Period Of Caloric Restriction Research Articles

Alterations in plasma protein N-glycosylation after caloric restriction and bariatric surgery

BackgroundProtein glycosylation is an enzymatic process known to reflect an individual’s physiologic state and changes thereof. The impact of metabolic interventions on plasma protein N-glycosylation has only been sparsely investigated. ObjectiveTo examine alterations in plasma protein N-glycosylation following changes in caloric intake and bariatric surgery. SettingUniversity of Texas Southwestern Medical Center, US and Oxford University Hospitals, UK. MethodsThis study included 2 independent patient cohorts that recruited 10 and 37 individuals with obesity undergoing a period of caloric restriction followed by bariatric surgery. In both cohorts, clinical data were collated, and the composition of plasma protein N-glycome was analyzed chromatographically. Linear mixed models adjusting for age, sex, and multiple testing (false discovery rate <.05) were used to investigate longitudinal changes in glycosylation features and metabolic clinical markers. ResultsA low-calorie diet resulted in a decrease in high-branched trigalactosylated and trisialylated plasma N-glycans and a concomitant increase in low-branched N-glycans in both cohorts. Participants from one cohort additionally underwent a washout period during which caloric intake and body weight increased, resulting in reversal of the initial low-calorie diet–related changes in the plasma N-glycome. Immediate postoperative follow-up revealed the same pattern of N-glycosylation changes in both cohorts—an increase in complex, high-branched, antennary fucosylated, extensively galactosylated and sialylated N-glycans and a substantial decline in simpler, low-branched, core fucosylated, bisected, agalactosylated, and asialylated glycans. A 12-month postoperative monitoring in one cohort showed that N-glycan complexity declines while low branching increases. ConclusionsPlasma protein N-glycosylation undergoes extensive alterations following caloric restriction and bariatric surgery. These comprehensive changes may reflect the varying inflammatory status of the individual following dietary and surgical interventions and subsequent weight loss.

Effects of Mineral and Vitamin Supplementation on Swimming Times and Other Parameters Related to Performance of Rats on a Low Calorie Regimen

The effect of mineral and vitamin supplementation was studied on certain performance characteristics of rats on a low calorie, semipurified diet regimen. Male, albino, rats of the Charles River strain, 6 months old, were used. At a one-third ad libitum caloric level or less, the rats at nonsupplemented mineral-vitamin levels, on the whole, swam 26% longer than the groups receiving additional minerals and vitamins. This trend was the same with a low fat diet with corn oil and a relatively high fat diet with butter as the fat source. Lifespan was not affected at the 5% probability level by the mineral-vitamin supplementation used. A significant difference in blood glucose levels between rats receiving mineral-vitamin supplements versus those receiving none was found only after 10 days with one-third ad libitum caloric intake plus 9 days of complete caloric deprivation. However, the pooled results of blood glucose measurements during the whole period of caloric restriction showed no significant effect of the mineral-vitamin supplementation used. Likewise, water consumption was not significantly affected by mineral-vitamin supplementation. The same was true for weight loss.

Effect of increased protein intake and exogenous ketosis on body composition, energy expenditure and exercise capacity during a hypocaloric diet in recreational female athletes.

