Effect of 6-month calorie restriction on biomarkers of longevity, metabolic adaptation, and oxidative stress in overweight individuals: a randomized controlled trial

Effect of 6-month calorie restriction and exercise on serum and liver lipids and markers of liver function

OBJECTIVE

Nonalcoholic fatty liver disease (NAFLD) and its association with insulin resistance are increasingly recognized as major health burdens. The main objectives of this study were to assess the relation between liver lipid content and serum lipids, markers of liver function and inflammation in healthy overweight subjects, and to determine whether caloric restriction (CR) (which improves insulin resistance) reduces liver lipids in association with these same measures.

METHODS AND PROCEDURES

Forty-six white and black overweight men and women (BMI = 24.7-31.3 kg/m(2)) were randomized to "control (CO)" = 100% energy requirements; "CR" = 25%; "caloric restriction and increased structured exercise (CR+EX)"= 12.5% CR + 12.5% increase in energy expenditure through exercise; or "low-calorie diet (LCD)" = 15% weight loss by liquid diet followed by weight-maintenance, for 6 months. Liver lipid content was assessed by magnetic resonance spectroscopy (MRS) and computed tomography (CT). Lipid concentrations, markers of liver function (alanine aminotransferase (ALT), alkaline phosphatase (ALK)), and whole-body inflammation (tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP)) were measured in fasting blood.

RESULTS

At baseline, increased liver lipid content (by MRS) correlated (P < 0.05) with elevated fasting triglyceride (r = 0.52), ALT (r = 0.42), and hsCRP (r = 0.33) concentrations after adjusting for sex, race, and alcohol consumption. With CR, liver lipid content was significantly lowered by CR, CR+EX, and LCD (detected by MRS only). The reduction in liver lipid content, however, was not significantly correlated with the reduction in triglycerides (r = 0.26; P = 0.11) or with the changes in ALT, high-density lipoprotein (HDL)-cholesterol, or markers of whole-body inflammation.

DISCUSSION

CR may be beneficial for reducing liver lipid and lowering triglycerides in overweight subjects without known NAFLD.

Caloric restriction but not exercise-induced reductions in fat mass decrease plasma triiodothyronine concentrations: a randomized controlled trial

Caloric restriction (CR) decreases circulating triiodothyronine (T(3)) concentration. However, it is not known if this effect is due to body fat mass reductions or due to CR, per se. The purpose of this study was to test the hypothesis that plasma T(3) concentration decreases with CR-induced reductions in fat mass but not in response to similar decreases in fat mass that are induced by exercise. Sedentary, nonobese 50- to 60-year-old men and women with no clinical evidence of cardiovascular or metabolic disease and not taking thyroid medications were randomly assigned to 12 months of caloric restriction (n = 18) or exercise-induced weight loss (n = 17) or to a control group (n = 9). Body weight and composition and plasma concentrations of the thyroid hormones T(3), thyrotropin (TSH), thyroxine (T(4)), and free thyroxine (FT(4)) were measured at baseline and 12 months. Fat mass changed significantly in the CR (-6.3 +/- 1.0 kg) and exercise (-5.5 +/- 1.0 kg) groups but not in the control group (-0.6 +/- 1.4 kg). The changes were not significantly different between the CR and exercise groups. Plasma T(3) concentration decreased in the CR group (-9.8 +/- 2.0 ng/dL, p < 0.0001) but not in the exercise (-3.8 +/- 2.1 ng/dL, p = 0.07) or control (-1.3 +/- 2.8 ng/dL, p = 0.65) groups. TSH, T(4), and FT(4) did not change in any of the study groups. Twelve months of CR decreased circulating T(3) concentrations in middle-aged adults. This effect does not appear to be attributable to changes in body fat mass because a comparable decrease in T(3) concentration was not observed in response to an exercise-induced fat mass reduction.

Insulin-like signaling, nutrient homeostasis, and life span

Insulin-like signaling is critical for nutrient homeostasis, growth and survival. However, work with lower metazoans-Caenorhabditis elegans and Drosophila-shows that reduced insulin-like signaling extends life span. In addition, reduced insulin signaling in higher animals-rodents and humans-causes glucose intolerance and hyperinsulinemia that progresses to diabetes and shortens the life span of affected individuals. Hyperinsulinemia usually develops to maintain glucose homeostasis and prevent the progression toward life-threatening type 2 diabetes; however, increased circulating insulin may have negative effects on the brain that promote age-related disease. We discuss the possibility that the brain is the site where reduced insulin-like signaling can consistently extend mammalian life span-just as reduced insulin-like signaling extends the life span of lower metazoans.

An overview of obesity in children with psychiatric disorders taking atypical antipsychotics

BACKGROUND

Children with psychiatric illness are at greater risk for obesity than those in the general population. In part, this greater risk is due to the escalating use of psychotropic medications. Second-generation antipsychotics effectively treat mental illness but are associated with weight gain. Data for management of obesity in this population is lacking.

METHODS

Articles on obesity, mental illness, and obesity management were reviewed. Keywords included children, adolescents, obesity, weight gain, psychiatric illness, therapy, treatment, and antipsychotic.

RESULTS

For pediatric obesity, educational, nutritional, behavioral, and family-based interventions were identified as nonpharmacological interventions. All nonpharmacological modalities indicate modest to moderate success in weight control or loss. Pharmacological agents, alone or with diet and exercise, appear promising in obesity management.

CONCLUSION

Since there are limited intervention studies available for obese children with psychiatric illness, general childhood obesity studies may be referenced for trials in this population. Long-term efficacy and safety of these interventions are not yet available. Methodological constraints of prior studies include small sample sizes and the absence of randomized, placebo-controlled, and longitudinal trials - highlighting the need for further trials addressing these issues. Clinical monitoring and management of medication-induced obesity remains an important public health concern.

Effect of exercise and calorie restriction on biomarkers of aging in mice

Unlike calorie restriction, exercise fails to extend maximum life span, but the mechanisms that explain this disparate effect are unknown. We used a 24-wk protocol of treadmill running, weight matching, and pair feeding to compare the effects of exercise and calorie restriction on biomarkers related to aging. This study consisted of young controls, an ad libitum-fed sedentary group, two groups that were weight matched by exercise or 9% calorie restriction, and two groups that were weight matched by 9% calorie restriction + exercise or 18% calorie restriction. After 24 wk, ad libitum-fed sedentary mice were the heaviest and fattest. When weight-matched groups were compared, mice that exercised were leaner than calorie-restricted mice. Ad libitum-fed exercise mice tended to have lower serum IGF-1 than fully-fed controls, but no difference in fasting insulin. Mice that underwent 9% calorie restriction or 9% calorie restriction + exercise, had lower insulin levels; the lowest concentrations of serum insulin and IGF-1 were observed in 18% calorie-restricted mice. Exercise resulted in elevated levels of tissue heat shock proteins, but did not accelerate the accumulation of oxidative damage. Thus, failure of exercise to slow aging in previous studies is not likely the result of increased accrual of oxidative damage and may instead be due to an inability to fully mimic the hormonal and/or metabolic response to calorie restriction.

