Iron homeostasis in older adults: balancing nutritional requirements and health risks.

Iron plays a crucial role in many physiological processes, including oxygen transport, bioenergetics, and immune function. Iron is assimilated from food and also recycled from senescent red blood cells. Iron exists in two dietary forms: heme (animal based) and non-heme (mostly plant based). The body uses iron for metabolic purposes, and stores the excess mainly in splenic and hepatic macrophages. Physiologically, iron excretion in humans is inefficient and not highly regulated, so regulation of intestinal absorption maintains iron homeostasis. Iron losses occur at a steady rate via turnover of the intestinal epithelium, blood loss, and exfoliation of dead skin cells, but overall iron homeostasis is tightly controlled at cellular and systemic levels. Aging can have a profound impact on iron homeostasis and induce a dyshomeostasis where iron deficiency or overload (sometimes both simultaneously) can occur, potentially leading to several disorders and pathologies. To maintain physiologically balanced iron levels, reduce risk of disease, and promote healthy aging, it is advisable for older adults to follow recommended daily intake guidelines and periodically assess iron levels. Clinicians can evaluate body iron status using different techniques but selecting an assessment method primarily depends on the condition being examined. This review provides a comprehensive overview of the forms, sources, and metabolism of dietary iron, associated disorders of iron dyshomeostasis, assessment of iron levels in older adults, and nutritional guidelines and strategies to maintain iron balance in older adults.

Does time-restricted eating add benefits to calorie restriction? A systematic review.

OBJECTIVE: A growing body of evidence has supported the health benefits of extended daily fasting, known as time-restricted eating (TRE); however, whether the addition of TRE enhances the known benefits of calorie restriction (CR) remains unclear. METHODS: PubMed, Scopus, the Cochrane Library, and Google Scholar were searched through April 2023. This systematic review includes randomized controlled trials (RCTs) that compared CR + TRE with CR alone in energy-matched conditions of at least 8 weeks in duration that assessed changes in body weight and cardiometabolic disease risk factors in adults with overweight and/or obesity. RESULTS: Seven studies were identified (n = 579). Two studies reported greater weight loss and reductions in diastolic blood pressure with CR + TRE compared with CR alone after 8 to 14 weeks, whereas one study reported greater improvements in triglycerides and glucose tolerance with CR + TRE (3 days/week) compared with CR alone following 26 weeks. One study reported significant increases in homeostatic model assessment of insulin resistance (HOMA-IR) levels with CR + TRE versus CR alone after 8 weeks. There were no statistically significant differences in any other outcome variable between the two interventions. CONCLUSIONS: The addition of TRE to CR regimens resulted in greater weight loss and improvements in cardiometabolic risk factors in some studies; however, the majority of studies did not find additional benefits.

Use of Minimally Invasive Methods to Assess Fuel Utilization and Circadian Rhythms in Older Adults.

Aging is associated with multiple physiological changes that contribute synergistically and independently to physical disability and the risk of chronic disease. Although the etiology of age-related physical disability is complex and multifactorial, the decline in mitochondrial function appears to coincide with the progression of functional decline in many older adults. The reason why there is a decrease in mitochondrial function with aging remains elusive, but emerging science indicates that both fuel metabolism and circadian rhythms can influence mitochondrial function. Recent studies have established that circadian rhythms become disturbed with aging, and that disrupted circadian rhythms have pathological consequences that impact mitochondrial function and overlap with many age-associated chronic diseases. Current quantitative methods for direct assessment of mitochondrial function are invasive and typically require a muscle biopsy, which can pose difficulties with participant recruitment and study adherence, given the perceived levels of potential pain and risk. Thus, an innovative and relatively noninvasive protocol to assess changes in mitochondrial function at the cellular level and circadian patterns in older adults was adapted. Specifically, a real-time metabolic flux analyzer is used to assess the mitochondrial bioenergetic function of white blood cells under differential substrate availability. The expression of circadian clock genes in white blood cells to cross-correlate with the mitochondrial bioenergetics and circadian rhythm outcomes are also analyzed. It is believed that these innovative methodological approaches will aid future clinical trials by providing minimally invasive methods for studying mitochondrial substrate preference and circadian rhythms in older adults.

Acute and chronic cardiovascular responses to concentric and eccentric exercise in older adults with knee osteoarthritis.