Introduction: Since low body weight is an important determinant of success in many sports such as gymnastics, martial arts and figure skating, athletes can benefit from effective weight loss strategies that preserve muscle mass and athletic performance. The present study investigates the effects of increased protein intake and exogenous ketosis on body composition, energy expenditure, exercise capacity, and perceptions of appetite and well-being during a hypocaloric diet in females. Methods: Thirty-two female recreational athletes (age: 22.2 ± .5years; body weight: 58.3 ± .8kg; BMI: 20.8 ± .2kg·m-2) underwent 4 weeks of 30% caloric restriction and were randomized to receive either an increased daily amount of dietary protein (PROT, ∼2.0-2.2g protein·kg-1·day-1), 3 × 20g·day-1 of a ketone ester (KE), or an isocaloric placebo (PLA). Body composition was measured by DXA, resting energy expenditure (REE) by indirect calorimetry, exercise capacity during a VO2max test, appetite hormones were measured in serum, and perceptions of general well-being were evaluated via questionnaires. Results: The hypocaloric diet reduced body weight by 3.8 ± .3kg in PLA, 3.2 ± .3kg in KE and 2.4 ± .2kg in PROT (Ptime<.0001). The drop in fat mass was similar between treatments (average: 2.6 ± .1kg, Ptime<.0001), while muscle mass was only reduced in PLA and KE (average: .8 ± .2kg, Ptime<.05), and remained preserved in PROT (Pinteraction<.01). REE [adjusted for lean mass] was reduced after caloric restriction in PLA (pre: 32.7 ± .5, post: 28.5 ± .6kcal·day-1·kg-1) and PROT (pre: 32.9 ± 1.0, post: 28.4 ± 1.0kcal·day-1·kg-1), but not in KE (pre: 31.8 ± .9, post: 30.4 ± .8kcal·day-1·kg-1) (Pinteraction<.005). Furthermore, time to exhaustion during the VO2max test decreased in PLA (by 2.5 ± .7%, p < .05) but not in KE and PROT (Pinteraction<.05). Lastly, the perception of overall stress increased in PLA and PROT (p < .05), but not in KE (Pinteraction<.05). Conclusion: Increased protein intake effectively prevented muscle wasting and maintained exercise capacity during a period of caloric restriction in female recreational athletes. Furthermore, exogenous ketosis did not affect body composition, but showed its potential in weight management by preserving a drop in exercise capacity and REE and by improving overall stress parameters during a period of caloric restriction.

A haven for T cells

Immunology Memory T cells (MTCs) help the host to respond quickly and effectively to subsequent challenges by the same pathogen. During times of nutritional stress, the host may have to balance productive immune responses with competing claims on limited resources. In mice subjected to dietary restriction, Collins et al. found that MTCs translocate to the bone marrow where they enter a quiescent, energy-conserving state accompanied by reduced mechanistic target of rapamycin signaling. Glucocorticoid hormones mediated accumulation of several cell types, not only other immune cells, but also adipocytes in bone marrow. Adipocytes were important for recruitment and survival of MTCs in this niche. This adaptive response ensures that immune responses can persist during periods of caloric restriction. Cell 178 , 1088 (2019).

Different effect of a period of caloric restriction following treatment with a normal lipid or hyperlipidic diet in the experimental animal model: Focus on mitochondrial dynamics proteins in the liver

Different effect of a period of caloric restriction following treatment with a normal lipid or hyperlipidic diet in the experimental animal model: Focus on mitochondrial dynamics proteins in the liver

Effect of Restricted Caloric Intake and Bariatric Surgery on PCSK9 Concentrations in Plasma

PCSK9 is a major modulator of LDLc through internalization and endosomal degradation of LDL receptor. It has been shown that PCSK9 plasma levels predict CVD risk. Bariatric surgery is known to reduce both LDLc and CVD. However, its exact effect on circulating PCSK9 levels has not been fully investigated. We have now investigated the effect of strict caloric restriction and Roux-en-Y bariatric surgery (RYGB) in 15 morbidly obese patients on plasma PCSK-9 levels. Subjects were instructed to follow a regimen of 4 liquid shakes (up to 16g carbohydrate, 0g fat, and 33g of protein, total daily intake was 550-785 calories) during the 2-weeks strict caloric restriction period prior to surgery and the usual dietary regime after surgery. Blood samples were obtained at 2 weeks before, at the time of surgery and 6 months after RYGB. There was a significant weight loss of 7.8±2.4 Kg during the 2 weeks prior to surgery and of additional 26.6±5.3 Kg 6 months after surgery. At completion of strict caloric restriction, subjects had a significant reductions in glucose, insulin and HOMA-IR (7.1±1.1 to 4.5± 1.0) which continued following surgery (HOMA-IR (4.5±1.0 to 2.1± 0.3). LDL(c) fell significantly by 11±7% (from 120±6 to 109±7mg/dl) following the strict caloric restriction and by 15±8% (from 109±7 to 95±6mg/dl) following surgery. There was a reduction of 38±11% (from 227±25 to 139±15 ng/ml) in plasma PCSK9 concentration in the 2 weeks of caloric restriction. Thereafter, PCSK9 levels increased to 166±22ng/ml over the next 6 months. Our data show that there is an impressive and concurrent fall in PCSK9, LDL(c) concentrations and insulin resistance following strict caloric restriction. The marked weight loss over 6 months has only a marginal effect on PCSK9 concentrations while metabolic improvements persisted. This reduction in PCSK9 may contribute to the known benefit in cardiovascular outcomes following bariatric surgery. Disclosure H. Ghanim: None. S. Abuaysheh: None. S. Monte: Stock/Shareholder; Self; Mobile Pharmacy Solutions (Community Pharmacy). Employee; Self; Synergy Bariatrics, a Department of ECMC. P. Dandona: Advisory Panel; Self; AstraZeneca. Consultant; Self; AstraZeneca. Research Support; Self; AstraZeneca.