Energy restriction results in a mass-adjusted decrease in energy expenditure in cats that is maintained after weight regain

Dietary energy restriction (ER) is used to treat obesity in cats but it is often unsuccessful. The purpose of this study was to determine whether ER results in a sustained decrease in mass-adjusted energy expenditure (EE) that may oppose weight loss and promote weight regain. EE and body composition were measured in 10 adult neutered cats at 3 time points: baseline (obese cats), during weight loss (40% ER), and following weight regain. The cats started with a body weight (BW) of 6.1 +/- 0.30 kg, body condition score (BCS) of 7.6 +/- 0.14 (on a 9-point scale), and fat body mass (FM) of 38 +/- 1.0% of BW. After weight loss, BW was 5.0 +/- 0.19 kg, BCS was 5.5 +/- 0.07 kg, and FM was 31 +/- 1.6% (P < 0.01). After weight regain, BW was 6.2 +/- 0.30 kg, BCS was 7.7 +/- 0.16, and FM was 42 +/- 1.8% (P < 0.01). Total EE decreased from 1258 +/- 33.7 kJ/d to 1025 +/- 39.6 kJ/d during weight loss (P < 0.001). After weight regain, EE was still lower than baseline (1103 +/- 41.5 kJ/d, P < 0.001). Energy intake (EI) at baseline (1337 +/- 50.6 kJ/d) was higher than EI after weight loss and regain (1217 +/- 61.2 kJ/d), resulting in no differences in energy balance (78 +/- 30.4 and 104 +/- 35.4 kJ/d, respectively, P = 0.581). These results support the hypothesis that ER results in a mass-adjusted decrease in EE in cats that is maintained after weight regain.

Obesity: a review of pathogenesis and management strategies

The prevalence of obesity in the developed world is increasing. Approximately 23% of adult Canadians (5.5 million people) are obese. Obesity is associated with an increased risk of developing several comorbid diseases, ranging from cardiovascular diseases to cholelithiasis and nonalcoholic fatty liver disease. The etiology of obesity is multifactorial, involving a complex interaction among genetics, hormones and the environment. The available evidence and recommendations for nonpharmacological management of obesity, including dietary therapy, physical activity and behavioural therapy, in addition to pharmacotherapy are discussed. A brief discussion on endoscopic and surgical procedures is undertaken. Several antiobesity treatment options are available and may be indicated in appropriate situations. Selecting obesity therapy may be guided by body mass index measurements, comorbid illnesses and patient preference.

Oxidative stress and vascular disease in diabetes: is the dichotomization of insulin signaling still valid?

The current wisdom indicates that insulin's positive effects, normoglycemia, vasodilation, and anti-inflammation, are mediated by the canonical phosphoinositide 3-kinase (PI3K)/Akt pathway whereas the negative effects are mediated by the mitogen-activated protein kinase (MAPK)/extracellular regulated kinase (ERK) pathway. Much of the intracellular oxidant stress is mediated by the MAPK/ERK pathway which is a downstream signal also for other proatherogenic hormones such as angiotensin II. However, recent evidence links MAPK activation to antioxidant activity and vascular protection. We argue against a dichotomization of insulin signaling also in light of the concept that ERK-MAPK represents a critical node in the intracellular insulin network responsible for several positive effects related not only to vascular function but also to life span.

Mechanisms underlying caloric restriction and lifespan regulation: implications for vascular aging

This review focuses on the emerging evidence that attenuation of the production of reactive oxygen species and inhibition of inflammatory pathways play a central role in the antiaging cardiovascular effects of caloric restriction. Particular emphasis is placed on the potential role of the plasma membrane redox system in caloric restriction-induced pathways responsible for sensing oxidative stress and increasing cellular oxidative stress resistance. We propose that caloric restriction increases bioavailability of NO, decreases vascular reactive oxygen species generation, activates the Nrf2/antioxidant response element pathway, inducing reactive oxygen species detoxification systems, exerts antiinflammatory effects, and, thereby, suppresses initiation/progression of vascular disease that accompany aging.

Psychosocial and behavioral pre-treatment predictors of weight loss outcomes

This study tested whether baseline behavioral and psychological variables predict weight and fat loss among overweight, non-obese individuals participating in a six-month calorie restriction trial. Participants (N=48) were randomly assigned to four groups, three of which included a calorie restriction program and one of which served as a healthy diet weight maintenance control. For the purposes of this study, data were analyzed only for participants assigned to the three calorie restriction groups (n=36). Ten psychological and behavioral measures were investigated through principal components factor analysis to examine whether these measures were assessing similar or distinct psychological and behavioral constructs. Based on the obtained six-factor solution, one measure from each domain was selected for inclusion in hierarchical regression analyses, which was used to test the relative importance of psychosocial and behavioral variables in predicting percent weight and fat loss over six months. After controlling for demographic and treatment variables, the behavioral and psychological measures of negative mood states, poor psychosocial functioning, and somatic symptoms were associated with less weight loss (R2=0.68, p<0.001) and fat loss (R2=0.65, p<0.001) over six months. Among overweight individuals, poor psychological adjustment, somatic symptoms, and negative mood states appear to form a psychosocial profile that is predictive of less weight and fat loss in calorie restriction programs.

Calorie restriction and cardiometabolic health

An epidemic of overweight/obesity and type 2 diabetes, caused by overeating nutrient-poor energy-dense foods and a sedentary lifestyle, is spreading rapidly throughout the world. Abdominal obesity represents a serious threat to health because it increases the risk of developing many chronic diseases, including cardiovascular disease and cancer. Calorie restriction (CR) with adequate nutrition improves cardiometabolic health, prevents tumorigenesis and increases life span in experimental animals. The purpose of this review is to evaluate the metabolic and clinical implications of CR with adequate nutrition in humans, within the context of data obtained in animal models. It is unlikely that information regarding the effect of CR on maximal life span in humans will become available in the foreseeable future. In young and middle-aged healthy individuals, however, CR causes many of the same cardiometabolic adaptations that occur in long-lived CR rodents, including decreased metabolic, hormonal and inflammatory risk factors for diabetes, hypertension, cardiovascular disease and cancer. Unraveling the mechanisms that link calorie intake and body composition with metabolism and aging will be a major step in understanding the age-dependency of a wide range of human diseases and will also contribute to improve the general quality of life at old ages.

Molecular mechanisms of life- and health-span extension: role of calorie restriction and exercise intervention

The aging process results in a gradual and progressive structural deterioration of biomolecular and cellular compartments and is associated with many pathological conditions, including cardiovascular disease, stroke, Alzheimer's disease, osteoporosis, sarcopenia, and liver dysfunction. Concomitantly, each of these conditions is associated with progressive functional decline, loss of independence, and ultimately disability. Because disabled individuals require care in outpatient or home care settings, and in light of the social, emotional, and fiscal burden associated with caring for an ever-increasing elderly population, research in geriatric medicine has recently focused on the biological mechanisms that are involved in the progression towards functional decline and disability to better design treatment and intervention strategies. Although not completely understood, the mechanisms underlying the aging process may partly involve inflammatory processes, oxidative damage, mitochondrial dysfunction, and apoptotic tissue degeneration. These hypotheses are based on epidemiological evidence and data from animal models of aging, as well as interventional studies. Findings from these studies have identified possible strategies to decrease the incidence of age-related diseases and delay the aging process. For example, lifelong exercise is known to extend mean life-span, whereas calorie restriction (CR) increases both mean and maximum life-span in a variety of species. Optimal application of these intervention strategies in the elderly may positively affect health-related outcomes and possibly longevity. Therefore, the scope of this article is to (i) provide an interpretation of various theories of aging from a "health-span" perspective; (ii) describe interventional testing in animals (CR and exercise); and (iii) provide a translational interpretation of these data.

