A comparative controlled trial comparing the effects of yoga and walking for overweight and obese adults

Background

The prevalence of obesity and metabolic syndrome are increasing in India and other South Asian countries [1]. Weight reduction can be achieved by several methods of varying degrees of usefulness [2], particularly high levels of physical activity [3,4] and a change in the attitude towards food choices [5,6]. Two methods compared in the present study are walking and yoga, due to their increasing popularity and relative safety when supervised [7,8]. The effects of these 2 methods individually are described below.

Participation in an organized walking program for 2 months significantly improved anthropometric variables, BMI, body weight, percent body fat, fat mass, lean mass, and lipid profile in participants with bulimia nervosa [9] and in those with cardiac disease [10].

The effects of walking have also been studied in obese persons of different age groups. Twenty-seven obese middle school girls, allocated to a walking group and a control group, showed significant differences in the waist circumference, triglycerides, body weight, fat mass, and percent body fat after 12 weeks [11]. The effects of walking on energy requirements were assessed in adult women, showing an overall increase in daily energy needs at the end of the program [12].

Walking influenced the lipid profile and other biochemical factors. Altered adipokine concentration is an early sign of adipose tissue dysfunction [13]. Obese persons showed a decrease in serum leptin and serum chemerin [13]. A separate study reported no change in serum adiponectin [14]. The study also reported a decrease in body mass index, systolic blood pressure, triglycerides, and TNF-alpha after 50 days.

The studies cited above have shown that walking favorably influences anthropometric measures, body composition, energy expenditure, the lipid profile, and certain adipokines in obese persons.

Yoga is a practice which origins in ancient India. The practice includes physical postures (asanas), voluntarily regulated breathing techniques (pranayamas), meditation, and certain philosophical principles [15].

Yoga practice has been used in the management of obesity associated with other disorders. Practicing yoga resulted in a reduction in BMI, glycemic control, malondialdehyde and increase in glutathione, and vitamin C in persons with type 2 diabetes mellitus [16].

Other benefits followed yoga practice in persons with coronary artery disease [17]. There was a decrease in percent body fat, total cholesterol, triglycerides, and low-density lipoprotein, as well as systolic blood pressure, diastolic blood pressure, and heart rate.

Yoga practice has also been shown to influence adipokine levels [18]. After yoga practice, healthy post-menopausal women with more than 36% body fat showed increased adiponectin, improved serum lipid profile, and beneficial changes in metabolic syndrome risk factors. Also, a short-term, intensive yoga program caused a decrease in serum leptin levels, along with favorable changes in the body mass index, waist-hip circumference, total cholesterol, better postural stability, and increased hand grip strength [19].

Hence, like walking, yoga also improved the BMI, anthropometric measurements, body composition, and relevant biochemical measurements in persons with obesity.

As described above, both walking and yoga have individually shown benefits in persons with obesity. There have also been studies comparing the effects of yoga with those of walking in obese persons. Walking and yoga interventions improved sub-domains of self-esteem for both walking and yoga [20]. Apart from this, there are few other studies comparing the effects of yoga with those of walking assessing the adipokine levels, lipid profile, anthropometric variables, and body composition.

The hypothesis of the present study was that 15 days of supervised walking or supervised yoga would have comparable effects in overweight and obese persons, when both interventions were separately evaluated in a residential setting where the diet was the same.

Material and Methods

PARTICIPANTS:

Sixty-eight participants, of whom 63 were obese (group mean BMI ±S.D., 37.9±5.6 kg/m2) and 5 were overweight (group mean BMI ±S.D., 28.5±0.6 kg/m2), with ages between 20 and 55 years (group average age ±S.D., 36.4±11.2 years; 35 females), were enrolled in the study. For the yoga group the sample size was calculated based on an earlier study [19]. A required sample size (n=32) was obtained by applying Cohen’s formula for an Effect size of 0.30 (medium) and an alpha of 0.05, powered at 0.90 using G power program [21]. The effect size was calculated from mean and S.D. of waist circumference, which was changed significantly in the study on 47 subjects. For the walking group a required sample size (n=31) was obtained for an Effect size of 0.34 (medium) and an alpha of 0.05, powered at 0.95 using G power program [21]. The effect size was calculated from mean and S.D. of triglycerides, which was changed significantly in the study [14] on 22 subjects. The post hoc analyses showed that for the present study, with a sample size as 23 in each group, and with the Cohen’s d of 0.74 (large) for the yoga group and 0.51 (large) for the walking group, obtained from data on total cholesterol, which changed significantly within each group, the power was 0.9999 and 0.9966, respectively [21]. Recruitment was done by an advertisement on a television channel. The study was conducted in a residential yoga center located in northern India, with no charge to the participants. Participants of both sexes were included if: (i) their BMI was ≥25 kg/m2 and (ii) they were able to perform mild to moderate physical activity. Participants were excluded from the trial if they had: (i) endocrine disorders (e.g., hypothyroidism, polycystic ovarian syndrome), (ii) drug-induced changes in the fat distribution (e.g., following the chronic intake of corticosteroids), and (iii) any other disease, some of which are complications of obesity (e.g., uncontrolled hypertension, hypercholesterolemia, and type 2 diabetes mellitus). The baseline characteristics of the participants are given in Table 1. The approval for the study was obtained from the ethics committee of Patanjali Research Foundation. Signed informed consent from all the participants was obtained. The study was registered with the Clinical Trials Registry of India (CTRI/2012/12/003210).

