Hepatic Effects of Low-Carbohydrate Diet Associated with Different Lipid Sources: Insights into Oxidative Stress, Cytotoxicity, and Epigenetic Markers in a mouse Model of Obesity.

BACKGROUND: Low-carbohydrate and high-fat diet (LCHF) models have been widely explored as alternatives for treating obesity and promoting weight loss. Their effect is attributed to the change in energy substrate that stimulates ketogenic pathways that can metabolically overload the liver. However, little has been studied about the impact of lipid sources prioritized in the LCHF diet. OBJECTIVES: This study aims to evaluate the impact of different fat sources in the LCHF diet on markers of liver injury, oxidative stress, and epigenetics in obesity. METHODS: Adult male mice were initially induced to obesity by a high-fat and high-sugar diet for 10 wk. Subsequently, they underwent a weight-loss treatment intervention involving an LCHF diet with various sources of fats, including saturated, omega-3 (ω-3) (n-3), omega-6 (ω-6) (n-6), and omega-9 (ω-9) (n-9). At the end of the treatment, markers of liver injury, oxidative stress, and epigenetics were evaluated. RESULTS: The LCHF diet was effective in inducing weight loss. However, unsaturated lipid sources (omegas) exhibited superior outcomes. Specifically, the ω-9 group displayed diminished oxidative stress concentrations and decreased markers of liver injury. The ω-3 group demonstrated efficacy in modulating epigenetic markers, thereby reducing oxidative stress, mutagenicity, and markers of liver injury. Correlation tests demonstrated that there was an interaction between the activity of antioxidants and epigenetic enzymes. CONCLUSIONS: Our results suggest that LCHF diets associated with ω-3 and ω-9 have the potential for weight loss and liver health recovery in obesity through antioxidant and epigenetic mechanisms.

Nutritional strategies cause memory damage and alter biochemical parameters without causing neuroinflammation.

Obesity results from an energy imbalance and has been considered an epidemic due to its increasing rates worldwide. It is classified as a low-grade chronic inflammatory disease and has associated comorbidities. Different nutritional strategies are used for the purpose of weight loss, highlighting low-carbohydrate (LC) diets, ketogenic diets, and intermittent fasting (IF). These strategies can lead to metabolic and behavioral changes as they stimulate different biochemical pathways. Therefore, this study evaluated memory, energy metabolism, neuroinflammation, oxidative stress, and antioxidant defense parameters in mice subjected to an LC diet, ketogenic diet (KD), or IF. Eighty male Swiss mice, 60 days old, were divided into 4 groups: control, LC, KD, or IF. Body weight was measured weekly, and food intake every 48 h. After 15 days of nutritional interventions, the animals were subjected to the behavioral object recognition test and subsequently euthanized. Then, visceral fat was removed and weighed, and the brain was isolated for inflammatory and biochemical analysis. We concluded from this study that the LC and KD strategies could damage memory, IF improves the production of adenosine triphosphate (ATP), and the LC, KD, and IF strategies do not lead to neuroinflammatory damage but present damage at the level of oxidative stress.

Increased low-density lipoprotein cholesterol on a low-carbohydrate diet in adults with normal but not high body weight: A meta-analysis.