Repeated weight cycling in obese mice causes increased appetite and glucose intolerance.

Obesity is an ongoing global public health problem. For many people dieting is the preferred method of combating elevated body fat. Weight lost during caloric restriction is often soon regained and so a pattern of recurrent dieting develops. Here an individual's food intake fluctuates up and down with intermittent periods of normal eating and restrained eating. The metabolic consequences of 'yoyo dieting' or 'weight cycling' are not well understood. Here we monitor the effects of multiple, repeated dieting periods on body composition and metabolic health in overweight mice. Compared to mice that were continuously fed a high fat diet, the energy expenditure of diet-cycled mice was reduced. This resulted in mice rapidly regaining body weight upon the reintroduction of high fat chow diet subsequent to periods of caloric restriction. Diet cycling also increased the appetite for high fat chow and diminished glucose tolerance. These data demonstrate the detrimental effects of diet cycling upon metabolic health.

Calorie restriction regime enhances physical performance of trained athletes

BackgroundCaloric restriction induces mitochondrial biogenesis and improves physical fitness in rodents. We aimed to provide evidence of how caloric restriction affects the body composition and physical performance of trained athletes and to evaluate the possible impact of an every-other-day feeding diet on nutritional deficiencies of micronutrients and essential fatty acids.MethodsThe study was performed with 12 healthy male athletes by carrying out a 33% caloric restriction with respect to their usual diet. Athletes performed a maximal exercise stress test both before and after the caloric restriction period. Blood samples were taken before and after the caloric restriction at basal conditions and 30 min post-exercise. Although energy intake was reduced by about 33%, the contribution of carbohydrates, proteins, and lipids to total energy intake during the caloric restriction was similar to the original diet.ResultsThe caloric restriction reduced the daily specific micronutrient intake to values lower than 90% of recommended dietary allowances. No effects were observed in blood parameters related to iron metabolism and tissue damage, glucose levels, lipid profiles, or erythrocyte fatty acid composition. In addition, oxidative damage markers decreased after the nutritional intervention. The caloric restriction intervention significantly reduced body weight and trunk, arm, and leg weights; it also caused a decrease in fat and lean body mass, the energy expenditure rate when performing a maximal exercise stress test, and the energy cost to run one meter at various exercise intensities. Furthermore, the intervention ameliorated the onset of the anaerobic phase of exercise.ConclusionA caloric restriction improves athletes’ performance and energy efficiency, but reduces the daily intake of micronutrients; so, when caloric restriction programs are implemented micronutrient supplementation should be considered.Trial registrationThe project was registered at ClinicalTrials.gov (NCT02533479).

Polyunsaturated Fatty Acids Stimulate De novo Lipogenesis and Improve Glucose Homeostasis during Refeeding with High Fat Diet.

