The Effects of Very-Low-Calorie Diets on HDL: A Review

The Impact of Weight Loss on Inflammation, Oxidative Stress, and Mitochondrial Function in Subjects with Obesity

Inflammation, oxidative stress, and mitochondrial function are implicated in the development of obesity and its comorbidities. The purpose of this study was to assess the impact of weight loss through calorie restriction on the metabolic profile, inflammatory and oxidative stress parameters, and mitochondrial respiration in an obese population. A total of 109 subjects underwent two cycles of a very low-calorie diet alternated with a low-calorie diet (24 weeks). We analyzed biochemical and inflammatory parameters in serum, as well as oxidative stress markers, mRNA antioxidant gene expression, and mitochondrial respiration in peripheral blood mononuclear cells (PBMCs). After the intervention, there was an improvement in both insulin resistance and lipid profiles, including cholesterol subfractions. Weight loss produced a significant reduction in mitochondrial ROSs content and an increase in glutathione levels, coupled with an enhancement in the mRNA expression of antioxidant systems (SOD1, GSR, and CAT). In addition, a significant improvement in basal oxygen consumption, maximal respiration, and ATP production was observed. These findings demonstrate that moderate weight loss can improve insulin resistance, lipid profiles and subfractions, inflammatory and oxidative stress parameters, and mitochondrial respiration. Therefore, we can affirm that dietary intervention can simultaneously achieve significant weight loss and improve metabolic profile and mitochondrial function in obesity.

Sweet swell of burning fat: emerging role of high-density lipoprotein in energy homeostasis

PURPOSE OF REVIEW

Metabolism of lipids and lipoproteins, including high-density lipoprotein (HDL), plays a central role in energy homeostasis. Mechanisms underlying the relationship between energy homeostasis and HDL however remain poorly studied.

RECENT FINDINGS

Available evidence reveals that HDL is implicated in energy homeostasis. Circulating high-density lipoprotein-cholesterol (HDL-C) levels are affected by energy production, raising with increasing resting metabolic rate. Lipolysis of triglycerides as a source of energy decreases plasma levels of remnant cholesterol, increases levels of HDL-C, and can be cardioprotective. Switch to preferential energy production from carbohydrates exerts opposite effects.

SUMMARY

Low HDL-C may represent a biomarker of inefficient energy production from fats. HDL-C-raising can be beneficial when it reflects enhanced energy production from burning fat.

Short-Term Effects of Weight-Loss Meal Replacement Programs with Various Macronutrient Distributions on Gut Microbiome and Metabolic Parameters: A Pilot Study

It has emerged the gut microbiome is crucially linked to metabolic health and obesity. Macronutrient distribution has been discussed as a key parameter in weight-loss programs, but little is known about its impact on the gut microbiome. We investigated the effects of weight-loss meal replacement programs with different macronutrient ratios on the gut microbiota and metabolic parameters in subjects with overweight and obesity. Three low-calorie meal replacement programs with different ratios of carbohydrates, proteins, and lipids were designed: a balanced diet (Group B, 60:15:30), a high-lipid-low-carbohydrate diet (Group F, 35:20:55), and a protein-enriched diet (Group P, 40:25:35). Sixty overweight or obese participants were provided with the meals twice daily for 3 weeks. In all groups, diet intervention resulted in reduced body weight and BMI. The relative abundance of Bacteroidetes and Firmicutes phyla decreased and increased, respectively, which increased the Firmicutes/Bacteroidetes (F/B) ratio in all subjects, particularly in Groups B and P. Alpha- and beta-diversity were augmented at the phylum level in Group P. In conclusion, short-term interventions with weight-loss meal replacement programs increased butyrate-producing bacteria and the F/B ratio. Moreover, the protein-enriched diet significantly increased alpha- and beta-diversity compared to the balanced diet and the high-lipid-low-carbohydrate diet.