BACKGROUND: Low-density lipoprotein (LDL) cholesterol change with consumption of a low-carbohydrate diet (LCD) is highly variable. Identifying the source of this heterogeneity could guide clinical decision-making. OBJECTIVES: To evaluate LDL cholesterol change in randomized controlled trials involving LCDs, with a focus on body mass index (BMI) in kg/m2. METHODS: Three electronic indexes (Pubmed, EBSCO, and Scielo) were searched for studies between 1 January, 2003 and 20 December, 2022. Two independent reviewers identified randomized controlled trials involving adults consuming <130 g/d carbohydrate and reporting BMI and LDL cholesterol change or equivalent data. Two investigators extracted relevant data, which were validated by other investigators. Data were analyzed using a random-effects model and contrasted with results of pooled individual participant data. RESULTS: Forty-one trials with 1379 participants and a mean intervention duration of 19.4 wk were included. In a meta-regression accounting for 51.4% of the observed variability on LCDs, mean baseline BMI had a strong inverse association with LDL cholesterol change [ß = -2.5 mg/dL/BMI unit, 95% confidence interval (CI): -3.7, -1.4], whereas saturated fat amount was not significantly associated with LDL cholesterol change. For trials with mean baseline BMI <25, LDL cholesterol increased by 41 mg/dL (95% CI: 19.6, 63.3) on the LCD. By contrast, for trials with a mean of BMI 25-<35, LDL cholesterol did not change, and for trials with a mean BMI ≥35, LDL cholesterol decreased by 7 mg/dL (95% CI: -12.1, -1.3). Using individual participant data, the relationship between BMI and LDL cholesterol change was not observed on higher-carbohydrate diets. CONCLUSIONS: A substantial increase in LDL cholesterol is likely for individuals with low but not high BMI with consumption of an LCD, findings that may help guide individualized nutritional management of cardiovascular disease risk. As carbohydrate restriction tends to improve other lipid and nonlipid risk factors, the clinical significance of isolated LDL cholesterol elevation in this context warrants investigation. This trial was registered at PROSPERO as CRD42022299278.

Biodiversity and brewing attitude of non-Saccharomyces strains isolated from Uruguayan vineyards and other ecosystems.

In recent years, interest in non-Saccharomyces yeasts for the innovation and development of different and alternative beer styles has been increasing, especially for the microbrewing industry. This work studied the biodiversity of non-Saccharomyces yeasts based on isolates from grapes of different Uruguayan vineyards, craft breweries and raw materials, with the aim of selecting autochthonous non-Saccharomyces yeasts with a brewing attitude. Brewing tests were performed on synthetic wort developed for this purpose, and the evolution of alcoholic fermentation was monitored by measuring glucose, maltose, maltotriose consumption, ethanol and glycerol production and final sensory analysis. A total of two hundred seventy-one yeast strains belonging to different genera were evaluated according to these parameters. After evaluating alcoholic fermentation performance, a native yeast strain belonging to the species Starmerella meliponinorum was selected due to its high maltotriose consumption and glycerol production, making it a very promising brewing yeast, especially for production of low carbohydrate beers.

Physiologic Adaptation to Macronutrient Change Distorts Findings from Short Dietary Trials: Reanalysis of a Metabolic Ward Study.

An influential 2-wk cross-over feeding trial without a washout period purported to show advantages of a low-fat diet (LFD) compared with a low-carbohydrate diet (LCD) for weight control. In contrast to several other macronutrient trials, the diet order effect was originally reported as not significant. In light of a new analysis by the original investigative group identifying an order effect, we aimed to examine, in a reanalysis of publicly available data (16 of 20 original participants; 7 female; mean BMI, 27.8 kg/m2), the validity of the original results and the claims that trial data oppose the carbohydrate-insulin model of obesity (CIM). We found that energy intake on the LCD was much lower when this diet was consumed first compared with second (a difference of -1164 kcal/d, P = 3.6 × 10-13); the opposite pattern was observed for the LFD (924 kcal/d, P = 2.0 × 10-16). This carry-over effect was significant (P interaction = 0.0004) whereas the net dietary effect was not (P = 0.4). Likewise, the between-arm difference (LCD - LFD) was -320 kcal/d in the first period and +1771 kcal/d in the second. Body fat decreased with consumption of the LCD first and increased with consumption of this diet second (-0.69 ± 0.33 compared with 0.57 ± 0.32 kg, P = 0.007). LCD-first participants had higher ß-hydroxybutyrate levels while consuming the LCD and lower respiratory quotients while consuming LFD when compared with LFD-first participants on their respective diets. Change in insulin secretion as assessed by C-peptide in the first diet period predicted higher energy intake and less fat loss in the second period. These findings, which tend to support rather than oppose the CIM, suggest that differential (unequal) carry-over effects and short duration, with no washout period, preclude causal inferences regarding chronic macronutrient effects from this trial.

