Abstract
Background:
While intentional weight loss in older adults with obesity yields clinically important health benefits there is a need to minimize the negative effects of weight loss on concomitant loss of muscle mass and strength. Data show wearing weighted vests during exercise improves lean mass and lower extremity strength, however the efficacy of wearing a weighted vest during a period of weight loss to mitigate muscle and strength loss is not known.
Objectives:
This study examined the feasibility of daily weighted vest use during a dietary weight loss intervention, and examined effects of vest use on body composition and physical function in well-functioning older adults with obesity.
Design:
Randomized, controlled pilot study.
Setting:
Wake Forest Baptist Medical Center in Winston-Salem, NC.
Participants:
37 older (age=65–79 yrs), obese (BMI=30–40 kg/m2) sedentary men and women.
Interventions:
22-week behavioral diet intervention (targeting 10% weight loss, 1100–1300 kcals/day) with (Diet+Vest; n=20) or without (Diet; n=17) weighted vest use (goal of 10 hours/day with weight added weekly according to individual loss of body mass).
Measurements:
Body composition by dual-energy x-ray absorptiometry and measures of physical function, mobility, and muscle strength/power.
Results:
Average weighted vest use was 6.7±2.2 hours/day and the vest-wear goal of 10 hrs/day was achieved for 67±22% of total intervention days. Five participants reported adverse events from wearing the vest (all back pain or soreness). Both groups lost a similar amount of weight (Diet= −11.2±4.4 kg; Diet+Vest = −11.0±6.3 kg; p<0.001), with no differences between groups (p=0.25). Fat mass, lean mass, and % body fat decreased significantly (p<0.0001), with no differences between groups. Compared to Diet+Vest, the Diet intervention resulted in greater decreases in leg power (p<0.02), with no other between group differences in physical function.
Conclusion:
This pilot study showed that vest use during dietary weight loss is feasible and safe in well-functioning older adults with obesity. Larger studies are needed to definitively determine whether external replacement of lost weight during caloric restriction may preserve lower extremity muscle strength and power.
Keywords: Caloric restriction, weighted vest, body composition, physical function, weight loss
Introduction
More than one-third of adults in the U.S. over 60 years of age are considered to be obese (body mass index (BMI) ≥30 kg/m2) (1), setting the stage for an acceleration of age- and obesity-related diseases and disability (2, 3). Both obesity and aging are independent risk factors for metabolic disturbances such as dyslipidemia and insulin resistance (4), and elevated BMI in older adults is strongly associated with poor physical function and development of disability (5).
There is growing evidence that planned and supervised weight loss in older adults with obesity yields clinically important benefits in metabolic and physical function (6, 7). However, since aging is associated with a loss of muscle mass (sarcopenia), and weight loss results in loss of muscle in addition to fat loss, there may also be undesired effects of weight loss in older adults who are already at a heightened risk for sarcopenia and dynapenia (8, 9). Thus, there is a need to minimize the negative effects of weight loss, while enhancing its health advantages (10).
Obesity treatment guidelines recommend a comprehensive lifestyle program involving behavioral counseling, caloric restriction, and physical activity (11). In addition, exercise during weight loss in older adults is highly recommended to counteract the loss of muscle mass during weight loss; however, conventional exercise training often requires expensive equipment and, ideally, safety supervision by trained leaders. Moreover, the exercises performed are not always tolerated or sustained, especially in adults with obesity (12). Thus, there is a need to identify novel strategies that are easily adaptable to the environment in which older adults reside. As such, the purpose of this study was to assess the feasibility of daily use of a weighted vest, and to examine the effects of daily vest use on body composition and physical function in older adults undergoing diet-induced weight loss.
Methods
Study Design
This 22-week randomized, controlled pilot study (Clinicaltrials.gov; NCT02239939) assessed the feasibility of daily use of a progressively weighted vest and examined the effects of randomization to daily vest use (Diet + Vest, n=20), compared to no vest use (Diet, n=17) during weight loss in older men and women with obesity.