Hormesis in aging

Hormesis in aging is represented by mild stress-induced stimulation of protective mechanisms in cells and organisms resulting in biologically beneficial effects. Single or multiple exposure to low doses of otherwise harmful agents, such as irradiation, food limitation, heat stress, hypergravity, reactive oxygen species and other free radicals have a variety of anti-aging and longevity-extending hormetic effects. Detailed molecular mechanisms that bring about the hormetic effects are being increasingly understood, and comprise a cascade of stress response and other pathways of maintenance and repair. Although the extent of immediate hormetic effects after exposure to a particular stress may only be moderate, the chain of events following initial hormesis leads to biologically amplified effects that are much larger, synergistic and pleiotropic. A consequence of hormetic amplification is an increase in the homeodynamic space of a living system in terms of increased defence capacity and reduced load of damaged macromolecules. Hormetic strengthening of the homeodynamic space provides wider margins for metabolic fluctuation, stress tolerance, adaptation and survival. Hormesis thus counter-balances the progressive shrinkage of the homeodynamic space, which is the ultimate cause of aging, diseases and death. Healthy aging may be achieved by hormesis through mild and periodic, but not severe or chronic, physical and mental challenges, and by the use of nutritional hormesis incorporating mild stress-inducing molecules called hormetins. The established scientific foundations of hormesis are ready to pave the way for new and effective approaches in aging research and intervention.

Effect of calorie restriction on resting metabolic rate and spontaneous physical activity

OBJECTIVE

It is unclear if resting metabolic rate (RMR) and spontaneous physical activity (SPA) decrease in weight-reduced non-obese participants. Additionally, it is unknown if changes in SPA, measured in a respiratory chamber, reflect changes in free-living physical activity level (PAL).

RESEARCH METHODS AND PROCEDURES

Participants (N = 48) were randomized into 4 groups for 6 months: calorie restriction (CR, 25% restriction), CR plus structured exercise (CR+EX, 12.5% restriction plus 12.5% increased energy expenditure via exercise), low-calorie diet (LCD, 890 kcal/d supplement diet until 15% weight loss, then weight maintenance), and control (weight maintenance). Measurements were collected at baseline, Month 3, and Month 6. Body composition and RMR were measured by DXA and indirect calorimetry, respectively. Two measures of SPA were collected in a respiratory chamber (percent of time active and kcal/d). Free-living PAL (PAL = total daily energy expenditure by doubly labeled water/RMR) was also measured. Regression equations at baseline were used to adjust RMR for fat-free mass and SPA (kcal/d) for body weight.

RESULTS

Adjusted RMR decreased at Month 3 in the CR group and at Month 6 in the CR+EX and LCD groups. Neither measure of SPA decreased significantly in any group. PAL decreased at Month 3 in the CR and LCD groups, but not in the CR+EX group, who engaged in structured exercise. Changes in SPA in the chamber and free-living PAL were not related.

DISCUSSION

Body weight is defended in non-obese participants during modest caloric restriction, evidenced by metabolic adaptation of RMR and reduced energy expenditure through physical activity.

Genome instability is increased in lymphocytes of women with polycystic ovary syndrome and is correlated with insulin resistance

BACKGROUND

Polycystic ovary syndrome (PCOS) is associated with insulin resistance and reproductive and metabolic abnormalities. The potential genetic contributors to PCOS are unclear. We tested the hypothesis that genomic instability (chromosome malsegregation and DNA damage) is increased in PCOS.

METHODS

Overweight age, weight and BMI-matched women with (n=14) and without (n=16) PCOS (age 34.2+/-6.0 years, weight 90.7+/-14.5 kg, BMI 34.0+/-5.6 kg/m(2), mean+/-S.D.) were assessed for chromosome malsegregation (assessed by X chromosome chromogenic in situ hybridisation) and micronucleus frequency (assessed by the cytokinesis block micronucleus index) in lymphocytes.

RESULTS

Women with PCOS had significantly elevated genomic instability as demonstrated by a significantly higher number of binucleated lymphocytes containing micronuclei, total number of micronuclei, a higher proportion of aneuploid X chromosome signals (2:1 X and 3:1 X) and a lower proportion of normal X chromosome segregation signals (2:2 X) in binucleated lymphocytes than women without PCOS. Surrogate measures of insulin resistance positively correlated with the proportion of aneuploid cells (2:1; 3:1 X chromosome signals) and inversely with the proportion of normal cells (2:2 X chromosome signals).

CONCLUSION

Women with PCOS display increased genomic instability (higher micronuclei and chromosome malsegregation) compared to women without PCOS and this increase may be related to the insulin resistance phenotype.

Small molecule activators of SIRT1 as therapeutics for the treatment of type 2 diabetes

Calorie restriction extends lifespan and produces a metabolic profile desirable for treating diseases of ageing such as type 2 diabetes. SIRT1, an NAD+-dependent deacetylase, is a principal modulator of pathways downstream of calorie restriction that produce beneficial effects on glucose homeostasis and insulin sensitivity. Resveratrol, a polyphenolic SIRT1 activator, mimics the anti-ageing effects of calorie restriction in lower organisms and in mice fed a high-fat diet ameliorates insulin resistance, increases mitochondrial content, and prolongs survival. Here we describe the identification and characterization of small molecule activators of SIRT1 that are structurally unrelated to, and 1,000-fold more potent than, resveratrol. These compounds bind to the SIRT1 enzyme-peptide substrate complex at an allosteric site amino-terminal to the catalytic domain and lower the Michaelis constant for acetylated substrates. In diet-induced obese and genetically obese mice, these compounds improve insulin sensitivity, lower plasma glucose, and increase mitochondrial capacity. In Zucker fa/fa rats, hyperinsulinaemic-euglycaemic clamp studies demonstrate that SIRT1 activators improve whole-body glucose homeostasis and insulin sensitivity in adipose tissue, skeletal muscle and liver. Thus, SIRT1 activation is a promising new therapeutic approach for treating diseases of ageing such as type 2 diabetes.

Lifelong caloric restriction and interleukin-6 secretion from adipose tissue: effects on physical performance decline in aged rats

We investigated whether caloric restriction (CR) improves physical performance in a rodent model of aging, and whether this effect is accompanied with a decrease in visceral adipose tissue production of proinflammatory cytokines. Body composition, standardized physical performance measures, as well as in vitro visceral adipose tissue cytokine secretion and circulating levels of an inflammatory marker were cross-sectionally assessed in ad libitum (AL)-fed and lifelong CR Fischer 344 x Brown Norway male rats aged 18, 24, and 29 months. Fat to lean mass ratio increased and physical performance declined with age in the AL rats. Compared to AL rats, CR rats had lower fat mass, fat to lean ratio, adipose tissue secretion of interleukin-6, and circulating levels of C-reactive protein, and higher physical performance scores. Therefore, CR may be an effective intervention for improving functional status into advanced age and is perhaps mediated via a reduction in adipose tissue-generated proinflammatory cytokine production.

Diet, energy metabolism and mitochondrial biogenesis

PURPOSE OF REVIEW

This review highlights some recent findings regarding nutritional and endocrine regulators of mitochondrial mass and function and their association with insulin resistance.

RECENT FINDINGS

Insulin resistance is central to many chronic metabolic diseases, including obesity, type 2 diabetes, dyslipidemia, and hypertension. Insulin resistance in skeletal muscle is associated with lower mitochondrial mass and reduced oxidative phosphorylation. Part of the mitochondrial dysfunction can be triggered by adverse nutrition. Increased fatty acid exposure, resulting from high fats diets or overfeeding, is linked to both decreased mitochondrial number and markers of oxidative phosphorylation. Caloric restriction and the adiponectin signaling pathway, however, can stimulate mitochondrial biogenesis by elevating the transcriptional machinery that regulates mitochondrial mass, improving mitochondrial efficiency, activating the peroxisome proliferator-activated receptor coactivator 1alpha mediated reactive oxygen species scavenging mechanism, and lowering reactive oxygen species production.

