Might Starvation-Induced Adaptations in Muscle Mass, Muscle Morphology and Muscle Function Contribute to the Increased Urge for Movement and to Spontaneous Physical Activity in Anorexia Nervosa?

Abstract

Severely undernourished and underweight anorexia nervosa (AN) patients typically remain active and mobile. Might such persistent physical activity in AN be supported by specific adaptations in muscle tissue during long term undernutrition? To identify potential differences, studies examining the effects of undernutrition on skeletal muscle mass, muscle morphology and muscle function in healthy humans and in AN patients were reviewed. Adjustments in muscle morphology and function in AN did not differ in substance from those in healthy humans, undernourished people, or undergoing semi-starvation. Loss of muscle mass, changes in muscle contractility and atrophy of muscle fibers (predominantly type II fibers) characterized both groups. Muscle innervation was unaffected. Work capacity in men in semi-starvation experiments and in females with AN declined by about 70% and 50%, respectively. Perceptions of fatigue and effort distinguished the groups: signs of general weakness, tiring quickly and avoidance of physical activity that were recorded in semi-starvation were not reported for AN patients. The absence of distinctive starvation-related adjustments in skeletal muscle in AN suggests that new methods, such as muscle gene expression profiles in response to deficient nutrient intake, and better knowledge of the central regulatory circuitries contributing to motor urgency will be required to shed light on the persistent mobility in AN patients.

Measurement of motivation states for physical activity and sedentary behavior: Development and validation of the CRAVE scale

“…Desires to rest and move, as measured by the 10-item version of the CRAVE, were related to tiredness but not other psychosomatic sensations. Likewise, Casper has found that urges to move, as retrospectively assessed over two weeks, were unrelated to physical and mental tiredness and energy (52, 60). Data from Study 5 support the notion that desires are states.…”

“…Indeed, in the current analysis stage-of-change for exercise predicted wants/desires for movement. However, it would be useful to determine whether those with higher movement desires actually have more energy expenditure (EE) from exercise or non-exercise sources (e.g., occupational activity, active transit, spontaneous physical activity [SPA]) (52, 149) and whether these change over time with chronic training. Movement desires and urges, or what has been termed “appetence”, is magnified with exercise addiction, anorexia, and possibly mania (9, 167).…”

“…Intense desires, manifested as psychophysiological cravings and urges, strongly predict future behavior, such as overeating, binging on alcohol, overconsumption of caffeine, excessive engagement in sexual activity, smoking of cigarettes and other behaviors (174-176). Casper and colleagues documented that the increased urge to move in severely underweight adolescent anorexia nervosa patients was positively associated with exercise intensity and actual exercise over a two-week period (52, 60). As demonstrated by the Dynamical Model of Desire (11), wants that emerge into focal attention in working memory often instigate active pursuit of that desire.…”

“…At this juncture, intersecting lines of research strongly suggest that humans possess wants/desires for movement and rest behaviors (8, 15, 17, 35, 38, 52). However, a review study in this special issue reports that “little to no research has been conducted to directly measure craving/desire for PA” (53).…”

Measurement of Motivation States for Physical Activity and Sedentary Behavior: Development and Validation of the CRAVE Scale

“…At this juncture, intersecting lines of research strongly suggest that humans possess wants/desires for movement and rest behaviors ( Iqbal et al, 2007 ; Beeler et al, 2012 ; Levitin et al, 2018 ; Williams et al, 2019 ; Casper, 2020 ; Stults-Kolehmainen et al, 2020a ). However, a review study in this special issue reports that “little to no research has been conducted to directly measure craving/desire for PA” ( Stevens et al, 2020 ).…”