Participant Eligibility
Participants were recruited and enrolled based on the following criteria: 1) 65–79 yrs; 2) sedentary; 3) BMI of 30–40 kg/m2; 4) nonsmoking (<1 cigarette/d or 4/wk within yr); 5) weight stable (<5% weight change in the past 6 mo); 6) willing and able to consume meal replacement products; 7) without insulin-dependent or uncontrolled diabetes, evidence of clinical depression, cognitive impairment, uncontrolled endocrine/metabolic disease, neurological or hematological disease, fibromyalgia, rheumatoid arthritis, cancer, liver or renal disease, chronic pulmonary disease, uncontrolled hypertension, physical impairment (requiring dependency on a cane or walker, osteoporosis, hip fracture, joint replacement or spinal surgery within the last 6 months, or chronic severe back pain) or any contraindication for weight loss. The study was approved by the Wake Forest School of Medicine Institutional Review Board, and all participants provided written informed consent to participate.
A total of 330 individuals were screened by telephone to assess general eligibility. Of these, 56 were invited for in-person screening visits that involved measuring height and weight, a cognition screen (Montreal Cognitive Assessment), physical activity assessment (Physical Activity for the Elderly questionnaire (13)) to insure a sedentary lifestyle, and, if still eligible, a medical history, blood pressure check, and a review of medications. Qualifying participants (n=41) then completed a 3-day run-in period during which they were asked to wear the vest with no weights added, to consume the Medifast® meal replacement products used in the weight loss intervention, and to complete a food record. Four participants withdrew consent during the run-in. Thus, a total of 37 participants met all inclusion and exclusion criteria and were tested on study outcomes before being randomly assigned to an intervention group.
Interventions
Dietary weight loss intervention
All participants underwent a dietary weight-loss intervention, without a formal exercise program. Caloric deficit was achieved through a combination of meal replacements (MR), conventional foods, and weekly group nutrition/behavioral counseling sessions led by a Registered Dietitian (RD). Participants were instructed to follow the Medifast® 4 & 2 & 1 Plan®, estimated to provide 1100–1300 calories per day. This meal plan includes a total of 4 MR products, with the addition of 2 lean and green meals and 1 healthy snack. The lean and green meals were prepared by the participants and each consisted of 5–7 oz. lean protein, 3 servings of non-starchy
vegetables and up to 2 servings of healthy fat. The healthy snack consisted of one serving of fruit, dairy, or grain. The MR from Medifast® each contained 90–110 kcals and 11–15 g protein. The RD guided participants on their food choices and portion sizes and encouraged participants to consume only what was approved as part of the plan. Daily food logs were collected and reviewed weekly by the RD to verify compliance to the dietary intervention. Compliance was calculated by the RD (based on the self-reported food logs) as the percent of total calories consumed daily relative to the estimated number of calories prescribed (~1200). In addition, body weight was measured weekly to ensure participants were losing weight at a rate approximating their prescribed energy deficit.
Weighted vest intervention
Participants randomized to the weighted vest group (Diet+Vest) each received an appropriately sized vest (Hyper Vest PRO®, Austin, TX) for the duration of the intervention. The vest’s fabric and design fits comfortably under clothing, allowing for full range of motion and movement, and full chest expansion without restricting breathing. The vest firmly and evenly distributes the weight inserts over the body’s core; weights come in 1/8th pound increments.
Participants in this group were asked to wear the vest (under their shirts) on a daily basis, progressing to a goal of 10 hrs/day during the most active part of their day. Initially, no extra weight was added to the vest (vest weight alone is ~0.5 kg). The vest weight was then incrementally increased weekly according to each participant’s rate of weight loss. As body mass decreased, the weight of the vest was increased to replace the lost weight, up to a maximum amount of 15% of the participant’s baseline weight. Participants also kept a daily log to record the time worn, vest weight, and any problems related to vest use. Staff monitored and discussed these logs and participants’ vest use during the weekly group sessions.
Assessments
All assessments were conducted before and after the interventions. Post-intervention testing occurred during the last week of intervention; participants did not wear the vest during testing.
Body composition and circumferences
Height (Heightronic 235D stadiometer, QuickMedical, Issaquah, WA) and body mass (Detecto scale, Detecto, Webb City, MO) were measured without shoes or outer garments. Whole-body fat mass (FM), lean body mass (LM), and percentage of body fat (%FM) were measured using dual-energy X-ray absorptiometry (Delphi QDR; Hologic, Marlborough, MA). All scans were performed and analyzed by a trained and certified technician. Waist (minimal circumference) and hip (maximal gluteal protuberance) were measured in triplicate with a tape measure; average values are reported and waist-to-hip (WHR) ratio was calculated.