A low-carbohydrate diet with different fatty acids' sources in the treatment of obesity: Impact on insulin resistance and adipogenesis.

BACKGROUND: The search for nutritional intervention strategies against obesity has grown, highlighting the low-carbohydrate diet model. However, little is known about the impact of the quality of fatty acids consumed in this diet. Thus, we aim to investigate the influence of fatty acid quality on dietary strategy on obesity. METHODS: Male Swiss mice were diet-induced to obesity. Afterward, mice consume a low-carb diet with different types of fat: saturated, polyunsaturated ω-3, ω-6, and monounsaturated ω-9 fatty acids. Weight gain and food consumption were monitored weekly. An oral glucose tolerance test was performed and blood and tissue samples were collected for analysis of insulin resistance markers. Protein expression of insulin signaling pathway molecules, lipid metabolism, mitochondrial function, macrophage polarization, and cytokine production were analyzed. RESULTS: The high-fat diet was able to induce obesity and glucose intolerance. The switch to a low-carbohydrate dietary pattern reversed the glucose intolerance, with better results in the ω-3 and ω-9 groups. After the low-carbohydrate diet, groups ω-3 and ω-9 presented improved fasting serum glucose, insulin, and HOMA indexes. The low-carbohydrate diet also increased the activity of insulin pathway proteins such as IR, IRS1, and AKT. Furthermore, the ω-3 diet group showed greater activity of mitochondrial complexes and AMPK signaling pathway proteins. The ω-6 and ω-9 -rich diet induced M2-type macrophage polarization, as well as cytokine production modulation by the low-carbohydrate diet in the ω-3 and ω-9 groups. CONCLUSIONS: Consuming a low-carbohydrate diet pattern promotes weight loss and improves glucose intolerance in obesity. Also, the quality of lipids has a direct influence, demonstrating that the consumption of ω-3 polyunsaturated and ω-9 monounsaturated lipids can lead to more favorable outcomes for the improvement of glucose intolerance, lipid metabolism, and anti-inflammatory effects.

Evidence for the carbohydrate-insulin model in a reanalysis of the Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) trial.

BACKGROUND: The Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) trial demonstrated that meaningful weight loss can be achieved with either a "healthy low-carbohydrate diet" (LCD) or "healthy low-fat diet" (LFD). However, because both diets substantially decreased glycemic load (GL), the dietary factors mediating weight loss remain unclear. OBJECTIVES: We aimed to explore the contribution of macronutrients and GL to weight loss in DIETFITS and examine a hypothesized relationship between GL and insulin secretion. DESIGN: This study is a secondary data analysis of the DIETFITS trial, in which participants with overweight or obesity (aged 18-50 y) were randomized to a 12-mo LCD (N = 304) or LFD (N = 305). RESULTS: Measures related to carbohydrate intake (total amount, glycemic index, added sugar, and fiber) showed strong associations with weight loss at 3-, 6-, and 12-mo time points in the full cohort, whereas those related to total fat intake showed weak to no associations. A biomarker of carbohydrate (triglyceride/HDL cholesterol ratio) predicted weight loss at all time points (3-mo: ß [kg/biomarker z-score change] = 1.1, P = 3.5 × 10-9; 6-mo: ß = 1.7, P = 1.1 × 10-9; and 12-mo: ß = 2.6, P = 1.5 × 10-15), whereas that of fat (low-density lipoprotein cholesterol + HDL cholesterol) did not (all time points: P = NS). In a mediation model, GL explained most of the observed effect of total calorie intake on weight change. Dividing the cohort into quintiles of baseline insulin secretion and GL reduction revealed evidence of effect modification for weight loss, with P = 0.0009 at 3 mo, P = 0.01 at 6 mo, and P = 0.07 at 12 mo. CONCLUSIONS: As predicted by the carbohydrate-insulin model of obesity, weight loss in both diet groups of DIETFITS seems to have been driven by the reduction of GL more so than dietary fat or calories, an effect that may be most pronounced among those with high insulin secretion. These findings should be interpreted cautiously in view of the exploratory nature of this study. TRIAL REGISTRATION: ClinicalTrials.gov (NCT01826591).

