High Compared with Moderate Protein Intake Reduces Adaptive Thermogenesis and Induces a Negative Energy Balance during Long-term Weight-Loss Maintenance in Participants with Prediabetes in the Postobese State: A PREVIEW Study

Changes in lean body mass with glucagon-like peptide-1-based therapies and mitigation strategies

Weight loss induced by glucagon-like peptide-1 receptor agonists (GLP-1RAs) and dual glucagon-like peptide-1 receptor (GLP-1R)/glucose-dependent insulinotropic polypeptide receptor agonists is coming closer to the magnitudes achieved with surgery. However, with greater weight loss there is concern about potential side effects on muscle quantity (mass), health and function. There is heterogeneity in the reported effects of GLP-1-based therapies on lean mass changes in clinical trials: in some studies, reductions in lean mass range between 40% and 60% as a proportion of total weight lost, while other studies show lean mass reductions of approximately 15% or less of total weight lost. There are several potential reasons underlying this heterogeneity, including population, drug-specific/molecular, and comorbidity effects. Furthermore, changes in lean mass may not always reflect changes in muscle mass as the former measure includes not only muscle but also organs, bone, fluids, and water in fat tissue. Based on contemporary evidence with the addition of magnetic resonance imaging-based studies, skeletal muscle changes with GLP-1RA treatments appear to be adaptive: reductions in muscle volume seem to be commensurate with what is expected given ageing, disease status, and weight loss achieved, and the improvement in insulin sensitivity and muscle fat infiltration likely contributes to an adaptive process with improved muscle quality, lowering the probability for loss in strength and function. Nevertheless, factors such as older age and severity of disease may influence the selection of appropriate candidates for these therapies due to risk of sarcopenia. To further improve muscle health during weight loss, several pharmacological treatments to maintain or improve muscle mass designed in combination with GLP-1-based therapies are under development. Future research on GLP-1-based and other therapies designed for weight loss should focus on more accurate and meaningful assessments of muscle mass, composition, as well as function, mobility or strength, to better define their impact on muscle health for the substantial number of patients who will likely be taking these medications well into the future.

Daily blood flow restriction does not preserve muscle mass and strength during 2 weeks of bed rest

We measured the impact of blood flow restriction on muscle protein synthesis rates, muscle mass and strength during 2 weeks of strict bed rest. Twelve healthy, male adults (age: 24 ± 3 years, body mass index: 23.7 ± 3.1 kg/m2 ) were subjected to 14 days of strict bed rest with unilateral blood flow restriction performed three times daily in three 5 min cycles (200 mmHg). Participants consumed deuterium oxide and we collected blood and saliva samples throughout 2 weeks of bed rest. Before and immediately after bed rest, lean body mass (dual-energy X-ray absorptiometry scan) and thigh muscle volume (magnetic resonance imaging scan) were assessed in both the blood flow restricted (BFR) and control (CON) leg. Muscle biopsies were collected and unilateral muscle strength (one-repetition maximum; 1RM) was assessed for both legs before and after the bed rest period. Bed rest resulted in 1.8 ± 1.0 kg lean body mass loss (P < 0.001). Thigh muscle volume declined from 7.1 ± 1.1 to 6.7 ± 1.0 L in CON and from 7.0 ± 1.1 to 6.7 ± 1.0 L in BFR (P < 0.001), with no differences between treatments (P = 0.497). In addition, 1RM leg extension strength decreased from 60.2 ± 10.6 to 54.8 ± 10.9 kg in CON and from 59.2 ± 12.1 to 52.9 ± 12.0 kg in BFR (P = 0.014), with no differences between treatments (P = 0.594). Muscle protein synthesis rates during bed rest did not differ between the BFR and CON leg (1.11 ± 0.12 vs. 1.08 ± 0.13%/day, respectively; P = 0.302). Two weeks of bed rest substantially reduces skeletal muscle mass and strength. Blood flow restriction during bed rest does not modulate daily muscle protein synthesis rates and does not preserve muscle mass or strength. KEY POINTS: Bed rest, often necessary for recovery from illness or injury, leads to the loss of muscle mass and strength. It has been postulated that blood flow restriction may attenuate the loss of muscle mass and strength during bed rest. We investigated the effect of blood flow restriction on muscle protein synthesis rates, muscle mass and strength during 2 weeks of strict bed rest. Blood flow restriction applied during bed rest does not modulate daily muscle protein synthesis rates and does not preserve muscle mass or strength. Blood flow restriction is not effective in preventing muscle atrophy during a prolonged period of bed rest.