SUMMARY

States of insulin resistance are characterized by defects in lipid and carbohydrate metabolism. Abnormalities in oxidative capacity, however, can be partially normalized by caloric restriction by modulating mitochondrial mass in an insulin sensitizing manner.

Inhibition of retinoic acid-induced skin irritation in calorie-restricted mice

Mice on a calorie-restricted (CR) diet (total calories restricted to 70% of ad libitum; AL) for periods of time ranging from 3 to 18 months were examined for response to topical treatment with all-trans retinoic acid (RA). Daily application of a 0.1% solution of RA to the shaved skin of UM-HET3 mice on an AL diet produced a severe irritation that was evident by day 4, maximal at day 7–8 and still detectable at day 14. Skin irritation was characterized by redness, dryness, flaking and failure of the hair to grow at the treated site. In CR mice, the same treatment produced little detectable irritation. Animals were sacrificed at the end of the retinoid-treatment period (day 7 or day 14) and skin from these animals was examined histologically. In both AL and CR mice, a similar degree of epidermal hyperplasia was observed. Numerous inflammatory cells (mononuclear cells and granulocytes) were present in the skin of both groups. Occasional S100-positive cells (presumably Langerhans cells) were also observed in the epidermis of skin from both groups. S100-positive cells were also observed in the dermis. When skin from CR and AL mice was incubated in organ culture for 3 days (on day 7 after initiation of RA treatment), similar levels of four different pro-inflammatory cytokines were found in the conditioned medium. Soluble type I collagen levels were also similar. In contrast, the level of matrix metalloproteinase-9 was lower in the conditioned medium of skin from CR mice than in conditioned medium from skin cultures of AL mice. Taken together, these studies suggest that CR may provide a way to mitigate the irritation that normally accompanies RA treatment without compromising the beneficial effects of retinoid use. CR appears to exert a protective effect at the target tissue level rather than by a reduction in pro-inflammatory events, per se.

Endocrine regulation of ageing

Over the past 15 years it has become clear that mutations in genes that regulate endocrine signalling pathways can prolong lifespan. Lifespan can be increased by altered endocrine signalling in a group of cells or a single tissue, which indicates that crosstalk between tissues functions to coordinate ageing of the organism. These endocrine pathways might serve as targets for the manipulation of the ageing process and prevention of age-related diseases.

Obesity in neurobiology

Obesity reflects an imbalance between energy uptake and expenditure that is mediated by behavior. Obesity is a growing epidemic and a major risk factor for neurobiological diseases like stroke, dementia, intracranial hypertension and sleep disorders. Conversely, obesity can also be induced by neurobiological disorders and drugs. The etiology of obesity is complex and includes biology, behavior and environment. Physicians are faced with the need to manage obesity while strategies for prevention and sustained weight reduction are limited. Present treatment options comprise lifestyle modification, diet, pharmacotherapy and bariatric surgery. Considerable headway has been made into elucidating the neurobiological underpinnings of obesogenic behavior. There is now a growing understanding of the metabolic, hormonal and behavioral circuitries that contribute to the complex and redundant system for energy balance. Changing the net balance of this system to prevent or reduce obesity requires multimodal and long-term interventions.

Effect of long-term caloric restriction on oxygen consumption and body temperature in two different strains of mice

The hypothesis, that a decrease in metabolic rate mediates the life span prolonging effect of caloric restriction (CR), was tested using two strains of mice, one of which, C57BL/6, exhibits life span extension as a result of CR, while the other, DBA/2, shows little or no effect. Comparisons of the rate of resting oxygen consumption and body temperature were made between the strains after they were fed ad libitum (AL) or maintained under 40% CR, from 4 to 16 months of age. Ad libitum-fed mice of the two strains weighed the same when young and consumed similar amounts of food throughout the experiment; however, the C57BL/6 mice weighed 25% more than DBA/2 mice at 15 months of age. The rate of oxygen consumption was normalized as per gram body weight, lean body mass or organ weight as well as per animal. The body temperature and the rate of oxygen consumption, expressed according to all of the four criteria, were decreased in the DBA/2 mice following CR. The C57BL/6 mice also showed a CR-related decrease in body temperature and in the rate of oxygen consumption per animal and when normalized according to lean body mass or organ weight. The results of this study indicate that CR indeed lowers the rate of metabolism; however, this effect by CR does not necessarily entail the prolongation of the life span of mice.

Life Extension by Calorie Restriction in Humans

Long-term reduction in energy intake in the diet (calorie restriction [CR]) extends the life of the laboratory rat by about 25%. However, in humans there are no life-long studies of CR, but only short-term trials which indicate that 20% CR acting over periods of 2-6 years is associated with reduced body weight, blood pressure, blood cholesterol, and blood glucose--risk factors for the major killer diseases of cardiovascular disease and diabetes. In addition, recent research has shown that CR for 6 months is able to improve biomarkers for longevity (deep body temperature and plasma insulin) and thus should increase life expectancy. The magnitude of the life-extension effect of CR in humans can only be estimated. The Okinawans, the longest-lived people on earth, consume 40% fewer calories than the Americans and live only 4 years longer. Similarly, women in United States consume 25% fewer calories than men and live 5 years longer. From the survival studies of overweight and obese people, it is estimated that long-term CR to prevent excessive weight gain could add only 3-13 years to life expectancy. Thus the effects of CR on human life extension are probably much smaller than those achieved by medical and public health interventions, which have extended life by about 30 years in developed countries in the 20th century, by greatly reducing deaths from infections, accidents, and cardiovascular disease.

Characterization of weight loss and weight regain mechanisms after Roux-en-Y gastric bypass in rats

Roux-en-Y gastric bypass (RYGB) is the most effective therapy for morbid obesity, but it has a ∼20% failure rate. To test our hypothesis that outcome depends on differential modifications of several energy-related systems, we used our established RYGB model in Sprague-Dawley diet-induced obese (DIO) rats to determine mechanisms contributing to successful (RGYB-S) or failed (RYGB-F) RYGB. DIO rats were randomized to RYGB, sham-operated Obese, and sham-operated obese pair-fed linked to RYGB (PF) groups. Body weight (BW), caloric intake (CI), and fecal output (FO) were recorded daily for 90 days, food efficiency (FE) was calculated, and morphological changes were determined. d-Xylose and fat absorption were studied. Glucose-stimulated vagal efferent nerve firing rates of stomach were recorded. Gut, adipose, and thyroid hormones were measured in plasma. Mitochondrial respiratory complexes in skeletal muscle and expression of energy-related hypothalamic and fat peptides, receptors, and enzymes were quantified. A 25% failure rate occurred. RYGB-S, RYGB-F, and PF rats showed rapid BW decrease vs. Obese rats, followed by sustained BW loss in RYGB-S rats. RYGB-F and PF rats gradually increased BW. BW loss in RYGB-S rats is achieved not only by RYGB-induced decreased CI and increased FO, but also via sympathetic nervous system activation, driven by increased peptide YY, CRF, and orexin signaling, decreasing FE and energy storage, demonstrated by reduced fat mass associated with the upregulation of mitochondrial uncoupling protein-2 in fat. These events override the compensatory response to the drop in leptin levels aimed at conserving energy.