The effects of a low carbohydrate diet on erectile function and serum testosterone levels in hypogonadal men with metabolic syndrome: a randomized clinical trial.

PURPOSE: Metabolic syndrome is a risk factor for several diseases. The relationship between metabolic syndrome and hypogonadism is well known. Our objetive is to assess whether a low carbohydrate diet can increase total serum testosterone and improve erectile function in hypogonadal men with metabolic syndrome. METHODS: An open label randomized clinical trial was conducted comparing a low carbohydrate diet and controls, during three months, in hypogonadal men with metabolic syndrome. Anthropometric measurements were evaluated as well as total serum testosterone levels, and symptoms of hypogonadism, using the ADAM and AMS scores, and sexual function using IIEF-5 score. RESULTS: Eighteen men were evaluated. Anthropometric measures were improved only in low carbohydrate diet group. The intervention group also had a statistically increase in IIEF-5 score and a significant reduction in AMS and ADAM scores (p < 0.001). The increase in serum total testosterone levels was statistically significant in the low carbohydrate group compared to the control group as well as calculated free testosterone (p < 0.001). CONCLUSIONS: Low carbohydrate diet may increase serum levels of testosterone and improve erectile function in hypogonadal men with metabolic syndrome. However, larger studies are necessary to strongly prove the effectiveness of low carbohydrate diet in treating male hypogonadism.

High-intensity functional training with an adequate and carbohydrate restricted hypocaloric diet promotes weight loss and cardiometabolic improvements

INTRODUCTION: Excess body weight and its comorbidities represent a major public health issue. Interventions based on diet and exercise have not only been shown to promote weight loss, but also improve overall health, including cardiovascular health. OBJECTIVE: This study aimed to evaluate the effects of a 12-week hypocaloric low-carbohydrate (CHO) diet coupled with high-intensity functional training (HIFT) on the cardiometabolic risk of overweight adults. METHODS: This is a randomized controlled trial. A total of 31 overweight adults participated in this study, divided into two groups based on the dietary intervention: reduced-CHO (R-CHO, ≤130 g/day; n=15) and adequate-CHO (A-CHO, >130 g/day; n=16). The cardiometabolic risk was assessed using lipidaemic, insulinemia, and glycaemic parameters. A two-way ANOVA with Bonferroni post hoc test was utilized to evaluate the effects of the intervention. A p-value < 0.05 was considered statistically significant. RESULTS: Participants from both groups displayed decreased low-density lipoprotein, very-low-density lipoprotein, total cholesterol, and triacylglycerol concentrations, as well as the number of risk factors for the metabolic disease after 12 weeks. The high-density lipoprotein (HDL) cholesterol concentration of both groups increased after 12 weeks, however, the result of the intragroup analysis revealed that a significant increase was only observed in the participants from the A-CHO group. CONCLUSION: Reduced or adequate CHO intake was both found to be effective in reducing cardiometabolic risk. However, improvements in HDL and final cardiometabolic classification risk indicated that CHO adequacy in the diet might be a better strategy associated with caloric restriction and HIFT.

From Young to Older, the 4 Phases Method Is Efficient in Promoting Quick Weight, BMI, and Waist Circumference Reductions.