Comparison of a pre-bariatric surgery very low-calorie ketogenic diet and the Mediterranean diet effects on weight loss, metabolic parameters, and liver size reduction

This study compared the effects on weight as well as on metabolic parameters and liver size of a very low-calorie ketogenic diet versus a Mediterranean diet in patients with morbid obesity preparing to undergo bariatric surgery. This prospective comparison study evaluated patients 18-65 years of age who enrolled for bariatric surgery. Study duration was limited to an immediate preoperative period of 15 days. The very low-calorie ketogenic diet incorporated 10-12 kcal/kg/day of energy and 1-1.2 g/kg of protein using Kalibra (Societa Dietetica Medica) (VLCKD-SDM). The Mediterranean diet (MD) included 15-20% protein, 45-50% carbohydrate, and 25-35% fat. Changes in body mass index (BMI), liver size, and anthropometric and metabolic measurements were assessed. Between January 2016 and March 2017, of 45 patients enrolled, 30 completed the study (VLCKD-SDM, n = 15; MD, n = 15). Respective median BMI loss after VLCKD-SDM was 2.7 kg/m² versus MD 1.4 kg/m² (p < 0.05); median fat percentage reduction was 3.2 units versus 1.7 units (p < 0.05). Median liver size decreased 5.5% in the VLCKD-SDM group versus 1.7% in the MD group (p < 0.05). Median total cholesterol, and LDL levels decreased in both groups (p < 0.05), with greater relative decreases in the VLCKD-SDM group. Short-term preoperative diet-based weight loss in patients with morbid obesity preparing for bariatric surgery was significantly greater following a very low-calorie ketogenic diet versus a Mediterranean diet. The very low-calorie diet also significantly improved anthropometric and metabolic parameters and reduced preoperative liver size above that of the MD.

Efficacy and Safety of a Long-Term Multidisciplinary Weight Loss Intervention under Hospitalization in Aging Patients with Obesity: An Open Label Study

The effects of the hypocaloric diet under hospitalization on blood biochemical parameters (lipid, glycaemic, thyroid and liver profiles) were not reported in literature. This study aims to evaluate the efficacy and safety of a hypocaloric diet under hospitalisation in obese patients. A total of 151 obese subjects (49 males and 102 females, aged 69.38 ± 14.1 years, BMI 41.78 ± 7.1) were enrolled in this study. Participants were treated with an hypocaloric diet for a maximum period of 3 months. Outcomes were assessed at the beginning and at the end of the recovery period. The average duration of the hospitalisation was 47.5 days ± 1.3. The effect of the diet on all the outcomes was evaluated using the Analysis of Covariance (ANCOVA) and the predictors of weight loss were identified using linear regression. The diet induced a reduction in the anthropometric (BMI decrease of -2.713 points) and DXA body measurements in addition to serum lipids, glucose, Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and C-reactive protein (CRP) levels without affecting the muscle mass, liver and thyroid profiles. During the intervention, there was a positive shift in body composition favouring fat free mass (FFM). Lower insulin but higher serum calcium and potassium levels were predictors of weight loss.

Clinical application of intermittent fasting for weight loss: progress and future directions

Intermittent fasting diets have become very popular in the past few years, as they can produce clinically significant weight loss. These diets can be defined, in the simplest of terms, as periods of fasting alternating with periods of eating. The most studied forms of intermittent fasting include: alternate day fasting (0-500 kcal per 'fast day' alternating with ad libitum intake on 'feast days'); the 5:2 diet (two fast days and five feast days per week) and time-restricted eating (only eating within a prescribed window of time each day). Despite the recent surge in the popularity of fasting, only a few studies have examined the health benefits of these diets in humans. The goal of this Review is to summarize these preliminary findings and give insights into the effects of intermittent fasting on body weight and risk factors for cardiometabolic diseases in humans. This Review also assesses the safety of these regimens, and offers some practical advice for how to incorporate intermittent fasting diets into everyday life. Recommendations for future research are also presented.

Fasting-Mimicking Diet Reduces Trimethylamine N-Oxide Levels and Improves Serum Biochemical Parameters in Healthy Volunteers