Aims: The recovery of body weight after a period of caloric restriction is accompanied by an enhanced efficiency of fat deposition and hyperinsulinemia—which are exacerbated by isocaloric refeeding on a high fat diet rich in saturated and monounsaturated fatty acids (SFA-MUFA), and poor in polyunsaturated fatty acids (PUFA), and associated with a blunting of de novo lipogenesis in adipose tissue and liver. As high fat diets rich in PUFA have been shown to limit the excess fat deposition and improve glucose homeostasis, we investigated here the extent to which de novo lipogenesis in liver and adipose tissues (white and brown), as well as hepatic oxidative stress, are influenced by refeeding on diets rich in PUFA.Design: In rats calorically restricted for 14 days and refed for 14 days on isocaloric amounts of a high fat diet rich in lard (i.e., high SFA-MUFA) or in safflower and linseed oils (rich in PUFA), we investigated energy balance, body composition, glycemic profile, and the regulation of fatty acid synthase (rate-limiting enzyme of de novo lipogenesis) in liver, white and brown adipose tissue. We also evaluated oxidative stress in liver and skeletal muscle and markers of hepatic inflammation.Results: Rats refed the PUFA diet gained less lipids and more proteins compared to rats refed SFA-MUFA diet and showed lower amount of visceral and epididymal white adipose tissue, but increased depots of interscapular brown adipose tissue, with higher expression of the uncoupling protein 1. A significant increase in non-protein respiratory quotient and carbohydrate utilization was found in rats refed PUFA diet. Rats refed PUFA diet showed improved glucose homeostasis, as well as lower triglycerides and cholesterol levels. Fatty acid synthase activity was significantly higher in liver, white and brown adipose tissue, while lipid peroxidation and the degree of inflammation in the liver were significantly lower, in rats refed PUFA diet.Conclusions: When considering the composition of high fat diets for nutritional rehabilitation, the inclusion of PUFA could be useful for improving protein deposition and maintaining glucose homeostasis, while limiting lipid storage in adipose tissue and oxidative stress and inflammation in the liver.

Pre-adult famine exposure and subsequent colorectal cancer risk in women.

Nutritional deprivation during growth and development may contribute to colorectal cancer (CRC) risk in later life. We studied 7906 women who were aged 0-21 years during the 1944-45 Dutch famine, who enrolled in the Prospect-EPIC study between 1993 and 1997. We used Cox proportional hazard analyses to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for colorectal (proximal, distal and rectal) cancer risk across self-reported famine exposure and exposure-age categories, while adjusting for potential confounders. During a median of 17.3 years of follow-up, 245 CRC cases occurred. Moderately and severely famine-exposed women showed a respective 24% and 44% higher CRC risk compared with women who reported no exposure [HR moderate 1.24 (95% CI: 0.93-1.64); HR severe 1.44 (1.03-2.03); P trend 0.027]. This relation attenuated when adjusted for potential confounders [adjusted HR moderate 1.15 (0.87-1.53); HR severe 1.35 (0.96-1.90); P trend 0.091]. Stratified results suggested that severe famine exposure between 10 and 17 years of age was particularly related to CRC risk[adjusted HR moderate 1.39 (0.91-2.11); HR severe 1.76 (1.10-2.83); P trend 0.019; P interaction(famine*10-17yrs) 0.096]. Overall, we found no differences in famine effects across CRC subsites, but age-at-exposure stratified results suggested an increased risk for proximal CRC in those aged 10-17 years during exposure to the famine [adjusted HR moderate 2.14 (1.06-4.32), HR severe 2.96 (1.35-6.46); P trend 0.005]. Overall and within age-at-exposure categories, tests for subsite specific heterogeneity in famine effects were not significant. Our findings suggest that severe exposure to a short period of caloric restriction in pre-adult women may relate to CRC risk decades later.

The data do not seem to support a benefit to BCAA supplementation during periods of caloric restriction.

J Int Soc Sports Nutr 13:1-015-0112-9, 2016 describe the efficacy of branched chain amino acid (BCAA) supplementation and resistance training for maintaining lean body mass during a calorie-restricted diet, and claim that this occurs with concurrent losses in fat mass. However, the reported results appear to be at odds with the data presented on changes in fat mass. This letter discusses the issues with the paper.

Metabolic Damage: do Negative Metabolic Adaptations During Underfeeding Persist After Refeeding in Non-Obese Populations?

Several researches have proposed that a prolonged period of caloric restriction (CR) may have a permanent, adverse effect on basal metabolism, fostering the development of obesity. This reported metabolic slowing has been associated with a reduction in resting metabolic rate (RMR) beyond what is predicted by the change in body composition, promoting the idea that metabolism can be permanently damaged. This systematic review investigates if prolonged CR exhibits a permanent, negative effect on basal metabolism.Here we review the literature reporting weight loss and weight regain of individuals who were initially within a healthy weight range, such as the long-term Minnesota starvation experiment, in addition to research on chronically undernourished individuals, such as patients with anorexia nervosa, before and after recovery. Quantification of basal metabolism before and after prolonged CR revealed that body composition is the most critical factor in determining absolute RMR in neutral energy balance. Changes in energy balance induce a rapid yet reversible increase or decrease in RMR. Previous reports may have come to erroneous conclusions in favor of the metabolic damage hypothesis because they did not examine the full recovery period in the Minnesota experiment or neglected the influence of energy balance on RMR. Our findings indicate that the theory of permanent, diet-induced metabolic slowing in non-obese individuals is not supported by the current literature.