Background: Investigate the effectiveness of the scientific 4 Phases Method, a methodology developed by EMAGRECENTRO, which is based on a ketogenic approach (total carbohydrate intake <40 g/day; including fibers) associated with health coach assistance, in promoting reductions in body weight, body mass index (BMI), and waist circumference after 5 weeks of methodology application. Methods: Record files from 354 individuals, both sexes, aged between 18 and 67, who took part in the 4 Phases Method were used to develop this study. Age, sex, weight, height, BMI, waist circumference measurement, and the presence of ketone bodies in the urine were evaluated before (baseline) and after 5 weeks of the 4 Phases application. Results: In general, a significant reduction in body weight (−7.8 ± 1.2 kg, p < 0.0001), BMI (−2.8 ± 0.4 kg/m2, p < 0.0001), and waist circumference measurement (−7.6 ± 0.4 cm, p < 0.0001) was found after the application of the 4 Phases Method, regardless of age, gender, and BMI. Conclusions: Taken together, our results demonstrated that the 4 Phases Method was able to promote significant body weight, BMI, and waist circumference reductions in the short term, particularly by associating a ketogenic intake strategy with a regular close follow-up weekly consultation with a health coach assistance.

Caffeine decreases ammonemia in athletes using a ketogenic diet during prolonged exercise.

OBJECTIVES: Both exercise and a ketogenic (low-carbohydrate) diet favor glycogen depletion and increase ammonemia, which can impair physical performance. Caffeine supplementation has been routinely used to improve exercise performance. Herein, the effect of xanthine was evaluated on ammonemia in cyclists who were placed on a ketogenic diet and engaged in prolonged exercise. METHODS: Fourteen male cyclists followed a ketogenic diet for 2 d before and during the experimental trial. The cyclists were assigned to either the caffeine- (CEx; n = 7) or placebo-supplemented (LEx; n = 7) group. Blood samples were obtained during cycling and the recovery periods. RESULTS: The CEx group showed a significant decrease (up to 25%) in blood ammonia at 60, 90, and 120 min after beginning exercise compared with the LEx group. A higher concentration of apparent blood urea was observed in the LEx group than in the CEx group at 60 to 90 min of exercise (~10%). In addition, a significant increase in blood glucose levels was evident at 30 min of exercise (~28%), and an increase in blood lactate levels was visible during the first 30 to 60 min of exercise (~80%) in the CEx group. CONCLUSIONS: Our results suggest that the consumption of caffeine might attenuate the increase in ammonemia that occurs during exercise.

Current Evidence Regarding Low-carb Diets for The Metabolic Control of Type-2 Diabetes.

The management of diabetes requires a medical nutrition therapy as an essential part of this treatment. There should be no "one-size-fits-all" eating pattern for different patient´s profiles with diabetes. It is clinically complex to suggest an ideal percentage of calories from carbohydrates, protein and lipids recommended for all patients with diabetes. Among the eating patterns that have shown beneficial effects on metabolic control of patients with type 2 diabetes is the lowcarb diet, since the carbohydrate ingestion is viewed as the most important determinant of postprandial glucose and insulin response. In this context, theoretically, it could make sense to reduce the daily amount of carbohydrates ingested, to achieve lower levels of HbA1c. There could be risks associated to this approach. The adherence to a low-carb diet is here also discussed. This narrative review shows on the current evidence for answering these questions regarding low-carb diet as a possible alternative eating pattern for type 2 diabetes.

Adjuvant effect of low-carbohydrate diet on outcomes of patients with recurrent glioblastoma under intranasal perillyl alcohol therapy.

BACKGROUND: Standard of care for glioblastoma (GB), consisting of cytotoxic chemotherapy, steroids, and high-dose radiation, induces changes in the tumor microenvironment through its effects on glucose availability, which is a determinant for tumor progression (TP). Low-carbohydrate diet (LCD) reduces the glucose levels needed to drive the Warburg effect. METHODS: To investigate LCD's effect on GB therapy, we have begun a clinical trial using LCD as an addition to intranasal perillyl alcohol (POH) for recurrent GB (rGB) patients. This study involved 29 individuals and evaluated, over a period of 1 year, the adjuvant effect of LCD associated with POH therapy in terms of toxicity, extent of peritumoral edema, reduced corticosteroid use, seizure frequency, and overall survival. POH group (n = 14) received solely intranasal POH without specific diet regimen, whereas POH/LCD group (n = 15) received intranasal POH in combination with nutritional intervention. Patients' assessment was based on clinical reviews and magnetic resonance data. RESULTS: In the 1-year follow-up, the POH/LCD group showed a 4.4-fold decrease in the proportion of patients who needed treatment with corticosteroids, as well as a reduction in tumor size and peritumoral edema, as compared to the POH group. While 75% of patients undergoing POH treatment experienced seizures, this fraction was reduced to 56% in the POH/LCD group. A 2.07-fold increase in the proportion of patients with stable disease, along with a 2.8-fold decrease in the proportion of patients with TP, was seen in the POH/LCD group. CONCLUSION: The results presented in this study show that the LCD associated with intranasal POH therapy may represent a viable option as adjunctive therapy for rGB to improve survival without compromising patients' quality of life. Prospective cohort studies are needed to confirm these findings and validate the efficacy of this novel therapeutic strategy.