Physical function, mobility and strength
The expanded version of the short physical performance battery (ExSPPB) (12) was used to measure lower-extremity function. The ExSPPB consists of 5 repeated chair stands, standing balance (semi- and full-tandem stands and a single leg stand for 30 seconds), a 4-meter walk at usual pace, and a narrow 4-meter walk test of balance (walking at usual pace within lines of tape spaced 20 cm apart). The continuous scoring system ranges from 0 to 4 with higher scores indicative of better performance. Participants also completed a 400- meter walk (as fast as possible), which is a measure of aerobic endurance (14). The timed stair climb task assessed the time it took each participant to ascend a standard flight of stairs (12 steps).
Maximal isokinetic knee extensor strength (in Newton meters (Nm)) was measured with a dynamometer (Biodex Medical Systems Inc., Shirley, NY) with the participant sitting and the hips and knees flexed at 90°. Participants were asked to extend the knee and push as hard as possible against the resistance pad. The best of 3 trials was selected for each leg. Lower extremity muscle power was measured using the Nottingham Power Rig (15). Power was averaged for each leg following five trials at maximal effort.
Statistical analyses
All statistical analyses were performed with SPSS software (version 21). An α level of <0.05 was used to denote significance and all data were analyzed according to randomly assigned group. Baseline descriptive characteristics are reported as mean (±SDs) or frequencies (percentages). Univariate analyses of variance (ANOVAs) were performed to assess between-group differences at baseline. Within- group differences between baseline and follow-up values were determined using a paired t-test. Between-group differences for change values (baseline minus follow-up) were analyzed using ANCOVA with adjustment for baseline age, gender, race and baseline value of the outcome.
Results
Baseline characteristics, retention, and adherence
The mean age of the randomized participants was 70.1 ± 3 years, and mean BMI was 35.3 ± 2.9 kg/m2, with the majority of participants being female and white. Hypertension was the most prevalent comorbidity. No significant group differences were observed for baseline characteristics (Table 1).
Table 1.
Baseline demographic characteristics by treatment group
| Diet only N=17 |
Diet + Vest N=20 |
|
|---|---|---|
| Age (yrs) | 69.9±2.6 | 70.3±3.4 |
| Female, N (%) | 14 (82%) | 15 (75%) |
| White, N (%) | 13 (77%) | 16 (80%) |
| Education (> High School) | 17 (100%) | 20 (100%) |
| Weight (kg) | 94±12 | 99±11 |
| Height (cm) | 163±7 | 168±9 |
| BMI (kg/m2) | 35.3±3.0 | 35.3±2.8 |
| Systolic blood pressure (mmHg) | 134.4±7.7 | 146.4±16.9 |
| Diastolic blood pressure (mm Hg) | 72.3±9.7 | 72.8±10.7 |
| Self-reported comorbidity, No. (%) | ||
| Osteoarthritis 1 | 17 (100%) | 20 (100%) |
| Hypertension | 10 (59%) | 14 (70%) |
| Diabetes 2 | 2 (12%) | 2 (10%) |
| Sleep apnea | 6 (35%) | 7 (35%) |
| Osteopenia | 2 (12%) | 1 (5%) |
All data are Mean ± SD or # (%);
Self-reported physician diagnosed osteoarthritis;
Non-insulin-treated diabetes;
There were no significant differences (at P<0.05) between groups by using ANOVA
Thirty-three of the 37 randomized participants (89%) completed the study (returned for final data collection). Retention of participants was not different between groups (Diet: 88%; Diet+Vest: 90%). Compliance to the diet intervention was high and did not differ between groups (Diet: 100.3 ± 4.5%; Diet+Vest: 96.3 ± 14.6% of prescribed calories). Over the entire intervention, participants in the Diet+Vest group wore the vest for an average of 6.7 ± 2.2 hours/day (range of 2.0–9.9 hrs/day); only four participants wore the vest for an average of less than five hrs/day. The mean weight in the vest over the intervention period was 6.3±2.5 kg or 7.1±3.0% of baseline body weight. Overall, participants reported meeting the vest-wear goal of 10 hrs/day for 67±22% of the total intervention days. Five participants reported adverse events from wearing the vest (all back pain or soreness); two completely stopped wearing the vest (at weeks 19 and 20), two had interrupted vest use for 2–3 weeks during intervention but resumed vest use for the remainder of the study, and the other one was resolved by decreasing the amount of weight in the vest and not adding additional weight past week 11.