Effect of feeding a weight loss food beyond a caloric restriction period on body composition and resistance to weight gain in dogs.

To determine the effect of feeding a food with coconut oil and supplemental L-carnitine, lipoic acid, lysine, leucine, and fiber on weight loss and maintenance in dogs. Prospective clinical study. 50 overweight dogs. The study consisted of 2 trials. During trial 1, 30 dogs were allocated to 3 groups (10 dogs/group) to be fed a dry maintenance dog food to maintain body weight (group 1) or a dry test food at the same amount on a mass (group 2) or energy (group 3) basis as group 1. During trial 2, each of 20 dogs was fed the test food and caloric intake was adjusted to maintain a weight loss rate of 1% to 2%/wk (weight loss phase). Next, each dog was fed the test food in an amount calculated to maintain the body weight achieved at the end of the weight loss phase (weight maintenance phase). Dogs were weighed and underwent dual-energy x-ray absorptiometry monthly. Metabolomic data were determined before (baseline) and after each phase. During trial 1, dogs in groups 2 and 3 lost significantly more weight than did those in group 1. During trial 2, dogs lost a significant amount of body weight and fat mass but retained lean body mass (LBM) during the weight loss phase and continued to lose body fat but gained LBM during the weight maintenance phase. Evaluation of metabolomic data suggested that fat metabolism and LBM retention were improved from baseline for dogs fed the test food. Results suggested that feeding overweight dogs the test food caused weight loss and improvements in body condition during the weight-maintenance phase, possibly because the food composition improved energy metabolism.

Effect of feeding a weight loss food beyond a caloric restriction period on body composition and resistance to weight gain in cats.

To determine the effect of feeding a food with coconut oil and supplemental L-carnitine, lysine, leucine, and fiber on weight loss and maintenance in cats. Prospective clinical study. 50 overweight cats. The study consisted of 2 trials. During trial 1, 30 cats were allocated to 3 groups (10 cats/group) to be fed a dry maintenance cat food to maintain body weight (group 1) or a dry test food at the same amount on a mass (group 2) or energy (group 3) basis as group 1. During trial 2, each of 20 cats was fed the test food and caloric intake was adjusted to maintain a weight loss rate of 1%/wk (weight loss phase). Next, each cat was fed the test food in an amount calculated to maintain the body weight achieved at the end of the weight loss phase (weight maintenance phase). Cats were weighed and underwent dual-energy x-ray absorptiometry monthly. Metabolomic data were determined before (baseline) and after each phase. During trial 1, cats in groups 2 and 3 lost significantly more weight than did those in group 1. During trial 2, cats lost a significant amount of body weight and fat mass but retained lean body mass during the weight loss phase and continued to lose body weight and fat mass but gained lean body mass during the weight maintenance phase. Evaluation of metabolomic data suggested that fat metabolism was improved from baseline for cats fed the test food. Results suggested that feeding overweight cats the test food caused weight loss and improvements in body condition during the weight maintenance phase, possibly because the food composition improved energy metabolism.

Effect of the Mediterranean diet on plasma adipokine concentrations in men with metabolic syndrome

ObjectiveWhile a Mediterranean dietary pattern (MedDiet) has been associated with favorable changes in several features of metabolic syndrome (MetS), its impact on plasma adipokine concentrations remains largely unknown. The objective of this study was to determine the impact of the MedDiet consumed under controlled feeding conditions, without (−WL) and with weight loss (+WL), on plasma adipokine concentrations in adult men with MetS (NCEP-ATP III). Materials/MethodsThe diet of 26 men with MetS (age 24 to 62yrs) was first standardized to a North American control diet for 5weeks. Participants then consumed a pre-determined MedDiet for 5weeks. Both diets were consumed under weight-maintaining isoenergetic feeding conditions. Participants then underwent a 20-week free-living caloric restriction period, after which they consumed the MedDiet again in weight stabilizing, isoenergetic feeding conditions. ResultsBody weight was reduced by 10.2%±2.9% and waist circumference by 8.6±3.3cm after the weight loss period and stabilization on MedDiet (P<0.001). MedDiet−WL had no impact on plasma concentrations of leptin, plasminogen activator inhibitor-1, resistin, visfatin, acylation stimulating protein and adiponectin. MedDiet+WL reduced plasma leptin concentrations (P<0.01) and increased plasma adiponectin concentrations (P<0.05) compared with the control diet and MedDiet−WL. ConclusionData from this nutritionally controlled study suggest that short-term consumption of MedDiet has little effect on the concentrations of many adipokines in the absence of weight loss.