Serious analytical inconsistencies challenge the validity of the energy balance theory.

Energy metabolism theory affirms that body weight stability is achieved as over time the average energy intake equals the average energy expenditure, a state known as energy balance. Here it is demonstrated, however, that weight stability coexists with a persistent energy imbalance. Such unexpected result emerges as a consequence of the answers to three fundamental problems: 1. Is it possible to model body weight fluctuations without the energy balance theory? And if so, what are the benefits over the energy balance strategy? 2. During energy balance, how the oxidized macronutrient distribution that underlies the average energy expenditure is related to the macronutrient distribution of the average energy intake? 3. Is energy balance possible under a low-fat diet that simultaneously satisfies the following conditions? (a) The fat fraction of the absorbed energy intake is always less than the oxidized fat fraction of the energy expenditure. (b) The carbohydrate fraction of the absorbed energy intake is always greater or equal to the oxidized carbohydrate fraction of the energy expenditure. The first of these issues is addressed with the axiomatic method while the rest are managed through analythical arguments. On the whole, this analysis identifies inconsistencies in the principle of energy balance. The axiomatic approach results also in a simple mass balance model that fits experimental data and explains body composition alterations. This model gives rise to a convincing argument that appears to elucidate the advantage of low-carbohydrate diets over isocaloric low-fat diets. It is concluded, according to the aforementioned model, that weight fluctuations are ultimately dependent on the difference between daily food mass intake and daily mass loss (e.g., excretion of macronutrient oxidation products) and not on energy imbalance. In effect, it is shown that assuming otherwise may caused unintended weight gain.

Efeitos da restrição de carboidratos no manejo do diabetes mellitus: revisão de literatura científica / Effects of carbohydrate-restricted diets in the management of diabetes mellitus: review of scientific literature

O objetivo do presente estudo foi avaliar, por meio de uma revisão da literatura, evidências da utilização de dietas com restrição de carboidratos no manejo do diabetes mellitus (DM). As buscas eletrônicas e manuais foram até abril de 2019, e incluíram trabalhos publicados a partir de 2008. Foram excluídos estudos de pesquisas in vitro e em animais, revisões de literatura, livros, monografias, dissertações, teses, estudos de caso e relatos de caso. Os artigos remanescentes foram submetidos à análise de sua qualidade metodológica pela Escala JADAD cinco pontos. Um total de 19 estudos randomizados e com qualidade média de três pontos foram selecionados e analisados quanto aos tipos de dieta utilizadas, adesão, tipo de DM, tempo de intervenção, consumo reportado de carboidratos e resultados observados para os grupos controle e intervenção. Dentre os parâmetros escolhidos para mensurar os possíveis efeitos das dietas, destacaram-se alteração de peso e IMC, Hb1Ac, variabilidade ou controle glicêmico, perfil lipídico e alteração nas doses de insulina ou medicação utilizadas. Em quatro estudos não foram observadas vantagens significativas de uma dieta restrita em carboidratos, e 15 trabalhos relataram melhoras em um ou mais parâmetros. Tais resultados podem representar uma grande vantagem na adoção desta estratégia alimentar no manejo do DM e na prevenção de complicações da doença. Contudo, existem limitações nos estudos, que precisam ter suas hipóteses verificadas no longo prazo, e pesquisas adicionais devem ser realizadas para configurar uma estratégia oficial no controle do DM. (AU)

