Effects of experimental weight perturbation on skeletal muscle work efficiency in human subjects

Laval University, Quebec City, Quebec, Canada
AJP Regulatory Integrative and Comparative Physiology (Impact Factor: 3.11). 07/2003; 285(1):R183-92. DOI: 10.1152/ajpregu.00474.2002
Source: PubMed


Maintenance of reduced or elevated body weight results in respective decreases or increases in energy expended in physical activity, defined as 24-h energy expenditure excluding resting energy expenditure and the thermic effect of feeding, beyond those attributable to weight change. We examined skeletal muscle work efficiency by graded cycle ergometry and, in some subjects, rates of gastrocnemius muscle ATP flux during exercise by magnetic resonance spectroscopy (MRS), in 30 subjects (15 males, 15 females) at initial weight and 10% below initial weight and in 8 subjects (7 males, 1 female) at initial weight and 10% above initial weight to determine whether changes in skeletal muscle work efficiency at altered body weight were correlated with changes in the energy expended in physical activity. At reduced weight, muscle work efficiency was increased in both cycle ergometry [mean (SD) change = +26.5 (26.7)%, P < 0.001] and MRS [ATP flux change = -15.2 (23.2)%, P = 0.044] studies. Weight gain resulted in decreased muscle work efficiency by ergometry [mean (SD) change = -17.8 (20.5)%, P = 0.043]. Changes in muscle efficiency at altered body weight accounted for 35% of the change in daily energy expended in physical activity.

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Available from: Denis R Joanisse, Nov 27, 2015
    • "The adaptive responses to energy restriction in individuals that are overweight or obese are numerous and have been reviewed elsewhere (Sainsbury A, Seimon RV, Hills AP, Wood RE, King NA, Gibson AA, Byrne NM, submitted manuscript; Sainsbury and Zhang, 2012; King et al., 2012; Melanson et al., 2013; Leibel et al., 2015; MacLean et al., 2015; Rosenbaum et al., 2010; Maclean et al., 2011; Sumithran and Proietto, 2013; Sainsbury and Zhang, 2010). They include increased appetite (Mason et al., 2015; Purcell et al., 2014; Sumithran et al., 2011, 2013), reduced physical activity (Hunter et al., 2015; Camps et al., 2013) or the energy cost of physical activity (Hunter et al., 2015; Martin et al., 2011; Rosenbaum et al., 2003; Novak and Levine, 2007; Bonomi et al., 2013), reduced energy expenditure greater than that expected from the reduction in body mass (Knuth et al., 2014; McNeil et al., 2015), and hormonal effects that can adversely affect body composition by promoting the accumulation of adipose tissue (particularly central adiposity) and stimulating the loss of lean tissues (Sainsbury and Zhang, 2012; Stolzenberg-Solomon et al., 2012; Carpenter et al., 2012; Seimon et al., 2013; Wright et al., 2013). Indeed, studies in lean animals and humans clearly show that negative energy balance markedly inhibits activity of the hypothalamo-pituitary-thyroid (de Vries et al., 2015), -gonadotropic and -somatotropic axes (or reduces circulating insulin-like growth factor-1 [IGF-1] levels) (Steyn et al., 2011), while concomitantly activating the hypothalamo-pituitary-adrenal axis (Sainsbury and Zhang, 2012; Seimon et al., 2013). "
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    ABSTRACT: Energy restriction induces physiological effects that hinder further weight loss. Thus, deliberate periods of energy balance during weight loss interventions may attenuate these adaptive responses to energy restriction and thereby increase the efficiency of weight loss (i.e. the amount of weight or fat lost per unit of energy deficit). To address this possibility, we systematically searched MEDLINE, PreMEDLINE, PubMed and Cinahl and reviewed adaptive responses to energy restriction in 40 publications involving humans of any age or body mass index that had undergone a diet involving intermittent energy restriction, 12 with direct comparison to continuous energy restriction. Included publications needed to measure one or more of body weight, body mass index, or body composition before and at the end of energy restriction. 31 of the 40 publications involved 'intermittent fasting' of 1-7-day periods of severe energy restriction. While intermittent fasting appears to produce similar effects to continuous energy restriction to reduce body weight, fat mass, fat-free mass and improve glucose homeostasis, and may reduce appetite, it does not appear to attenuate other adaptive responses to energy restriction or improve weight loss efficiency, albeit most of the reviewed publications were not powered to assess these outcomes. Intermittent fasting thus represents a valid - albeit apparently not superior - option to continuous energy restriction for weight loss.
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    • "(−10.5% to −20.4% vs. −1.4% to −2.1%, respectively for energy cost and body fat) as well as the literature (Lazzer et al., 2004; Ohrström, Hedenbro, & Ekelund, 2001). Consequently, other parameters were suggested to play an important role in the reduced energy cost of walking (Hunter et al., 2008; Peyrot et al., 2012; Rosenbaum et al., 2003). "
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    • "Interestingly, when external weight is added to match the subject’s baseline weight, energy expenditure to complete a given workload remains below baseline [41]. It has been speculated that this increase in skeletal muscle efficiency may be related to the persistent hypothyroidism and hypoleptinemia that accompany weight loss, resulting in a lower respiratory quotient and greater reliance on lipid metabolism [43]. "
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    ABSTRACT: Optimized body composition provides a competitive advantage in a variety of sports. Weight reduction is common among athletes aiming to improve their strength-to-mass ratio, locomotive efficiency, or aesthetic appearance. Energy restriction is accompanied by changes in circulating hormones, mitochondrial efficiency, and energy expenditure that serve to minimize the energy deficit, attenuate weight loss, and promote weight regain. The current article reviews the metabolic adaptations observed with weight reduction and provides recommendations for successful weight reduction and long term reduced-weight maintenance in athletes.
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