The participants in the Diet+Vest group completed a Satisfaction Survey to identify their comfort level and difficulty with wearing the vests during their daily life using a Likert Scale (1–5). These results are shown in Table 2, along with participant comments from an open text field regarding overall satisfaction with daily use of the weighted vest. The majority of participants reported at least some discomfort and some difficulty with putting the vest on, but the majority also reported their daily life was not impeded and little to no pain or soreness from the vest use.
Table 2.
Participant satisfaction survey results from Diet+Vest group (n=17)
| Likert Scale | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| How comfortable was it for you to wear the vest for extended periods of time? | Very Uncomfortable 3 | 7 | 3 | 3 | Very Comfortable 1 |
| How difficult was it for you to put on and take off the vest daily? | Very Difficult 1 | 10 | 2 | 1 | Very Easy 3 |
| Did the vest impede your daily lifestyle? | Very Impeding 2 | 5 | 1 | 7 | Not at all impeding 2 |
| Did you experience any pain or soreness from wearing the vest? | Very Painful 1 | 5 | 2 | 5 | No Pain or Soreness |
Participant Comments about Vest Use: “Got to the point if felt good to wear and helped posture”; “Not as bad as thought, except had back pain flare up”; “Uncomfortable when vest got heavier”; “Makes you realize your weight loss”; “Vest color was appealing/not as taxing as thought”; “Putting on vest was hardest part”; “Bought own vest to wear”
Intervention effects on weight and body composition
There were no group differences at baseline for body mass, circumferences, or body composition (Table 3). Both groups experienced similar and significant weight loss (Diet= −11.2±4.4 kg; 11.9% and Diet+Vest= −11.0±6.3 kg; 10.9%; both p<0.001 compared to baseline), with no difference between groups. Waist and hip circumferences significantly decreased in both groups with no difference between groups. WHR did not change in either group. FM, LM and %FM all decreased significantly (p<0.0001) in both groups, with no significant difference between groups.
Table 3.
Circumference measures and body composition at baseline and changes with intervention by study group
| Diet only (n=15) | Diet + Vest (n=18) | P-between groups | |||
|---|---|---|---|---|---|
| Baseline | Changes relative to baseline | Baseline | Changes relative to baseline | ||
| Body mass (kg) | 93.8 ±12.5 | −11.2 ± 4.4† | 100.7 ± 8.2 | −11.0 ± 6.3† | 0.254 |
| BMI (kg/m2) | 35.0 ± 3.0 | −4.1 ± 1.5† | 35.4 ± 2.6 | −3.8 ± 2.1† | 0.464 |
| Waist (cm) | 103.4 ± 11.4 | −7.1 ± 7.2* | 105.6 ± 9.9 | −7.0 ±7.2* | 0.595 |
| Hip (cm) | 117.4 ± 9.8 | −7.7 ± 3.9† | 120.5 ± 9.6 | −7.4 ± 4.3† | 0.315 |
| Waist to hip ratio | 0.89 ± 0.12 | −0.01 ± 0.05 | 0.88 ± 0.09 | −0.01 ± 0.04 | 0.817 |
| Fat mass (kg) | 43.2 ± 7.4 | −7.9 ± 3.2† | 46.3 ± 8.8 | −7.6 ± 4.5† | 0.255 |
| Body fat (%) | 46.2 ± 5.8 | −3.7 ± 1.9† | 45.7 ± 7.6 | −3.1 ± 2.1† | 0.314 |
| Lean mass (kg) | 48.6 ± 9.1 | −2.3 ± 1.9† | 52.3 ± 8.7 | −2.9 ± 1.6† | 0.795 |
All values are mean ± SD; BMI, body mass index; Compared to baseline within each group using paired t-test;
P<0.05;
P<0.0001; Between-group differences on the change values were analyzed with an ANCOVA, adjusted for age, gender, race and baseline value.
