To the Editor
The continuing rapid increase in the number of obese older adults in the United States is a major public health issue.1 Obesity exacerbates the age-related decline in endurance capacity, leading to physical dysfunction and impaired quality of life.2–4 The aim of this pilot study was to determine the effects of diet-induced weight loss on endurance capacity in obese older adults.
This six-month weight loss intervention study in obese older adults was approved by the Washington University Human Studies Committee. Volunteers were recruited from the community through advertisements, and underwent a screening procedure including medical history, physical examination, and biochemistries. Participants underwent weekly diet and group behavioral therapy for weight loss. A symptom-limited treadmill stress test was performed to assess endurance capacity and exercise tolerance5 before and after six months of diet-induced weight loss. Body composition was assessed using dual-energy x-ray absorptiometry.
Of the seventeen participants enrolled, fourteen (age: 70.9±3.1 yrs; body mass index: 36.7±4.4 kg/m2; 9 females/5 males) completed the six-month weight loss intervention. Attendance at the weekly group behavioral therapy sessions was 82.1±5.9%. Total energy intake assessed using food diaries decreased (from 1993±160 to 1557±92 kcal/day; p=.008), whereas levels of physical activity assessed using physical activity questionnaires did not change (from 8.9±1.3 to 9.1±1.6 MET-h/day; p=.75) over the study period. Accordingly, body weight (10.2±3.6 %), fat mass (16.3±6.7%), and fat-free mass (FFM) (5.6±4.1%) decreased (all p<.001) in response to diet-induced weight loss (Table 1). The peak oxygen uptake (VO2peak) relative to body weight (9.7±8.5%) and VO2 peak relative to appendicular lean mass (7.1±8.8%) increased (p<.05) after weight loss. Moreover, the participants achieved higher speed (11.8 ±9.4%), grade (15±21%), respiratory exchange ratio (3.3±6.1%), and metabolic equivalents (10.4±8.0%) during peak exercise after weight loss (all p<.05). Absolute VO2peak, VO2 peak relative to FFM, cardiovascular efficiency, and pulmonary efficiency did not change after weight loss. None of the participants experienced any clinical adverse effects related to the weight-loss therapy. Changes in fat mass correlated negatively with changes in VO2 peak relative to body weight (r=−0.55; p=0.04) and tended to correlate negatively with changes in VO2peak relative to appendicular lean mass (r=−0.41; p=.15).
Table 1.
Metabolic data before and after diet-induced weight loss in obese older adults
| Variable | Baseline | Final |
|---|---|---|
| Weight (kg) | 103.0 ± 15.2 | 92.5 ± 14.1* |
| Fat mass (kg) | 42.6 ± 7.7 | 35.8 ± 8.0* |
| FFM (kg) | 60.5 ± 1.3 | 57.0 ± 1.3* |
| Appendicular lean mass (kg) | 26.1 ± 6.5 | 24.0 ± 5.8* |
| Endurance capacity | ||
| VO2peak (L/min) | 1.9 ± 0.4 | 1.9 ± 0.5 |
| VO2peak (ml/kg/min) | 18.1 ± 2.5 | 19.9 ± 3.1* |
| VO2peak (ml/kg FFM/min) | 31.1 ± 4.1 | 31.2 ± 5.6 |
| VO2peak (ml/kg APP lean/min) | 73.2 ± 12.7 | 77.9 ± 12.8* |
| Exercise tolerance | ||
| Speed (mph) | 2.4 ± 0.6 | 2.6 ± 0.6* |
| Grade (% incline) | 12.2 ± 3.2 | 13.5 ± 2.6* |
| METS | 5.0 ± 0.7 | 5.6 ± 0.9* |
| Respiratory exchange ratio | 1.10 ± 0.1 | 1.14 ± 0.1* |
| Cardiovascular efficiency | ||
| Heart rate (pulse/min) | 143.4 ± 17.6 | 146.1 ± 13.4 |
| Predicted heart rate (%) | 90.9 ± 12.4 | 92.8 ± 9.4 |
| Systolic blood pressure (mmHg) | 183.1 ± 14.0 | 183.4 ± 19.1 |
| Diastolic blood pressure (mmHg) | 92.6 ± 11.9 | 87.6 ± 10.0 |
| Oxygen pulse (ml/beat) | 13.3 ± 4.0 | 12.2 ± 2.1 |
| Oxygen pulse (ml/kg FFM/beat) | 0.22 ± 0.0 | 0.21 ± 0.0 |
| RPP (beats mmHg/min) | 26,198 ± 3,474 | 26,750 ± 3,268 |
| Pulmonary efficiency | ||
| Respiratory Rate (breaths/min) | 33.7 ± 5.7 | 34.7 ± 8.2 |
| Ventilation (L/min) | 53.8 ± 13.3 | 55.3 ± 16.4 |
| Ventilation/VO2 | 28.9 ± 3.0 | 30.0 ± 4.2 |
Values are mean ± SD;
Value significantly different from baseline, p<0.05;
VO2peak, peak oxygen consumption; FFM, fat-free mass; APP, appendicular; METS, metabolic equivalents; RPP, rate pressure product
The results of this study demonstrate that diet-induced weight loss improves endurance capacity and exercise tolerance in obese older adults. Despite reductions in FFM, there were significant improvements in 1) VO2peak relative to body weight and 2) VO2peak relative to appendicular lean mass. Furthermore, absolute VO2peak and VO2peak relative to FFM were maintained.