Elevated plasma levels of trimethylamine N-oxide (TMAO) have been proposed as a diet-derived biomarker of cardiometabolic disease risk. Caloric restriction is the most common dietary intervention used to improve cardiometabolic health; however, novel trends suggest a fasting-mimicking diet (FMD) as a more feasible alternative. FMD is a variation of intermittent fasting, based on caloric restriction and limitation of protein sources of animal origin, applied in daily cycles during a 5-day period. As TMAO is intensively produced by gut microbiota after the consumption of animal-derived products, we aim to investigate whether a 5-day FMD affects plasma TMAO levels and markers of metabolic health. To investigate whether an increase in vegetable intake possesses similar effects on TMAO levels and metabolic parameters, healthy volunteers (n = 24) were subjected to a 5-day FMD and 19 volunteers served as a reference group (VEG). This group of volunteers consumed an additional four servings of vegetables per day, but otherwise stayed on their usual diet. FMD resulted in a twofold decrease in plasma TMAO levels, which was not evident in the volunteers from the VEG group. Moreover, FMD led to a weight loss of 2.8 ± 0.2 kg and a subsequent reduction in BMI compared to baseline. The FMD group exhibited a significant elevation in plasma ketone bodies (14-fold compared to baseline) and a decrease in IGF-1 levels by 37 ± 8 ng/mL. Since fasting glucose and C-peptide levels decreased, all volunteers in the FMD group showed improved insulin sensitivity and a decreased HOMA-IR index. In contrast, in the VEG group, only a slight reduction in plasma levels of fasting glucose and triglycerides was noted. In conclusion, we show that FMD is a viable strategy to reduce plasma levels of TMAO by limiting caloric intake and animal-derived protein consumption. The reduction in the level of TMAO could be an additional benefit of FMD, leading to a reduced risk of cardiometabolic diseases.

Effect of a weight-loss stabilization following a weight reduction with or without meal replacement on cardiometabolic risk in overweight women. A randomized controlled trial

The objective of this study was to examine the effect of a 3-month weight-loss-stabilization phase (phase 2) following a successful 3-month weight-loss phase (phase 1), including a conventional energy-restricted diet with (MR) or without (C) meal replacement, on the cardiometabolic risk profile in 80 overweight women. In phase 2, both groups continued to significantly reduce weight and sustained the significant decreases in waist circumference and LDL-C. During the study, folic acid concentration significantly increased in the MR-group, while homocysteine concentration significantly worsened in the C-group. After 6 months, the number of women with hypertriglyceridemic waist was significantly reduced in both the groups, however with metabolic syndrome and metabolically unhealthy abdominal obesity (MUHAO) only in the MR-group. In conclusion, both strategies were equally effective for weight loss and weight-loss stabilization. The micronutrient supplementation with MR seemed to have an additional beneficial impact on the cardiometabolic risk in the MR-group versus the C-group.

Nuts and Cardiovascular Disease Prevention

PURPOSE OF REVIEW

We review recent epidemiological and clinical studies investigating the consumption of tree nuts and peanuts and cardiovascular disease (CVD) mortality as well as CVD risk factors.

RECENT FINDINGS

A greater consumption of tree nuts and peanuts is associated with a reduced risk of CVD mortality, as well as lower CVD events. Furthermore, risk factors associated with the development of CVD such as dyslipidemia, impaired vascular function, and hypertension are improved with regular tree nut and peanut consumption through a range of mechanism associated with their nutrient-rich profiles. There is weak inconsistent evidence for an effect of nut consumption on inflammation. There is emerging evidence that consuming tree nuts reduces the incidence of non-alcoholic fatty liver disease (NAFLD) and promotes diversity of gut microbiota, which in turn may improve CVD outcomes. Evidence for CVD prevention is strong for some varieties of tree nuts, particularly walnuts, and length of supplementation and dose are important factors for consideration with recommendations.

Meal frequency and timing: impact on metabolic disease risk

PURPOSE OF REVIEW

The purpose of this article is to provide an overview of the most recent human intervention trials that have examined the impact of meal frequency or meal timing on metabolic disease risk factors.

RECENT FINDINGS

Findings from intervention studies published over the past 12 months indicate that weight loss may be more pronounced with decreased meal frequency (two meals per day) versus increased meal frequency (six meals per day) under hypocaloric conditions. However, under isocaloric conditions, no effect on body weight was noted. Plasma lipid concentrations and glucoregulatory factors (fasting glucose, insulin, and insulin sensitivity) were not affected by alterations in meal frequency. As for meal timing, delaying the lunchtime meal by 3.5 h (from 1.30 p.m. to 4.30 p.m.) has no impact on body weight, but may impair glucose tolerance in young healthy adults.

SUMMARY

In sum, altering meal frequency has little impact on body weight, plasma lipids, or glucoregulatory factors, whereas eating the majority of calories later in the day may be detrimental for glycemic control. These preliminary findings, however, still require confirmation by longer term, larger scale controlled trials.

