Could calorie restriction increase longevity in humans?

Caloric restriction in humans: impact on physiological, psychological, and behavioral outcomes

The current societal environment is marked by overabundant accessibility of food coupled with a strong trend of reduced physical activity, both leading to the development of a constellation of disorders, including central obesity, insulin resistance, dyslipidemia, and hypertension (metabolic syndrome). Prolonged calorie restriction (CR) has been shown to extend both the median and maximal lifespan in a variety of lower species such as yeast, worms, fish, rats, and mice. Mechanisms of this CR-mediated lifespan extension are not fully elucidated, but possibly involve significant alterations in energy metabolism, oxidative damage, insulin sensitivity, inflammation, and functional changes in both the neuroendocrine and sympathetic nervous systems. Here we review some of the major physiological, psychological, and behavioral changes after 6 months of CR in overweight otherwise healthy volunteers. Special emphasis is given to the first completed clinical studies that have investigated the effects of controlled, high-quality energy-restricted diets on both biomarkers of longevity and on the development of chronic diseases related to age in humans. With the incremental expansion of research endeavors in the area of energy or caloric restriction, data on the effects of CR in animal models and human subjects are becoming more accessible.

Changing course in ageing research: The healthy ageing phenotype

Ageing is often associated with the aged and the diseased, nevertheless ageing is a process that starts in-uterus and is characterised by a progressive functional loss but not necessarily by the presence of disease and poor quality of life. How to meander through life without crossing the confines of major chronic disease and cognitive and physical impairment remains one of the most relevant challenges for science and humankind. Delimiting that 'immaculate' trajectory - that we dub as the 'Healthy Ageing Phenotype' - and exploring solutions to help the population to stay or return to this trajectory should constitute the core focus of scientific research. Nevertheless, current efforts on ageing research are mainly focused on developing animal models to disentangle the human ageing process, and on age-related disorders often providing merely palliative solutions. Therefore, to identify alternative perspectives in ageing research, Unilever and the Medical Research Council (MRC) UK convened a Spark workshop entitled 'The Healthy Ageing Phenotype'. In this meeting, international specialists from complementary areas related to ageing research, gathered to find clear attributes and definitions of the 'Healthy Ageing Phenotype', to identify potential mechanisms and interventions to improve healthy life expectancy of the population; and to highlight areas within ageing research that should be prioritised in the future. General agreement was reached in recognising ageing research as a disaggregated field with little communication between basic, epidemiological and clinical areas of research and limited translation to society. A more holistic, multi-disciplinary approach emanating from a better understanding of healthy ageing trajectories and centred along human biological resilience, its maintenance and the reversibility from early deviations into pathological trajectories, is urgently required. Future research should concentrate on understanding the mechanisms that permit individuals to maintain optimal health when facing pathological hazards and on developing and assessing potential interventions that could aid to re-establish resilience when lost or guarantee its integrity if present. Furthermore it is fundamental that scientific findings are translated incessantly into clear messages delivered to governmental institutions, the industry and society in general.

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

The focus of this review is on current research involving long-term calorie restriction (CR) and the resulting changes observed in physiological and behavioral outcomes in humans. Special emphasis will be given to the first completed clinical studies which are currently investigating the effects of controlled, high-quality energy-restricted diets on both biomarkers of longevity and on the development of chronic diseases related to age in humans. Prolonged CR has been shown to extend both the median and maximal lifespans in a variety of lower species such as yeast, worms, fish, rats, and mice. Mechanisms of this CR-mediated lifespan extension are not fully elucidated, but possibly involve significant alterations in energy metabolism, oxidative damage, insulin sensitivity, and functional changes in both the neuroendocrine and sympathetic nervous systems. In this brief report, we review some of the major physiological, psychological and behavioral changes after 6 months of CR in overweight otherwise healthy volunteers. Ongoing studies of prolonged CR in humans are now making it possible to analyze changes in "biomarkers of longevity" to unravel some of the mechanisms of its anti-aging phenomenon. With the incremental expansion of research endeavors in the area of energy or calorie restriction, data on the effects of CR in animal models and human subjects are becoming more accessible. Detailed analyses from controlled human trials involving long-term CR will allow investigators to link observed alterations from body composition down to changes in molecular pathways and gene expression, with their possible effects on the biomarkers of aging.