The VO2peak relative to body weight is a measure of one’s endurance to perform weight-bearing activities such as walking and climbing stairs; hence, any improvement in this functional outcome might have the greatest impact on the daily function of obese older adults.3,6 The improvement in VO2peak relative to body weight that we observed is in accordance with previous studies in young and middle-aged adults.7,8 Although younger adults have a more robust improvement (>15%), the modest improvement that we observed in obese older adults (~10%) may have major functional implications in this population. Furthermore, our participants were able to walk with a greater speed and grade in the same amount of time after weight loss, suggesting that weight loss improved their ability to tolerate higher work loads.
As previously reported,3 physical dysfunction in obese older adults is associated with low muscle mass relative to body weight (relative sarcopenia), despite greater amount of absolute muscle mass. Therefore, obese older adults are particularly susceptible to the adverse effects of excess body weight on physical function because of 1) smaller muscle mass relative to body weight and 2) age-related decline in muscle mass.9 Weight-loss therapy in our participants resulted in a greater loss of fat mass (~7 kg) than metabolically active muscle mass [appendicular lean mass (~2 kg)] resulting in improvement in relative sarcopenia.3,9 This positive effect of weight-loss therapy on body composition may explain the improvement in endurance capacity. In addition, it is possible that weight-loss therapy improved muscle oxidative capacity.10
To our knowledge, this is the first study to investigate the effects of diet-induced weight loss on endurance capacity in obese older adults. Contrary to common belief that older adults may have difficulty with lifestyle change, our intervention was successful in achieving weight loss and was well tolerated. In conclusion, the results of this study provide preliminary evidence that moderate diet-induced weight loss improves endurance capacity and exercise tolerance in obese older adults. This improvement is likely to increase their ability to perform daily activities and thus prevent further functional decline.
Acknowledgments
We thank Nicole Wright for study coordination.
Sponsor's role: None
Footnotes
Author contributions: Study concept and design: Shah, Villareal; Acquistion of participants and data: Shah, Wright, Wingkun, Villareal. Analysis and interpretation of data: Shah, Wingkun, Lambert, Villareal. Preparation of manuscript. Shah, Lambert, Villareal
Conflict of interest: None. Funding source. NIH grant AG025501, RR00036 and DK56341.
References
- 1.Arterburn DE, Crane PK, Sullivan SD. The coming epidemic of obesity in elderly Americans. J Am Geriatr Soc. 2004;52:1907–1912. doi: 10.1111/j.1532-5415.2004.52517.x. [DOI] [PubMed] [Google Scholar]
- 2.Villareal DT, Apovian CM, Kushner RF, et al. Obesity in older adults: technical review and position statement of the American Society for Nutrition and NAASO, The Obesity Society. Am J Clin Nutr. 2005;82:923–934. doi: 10.1093/ajcn/82.5.923. [also published in: Obes Res. 2005: 13:1849–1863] [DOI] [PubMed] [Google Scholar]
- 3.Villareal DT, Banks M, Siener C, et al. Physical Frailty and Body Composition in Obese Elderly Men and Women. Obes Res. 2004;12:913–920. doi: 10.1038/oby.2004.111. [DOI] [PubMed] [Google Scholar]
- 4.Blaum CS, Xue QL, Michelon E, et al. The association between obesity and the frailty syndrome in older women: the women’s health and aging studies. J Am Geriatr Soc. 2005;53:927–934. doi: 10.1111/j.1532-5415.2005.53300.x. [DOI] [PubMed] [Google Scholar]
- 5.Fletcher GF, Balady GJ, Amsterdam EA, et al. Exercise standards for testing and training: a statement for healthcare professionals from the American Heart Association. Circulation. 2001;104:1694–1740. doi: 10.1161/hc3901.095960. [DOI] [PubMed] [Google Scholar]
- 6.Binder EF, Birge SJ, Spina R, et al. Peak aerobic power is an important component of physical performance in older women. J Gerontol A Biol Sci Med Sci. 1999;54:M353–M356. doi: 10.1093/gerona/54.7.m353. [DOI] [PubMed] [Google Scholar]
- 7.Seres L, Lopez-Ayerbe J, Coll R, et al. Increased exercise capacity after surgically induced weight loss in morbid obesity. Obesity (Silver Spring) 2006;14:273–279. doi: 10.1038/oby.2006.35. [DOI] [PubMed] [Google Scholar]
- 8.Kanoupakis E, Michaloudis D, Fraidakis O, et al. Left ventricular function and cardiopulmonary performance following surgical treatment of morbid obesity. Obes Surg. 2001;11:552–558. doi: 10.1381/09608920160556715. [DOI] [PubMed] [Google Scholar]
- 9.Roubenoff R. Sarcopenic obesity: the confluence of two epidemics. Obes Res. 2004;12:887–888. doi: 10.1038/oby.2004.107. [DOI] [PubMed] [Google Scholar]
- 10.Kern PA, Simsolo RB, Fournier M. Effect of weight loss on muscle fiber type, fiber size, capillarity, and succinate dehydrogenase activity in humans. J Clin Endocrinol Metab. 1999;84:4185–4190. doi: 10.1210/jcem.84.11.6090. [DOI] [PubMed] [Google Scholar]