Glucose restriction extends Caenorhabditis elegans life span by inducing mitochondrial respiration and increasing oxidative stress

Increasing cellular glucose uptake is a fundamental concept in treatment of type 2 diabetes, whereas nutritive calorie restriction increases life expectancy. We show here that increased glucose availability decreases Caenorhabditis elegans life span, while impaired glucose metabolism extends life expectancy by inducing mitochondrial respiration. The histone deacetylase Sir2.1 is found here to be dispensable for this phenotype, whereas disruption of aak-2, a homolog of AMP-dependent kinase (AMPK), abolishes extension of life span due to impaired glycolysis. Reduced glucose availability promotes formation of reactive oxygen species (ROS), induces catalase activity, and increases oxidative stress resistance and survival rates, altogether providing direct evidence for a hitherto hypothetical concept named mitochondrial hormesis or "mitohormesis." Accordingly, treatment of nematodes with different antioxidants and vitamins prevents extension of life span. In summary, these data indicate that glucose restriction promotes mitochondrial metabolism, causing increased ROS formation and cumulating in hormetic extension of life span, questioning current treatments of type 2 diabetes as well as the widespread use of antioxidant supplements.

Human reproductive costs and the predicted response to dietary restriction

The question has arisen in the literature as to whether dietary restriction (DR) will have a significant effect on human longevity. I initially use literature data to estimate the energy costs necessary to carry a human from conception to caloric self-sufficiency to be approximately 12.6 x 10(6)kcal, which amounts to approximately 25% of the the two parents' combined daily caloric intake for 20 years. Similar levels of financial costs are expended in developed societies. Thus, human reproductive costs are high enough to permit a DR response. I then review four different models relating diet and life span, three of which have been previously used to estimate the effects of DR on humans. A review of the pertinent literature suggests that these three models, while plausible, are not capable of making robust predictions that are consistent with human data not used in their development. Given this weakness, none of the predictions made by these theories should be relied on for policy development at this time. The fourth, or biocultural model, examined combines biologic and cultural factors. Human longevity is more complex than our model systems have led us to believe, and thus any solution will require the development of a new quantitative model. The outlines of a suggested quantitative biocultural model based on the prior model of Crews and the disposable soma model of Shanley and Kirkwood are presented and a prediction of the possible data outcomes is made. If the human cultural pro-longevity practices can be quantified in terms of their effect on energy allocation, then this model may serve in future as a realistic quantitative model capable of identifying pertinent pathways and making robust predictions.

One hundred pound weight losses with an intensive behavioral program: changes in risk factors in 118 patients with long-term follow-up

BACKGROUND

Treatment of severe obesity is difficult; in the past, lifestyle measures did not prove effective. Recently, however, intensive behavioral interventions using meal replacements and low-energy diets have enabled some severely obese persons to achieve nonobese weights.

OBJECTIVE

We assessed rates of weight loss, changes in risk factors and medication requirements, and long-term weight maintenance in patients who lost >or=100 pounds (45.5 kg).

DESIGN

Over a 9-y period, we prospectively identified patients who lost >or=100 pounds (45.5 kg) and actively recorded follow-up weights. Charts were systematically reviewed to assess outcome measures and side effects. The intervention included meal replacements (shakes and entrées), low-energy diets, weekly classes, and training in record keeping and physical activity. Assessments included weekly weights, laboratory studies, medication use, lifestyle behaviors, side effects, and follow-up weights.

RESULTS

Sixty-three men and 55 women lost >or=100 pounds. At baseline, the subjects' average weight was 160 kg, 97% had >or=1 obesity-related comorbidity, and 74% were taking medications for comorbidities. Weight losses averaged 61 kg in 44 wk. Medications were discontinued in 66% of patients with a cost savings of $100/mo. Despite medication discontinuation, significant decreases in LDL cholesterol (20%), triacylglycerol (36%), glucose (17%), and systolic (13%) and diastolic (15%) blood pressure values were seen. Side effects were mild, and only 2 patients had severe or serious adverse events. At an average of 5 y of follow-up, patients were maintaining an average weight loss of 30 kg.

CONCLUSION

Intensive behavioral intervention can be very effective with minimal risk for certain severely obese persons.

Caloric restriction in humans

Studies on mice and rats have demonstrated that calorie restriction (CR) slows primary aging, has a protective effect against secondary aging, and markedly decreases the incidence of malignancies. However, the only way to determine whether CR "works" in humans is to conduct studies on people. Such studies are difficult to perform in free-living people. While research on CR in humans is still at an early stage, a modest amount of information has accumulated. Because it is not feasible to conduct studies of the effects of CR on longevity in humans, surrogate measures have to be used. Preliminary information obtained using this approach provides evidence that CR provides a powerful protective effect against secondary aging in humans. This evidence consists of the finding that risk factors for atherosclerosis and diabetes are markedly reduced in humans on CR. Humans on CR also show some of the same adaptations that are thought to be involved in slowing primary aging in rats and mice. These include a very low level of inflammation as evidenced by low circulating levels of c-reactive protein and TNFalpha, serum triiodothyronine levels at the low end of the normal range, and a more elastic "younger" left ventricle (LV), as evaluated by echo-doppler measures of LV stiffness.

Alternate-day fasting and chronic disease prevention: a review of human and animal trials

Calorie restriction (CR) and alternate-day fasting (ADF) represent 2 different forms of dietary restriction. Although the effects of CR on chronic disease prevention were reviewed previously, the effects of ADF on chronic disease risk have yet to be summarized. Accordingly, we review here animal and human evidence concerning ADF and the risk of certain chronic diseases, such as type 2 diabetes, cardiovascular disease, and cancer. We also compare the magnitude of risk reduction resulting from ADF with that resulting from CR. In terms of diabetes risk, animal studies of ADF find lower diabetes incidence and lower fasting glucose and insulin concentrations, effects that are comparable to those of CR. Human trials to date have reported greater insulin-mediated glucose uptake but no effect on fasting glucose or insulin concentrations. In terms of cardiovascular disease risk, animal ADF data show lower total cholesterol and triacylglycerol concentrations, a lower heart rate, improved cardiac response to myocardial infarction, and lower blood pressure. The limited human evidence suggests higher HDL-cholesterol concentrations and lower triacylglycerol concentrations but no effect on blood pressure. In terms of cancer risk, there is no human evidence to date, yet animal studies found decreases in lymphoma incidence, longer survival after tumor inoculation, and lower rates of proliferation of several cell types. The findings in animals suggest that ADF may effectively modulate several risk factors, thereby preventing chronic disease, and that ADF may modulate disease risk to an extent similar to that of CR. More research is required to establish definitively the consequences of ADF.

Mitochondria as key components of the stress response

The exquisitely orchestrated adaptive response to stressors that challenge the homeostasis of the cell and organism involves important changes in mitochondrial function. A complex signaling network enables mitochondria to sense internal milieu or environmental changes and to adjust their bioenergetic, thermogenic, oxidative and/or apoptotic responses accordingly, aiming at re-establishment of homeostasis. Mitochondrial dysfunction is increasingly recognized as a key component in both acute and chronic allostatic states, although the extent of its role in the pathogenesis of such conditions remains controversial. Genetic and environmental factors that determine mitochondrial function might contribute to the significant variation of the stress response. Understanding the often reciprocal interplay between stress mediators and mitochondrial function is likely to help identify potential therapeutic targets for many stress and mitochondria-related pathologies.

Aging, resting metabolic rate, and oxidative damage: results from the Louisiana Healthy Aging Study

BACKGROUND

The aging process occurs at variable rates both among and within species and may be related to the variability in oxygen consumption and free radical production impacting oxidative stress. The current study was designed to test whether nonagenarians have a relatively low metabolic rate and whether it is associated with low levels of oxidative stress relative to age.