Intervention effects on physical function
Table 4 shows physical function and muscle strength by treatment group. Within the Diet group, usual gait speed (0.08 ± 0.10 m/sec) and ExSPPB score (0.15 ± 0.16) improved (p<0.05), whereas muscle power in the right (−11.4 ± 20.9 Watta) and left leg (−9.2 ± 15.2 Watts) decreased (p<0.05). Within the Diet+Vest group, usual gait speed improved (0.11 ± 0.10 m/sec; p<0.0001). Compared to Diet+Vest, Diet resulted in greater decreases in left and right leg power (p<0.05). There were no between group differences in the other measures of physical function.
Table 4.
Physical function variables at baseline and changes with intervention by study group
| Diet only (n=15) |
Diet + Vest (n=18) |
P-between groups | |
|---|---|---|---|
| 4-m gait speed (m/sec) | 0.98 ± 0.11 | 0.98 ± 0.13 | |
| Post | 1.06 ± 0.12 | 1.09 ± 0.10 | |
| Change | 0.08 ± 0.10* | 0.11 ± 0.10† | 0.383 |
| Chair rise time (sec) | 11.8 ± 2.23 | 12.8 ± 2.49 | |
| Post | 11.4 ± 2.05 | 12.4 ± 2.24 | |
| Change | −0.37 ±1.16 | −0.47 ± 1.81 | 0.523 |
| ExSPPB (score, 0–4) | 2.21 ± 0.37 | 2.28 ± 0.38 | |
| Post | 2.37 ± 0.26 | 2.38 ± 0.41 | |
| Change | 0.15 ± 0.16* | 0.10 ± 0.34 | 0.633 |
| Stair climb time (sec) | 7.94 ± 2.60 | 8.23 ± 3.11 | |
| Post | 7.90 ± 1.68 | 7.20 ± 1.34 | |
| Change | −0.04 ± 2.22 | −1.03 ± 2.87 | 0.151 |
| 400-m walk time (sec) | 318.5 ± 31.5 | 335.3 ± 37.1 | |
| Post | 319.7 ± 34.9 | 341.9 ± 43.9 | |
| Change | 1.27 ± 16.7 | 6.67 ± 55.0 | 0.294 |
| Leg Power in W (right) | 114.0 ± 43.2 | 128.0 ± 45.3 | |
| Post | 102.6 ± 37.9 | 130.5 ± 39.6 | |
| Change | −11.4 ± 20.9* | 2.5 ± 29.8 | 0.022 |
| Leg Power in W (left) | 114.1 ± 44.1 | 133.5 ± 58.0 | |
| Post | 104.9 ± 45.1 | 132.7 ± 49.4 | |
| Change | −9.2 ± 15.2* | −0.78 ± 22.1 | 0.007 |
| Leg Strength in Nm (right) | 84.7 ± 36.9 | 91.4 ± 28.1 | |
| Post | 79.3 ± 30.4 | 89.2 ± 24.5 | |
| Change | −5.1 ± 12.7 | −2.1 ± 15.5 | 0.287 |
| Leg Strength in Nm (left) | 80.7 ± 30.2 | 104.8 ± 35.4 | |
| Post | 78.6 ± 27.4 | 99.5 ± 31.5 | |
| Change | −2.2 ± 10.7 | −5.3 ± 12.1 | 0.590 |
All values are mean ± SD;ExSPPB, expanded short physical performance battery; Nm, Newton meters; W, Watts; Compared to baseline within each group using paired t-test:
P<0.05;
P<0.0001; Between-group differences on the change values were analyzed with an ANCOVA, adjusted for age, gender, race and baseline value.
Discussion
Results of this study suggest that external replacement of lost weight via daily use of a weighted vest during caloric restriction in well-functioning older adults with obesity is feasible and may have a beneficial impact on health outcomes. Overall, adherence to wearing the vest was good, with average vest wear time of over six hours per day and the daily goal of ten hours of vest use met on 2/3rds of intervention days. In this small pilot, vest use did not differentially affect decreases in body mass, fat mass or lean mass, but decreases in leg muscle power were attenuated with vest use.