PURPOSE: Muscle contraction type in resistance exercise training may confer benefits besides strength in individuals with osteoarthritis and cardiovascular disease (CVD) risks. The purpose of the study was to explore whether Eccentric-resistance training (RT) improved hemodynamic responses to acute walking exercise stress compared to Concentric-RT among individuals with knee OA over four months. METHODS: This was a secondary analysis from a randomized, controlled, single-blinded study. Participants (N = 88; 68.3 ± 6.4 yrs; 67.4% female) were randomized to one of two work-matched resistance training (RT) programs against a non-RT control group. Pre-training and month four, participants completed a self-paced Six-Minute Walk Test (6MWT) and progressive treadmill exercise test. Heart rates, blood pressures and mean arterial pressures (MAP) were captured during each test. Antihypertensive medications use was documented at each time point. RESULTS: Leg strength improved in both training groups by month four (p < .05). Changes in 6MWT distance and progressive treadmill test time were not different across groups over four months. Neither Concentric or Eccentric RT produced different hemodyamic responses during the 6MWT compared to the control group post-training. However, Concentric RT was associated with 6.0%-7.4% reductions in systolic blood pressure during the graded treadmill walking test at 50%, 75% and 100% of the test time compared to Eccentric RT and the controls (p = .045). MAP values were lower at 75% and 100% of the treadmill test after Concentric RT (5.7%-6.0% reductions) compared to Eccentric RT (1.0%-2.4% reductions) and controls (1.5% and 4.0% elevations) post-training (p = .024). Antihypertensive medication use did not change in any group. CONCLUSIONS: The repeated, progressive exposures of Concentric RT-induced blunted the hypertensive responses to acute exercise compared to Eccentric-RT. Among people with knee OA, Concentric-RT may confer strength benefits to manage OA and possibly reduce cardiovascular stress during exercise.

The effects of intermittent fasting regimens in middle-age and older adults: Current state of evidence.

Aging is associated with a host of biological changes that contribute to a progressive decline in cognitive and physical function, ultimately leading to a loss of independence and an increased risk of mortality. The unprecedented growth of the aging population has thus created an urgent need for interventions that can preserve older adults' capacity to live independently and to function well. To date, there is no conclusive evidence supporting the efficacy of an intervention to prevent or reverse physical disability in older persons at risk of functional decline. A growing body of evidence indicates that prolonged fasting periods and different types of intermittent fasting regimens can have positive effects on anthropometric and metabolic health parameters in middle-aged adults similar to that of calorie restriction. For this reason, there is increasing scientific interest in further exploring the biological and metabolic effects of intermittent fasting approaches, as well as the feasibility and safety of popular types of intermittent fasting regimens in older adults. Thus, the purpose of the present review is to describe the state of evidence of different types of intermittent fasting regimes, specifically time-restricted eating and 5:2 intermittent fasting, in the growing population of middle-aged and older adults. A small, but growing body of evidence indicates both time restricted eating (TRE) and 5:2 intermittent fasting approaches can produce modest weight loss; however, only the 5:2 approach produced clinically meaningful weight losses. Reductions in blood pressure were observed for both TRE and 5:2 fasting approaches, but the effects were not consistent across studies. The majority of studies to date, in middle-age and older adults, however, have been of short duration in small study samples. Future clinical trials with larger populations and longer intervention durations are required to better understand the risks versus benefits of different types of intermittent fasting regimens in middle-age and older individuals.

Application of social cognitive theory in weight management: Time for a biological component?

Despite the utility of social cognitive theory for facilitating individual behavior changes needed for initial weight loss, this model has been less effective in facilitating adherence to recommended lifestyle changes required for sustainable weight-loss maintenance. One potential reason for the limited long-term effectiveness of lifestyle interventions guided by this model is that the model does not consider the important influence that biology can have on weight-relevant behaviors, during both weight loss and weight-loss maintenance, via sensations of hunger and satiety and changes in energy metabolism (expenditure and fat oxidation). We describe here a proposed revision to social cognitive theory that allows for biological factors to exist in reciprocal determinism with behavioral, environmental, and personal factors, with the goal of creating a theoretical basis for lifestyle interventions with greater personalization in order to facilitate better long-term adherence and improve weight-loss maintenance.

Innovations in Geroscience to enhance mobility in older adults.