DESIGN:

The trial was a comparative study with randomization between 2 interventions known to help in weight regulation. Participants were assigned random numbers from a standard table [22] and then blindly allocated to the 2 groups. The participants were recruited in July 2011 and post-intervention assessment was done in August 2011. The final number in each group is shown in the Trial Profile (Figure 1).

ASSESSMENTS:

The primary outcome variables were (i) biochemical measures, (ii) anthropometric measurements, and (iii) body composition. The secondary outcome variables were (i) postural stability and (ii) bilateral hand grip strength.

BIOCHEMICAL MEASURES:

Blood samples were taken from the antecubital vein following an overnight 12-hour fast. Fasting serum leptin and serum adiponectin were estimated using ELISA. Estimation of total cholesterol was done using the Cholesterol Oxidase Peroxidase method. Triglycerides were estimated using the Glycerol-3-Phosphate Oxidase and Peroxidase method. High-density lipoprotein, and low-density lipoprotein were estimated using the Direct Enzyme Clearance method.

ANTHROPOMETRIC MEASUREMENTS: (i) Body weight, (ii) BMI, (iii) waist circumference, (iv) hip circumference, (v) waist-hip ratio, and (vi) mid-arm circumference were assessed using standard methods [19].

BODY COMPOSITION:

Body composition was determined by the bio-electrical impedance analysis method using a body composition analyzer (BF-907, Maltron, U.K.). A standard method for recording, with participants resting supine, with their legs and arms slightly apart, was used. All relevant parameters such as height, weight, age, sex, and ethnicity were entered in the recording unit. The duration for recording was approximately 5 minutes.

POSTURAL STABILITY: Postural stability was measured using a stability platform (Lafayette Instrument, Model 16030, U.S.A.). In the present study, a standard method was used [19] with 3 test times of 20, 40, and 60 seconds. The time spent tilted towards the left, the right, or at the center was displayed on the screen.

HAND GRIP STRENGTH: Handgrip strength was measured using a hand grip dynamometer (Lafayette Instrument, Model 7498-05, U.S.A.). Participants held the dynamometer with their arm at right angles to the trunk of the body and their elbow touching the side of the body. The participants were instructed to squeeze the dynamometer with maximum isometric strength. Each hand was tested in 3 trials alternately, spaced 10 seconds apart. All participants were right hand dominant based on a standard handedness inventory [23]. For each hand the best value obtained of 3 trials was used for analysis.

YOGA: The participants of the yoga group practiced yoga for 45 minutes twice a day between (i) 05:00 hours and 05: 45 hours and (ii) 17:00 hours and 17:45 hours, for 15 days. Two sessions of yoga were selected as being fairly feasible to carry out at home. An instructor, who had been studying yoga for 5 years leading to a university degree, with a total of 17 years of study including practice, supervised the participants throughout the yoga session. Each 45-minute yoga session included breathing techniques for 33 minutes. The remaining time was spent in specific yoga postures. Participants repeated postures as many times as was possible within the time. The details of the yoga intervention are given in Table 2.

WALKING:

At the same times of the day, (i.e., 05:00–05:45 hours and 17:00–17:45 hours), there were two sessions of walking. The participants walked at their own paces. The walking track was cemented and rectangular. The total perimeter of the track was approximately 1200 meters. An instructor, who had been studying science for 5 years leading to a university degree, with a total of 17 years of study, supervised the participants throughout the walking session. The instructors for the 2 interventions were different. On average, the participants walked approximately 2600 meter/session at the average speed of 3.5 km/hr.

COMMON ACTIVITIES:

Between the 2 interventions in the morning and evening participants carried out routine activities such as laundry, reading, watching the television, and so on. None of them practiced yoga or walking on their own at other times, because they were instructed to avoid this. On questioning, all of them compiled with the instructions. All individuals went to sleep at 21:30 and woke up at 04:45, which was regulated by the experimenter.

DIET (COMMON TO BOTH GROUPS):

Participants of both groups were given a plant-based diet regulated at approximately 1650 kcal/day. This calorie restricted diet was part of the weight loss program. The energy intake of nutritive values of Indian foods was determined from a database available at http://www.medindia.net/calories-in-indian-food/.

DATA ANALYSIS:

Repeated measures analyses of variance (ANOVA) followed by post hoc analyses with Bonferroni adjustment (corrected Bonferroni value of 0.025) were done to compare data after the 2 interventions with pre-intervention data using PASW Version 18.0. There was 1 Within subjects factor (States with 2 levels (pre and post)) and 1 Between subjects factor (Groups with 2 levels [yoga and walking]). Missing value analyses were used for leptin and adiponectin data when performing the Repeated Measures Analyses of Variance. Statistical significance was set at α=0.05.