This study aimed to evaluate, through a literature review, evidence of the use of diets with carbohydrate restriction in the management of diabetes mellitus (DM). Electronic and manual searches were conducted until April 2019, including works published from 2008 onwards. Studies on in vitro and animal research, literature reviews, books, monographs, dissertations, theses, case studies and case reports were excluded. The remaining articles were submitted to analysis of their methodological quality by the five-point JADAD Scale. Nineteen randomized studies with an average quality of three points were selected and analyzed regarding the types of diet used, adherence, type of DM, time of intervention, reported consumption of carbohydrates and results observed for the control and intervention group. Among the parameters chosen to measure the possible effects of diets, weight and BMI changes, Hb1Ac, variability or glycemic control, lipid profile and changes in insulin doses or medication used stood out. In four studies, no significant advantages were observed from a carbohydraterestricted diet, and 15 studies reported improvements in one or more parameters. Such results can represent a great advantage in adopting this dietary strategy in the management of DM and in preventing complications of the disease. However, there are limitations in the studies, which need to have their hypotheses verified in the long term, and additional research must be carried out to configure an official strategy in the control of DM. (AU)

Keto analogues and amino acid supplementation and its effects on ammonaemia during extenuating endurance exercise in ketogenic diet-fed rats.

Keto analogues and amino acids (KAAA) supplementation can reduce blood ammonia concentrations in athletes undergoing high-intensity exercise under both ketogenic and thermoneutral conditions. This study evaluated the acute effects of KAAA supplementation on ammonia metabolism during extenuating endurance exercise in rats fed a ketogenic diet. In all, eighty male Fischer rats at 90 d of age were divided into eight groups, and some were trained using a swimming endurance protocol. A ketogenic diet supplemented with keto analogues was administered for 10 d. Administration of the ketogenic diet ended 3 d before the exhaustion test (extenuating endurance exercise). A ketogenic diet plus KAAA supplementation and extenuating endurance exercise (trained ketogenic diet supplemented with KAAA (TKKa)) increased blood ammonia concentrations by approximately 50 % compared with the control diet (trained control diet supplemented with KAAA (TCKa)) and similar training (effect size=1·33; statistical power=0·50). The KAAA supplementation reduced blood urea concentrations by 4 and 18 % in the control and ketogenic diet groups, respectively, compared with the groups fed the same diets without supplementation. The trained groups had 60 % lower blood urate concentrations after TCKa treatment than after TKKa treatment. Our results suggest that KAAA supplementation can reduce blood ammonia concentrations after extenuating endurance exercise in rats fed a balanced diet but not in rats fed a ketogenic diet.

Apoptosis induced by a low-carbohydrate and high-protein diet in rat livers.

AIM: To determine whether high-protein, high-fat, and low-carbohydrate diets can cause lesions in rat livers. METHODS: We randomly divided 20 female Wistar rats into a control diet group and an experimental diet group. Animals in the control group received an AIN-93M diet, and animals in the experimental group received an Atkins-based diet (59.46% protein, 31.77% fat, and 8.77% carbohydrate). After 8 wk, the rats were anesthetized and exsanguinated for transaminases analysis, and their livers were removed for flow cytometry, immunohistochemistry, and light microscopy studies. We expressed the data as mean ± standard deviation (SD) assuming unpaired and parametric data; we analyzed differences using the Student's t-test. Statistical significance was set at P < 0.05. RESULTS: We found that plasma alanine aminotransferase and aspartate aminotransferase levels were significantly higher in the experimental group than in the control group. According to flow cytometry, the percentages of nonviable cells were 11.67% ± 1.12% for early apoptosis, 12.07% ± 1.11% for late apoptosis, and 7.11% ± 0.44% for non-apoptotic death in the experimental diet group and 3.73% ± 0.50% for early apoptosis, 5.67% ± 0.72% for late apoptosis, and 3.82% ± 0.28% for non-apoptotic death in the control diet group. The mean percentage of early apoptosis was higher in the experimental diet group than in the control diet group. Immunohistochemistry for autophagy was negative in both groups. Sinusoidal dilation around the central vein and small hepatocytes was only observed in the experimental diet group, and fibrosis was not identified by hematoxylin-eosin or Trichrome Masson staining in either group. CONCLUSION: Eight weeks of an experimental diet resulted in cellular and histopathological lesions in rat livers. Apoptosis was our principal finding; elevated plasma transaminases demonstrate hepatic lesions.

