Caloric restriction for longevity: II—The systematic neglect of behavioural and psychological outcomes in animal research

Abstract

Research on caloric restriction for longevity (CRL) has generated hundreds of articles on the physiology of food deprivation, yet almost no data on consequences in other domains. The first paper in this series outlined the generally positive physical effects of CRL; the second analyses the meagre and sometimes disturbing record of research on behaviour, cognition and affect. The available evidence suggests that nutrient-dense CRL in animals-just like nutrientpoor semi-starvation in people-is associated with a number of adverse effects. Changes include abnormal food-related behaviour, heightened aggression and diminished sexual activity. Studies of learning and memory in underfed rodents yield inconsistent findings; no information is available on cognitive effects in primates. To date, the CRL field has ignored other variables that are crucial to the human case and known to be disrupted by chronic hunger, including sociability, curiosity and emotionality. Promotion of CRL for people is irresponsible in the absence of more reassuring data on the full range of expected outcomes. Eating disorder specialists should be contributing to scientific and public discussions of this increasingly prominent paradigm.

Examination of Cognitive Function During Six Months of Calorie Restriction: Results of a Randomized Controlled Trial

“…3 The results of the present study add to the literature by addressing some of the limitations of previous studies. First, a group of nondieting middle-age men and women were recruited for this randomized controlled trial.…”

“…2 As calorie restriction research moves from animal models to human trials, it is important to measure the full effect of calorie restriction on cognition, including learning and memory. 3 Calorie restriction inhibits age-related cognitive decline in rats, 4 yet a number of human studies report that self-reported dieting or calorie restriction is associated with cognitive impairment, e.g., memory, attention, processing speed, and concentration deficits. 5-9 However, cognitive impairment is frequently mediated by self-reported dieters' preoccupying thoughts about food and body weight/shape.…”

Caloric Restriction in Humans: Impact on Physiological, Psychological, and Behavioral Outcomes

“…Additionally, CR or the intent to restrict intake has been associated with the onset of eating disorders, including anorexia (105) and bulimia nervosa (65), and binge eating disorder (106). Hence, there is a need to examine both the benefit and potential harm of CR in humans, particularly for people who are not obese, and to answer important safety questions before CR is recommended (93,94).…”

Effect of caloric restriction in non-obese humans on physiological, psychological and behavioral outcomes

“…Additionally, CR or the intent to restrict intake has been associated with the onset of eating disorders, including anorexia [48] and bulimia nervosa [49], and binge eating disorder [50]. Hence, there is a need to examine both the benefit and potential harm of CR in humans, particularly for people who are not obese, and to answer important safety questions before CR is recommended [51,52].…”