Glucose uptake by the brain on chronic high-protein weight-loss diets with either moderate or low amounts of carbohydrate

Low-carbohydrate and ketogenic diets: a scoping review of neurological and inflammatory outcomes in human studies and their relevance to chronic pain

Dietary restriction of carbohydrate has been demonstrated to be beneficial for nervous system dysfunction in animal models and may be beneficial for human chronic pain. The purpose of this review is to assess the impact of a low-carbohydrate/ketogenic diet on the adult nervous system function and inflammatory biomarkers to inform nutritional research for chronic pain. An electronic database search was carried out in May 2021. Publications were screened for prospective research with dietary carbohydrate intake <130 g per day and duration of ≥2 weeks. Studies were categorised into those reporting adult neurological outcomes to be extracted for analysis and those reporting other adult research outcomes. Both groups were screened again for reported inflammatory biomarkers. From 1548 studies, there were 847 studies included. Sixty-four reported neurological outcomes with 83% showing improvement. Five hundred and twenty-three studies had a different research focus (metabolic n = 394, sport/performance n = 51, cancer n = 33, general n = 30, neurological with non-neuro outcomes n = 12, or gastrointestinal n = 4). The second screen identified sixty-three studies reporting on inflammatory biomarkers, with 71% reporting a reduction in inflammation. The overall results suggest a favourable outcome on the nervous system and inflammatory biomarkers from a reduction in dietary carbohydrates. Both nervous system sensitisation and inflammation occur in chronic pain, and the results from this review indicate it may be improved by low-carbohydrate nutritional therapy. More clinical trials within this population are required to build on the few human trials that have been done.

The 13C-bicarbonate technique as a tool for measurement of energy expenditure in overweight dogs undergoing body weight reduction and the effect of different dietary composition

Changes in body size and composition, i.e., body weight (BW) gain or loss, affect the daily energy expenditure (EE). To ensure an appropriate BW reduction and to find an efficient strategy to reduce and maintain a target BW, regular evaluations and adjustments of energy allowance are important. This study aimed to provide a detailed knowledge about the possible changes in resting EE using the oral 13C-bicarbonate technique (o13CBT) as a research tool in 16 overweight pet dogs undergoing BW reduction. Dietary composition (i.e., in % of dry matter [DM] being a high protein [33.3], low fat [9.6], and high crude fiber [18.0] diet [LFHFibre], and a high protein [37.9], high fat [52.0], carbohydrate-free diet [HFat]) during 16 wk of energy restriction were evaluated regarding effects on resting EE, rate of BW reduction, body composition, and plasma concentrations of metabolic hormones involved in energy metabolism and appetite regulation. The mean BW loss was higher (P < 0.05) for the dogs fed the LFHFibre diet (1.1%/wk) than that for dogs fed the HFat diet (0.8%/wk), but the total BW reduction of 14.6% and 12.0% of initial BW did not differ significantly (P > 0.05). Resting EE was lower (P < 0.02) after the BW reduction; 414 kJ (99 kcal)/kg BW0.75/d at the start (week 0) and 326 kJ (78 kcal)/kg BW0.75/d at the end (week 16) of the study. The BW reduction in both groups (P > 0.05) consisted of both fat mass (FM) and fat-free mass (FFM). Energy expenditure, calculated in relation to amount of FFM, was not significantly (P > 0.05) affected by BW reduction. Dietary composition did not significantly affect (P > 0.05) plasma concentrations of insulin, leptin, and ghrelin, and no effect (P > 0.05) of BW reduction was observed on hormone concentrations. In conclusion, the o13CBT proved to be a useful research method for studying short-term EE in overweight dogs. Even though all dogs lost BW, most dogs were still overweight at the end of the study. Due to a high individual variation among dogs, a longer experimental period with a larger sample size would be desirable.

The Effect of a Low-Carbohydrate, High-Fat Diet versus Moderate-Carbohydrate and Fat Diet on Body Composition in Patients with Lipedema

INTRODUCTION

Lipedema is a disorder characterized by an excessive accumulation of subcutaneous body fat, mainly bilateral and symmetrical accumulation of fat deposits, particularly in the lower extremities excluding feet. Pain (spontaneous or with palpation) and increased capillary fragility with bruising are also part of clinical presentation. It is estimated to occur in approximately 11.0% of women worldwide. Management of obesity among patients with lipedema is a key component in its treatment.

PURPOSE

The aim of this study was to compare effectiveness of two diets: low-carbohydrate-high-fat diet (LCHF) and medium-fat-medium-carbohydrate diet (MFMC) in body weight, body fat and limb circumference reduction in patients with lipedema.

MATERIAL AND METHODS

The studied women (n = 91) were divided into 2 groups and submitted to 1 of the 2 diets for 16 weeks. Anthropometric measurements such as body height [cm], body weight [kg], body fat percentage [%], body fat [kg], lean body mass [kg], and visceral fat level were collected at the beginning and end of the study.

RESULTS

We have not found any significant differences in anthropometric measurements at the baseline between groups. Body weight and all anthropometric parameters decreased significantly in both groups after 16 weeks of diets, excluding the circumference above the right ankle for the MFMC diet which did not change. The LCHF diet contributed to reduction of body weight (-8.2 ± 4.1 kg vs -2.1 ± 1.0 kg; p < 0.0001), body fat (-6.4 ± 3.2 kg vs 1.6 ± 0.8 kg; p < 0.0001), waist (-7.8 ± 3.9 cm vs -2.3 ± 1.1 cm; p < 0.0001), hips (-7.4 ± 3.7 cm vs -2.5 ± 1.3 cm; p < 0.0001), thighs and calves' circumferences compared with the MFMC diet. We observed reduction of pain in the extremities and mobility improvement in LCHF group (data not shown).

