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?

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.

Increased urge for movement, physical and mental restlessness, fundamental symptoms of restricting anorexia nervosa?

OBJECTIVE

Continued mobility in the presence of severe weight loss is a well known, yet insufficiently researched characteristic of anorexia nervosa (AN). This study was designed to assess the prevalence of the drive for activity, here operationalized as an increased urge for movement, physical restlessness, and mental restlessness.

METHOD

Participants were 83 female consecutively admitted adolescent patients qualifying for a diagnosis of AN (ICD-10), restricting subtype. Information collected included responses to a questionnaire inquiring retrospectively about physical and psychological reactions after significant weight loss (on average 12.5 kg) and to measures of psychiatric and eating disorder pathology and exercise behaviors at hospital admission.

RESULTS

Over 80% of AN patients reported experiencing, at least partly, either, an increased urge for movement, physical or mental restlessness after significant weight loss. Altogether 95.1% reported, at least partly, one or a combination of two or all three symptoms. The sensations coexisted with equally high levels of fatigue and loss of energy, typically observed in starvation. The increased urge for movement and physical restlessness were foremost associated with reported actual physical activity and with weight loss. By contrast, mental restlessness was strongly linked to the degree of eating disorder pathology and to the severity of psychiatric symptoms.

DISCUSSION

This is the first investigation of the presence of an increased urge for movement, physical restlessness, and mental restlessness after significant weight loss in patients with acute AN. The symptoms, given their high frequency and specificity, are likely pathogenic for AN and, if replicated, deserve to be considered for inclusion as diagnostic criteria for AN.

Not the Function of Eating, but Spontaneous Activity and Energy Expenditure, Reflected in "Restlessness" and a "Drive for Activity" Appear to Be Dysregulated in Anorexia Nervosa: Treatment Implications

Anorexia nervosa (AN) is uncommon as a syndrome, despite widespread dieting or voluntary food restriction, especially among female adolescents. This suggests that restriction of caloric intake might not be the only component driving weight loss in AN. Historical observations and experimental evidence from energy expenditure studies and recordings from movement sensors reviewed in this paper reveal that AN is associated with motor activity levels and with an energy output not significantly different from that in normal-weight healthy age-matched controls. By contrast, other conditions of prolonged caloric under-nutrition are typically associated with loss of energy, slowing of movements and a decrease in self-initiated activity and well-being. Several hypotheses can be inferred from the findings: (a) that long term severe caloric restriction fails in downregulating movements and energy expenditure in AN. (b) Clinically and subjectively observable as mental and physical restlessness and continued motor activity, this restless energy, differing in intensity, seems to serve as the permissive factor for and possibly to drive exercise and hyperactivity in AN. (c) Such restless energy and increased arousal, generated sometime in the course of the weight loss process, appear to enhance the person's self-perception and wellbeing, to heighten proprioception, to intensify body awareness and to improve self-esteem. (d) Restlessness and continued motor activity may constitute a phenotype of AN. The therapeutic value of the concept of an abnormality in the energy regulatory system, likely the result of a host of genetic and epigenetic changes in AN, lies primarily in its heuristic and explanatory power and its potential for disease prevention. Restless energy as a permissive and important component for the development and in the maintenance of AN, does not fundamentally alter treatment, since prolonged food deprivation is the principal causal factor for the development of AN. Re-nutrition within a structured treatment plan, to include individual and family therapy and, if indicated, heat application, remains the most effective symptomatic treatment for AN. Corroboration of the concept of restless activation will require the patient's cooperation and input to identify and capture more precisely the experiences, sensations, and changes that allow the emaciated patient to remain mobile and active.

Drive for activity in patients with anorexia nervosa

OBJECTIVE

Hyperactivity and elevated physical activity are both considered symptom characteristics of anorexia nervosa (AN). It has been suggested that a drive for activity (DFA) may underlie these expressions, yet research into DFA in AN remains scant. This study investigated DFA levels in patients with AN and its relation to AN severity. Furthermore, as physical exercise may be a way to reduce negative affect, the influence of negative affect (anxiety) on the role of DFA in AN was tested.

METHOD

Two hundred and forty female patients with AN completed measures for DFA, eating disorder (ED) pathology, anxiety, and clinical parameters.

RESULTS

A strong relation between DFA levels and ED pathology was found, which remained significant even after controlling for negative affect (anxiety).

DISCUSSION

After much theorizing about DFA in AN this study provides empirical evidence for DFA as a hallmark feature of AN, independent of anxiety levels. Future research should shed light on the relationships between DFA, actual physical activity, and the course of AN.