Comparison of the digestive efficiency of extruded diets fed to ferrets (Mustela putorius furo), dogs (Canis familiaris) and cats (Felis catus).

The digestive tract of ferrets is anatomically simple, with no caecum, ileocolic valve or external differentiation between the transition of ileum and colon. The species has a short large intestine that provides minor contributions to the digestive process. Aiming to better understand the digestibility efficiency of ferrets, the present study compared the digestibility of extruded diets with different amounts of macronutrients fed to dogs, cats and ferrets. Three formulations for cat maintenance were used (values in % of DM basis): high carbohydrate (HC; nitrogen-free extract (NFE) = 54 %, protein = 31 % and fat = 8 %); moderate carbohydrate (MC; NFE = 37 %, protein = 41 % and fat = 10 %); and low carbohydrate (LC; NFE = 19 %, protein = 46 % and fat = 23 %). Apparent total tract macronutrient digestibility was determined by the method of total collection of faeces. Results were compared by ANOVA, considering the diet and species effects and their interactions. Means were compared by the Tukey's test (P < 0·05). Dogs and cats presented similar food intakes, but ferrets consumed almost two times more food (g/kg body weight). Species × diet interactions were verified for apparent total tract digestibility (ATTD; P < 0·05). Ferrets presented lower DM digestibility than dogs and cats for all three diets (P < 0·05), lower NFE digestibility than dogs for the three diets and lower NFE digestibility than cats for the HC and LC diets (P < 0·05). For crude protein (CP), ferrets presented lower ATTD than dogs and cats (P < 0·05), whereas for fat, dogs and ferrets presented similar ATTD, and higher values than those presented by cats (P < 0·05). Kibble diets had a lower DM, CP and NFE digestibility when fed to ferrets compared with dogs and cats. Fat digestibility was similar between dogs and ferrets and higher than that for cats.

Las dietas cetogénicas: fundamentos y eficacia para la pérdida de peso

El consenso internacional es que los carbohidratos son la base de la pirámide alimenticia de una dieta saludable, de tal forma que la mayoría de los especialistas de hoy en día piensan que la mejor forma de perder peso es mediante una reducción en el número total de calorías ingeridas diariamente, principalmente las que vienen en forma de grasa. No obstante, esta revisión intentará demostrar que las dietas cetogénicas son desde un punto de vista fisiológico, bioquímico y práctico, un camino mucho más efectivo para perder peso. Además se argumenta cómo este tipo de dietas proporciona ventajas metabólicas como son la capacidad de preservar la masa muscular, reducir el apetito, tener una eficiencia metabólica más baja, producir una activación de la termogénesis y favorecer una mayor pérdida de grasa incluso en presencia de una mayor cantidad de calorías.

Ketogenic diets and weight loss: basis and effectiveness. The international consensus is that carbohydrates are the basis of the food pyramid of a healthy diet. Today’s specialists believe that the best way to lose weight is by cutting down on calories, essentialy in the form of fat. However, this paper will clarify that ketogenic diets are, from a physiological, biochemicale and practical point of view, a much more effective way of losing weight, since such diets provide metabolic advantages such as the capacity to preserve muscle mass, reduce appetite, to have a lower metabolic efficiency, produce a metabolic activation of thermogenesis and favour a greater fat loss even with a greater number of calories.