Caloric Restriction Followed by High Fat Feeding Predisposes to Oxidative Stress in Skeletal Muscle Mitochondria

The purpose of the present study was to assess the impact of previous period of caloric restriction on energy balance and skeletal muscle mitochondrial energetics in response to high-fat (HF) diet. To this end, 1 group of rats was subjected to 2 weeks of caloric restriction with nonpurified diet and then fed HF diet (430 kJ metabolizable energy/day) for 1 week, while the second group was fed ad libitum with nonpurified diet for 2 weeks and then fed HF diet (430 kJ metabolizable energy/day) for 1 week. Body composition, energy balance, and glucose homeostasis were measured. Mitochondrial mass, oxidative capacity and efficiency, parameters of oxidative stress, and antioxidant defense were evaluated in subsarcolemmal and intermyofibrillar mitochondria from skeletal muscle. Body energy and lipid content, plasma insulin, and metabolic efficiency were significantly higher, while energy expenditure significantly decreased, in food-restricted rats fed HF diet compared to controls. Mitochondrial efficiency and oxidative damage in skeletal muscle were significantly increased, while antioxidant defence was significantly lower in food-restricted rats fed HF diet, compared with controls. Finally, food-restricted rats fed HF diet exhibited significant reduction in subsarcolemmal mitochondrial mass. In conclusion, caloric restriction elicits higher mitochondrial efficiency and predisposes skeletal muscle to high fat-induced oxidative damage, which in turn could lead to impaired glucose homeostasis in food-restricted rats fed HF diet.

Hypothalamic inflammation: marker or mechanism of obesity pathogenesis?

Obesity and its associated metabolic and cardiovascular disorders are among the most challenging health problems confronting developed countries. Not only is obesity remarkably common, affecting more than one-third of U.S. adults, and very challenging to treat, but it is also tightly linked to type 2 diabetes and related metabolic disorders. A major obstacle to effective obesity treatment is that lost weight tends to be regained over time (1). Although the mechanisms underlying recovery of lost weight are incompletely understood, a large literature suggests that body fat stores are subject to homeostatic regulation, and that this process occurs in obese as well as normal-weight individuals. From this perspective, obesity can be viewed as a disorder in which the biologically defended level of body fat mass is increased. Recent findings implicate inflammation in key hypothalamic areas for body weight control in this process. In this review, we present an overview of energy homeostasis—the biological process that underlies the control of body fat mass—and describe evidence that defects in this regulatory system contribute to obesity pathogenesis. We then address molecular characteristics of hypothalamic inflammation and their implications for obesity pathogenesis (detailed more extensively in refs. 2,3), followed by evidence linking high-fat diet (HFD) feeding to neuropathological alteration of key hypothalamic areas controlling energy balance. We conclude by considering how cell-cell interactions may contribute to this deleterious hypothalamic response and the implications of these interactions for obesity pathogenesis. ### Homeostatic response to weight loss. Following a period of caloric restriction, lost weight is gradually but inexorably recovered in most individuals. This effect involves the capacity of the brain to sense the reduction of body energy stores and activate responses to compensate for this deficit. In simple terms, voluntary weight loss triggers increases of both appetite and energy efficiency, such that both sides of the energy balance equation shift …

Caloric restriction, but not caloric loading, affects circulating fetal and maternal C-type natriuretic peptide concentrations in late ovine gestation