Results

Repeated measures analysis of variance (ANOVA)

REPEATED MEASURES ANALYSIS OF VARIANCE (ANOVA):

The ANOVA values for the Within-Subjects factors (States), Between-Subjects factors (Groups), and interaction between the 2 for the different variables for (i) biochemical measurements, (ii) anthropometric variables, (iii) body composition, and (iv) postural stability with bilateral hand grip strength are given in Tables 7–10, respectively. A significant interaction between Groups and States for any variable suggests that 2 are interdependent.

For the variables mentioned above, there were no significant differences between Groups and no significant interaction between States and Groups.

POST-HOC ANALYSES:

All comparisons were made with respective ‘pre’ states within a group, hence changes reported are pre-post, not between groups.

BIOCHEMICAL MEASUREMENTS:

The yoga group alone showed a significant increase in the leptin levels (p<0.01) with 95% Confidence Interval (CI) of [−2.420, −9.046], while the walking group alone showed a significant reduction in adiponectin levels (p<0.05) with 95% CI of [8.922, 0.045]. There was a significant reduction in total cholesterol (p<0.05) with 95% CI of [38.931, 0.982] for the yoga group; (p<0.05) with 95% CI of [38.540, 0.591] for the walking group. Triglycerides levels were decreased significantly in the walking group alone (p<0.05) with 95% CI of [111.328, 8.672], while LDL cholesterol was reduced significantly in the yoga group alone (p<0.05) with 95% CI of [30.267, 0.081].

ANTHROPOMETRIC MEASUREMENTS:

There was a significant decrease in: (i) BMI (p<0.001) with 95% CI of [1.910, 1.335] for the yoga group, (p<0.001) with 95% CI of [2.198, 1.621] for the walking group; (ii) hip circumference (p<0.001) with 95% CI of [3.899, 1.765] for the yoga group, (p<0.001) with 95% CI of [5.190, 3.056] for the walking group; and (iii) in waist circumference (p<0.05) with 95% CI of [4.563, 0.482] for the yoga group,(p<0.01) with 95% CI of [4.858, 0.778] for the walking group. Mid-arm circumference was reduced significantly in the walking group alone (p<0.05) with 95% CI of [2.025, 0.257].

BODY COMPOSITION:

There was a significant reduction in (i) lean mass (p<0.001) with 95% CI of [4.792, 2.198] for the yoga group; (p<0.001) with 95% CI of [5.845, 3.250] for the walking group and (ii) in body water (p<0.001) with 95% CI of [3.644, 1.727] for the yoga group; (p<0.001) with 95% CI of [4.378, 2.460] for the walking group.

POSTURAL STABILITY:

The walking group showed a significant increase in postural stability when the stability platform was centered in the: (i) 20-second trial (p<0.05) with 95% CI of [−0.234, −3.989], and (ii) 40-second trial (p<0.01) with 95% CI of [−1.553, −8.526]. The yoga group showed a significant increase in postural stability when the stability platform was centered in the 60-second trial (p<0.01) with 95% CI of [−2.005, −11.349].

HAND GRIP STRENGTH:

The walking group showed a significant increase in right hand grip strength (p<0.05) with 95% CI of [−0.111, −5.525] and in left hand grip strength (p<0.001) with 95% CI of [−2.086, −7.459]. The yoga group showed a significant increase in the right hand grip strength alone (p<0.05) with 95% CI of [−0.475, −5.8889].

Discussion

LIMITATIONS AND FUTURE DIRECTIONS:

The present study has demonstrated several benefits of both supervised yoga and supervised walking for obese persons. However, the findings are limited by the following factors: (i) The adipokines leptin and adiponectin were evaluated in a small sample based on the funds allocated by the funding agency and due to the high cost per test (approximately USD $180 for leptin/person and USD $300 for adiponectin/person). This was particularly difficult to finance because the program was free. (ii) The absence of a control group limits attributing changes seen to either yoga or walking. (iii) The high drop-out rate (approximately 33%), which was due to factors such as lack of compliance with the program (participants who practiced yoga/walking in between the sessions were excluded), and personal reasons requiring them to leave before the 15 days were complete. (iv) The age range for both groups was similar, but wide (21–54 years in the yoga group and 20–55 years in the walking group). Hence, the groups included participants whose metabolism would be influenced by different physiological factors. (v) The interventions were 15 days in duration and it was not possible to determine whether the effects extended beyond that period or not. The participants were contacted 1 month after the program to find out how many of them were continuing yoga/walking, revealing that 78.3% continued yoga and 69.5% continued walking. However, there was no attempt to note their weight. These limitations suggest possible directions for future study in this area of considerable medical concern.

Conclusions

Supervised yoga and supervised walking favorably and similarly influence multiple outcomes in overweight and obese adults. However, yoga increased serum leptin levels and walking reduced serum adiponectin levels. The findings suggest the usefulness of these interventions in obesity and also suggest directions for further investigation.