CONCLUSION

The LCHF diet was more effective than MFMC in body weight, body fat and lower limb circumferences reduction.

Activation of G protein-coupled receptors by ketone bodies: Clinical implication of the ketogenic diet in metabolic disorders

Ketogenesis takes place in hepatocyte mitochondria where acetyl-CoA derived from fatty acid catabolism is converted to ketone bodies (KB), namely β-hydroxybutyrate (β-OHB), acetoacetate and acetone. KB represent important alternative energy sources under metabolic stress conditions. Ketogenic diets (KDs) are low-carbohydrate, fat-rich eating strategies which have been widely proposed as valid nutritional interventions in several metabolic disorders due to its substantial efficacy in weight loss achievement. Carbohydrate restriction during KD forces the use of FFA, which are subsequently transformed into KB in hepatocytes to provide energy, leading to a significant increase in ketone levels known as "nutritional ketosis". The recent discovery of KB as ligands of G protein-coupled receptors (GPCR) - cellular transducers implicated in a wide range of body functions - has aroused a great interest in understanding whether some of the clinical effects associated to KD consumption might be mediated by the ketone/GPCR axis. Specifically, anti-inflammatory effects associated to KD regimen are presumably due to GPR109A-mediated inhibition of NLRP3 inflammasome by β-OHB, whilst lipid profile amelioration by KDs could be ascribed to the actions of acetoacetate via GPR43 and of β-OHB via GPR109A on lipolysis. Thus, this review will focus on the effects of KD-induced nutritional ketosis potentially mediated by specific GPCRs in metabolic and endocrinological disorders. To discriminate the effects of ketone bodies per se, independently of weight loss, only studies comparing ketogenic vs isocaloric non-ketogenic diets will be considered as well as short-term tolerability and safety of KDs.

The effects of a low-carbohydrate diet on appetite: A randomized controlled trial

BACKGROUND AND AIMS

The relationship between dietary macronutrient composition and appetite is controversial. We examined the effects of a year-long low-carbohydrate diet compared to a low-fat diet on appetite-related hormones and self-reported change in appetite.

METHODS AND RESULTS

A total of 148 adults with a body mass index 30-45 kg/m(2), who were free of diabetes, cardiovascular disease and chronic kidney disease at baseline were randomly assigned to either a low-carbohydrate diet (carbohydrate [excluding dietary fiber]<40 g/day; N = 75) or a low-fat diet (<30% energy from fat, <7% from saturated fat; N = 73). Participants in both groups attended individual and group dietary counseling sessions where they were provided the same behavioral curriculum and advised to maintain baseline levels of physical activity. Appetite and appetite-related hormones were measured at 0, 3, 6 and 12 months of intervention. At 12 months, mean changes (95% CI) in peptide YY were -34.8 pg/mL (-41.0 to -28.6) and in the low-carbohydrate group and -44.2 pg/mL (-50.4 to -38.0) in the low-fat group (net change: 9.54 pg/mL [0.6 to 18.2]; p = 0.036). Approximately 99% of dietary effects on peptide YY are explained by differences in dietary macronutrient content. There was no difference in change in ghrelin or self-reported change in appetite between the groups.

CONCLUSIONS

A low-fat diet reduced peptide YY more than a low-carbohydrate diet. These findings suggest that satiety may be better preserved on a low-carbohydrate diet, as compared to a low fat diet.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00609271.

Ketone bodies effectively compete with glucose for neuronal acetyl-CoA generation in rat hippocampal slices

Ketone bodies can be used for cerebral energy generation in situ, when their availability is increased as during fasting or ingestion of a ketogenic diet. However, it is not known how effectively ketone bodies compete with glucose, lactate, and pyruvate for energy generation in the brain parenchyma. Hence, the contributions of exogenous 5.0 mM [1-(13)C]glucose and 1.0 mM [2-(13)C]lactate + 0.1 mM pyruvate (combined [2-(13)C]lactate + [2-(13)C]pyruvate) to acetyl-CoA production were measured both without and with 5.0 mM [U-(13)C]3-hydroxybutyrate in superfused rat hippocampal slices by (13)C NMR non-steady-state isotopomer analysis of tissue glutamate and GABA. Without [U-(13)C]3-hydroxybutyrate, glucose, combined lactate + pyruvate, and unlabeled endogenous sources contributed (mean ± SEM) 70 ± 7%, 10 ± 2%, and 20 ± 8% of acetyl-CoA, respectively. With [U-(13)C]3-hydroxybutyrate, glucose contributions significantly fell from 70 ± 7% to 21 ± 3% (p < 0.0001), combined lactate + pyruvate and endogenous contributions were unchanged, and [U-(13)C]3-hydroxybutyrate became the major acetyl-CoA contributor (68 ± 3%)--about three-times higher than glucose. A direct analysis of the GABA carbon 2 multiplet revealed that [U-(13)C]3-hydroxybutyrate contributed approximately the same acetyl-CoA fraction as glucose, indicating that it was less avidly oxidized by GABAergic than glutamatergic neurons. The appearance of superfusate lactate derived from glycolysis of [1-(13)C]glucose did not decrease significantly in the presence of 3-hydroxybutyrate, hence total glycolytic flux (Krebs cycle inflow + exogenous lactate formation) was attenuated by 3-hydroxybutyrate. This indicates that, under these conditions, 3-hydroxybutyrate inhibited glycolytic flux upstream of pyruvate kinase.