Metabolic and structural bone disturbances induced by hyperlipidic diet in mice treated with simvastatin

Simvastatin can modulate lipid and bone metabolism. However, information related to the interaction between diet and simvastatin on bone structure and biomechanics is scarce. Thus, this study evaluated the effects of simvastatin on femoral biomechanics and cortical/trabecular bone structure in wild-type mice nourished with a hyperlipidic diet. Three-month-old male wild-type mice (C57BL6 strain) were divided into four groups: (1) group W, nourished with a standard diet; (2) group WH, fed a hyperlipidic diet; (3) group WS, nourished with a standard diet plus oral simvastatin (20 mg/kg/day); and (4) group WHS, fed a hyperlipidic diet plus oral simvastatin (20 mg/kg/day). All animals received only their specific diet and water for 60 days. Blood samples were collected for the analysis of calcium, triglycerides, total cholesterol (TC) and fraction serum levels. Diet manipulation was able to induce a dyslipidaemic status in mice, characterized by triglyceride and TC rise in WH animals. Simvastatin prevented hypercholesterolaemia and reduced TC and LDL serum levels, but did not prevent hypertriglyceridaemia and HDL serum levels in the WHS group. In the WH mice the hyperlipidaemia was associated with reduction in trabecular bone thickness, femur structural and material property alterations. Simvastatin prevented these morphological alterations and minimized femur biomechanical changes in WHS mice. Taken together, the results indicated that the hyperlipidic diet intake acts as a risk factor for bone integrity, generating bones with reduced resistance and more susceptible to fractures, an effect attenuated by simvastatin that is potentially related to the modulatory action of this drug on lipid and bone metabolism.

A pilot Internet-based behavioral weight loss intervention with or without commercially available portion-controlled foods

OBJECTIVE

To evaluate the short-term impact of portion-controlled food provision in combination with an Internet behavioral weight loss program on weight, blood cholesterol, and blood glucose levels.

DESIGN AND METHODS

Fifty participants, mean age 46 ± 10.7 years and mean body mass index 35.1 ± 3.8 kg/m2 , were randomized to one of two study groups, an Internet behavioral weight loss program (Internet-alone; n = 25) or an Internet behavioral weight loss program plus a commercially available portion-controlled diet (Internet + PCD; n = 25) for 12 weeks.

RESULTS

An intent-to-treat analysis found that the mean weight change in the Internet + PCD group was -5.7 ± 5.6 kg and in the Internet-alone group (n = 25) was -4.1 ± 4.0 kg (P = 0.26). Participants in the Internet + PCD group achieved significantly greater improvements in blood glucose (-2.6 ± 5.7 vs. 1.4 ± 11.0 mg/dl; P = 0.05) and LDL cholesterol (-8.2 ± 18.0 vs. -0.6 ± 21.0 mg/dl; P = 0.04), compared with Internet-alone group.

CONCLUSIONS

These data suggest that there may be short-term clinical benefit in using a PCD in conjunction with a behavioral Internet-based weight loss program to enhance weight loss and improve health indicators.

Very-low-energy diets and morbidity: a systematic review of longer-term evidence

Evidence from the literature supports the safe use of very-low-energy diets (VLED) for up to 3 months in supervised conditions for patients who fail to meet a target weight loss using a standard low-fat, reduced-energy approach. There is, however, a need for longer-term outcomes on obesity and associated morbidities following a VLED. The present systematic review aims to investigate longer-term outcomes from studies using VLED, with a minimum duration of 12 months, published between January 2000 and December 2010. Studies conducted in both children and adults, with a mean/median BMI of ≥ 28 kg/m2 were included. PubMed, MEDLINE, Web of Science and Science Direct were searched. Reference lists of studies and reviews were manually searched. Weight loss or prevention of weight gain and morbidities were the main outcomes assessed. A total of thirty-two out of 894 articles met the inclusion criteria. The duration of the studies ranged from 12 months to 5 years. Periods of VLED ranged from 25 d to 9 months. Several studies incorporated aspects of behaviour therapy, exercise, low-fat diets, low-carbohydrate diets or medication. Current evidence demonstrates significant weight loss and improvements in blood pressure, waist circumference and lipid profile in the longer term following a VLED. Interpretation of the results, however, was restricted and conclusions with which to guide best practice are limited due to heterogeneity between the studies. The present review clearly identifies the need for more evidence and standardised studies to assess the longer-term benefits from weight loss achieved using VLED.