The factors regulating the greatly elevated concentrations of maternal plasma C-type natriuretic peptide (CNP) forms in ruminant pregnancy are largely unknown, but nutrient status is likely to be important. Previous work has shown that increases in maternal plasma CNP, sourced from the placenta, occur in response to caloric restriction in late gestation. Whether oversupply of nutrients also regulates CNP secretion in pregnancy has not been studied. Hypothesising that CNP in fetal and maternal tissues will be responsive to both deficiency and excess, we studied changes in CNP and a cosecreted fragment, namely N-terminal pro-CNP (NTproCNP), during short-term periods of caloric restriction (CR) and loading (CL). Twin-bearing ewes received CR (fasted Days 121-124), CL (Days 110-124) or control maintenance diets. During CR, fetal plasma CNP forms, insulin-like growth factor (IGF)-1 and liveweight all fell, and maternal plasma NTproCNP increased. During CL, fetal IGF-1 increased, whereas CNP forms and liveweight were unchanged, as were maternal concentrations of CNP forms. The high abundance of CNP peptides in placental tissues was unaffected by these short-term changes in nutrient supply. We conclude that CNP in the fetal-maternal unit is acutely responsive to undernutrition, but is unaffected by oversupply in late gestation.

Physiological and Nutritional Aspects of Post-Exercise Recovery

Gender-based differences in the physiological response to exercise have been studied extensively for the last four decades, and yet the study of post-exercise, gender-specific recovery has only been developing in more recent years. This review of the literature aims to present the current state of knowledge in this field, focusing on some of the most pertinent aspects of physiological recovery in female athletes and how metabolic, thermoregulatory, or inflammation and repair processes may differ from those observed in male athletes. Scientific investigations on the effect of gender on substrate utilization during exercise have yielded conflicting results. Factors contributing to the lack of agreement between studies include differences in subject dietary or training status, exercise intensity or duration, as well as the variations in ovarian hormone concentrations between different menstrual cycle phases in female subjects, as all are known to affect substrate metabolism during sub-maximal exercise. If greater fatty acid mobilization occurs in females during prolonged exercise compared with males, the inverse is observed during the recovery phase. This could explain why, despite mobilizing lipids to a greater extent than males during exercise, females lose less fat mass than their male counterparts over the course of a physical training programme. Where nutritional strategies are concerned, no difference appears between males and females in their capacity to replenish glycogen stores; optimal timing for carbohydrate intake does not differ between genders, and athletes must consume carbohydrates as soon as possible after exercise in order to maximize glycogen store repletion. While lipid intake should be limited in the immediate post-exercise period in order to favour carbohydrate and protein intake, in the scope of the athlete's general diet, lipid intake should be maintained at an adequate level (30%). This is particularly important for females specializing in long-duration events. With protein balance, it has been shown that a negative nitrogen balance is more often observed in female athletes than in male athletes. It is therefore especially important to ensure that this remains the case during periods of caloric restriction, especially when working with female athletes showing a tendency to limit their caloric intake on a daily basis. In the post-exercise period, females display lower thermolytic capacities than males. Therefore, the use of cooling recovery methods following exercise, such as cold water immersion or the use of a cooling vest, appear particularly beneficial for female athletes. In addition, a greater decrease in arterial blood pressure is observed after exercise in females than in males. Given that the return to homeostasis after a brief intense exercise appears linked to maintaining good venous return, it is conceivable that female athletes would find a greater advantage to active recovery modes than males. This article reviews some of the major gender differences in the metabolic, inflammatory and thermoregulatory response to exercise and its subsequent recovery. Particular attention is given to the identification of which recovery strategies may be the most pertinent to the design of training programmes for athletic females, in order to optimize the physiological adaptations sought for improving performance and maintaining health.

Dietary Lysine: Calorie Ratios and Their Influence on Nitrogen Metabolism and Digestibility in Moderately Obese Mature Dogs

Problem statement: A goal during weight loss is to reduce body fat while maintaining body protein. We hypothesized that an increased dietary lysine: calorie might be beneficial during periods of caloric restriction. Approach: Two experiments were conducted to determine if changing the ratio of lysine: calories (lysine g/kg: Mcal ME/kg) while maintaining an ideal profile of amino acids will change nitrogen metabolism and weight loss in obese mature dogs. Results: The results of these experiments imply that if all essential amino acids are in adequate supply in the food, foods with an optimal balance of nutrients can reduce muscle degradation during periods of caloric restriction. Conclusion: Our optimum food for decreasing protein degradation was the food containing 3.0 lysine: calorie. However, the present experiments were relatively short and these results may not be sustained over longer periods of restriction.