METHODS

Resting metabolic rate (RMR) and markers of oxidative stress to lipids, proteins, and DNA were measured in three groups of individuals aged 20-34 (n=47), 60-74 (n=49), and>or=90 years (n=74).

RESULTS

RMR, adjusted for fat-free mass, fat mass, and sex, was lower in both older groups when compared to the young group (p

CONCLUSIONS

This study confirms an age-related decline in RMR independent of changes in body composition but surprisingly did not show an accumulation of oxidative damage with increasing age. Our data challenge the theory that RMR is a significant determinant of oxidative stress and therefore contributes to the aging process.

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Key Words Collapse

MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Aging/physiology
• Basal Metabolism/physiology
• Body Composition
• DNA/metabolism
• Female
• Humans
• Lipid Metabolism
• Male
• Middle Aged
• Oxidative Stress/physiology
• Proteins/metabolism

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Grants

• R01 GM042056 NIGMS NIH HHS
• P30 DK072476 NIDDK NIH HHS
• P01 AG022064 NIA NIH HHS
• P01 GM015431 NIGMS NIH HHS
• R37 GM042056 NIGMS NIH HHS
• P50 GM015431 NIGMS NIH HHS

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Affiliation(s)

Madlyn I. Frisard Pennington Biomedical Research Center, Baton Rouge, Louisiana
Amanda Broussard Pennington Biomedical Research Center, Baton Rouge, Louisiana
Sean S. Davies Vanderbilt University, Nashville, Tennessee
L. Jackson Roberts Vanderbilt University, Nashville, Tennessee
Jennifer Rood Pennington Biomedical Research Center, Baton Rouge, Louisiana
Lillian de Jonge Pennington Biomedical Research Center, Baton Rouge, Louisiana
Xiaobing Fang Pennington Biomedical Research Center, Baton Rouge, Louisiana
S. Michal Jazwinski Pennington Biomedical Research Center, Baton Rouge, Louisiana
Walter A. Deutsch Pennington Biomedical Research Center, Baton Rouge, Louisiana
Eric Ravussin Pennington Biomedical Research Center, Baton Rouge, Louisiana

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Collaborators Collapse

Rat models of caloric intake and activity: relationships to animal physiology and human health

Every rodent experiment is based on important parameters concerning the levels of caloric intake and physical activity. In many cases, these decisions are not made consciously, but are based on traditional models. For experimental models directed at the study of caloric intake and activity, the selection of parameters is usually aimed at modeling human conditions, the ultimate goal of which is to gain insight into the pathophysiology of the disease process in man. In each model, it is important to understand the influence of diet, exercise, and genetic background on physiology and the development of disease states. Along the continuum of energy intake from caloric restriction to high-fat feeding, and of energy output from total inactivity to forced exercise, a number of models are used to study different disease states. In this paper, we will evaluate the influence of the quantity and composition of diet and exercise in several animal models, and will discuss how each model can be applied to various human conditions. This review will be limited to traditional models using the rat as the experimental animal, and although it is not an exhaustive list, the models presented are those most commonly represented in the literature. We will also review the mechanisms by which each affects rat physiology, and will compare these to the analogous mechanisms in the modeled human disease state. We hope that the information presented here will help researchers make choices among the available models and will encourage discussion on the interpretation and extrapolation of results obtained from traditional and novel rodent experiments on diet, exercise, and chronic disease.

Cancer control through principles of systems science, complexity, and chaos theory: a model

Cancer is a significant medical and societal problem. This reality arises from the fact that an exponential and an unrestricted cellular growth destabilizes human body as a system. From this perspective, cancer is a manifestation of a system-in-failing.A model of normal and abnormal cell cycle oscillations has been developed incorporating systems science, complexity, and chaos theories. Using this model, cancer expresses a failing subsystem and is characterized by a positive exponential growth taking place in the outer edge of chaos. The overall survival of human body as a system is threatened. This model suggests, however, that cancer's exponential cellular growth and disorganized complexity could be controlled through the process of induction of differentiation of cancer stem cells into cells of low and basic functionality. This concept would imply reorientation of current treatment principles from cellular killing (cyto-toxic therapies) to cellular retraining (cyto-education).

Examination of cognitive function during six months of calorie restriction: results of a randomized controlled trial

BACKGROUND

Calorie restriction increases longevity in many organisms, and calorie restriction or its mimetic might increase longevity in humans. It is unclear if calorie restriction/dieting contributes to cognitive impairment. During this randomized controlled trial, the effect of 6 months of calorie restriction on cognitive functioning was tested.

METHODS

Participants (n = 48) were randomized to one of four groups: (1) control (weight maintenance), (2) calorie restriction (CR; 25% restriction), (3) CR plus structured exercise (CR + EX, 12.5% restriction plus 12.5% increased energy expenditure via exercise), or (4) low-calorie diet (LCD; 890 kcal/d diet until 15% weight loss, followed by weight maintenance). Cognitive tests (verbal memory, visual memory, attention/concentration) were conducted at baseline and months 3 and 6. Mixed linear models tested if cognitive function changed significantly from baseline to months 3 and 6, and if this change differed by group. Correlation analysis was used to determine if average daily energy deficit (quantified from change in body energy stores) was associated with change in cognitive test performance for the three dieting groups combined.

RESULTS

No consistent pattern of verbal memory, visual retention/memory, or attention/concentration deficits emerged during the trial. Daily energy deficit was not significantly associated with change in cognitive test performance.

CONCLUSIONS

This randomized controlled trial suggests that calorie restriction/dieting was not associated with a consistent pattern of cognitive impairment. These conclusions must be interpreted in the context of study limitations, namely small sample size and limited statistical power. Previous reports of cognitive impairment might reflect sampling biases or information processing biases.

Has natural selection in human populations produced two types of metabolic syndrome (with and without fatty liver)?

Fatty liver is closely related to the development of the insulin resistance syndrome that largely results from abnormal insulin signaling in three major organs: (i) skeletal muscle in which insulin sensitivity depends on fat content and metabolic activity (exercise); (ii) adipose tissue, which serves as a reservoir of energy in the form of triglycerides; and (iii) the liver, which variably serves as a source or storage site of carbohydrates and lipids. In many respects, the fatty liver resembles a mixture of brown adipose tissue (microvesicular steatosis) and white adipose tissue (macrovesicular steatosis) including the stages of fatty droplet accumulation, and the expression of uncoupling proteins and perilipin-like substances. Furthermore, the development of an inflammatory infiltrate and the increased production of cytokines as occurs in adipose tissue, suggest that the liver in some individuals serves as an extension of adipose tissue. Moreover, current evidence indicates that these morphological changes represent altered gene expression similar to that of adipocytes. However, fatty liver does not appear to be a uniform feature of the metabolic syndrome and there is substantial variation in humans in the development of fatty liver independent of insulin resistance. In this regard, the variable development of fatty liver in Palmipedes (migratory fowl) and its close relationship to skeletal muscle utilization of fatty acids, lipoprotein metabolism and thermoregulation are instructive. The predilection to non-alcoholic fatty liver disease among some varieties of Palmipedes suggests that the development of fatty liver represents an adaptive process, closely integrated with skeletal muscle fat utilization and adipose tissue distribution, and facilitates survival in a very cold, resource-scarce environment. Variation in human populations with metabolic syndrome likewise suggests that the trait evolved in populations exposed in ancient times to different environmental challenges and, because the liver plays a central role in lipid metabolism, the presence or absence of fatty liver is likely to be integrated with insulin sensitivity in other target organs and with lipoprotein metabolism.

