affect the ability of patients with obesity to engage in common activities of daily living. This finding expands the scientific literature of observed changes in body weight, BMI, and waist circumference and other cardiometabolic risk factors in participants engaged in a commercial weight loss program. Moreover, these improvements are observed, regardless of initial level of BMI and can be observed within a period of 3–6 months. Given these findings, commercial weight loss programs that possess characteristics of the interventions implemented in this study may result in weight loss that is associated with improvements in health outcomes, which includes improvements in physical function.

The authors acknowledge the contributions of the staff and students at the Healthy Lifestyle Institute for their work on the two trials that contributed to this manuscript. Results of the present study do not constitute endorsement by the American College of Sports Medicine.

Both studies that contributed data to this manuscript were supported by research grants from Weight Watchers International, Inc. awarded to the University of Pittsburgh. The funder (WW, formerly Weight Watchers International, Inc.) developed and implemented the interventions and was involved in decisions regarding measures to include in the studies; however, the recruitment of participants, data collection, and statistical analysis were performed by the investigators without involvement of the funder.

Renee J. Rogers, Ph.D., received funding as the principal investigator for WW (formerly Weight Watchers International, Inc.) to conduct this study with the funding awarded to the University of Pittsburgh.

Sara J. Kovacs, Ph.D.; Katherine A. Collins, Ph.D.; Shawn Raybuck, M.S.; Audrey M. Collins, M.S.; and Marissa L. Marcin, M.S. have no disclosures to report.

Gary Foster, Ph.D., is Chief Science Officer at WW (formerly Weight Watchers International, Inc.). Dr. Foster was not involved with implementation of the interventions or assessment of outcomes in this study. Dr. Foster had input on the study design and assisted with manuscript preparation.

John M. Jakicic, Ph.D., is a member of the scientific advisory board for WW (formerly Weight Watchers International, Inc.). Dr. Jakicic was not involved with implementation of the interventions or assessment of outcomes in this study. Dr. Jakicic served as an advisor to Dr. Rogers during the conduct of this study and assisted with data analysis and manuscript preparation.

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