Review
Obesity and Physical Frailty in Older Adults: A Scoping Review of Lifestyle Intervention Trials

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Abstract

Many frail older adults are thin, weak, and undernourished; this component of frailty remains a critical concern in the geriatric field. However, there is also strong evidence that excessive adiposity contributes to frailty by reducing the ability of older adults to perform physical activities and increasing metabolic instability. Our scoping review explores the impact of being obese on physical frailty in older adults by summarizing the state of the science for both clinical markers of physical function and biomarkers for potential underlying causes of obesity-related decline. We used the 5-stage methodological framework of Arksey and O'Malley to conduct a scoping review of randomized trials of weight loss and/or exercise interventions for obesity (body mass index ≥ 30 kg/m2) in older adults (aged >60 years), examining the outcomes of inflammation, oxidative stress, and lipid accumulation in muscle, as well as direct measures of physical function. Our initial search yielded 212 articles; exclusion of cross-sectional and observational studies, cell culture and animal studies, disease-specific interventions, and articles published before 2001 led to a final result of 21 articles. Findings of these trials included the following major points. The literature consistently confirmed benefits of lifestyle interventions to physical function assessed at the clinical level. Generally speaking, weight loss alone produced a greater effect than exercise alone, and the best outcomes were achieved with a combination of weight loss and exercise, especially exercise programs that combined aerobic, resistance, and flexibility training. Weight loss interventions tended to reduce markers of inflammation and/or oxidative damage when more robust weight reduction was achieved and maintained over time, whereas exercise did not change markers of inflammation. However, participation in a chronic exercise program did reduce the oxidative stress induced by an acute bout of exercise. Weight loss interventions consistently reduced lipid accumulation in the muscle; however, in response to exercise, 3 studies showed an increase and 2 a decrease in muscle lipid infiltration. In summary, this scoping review identified strong clinical evidence that weight reduction and/or exercise interventions can improve physical function and biomarkers of physical dysfunction among overweight/obese older adults, supporting the suggestion that excessive adiposity contributes to physical frailty. However, the evidence also suggests a complexity of metabolic influences, both systemically and within muscle, which has not been elucidated to date. Considerable further study is needed to examine the mechanisms by which lifestyle interventions influence physical frailty before the net impact of such interventions can be fully understood.

Section snippets

Oxidative Stress and Inflammation

Age-associated increases in markers of oxidative stress, accumulation of oxidative damage, and systemic inflammation are well recognized. These observed changes led to the oxidative stress theory of aging, which hypothesizes that oxidative stress and the related inflammation cause cellular and molecular damage when reactive oxygen species (ROS) overwhelm antioxidant defenses, leading to progressive deleterious changes over time.33 The ROS imbalance not only leads to structural damage to

Approach and Methods

The purpose of this scoping review was to assess the breadth of scientific evidence linking excess adiposity in older adults with detrimental effects on function; to accomplish this, we reviewed the impact of lifestyle interventions, namely weight loss diets and exercise regimens, on these parameters. We used the 5-stage methodological framework of Arksey and O'Malley43 to conduct this scoping review. The steps followed were (1) identify the research questions; (2) identify relevant studies;

Overview

The flow chart shown in Figure 1 illustrates the process by which 21 studies were selected from the original 212 papers identified by the literature search. The most common reason for excluding studies was that they did not meet the criteria of being a prospective lifestyle intervention trial. The 21 papers represented 20 distinct major trials; in 1 case, 2 articles were written about different aspects of the same subjects within the same trial.

The characteristics, outcomes, and key findings

Interventions Affecting Physical Function

This scoping review has confirmed robust beneficial effects of lifestyle interventions on physical function and body composition in obese older adults. Improvements in an array of functional measures were identified in WL arms, EX arms, and WL+ EX arms. Notwithstanding the functional improvements observed with WL, however, it should be noted that LBM was not preserved in WL interventions, a potentially negative consequence for frail older adults.70 More research is needed to determine the

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    Research reported in this publication was supported by the National Institute on Aging of the National Institutes of Health under Award Number T32AG000029. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Research reported in this publication was also supported by Donald W. Reynolds Foundation FD∼AGE Grant and the Health Resources and Services Administration Fellowship Grant, Grant Number D01HP08791.

    The authors declare no conflicts of interest.

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