Beneficial biochemical outcomes of late-onset dietary restriction in rodents

Dietary restriction (DR) or caloric restriction (CR) is the well-established means to retard aging, leading to prolongation of mean and maximum life span in many animal models. We have been interested in the possibility of extending the span of health of elderly people rather than increasing longevity, and therefore studied the effects of DR/CR initiated late in life in rodent models. We restricted food for 2-3.5 months in mice or rats of middle or old ages, which would perhaps be equivalent to 50-70 years of age in humans. We found that: (1) Potentially harmful altered proteins were reduced in the animals' tissues. (2) Extended half-life of protein in aged animals was shortened in mouse hepatocytes, suggesting improved protein turnover. (3) Reduced proteasome activity was upregulated in rat liver and skeletal muscle. (4) Protein carbonyls were decreased in rat liver mitochondria and skeletal muscle cytoplasm, and also oxidative DNA damage was reduced in rat liver nucleus, suggesting amelioration of oxidative stress. (5) Reduced apo A-IV and C-III metabolism in aged mouse was restored, suggesting increase in reduced fatty acid mobilization. (6) The carbonyl modification in histones that was paradoxically reduced in aged rat was increased to the level of a young animal, suggesting restoration of reduced transcription. These findings in rodents suggest a possibility that DR/CR is beneficial if applied in middle-aged or early senescent obese people. We argue, however, that application of late life DR/CR can be harmful if practiced in people who are already eating modestly.

How dietary restriction catalyzed the evolution of the human brain: An exposition of the nutritional neurotrophic neoteny theory

The purpose of this theoretical treatise is to explain the evolution of human encephalization. The evolutionary expansion of the human brain is herein regarded as a single component of an interrelated complex encompassing depressed somatic and sexual development and increased longevity. These cardinal phenotypic features, termed the Quadripartite Complex, were selected for their adaptiveness amidst the environmental deterioration extant during the formative phase of human evolution--the Plio-Pleistocene period. This interval of environmental transformation inevitably eventuated in ecological alteration and dietary diminution. Suggestively, experimentally imposed dietary restriction routinely results in lengthened lifespan, delayed sexual maturation, depressed growth and increased encephalization as a concomitant consequence of body mass reduction and brain mass maintenance. Thus, dietary restriction ostensibly induces discernible metabolic adaptations whether incurred ontologically or evolutionarily. Several experiments indicate that dietary restriction promotes the preservation and generation of neurons via induction of neurotrophic factors. To the extent that neurogenesis is a molecular mediator of mental acuity, it is evident that nutrition and cognition are intimately linked. Extrapolating to an evolutionary context, increased intelligence ought to confer advantages to organisms enduring dietary deprivation insofar as increased intelligence ensures more facile food acquisition. This reasoning underlies the nutritional neurotrophic neoteny (N(3)) theory, which holds that humans exhibit an altered pattern of neurotrophin expression resulting from positive selection for heightened intelligence amidst environmental deterioration and consequent dietary deficiency. The altered pattern of neurotrophin expression exhibited by humans, it is deduced, results in a protracted phase of developmental neurogenesis and a resultant retention of neurons that would otherwise be extirpated due to programmed cell death. Importantly, during neonatal neurogenesis mammals produce an excess number of neurons whose eventual destruction is dictated by neurotrophic factors. An altered pattern of neurotrophin expression during neurogenesis, as N(3) proposes, could therefore furnish a larger adult brain. As to how humans could afford to accrete exuberant neural tissue under conditions of chronic food scarcity the homo hypothalamic hypometabolism (H(3)) theory offers a plausible answer: reduced growth and delayed sexual maturation, mediated by the hypothalamus and its endocrine effectors, offset the energetic costs of increased encephalization in humans. H(3) is herein presented as a general theory of human evolution while N(3) may be regarded as a special theory of human encephalization.

Vertebrate aging research 2006

This Hot Topics review, the first in a projected annual series, discusses those articles, published in the last year, which seem likely to have a major impact on our understanding of the aging process in mammals and the links between aging and late-life illnesses. The year's highlights include studies of oxidation damage in the very-long-lived naked mole-rat, and of caloric restriction in monkeys, humans, and growth hormone-unresponsive mice. Two studies of resveratrol, one showing its ability to extend lifespan in a short-lived fish, the other demonstrating beneficial effects in mice subjected to a diet high in fat, may well be harbingers of a parade of intervention studies in the coming decade.

Caloric restriction reduces age-related pseudocapillarization of the hepatic sinusoid

Age-related changes in the hepatic sinusoid, called pseudocapillarization, may contribute to the pathogenesis of dyslipidemia. Caloric restriction (CR) is a powerful model for the study of aging because it extends lifespan. We assessed the effects of CR on the hepatic sinusoid to determine whether pseudocapillarization is preventable and hence a target for the prevention of age-related dyslipidemia. Livers from young (6 months) and old (24 months) CR and ad libitum fed (AL) F344 rats were examined using electron microscopy and immunohistochemistry. In old age, there was increased thickness of the liver sinusoidal endothelium and reduced endothelial fenestration porosity. In old CR rats, endothelial thickness was less and fenestration porosity was greater than in old AL rats. Immunohistochemistry showed that CR prevented age-related decrease in caveolin-1 expression and increase in peri-sinusoidal collagen IV staining, but did not alter the age-related increase of von Willebrand's factor. CR reduces age-related pseudocapillarization of the hepatic sinusoid and correlates with changes in caveolin-1 expression.

Long Term Effects of Energy-Restricted Diets Differing in Glycemic Load on Metabolic Adaptation and Body Composition

A randomized controlled trial of high glycemic load (HG) and low glycemic load (LG) diets with food provided for 6 months and self-administered for 6 additional months at 30% caloric restriction (CR) was performed in 29 overweight adults (mean+/-SD, age 35+/-5y; BMI 27.5+/-1.5 kg/m(2)). Total energy expenditure (TEE), resting metabolic rate (RMR), fat and fat free mass (FFM), were measured at 3, 6 and 12 months. Changes in TEE, but not changes in RMR, were greater than accounted for by the loss of FFM and fat mass (P=0.001-0.013) suggesting an adaptive response to long-term CR. There was no significant effect of diet group on change in RMR or TEE. However, in subjects who lost >5% body weight (n=26), the LG diet group had a higher percentage of weight loss as fat than the HG group (p<0.05), a finding that may have implications for dietary recommendations during weight reduction.

Empirical evaluation of the ability to learn a calorie counting system and estimate portion size and food intake

The aim of this study was to determine if: (1) participants could learn the HMR Calorie System by testing if their use of the system was more accurate after training; and (2) estimated portion size and food intake improved with training. A secondary aim was to use PACE (photographic assessment of calorie estimation) to assess if participants learned the HMR system. The PACE consists of pictures of foods, the energy content of which is known. A within-subjects design was used to test the aims of this study. Participants were 44 overweight (25 <or= BMI < 30) adults who were randomly assigned to one of three calorie restriction groups or a weight maintenance group for 6 months. Participants attended weekly sessions and were trained to use the HMR system from weeks 5 to 8. Participants were provided with foods to test if they could effectively use the HMR system and accurately estimate portion size and the amount of food eaten. The PACE was also used to quantify accuracy at using the HMR system. Training resulted in more accurate estimation of food intake, use of the HMR system and estimated portion size when presented with food. Additionally, training resulted in significantly more accurate use of the HMR system when measured with PACE. It is concluded that people can learn the HMR Calorie System and improve the accuracy of portion size and food intake estimates. The PACE is a useful assessment tool to test if participants learn a calorie counting system.