Obesity is a strong predictor of limitations in physical function in older adults (16, 17), and weight loss with exercise results in improved function and mobility in this population (7, 18). In this study, both groups achieved a therapeutic level of weight loss (greater than 10% decrease), moving them close to the overweight BMI range. Weight loss of this magnitude is consistent with that observed in a previous study using meal replacements for weight loss in overweight/obese older adults (19), and is similar to the level of weight loss generally seen in even longer-term (12–18 month) caloric restriction studies in older adults (6, 7).
Even when combined with exercise and higher protein intake, weight loss naturally results in a loss of some muscle mass, in addition to fat loss (9, 20). The loss of muscle during weight loss is partially attributed to the decrease in mechanical stress as weight is reduced (21). Thus, enhancing gravitational load on muscle via weighted vest use during a period of caloric restriction could potentially diminish the amount of muscle lost for a given weight loss (22, 23). In this study, both groups lost a similar and significant amount of both fat and lean mass, with the majority of total weight lost being fat; however, the added mechanical load from the weighted vest did not result in greater preservation of lean mass in this small sample. This is contrary to findings from animal studies, where mechanisms regulating skeletal tissue structure and function responded in a similar fashion to increases in actual or externally added body mass (21, 24). Previous studies of older adults wearing a weighted vest, but just while exercising, did not examine effects on muscle mass per se (25–27), making it difficult to compare the changes in muscle mass we observed with results from other studies.
Conservation of muscle mass is a particularly important consideration for older adults as the age-related decreases in muscle strength and power are well characterized and associated with decreased functional capacity in this population. Very little research to date examined effects of weight loss on muscle strength and power in older adults (7). In this study, both groups maintained muscle strength, with no differences between groups. On the other hand, the weighted vest prevented declines in leg muscle power, suggesting this may be a safe and effective method for preserving and potentially improving muscle power during weight loss. These results are similar to a prior study by our group, where we found improved leg power, but not knee extensor strength in older women performing resistance training (RT) during caloric restriction compared to caloric restriction without RT (28).
The preservation of lower extremity muscle power we observed in the Diet+Vest group did not transfer into an improvement on power-related functional tasks such as rising from a chair or stair climbing. However, an interesting observation of our results, that is of relevance to the controversy surrounding promoting intentional weight loss in older adults, is that the caloric restriction alone (i.e. without a structured exercise regimen) which resulted in significant reductions in body mass and lean mass, did not negatively affect key measures of physical function, including chair rise time, global score of physical function (ExSPPB), stair climb time, or 400- meter walk time. In fact, both groups experienced significant improvements in usual gait speed, and the Diet group significantly improved ExSPPB scores. It should also be noted that the adults who volunteered for this study were all relatively high-functioning at baseline and it is not known whether similar results would be found in those with impaired function.
The results of this study need to be interpreted within the context that it was an exploratory pilot study with a relatively small number of participants who were well-functioning at baseline. However, the study provided important insights into the feasibility, practicality and compliance of using a weighted vest during a dietary weight loss intervention in older adults. While, on average, compliance to vest use was good, one- fourth of the participants in this group reported additional back pain and had to disrupt vest use or limit the amount of weight added. Future studies will need to examine the risk:benefit ratio of weighted vest use in this population of older adults with obesity.
In summary, diet-induced weight loss, with or without daily weighted vest use, produced significant decreases in body weight, fat and lean mass, without impacting physical function in older adults with obesity. Further, use of the vest during weight loss was feasible and safe and appears to help preserve lower extremity muscle power. The implication of these findings are that countering the decreased mechanical load with weight loss by externally replacing lost weight appears to be a promising approach to counteract some aging and obesity- associated conditions; however, future studies using a larger sample size are needed to confirm these findings.
Funding:
This work was supported by the Arthritis and Musculoskeletal Disease Research Center; Translational Science Center; and Center for Integrated Medicine at Wake Forest School of Medicine. These sponsors had no role in the design and conduct of the study, in the collection, analysis, and interpretation of data, or in the preparation of the manuscript. An in-kind product donation was made by Jason Pharmaceuticals, Inc., a wholly owned subsidiary of Medifast, Inc.
Footnotes
Conflict of Interest: The researchers do not hold a direct financial interest in the sponsors or the product being studied.
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