Aging (Albany NY) | 2019
Is obesity a risk factor for skeletal muscle ageing?
Abstract
The proportion of the European population aged >65 years is expected to be 25% by 2030, with 20% of the global population projected to be obese by 2030 [1]. Understating the interaction between ageing and obesity has become an important area of research given the increased risk of serious health conditions and diseases. Given the importance of skeletal muscle in metabolism, completing tasks of daily living and being physically active, it is of importance to better understand the concomitant effects of obesity and old age on skeletal muscle health and performance. Evidence has demonstrated that ageing and obesity in younger adults independently alter the contractile performance of skeletal muscle, resulting in impaired locomotor and respiratory muscle function. Both ageing and obesity independently have been associated with chronic inflammation, muscle atrophy and reduced myogenesis, fibre type shifting and impaired excitation-contraction coupling [1,2], providing a strong mechanistic justification to support an obesity-induced exacerbation of the typical muscle ageing process. Consequently, sarcopenic obesity, characterised by a high fat mass and low muscle mass, has been demonstrated to contribute to a greater risk of developing type 2 diabetes, cardiovascular diseases, and has been linked to reduced longevity of life [2]. Despite this, the body of evidence directly examining the synergism between obesity and ageing on muscle function is lacking and controversial. The effects of ageing on the contractile function of skeletal muscle has been thoroughly investigated, categorised by a reduction in both isometric strength and concentric power when quantified in both absolute and relative terms [3]. The effect of obesity on contractile function is a growing area of interest, with results being far less conclusive compared to the ageing literature. A recent review has demonstrated that obesity effects on contractile performance are muscle specific, with evidence for a reduction in both force and power normalised to body mass, and a reduction in muscle quality (performance relative to muscle size) [4]. Contrary to the typical ageing response, there is evidence indicating that obesity may increase the absolute force producing capacity of the postural muscles; a response to an elevated overload stimulus due to an increased body mass. Given that the magnitude of this response is lower than the increase in Editorial