Effect of calorie restriction with or without exercise on body composition and fat distribution

CONTEXT

There is debate over the independent and combined effects of dieting and increased physical activity on improving metabolic risk factors (body composition and fat distribution).

OBJECTIVE

The objective of the study was to conduct a randomized, controlled trial (CALERIE) to test the effect of a 25% energy deficit by diet alone or diet plus exercise for 6 months on body composition and fat distribution.

DESIGN

This was a randomized, controlled trial.

SETTING

The study was conducted at an institutional research center.

PARTICIPANTS

Thirty-five of 36 overweight but otherwise healthy participants (16 males, 19 females) completed the study.

INTERVENTION

Participants were randomized to either control (healthy weight maintenance diet, n = 11), caloric restriction (CR; 25% reduction in energy intake, n = 12), or caloric restriction plus exercise (CR+EX; 12.5% reduction in energy intake + 12.5% increase in exercise energy expenditure, n = 12) for 6 months.

MAIN OUTCOME MEASURES

Changes in body composition by dual-energy x-ray absorptiometry and changes in abdominal fat distribution by multislice computed tomography were measured.

RESULTS

The calculated energy deficit across the intervention was not different between CR and CR+EX. Participants lost approximately 10% of body weight (CR: - 8.3 +/- 0.8, CR+EX: - 8.1 +/- 0.8 kg, P = 1.00), approximately 24% of fat mass (CR: - 5.8 +/- 0.6, CR+EX: - 6.4 +/- 0.6 kg, P = 0.99), and 27% of abdominal visceral fat (CR: 0.9 +/- 0.2, CR+EX: 0.8 +/- 0.2 kg, P = 1.00). Both whole-body and abdominal fat distribution were not altered by the intervention.

CONCLUSION

Exercise plays an equivalent role to CR in terms of energy balance; however, it can also improve aerobic fitness, which has other important cardiovascular and metabolic implications.

Measurement of dietary restraint: validity tests of four questionnaires

This study tested the validity of four measures of dietary restraint: Dutch Eating Behavior Questionnaire, Eating Inventory (EI), Revised Restraint Scale (RS), and the Current Dieting Questionnaire. Dietary restraint has been implicated as a determinant of overeating and binge eating. Conflicting findings have been attributed to different methods for measuring dietary restraint. The validity of four self-report measures of dietary restraint and dieting behavior was tested using: (1) factor analysis, (2) changes in dietary restraint in a randomized controlled trial of different methods to achieve calorie restriction, and (3) correlation of changes in dietary restraint with an objective measure of energy balance, calculated from the changes in fat mass and fat-free mass over a six-month dietary intervention. Scores from all four questionnaires, measured at baseline, formed a dietary restraint factor, but the RS also loaded on a binge eating factor. Based on change scores, the EI Restraint Scale was the only measure that correlated significantly with energy balance expressed as a percentage of energy required for weight maintenance. These findings suggest that, of the four questionnaires tested, the EI Restraint Scale was the most valid measure of the intent to diet and actual caloric restriction.

Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma

Asthma is an increasingly common disorder responsible for considerable morbidity and mortality. Although obesity is a risk factor for asthma and weight loss can improve symptoms, many patients do not adhere to low calorie diets and the impact of dietary restriction on the disease process is unknown. A study was designed to determine if overweight asthma patients would adhere to an alternate day calorie restriction (ADCR) dietary regimen, and to establish the effects of the diet on their symptoms, pulmonary function and markers of oxidative stress, and inflammation. Ten subjects with BMI>30 were maintained for 8 weeks on a dietary regimen in which they ate ad libitum every other day, while consuming less than 20% of their normal calorie intake on the intervening days. At baseline, and at designated time points during the 8-week study, asthma control, symptoms, and Quality of Life questionnaires (ACQ, ASUI, mini-AQLQ) were assessed and blood was collected for analyses of markers of general health, oxidative stress, and inflammation. Peak expiratory flow (PEF) was measured daily on awakening. Pre- and postbronchodilator spirometry was obtained at baseline and 8 weeks. Nine of the subjects adhered to the diet and lost an average of 8% of their initial weight during the study. Their asthma-related symptoms, control, and QOL improved significantly, and PEF increased significantly, within 2 weeks of diet initiation; these changes persisted for the duration of the study. Spirometry was unaffected by ADCR. Levels of serum beta-hydroxybutyrate were increased and levels of leptin were decreased on CR days, indicating a shift in energy metabolism toward utilization of fatty acids and confirming compliance with the diet. The improved clinical findings were associated with decreased levels of serum cholesterol and triglycerides, striking reductions in markers of oxidative stress (8-isoprostane, nitrotyrosine, protein carbonyls, and 4-hydroxynonenal adducts), and increased levels of the antioxidant uric acid. Indicators of inflammation, including serum tumor necrosis factor-alpha and brain-derived neurotrophic factor, were also significantly decreased by ADCR. Compliance with the ADCR diet was high, symptoms and pulmonary function improved, and oxidative stress and inflammation declined in response to the dietary intervention. These findings demonstrate rapid and sustained beneficial effects of ADCR on the underlying disease process in subjects with asthma, suggesting a novel approach for therapeutic intervention in this disorder.

Calorie restriction increases muscle mitochondrial biogenesis in healthy humans

BACKGROUND

Caloric restriction without malnutrition extends life span in a range of organisms including insects and mammals and lowers free radical production by the mitochondria. However, the mechanism responsible for this adaptation are poorly understood.

METHODS AND FINDINGS

The current study was undertaken to examine muscle mitochondrial bioenergetics in response to caloric restriction alone or in combination with exercise in 36 young (36.8 +/- 1.0 y), overweight (body mass index, 27.8 +/- 0.7 kg/m(2)) individuals randomized into one of three groups for a 6-mo intervention: Control, 100% of energy requirements; CR, 25% caloric restriction; and CREX, caloric restriction with exercise (CREX), 12.5% CR + 12.5% increased energy expenditure (EE). In the controls, 24-h EE was unchanged, but in CR and CREX it was significantly reduced from baseline even after adjustment for the loss of metabolic mass (CR, -135 +/- 42 kcal/d, p = 0.002 and CREX, -117 +/- 52 kcal/d, p = 0.008). Participants in the CR and CREX groups had increased expression of genes encoding proteins involved in mitochondrial function such as PPARGC1A, TFAM, eNOS, SIRT1, and PARL (all, p < 0.05). In parallel, mitochondrial DNA content increased by 35% +/- 5% in the CR group (p = 0.005) and 21% +/- 4% in the CREX group (p < 0.004), with no change in the control group (2% +/- 2%). However, the activity of key mitochondrial enzymes of the TCA (tricarboxylic acid) cycle (citrate synthase), beta-oxidation (beta-hydroxyacyl-CoA dehydrogenase), and electron transport chain (cytochrome C oxidase II) was unchanged. DNA damage was reduced from baseline in the CR (-0.56 +/- 0.11 arbitrary units, p = 0.003) and CREX (-0.45 +/- 0.12 arbitrary units, p = 0.011), but not in the controls. In primary cultures of human myotubes, a nitric oxide donor (mimicking eNOS signaling) induced mitochondrial biogenesis but failed to induce SIRT1 protein expression, suggesting that additional factors may regulate SIRT1 content during CR.

CONCLUSIONS

The observed increase in muscle mitochondrial DNA in association with a decrease in whole body oxygen consumption and DNA damage suggests that caloric restriction improves mitochondrial function in young non-obese adults.