Aging is the primary risk factor for functional decline; thus, understanding and preventing disability among older adults has emerged as an important public health challenge of the 21st century. The science of gerontology - or geroscience - has the practical purpose of "adding life to the years." The overall goal of geroscience is to increase healthspan, which refers to extending the portion of the lifespan in which the individual experiences enjoyment, satisfaction, and wellness. An important facet of this goal is preserving mobility, defined as the ability to move independently. Despite this clear purpose, this has proven to be a challenging endeavor as mobility and function in later life are influenced by a complex interaction of factors across multiple domains. Moreover, findings over the past decade have highlighted the complexity of walking and how targeting multiple systems, including the brain and sensory organs, as well as the environment in which a person lives, can have a dramatic effect on an older person's mobility and function. For these reasons, behavioral interventions that incorporate complex walking tasks and other activities of daily living appear to be especially helpful for improving mobility function. Other pharmaceutical interventions, such as oxytocin, and complementary and alternative interventions, such as massage therapy, may enhance physical function both through direct effects on biological mechanisms related to mobility, as well as indirectly through modulation of cognitive and socioemotional processes. Thus, the purpose of the present review is to describe evolving interventional approaches to enhance mobility and maintain healthspan in the growing population of older adults in the United States and countries throughout the world. Such interventions are likely to be greatly assisted by technological advances and the widespread adoption of virtual communications during and after the COVID-19 era.

Determinants of Adherence in Time-Restricted Feeding in Older Adults: Lessons from a Pilot Study.

Time-restricted feeding (TRF) is a type of intermittent fasting in which no calories are commonly consumed for approximately 12-18 hours on a daily basis. The health benefits of this eating pattern have been shown in overweight adults, with improvements in cardiometabolic risk factors as well as the preservation of lean mass during weight loss. Although TRF has been well studied in younger and middle-aged adults, few studies have evaluated the effects of TRF in older adults. Thus, the goal of this study was to evaluate older-adult perspectives regarding the real-world advantages, disadvantages, and challenges to adopting a TRF eating pattern among participants aged 65 and over. A four-week single-arm pre- and post-test design was used for this clinical pilot trial TRF intervention study. Participants were instructed to fast for approximately 16 h per day with the daily target range between 14 and 18 h. Participants were provided with the TRF protocol at a baseline visit, along with a pictorial guide that depicted food items and beverages that were allowed and not allowed during fasting windows to reinforce that calorie-containing items were to be avoided. The trial interventionist called each participant weekly to promote adherence, review the protocol, monitor for adverse events, and provide support and guidance for any challenges faced during the intervention. Participants were instructed to complete daily eating time logs by recording the times at which they first consumed calories and when they stopped consuming calories. At the end of the intervention, participants completed an exit interview and a study-specific Diet Satisfaction Survey (Table 1) to assess their satisfaction, feasibility, and overall experience with the study intervention. Of the 10 participants who commenced the study (mean age = 77.1 y; 6 women, 4 men), nine completed the entire protocol. Seven of the ten participants reported easy adjustment to a 16-hour fast and rated the difference from normal eating patterns as minimal. Eight participants reported no decrease in energy during fasting periods, with greater self-reported activity levels in yardwork and light exercise. Adverse events were rare, and included transient headaches, which dissipated with increased water intake, and dizziness in one participant, which subsided with a small snack. The findings of the current trial suggest that TRF is an eating approach that is well tolerated by most older adults. Six participants, however, did not fully understand the requirements of the fasting regimen, despite being provided with specific instructions and a pictorial guide at a baseline visit. This suggests that more instruction and/or participant contact is needed in the early stages of a TRF intervention to promote adherence.

The Effects of Time Restricted Feeding on Overweight, Older Adults: A Pilot Study.

A growing body of evidence indicates that time restricted feeding (TRF), a popular form of intermittent fasting, can activate similar biological pathways as caloric restriction, the only intervention consistently found to extend healthy lifespan in a variety of species. Thus, TRF may have the potential to also improve function in older adults. Given the challenges many individuals have in following calorie restriction regimens over long-time periods, evaluation of alternative approaches that may produce weight loss and improve function in overweight, older adults is important. Ten overweight, sedentary older adults (≥65 years) at risk for, or with mobility impairments, defined by slow gait speed (<1.0 m/s) participated in this trial. All participants received the intervention and were instructed to fast for approximately 16 h per day over the entire four-week intervention. Outcomes included changes in body weight, waist circumference, cognitive and physical function, health-related quality of life, and adverse events. Adherence levels were high (mean = 84%) based on days goal was met, and mean weight loss was 2.6 kg (p < 0.01). Since body composition was not measured in this study, it is unclear if the observed weight loss was due to loss of fat mass, muscle mass, or the combination of fat and muscle mass. There were no significant changes in other outcomes; however, there were clinically meaningful changes in walking speed and improvements in quality of life, with few reported adverse events. The findings of this pilot study suggest that time restricted feeding is an acceptable and feasible eating pattern for overweight, sedentary older adults to follow.