Resting energy expenditure depends on energy intake during weight loss in people with obesity: a retrospective cohort study

Objective

Resting energy expenditure (REE) decreases if there is reduced energy intake and body weight (BW). The decrease in REE could make it difficult for patients with obesity to maintain decreased BW. This study aimed to investigate the correlation among changes in REE, energy intake, and BW during the weight loss process in patients with obesity.

Materials and methods

We conducted a retrospective cohort study of patients hospitalized for the treatment of obesity in Japan. Patients received fully controlled diet during hospitalization and performed exercises if able. REE was measured once a week using a hand-held indirect calorimetry. Energy intake was determined by actual dietary intake.

Results

Of 44 inpatients with obesity, 17 were included in the analysis. Their BW decreased significantly after 1 week (-4.7 ± 2.0 kg, P < 0.001) and 2 weeks (-5.7 ± 2.2 kg, P < 0.001). The change in REE after 1 and 2 weeks was positively correlated with the energy intake/energy expenditure ratio (r = 0.66, P = 0.004 at 1 week, r = 0.71, P = 0.002 at 2 weeks). Using a regression equation (y = 0.5257x - 43.579), if the energy intake/energy expenditure ratio within the second week was 82.9%, the REE after 2 weeks was similar to the baseline level. There was no significant correlation between the change in REE and BW.

Conclusion

Our data suggest that changes in REE depend on energy intake/energy expenditure ratio and that the decrease in REE can be minimized by matching energy intake to energy expenditure, even during the weight loss process.

Changes in 24-h energy expenditure, substrate oxidation, and body composition following resistance exercise and a high protein diet via whey protein supplementation in healthy older men

PURPOSE

To investigate changes in 24-h energy expenditure (EE), substrate oxidation, and body composition following resistance exercise (RE) and a high protein diet via whey protein supplementation (alone and combined) in healthy older men.

METHODS

In a pooled groups analysis, 33 healthy older men [(mean ± SE) age: 67 ± 1 years; BMI: 25.4 ± 0.4 kg/m2] were randomized to either RE (2×/week; n = 17) or non-exercise (n = 16) and either a high protein diet via whey protein supplementation (PRO, 2 × 25 g whey protein isolate/d; n = 17) or control (CON, 2 × 23.75 g maltodextrin/d; n = 16). An exploratory sub-analysis was also conducted between RE+CON (n = 8) and RE+PRO (n = 9). At baseline and 12 weeks, participants resided in respiration chambers for measurement of 24-h EE and substrate oxidation and wore an accelerometer for 7 days for estimation of free-living EE.

RESULTS

Resistance exercise resulted in greater increases in fat-free mass (1.0 ± 0.3 kg), resting metabolic rate [(RMR) 36 ± 14 kcal/d], sedentary EE (60 ± 33 kcal/d), and sleeping metabolic rate [(SMR) 45 ± 7 kcal/d] compared to non-exercise (p < 0.05); however, RE decreased activity energy expenditure in free-living (-90 ± 25 kcal/d; p = 0.049) and non-exercise activity inside the respiration chamber (-1.9 ± 1.1%; p = 0.049). PRO decreased fat mass [(FM) -0.5 ± 0.3 kg], increased overnight protein oxidation (30 ± 6 g/d), and decreased 24-h protein balance (-20 ± 4 g/d) greater than CON (p < 0.05). RE+PRO decreased FM (-1.0 ± 0.5 kg) greater than RE+CON (p = 0.04).

CONCLUSION

Resistance exercise significantly increased RMR, SMR, and sedentary EE in healthy older men, but not total EE. PRO alone and combined with RE decreased FM and aided body weight maintenance. This study was registered at clinicaltrials.gov as NCT03299972.

Prediabetes: Challenges, Novel Solutions, and Future Directions

Prediabetes: Prediabetes is a salient state of hyperglycaemia and/or hyperinsulinaemia that often precedes a diagnosis of Type 2 diabetes (T2D). It is projected that by 2040, almost 8% of the global population will have prediabetes, with approximately 70% progressing to T2D within their lifetime. Abnormal glucose tolerance increases the risk of associated complications, including cardiovascular disease, stroke, and microvascular diseases, all of which are major contributors to the global healthcare burden. T2D alone is predicted to cost the healthcare system upwards of 490 billion USD by 2030, thus addressing this growing burden is vital. Challenge One. Diagnosis and classification: Diagnosis poses a challenge and there is debate between leading world expert panels regarding thresholds, notably between the World Health Organization (WHO) and American Diabetes Association (ADA) for impaired fasting glucose. Hyperinsulinaemia may also go undetected as this is not currently routinely tested or used as diagnostic criteria. This has been largely due to cost and lack of consensus data for appropriate diagnostic threshold; however, with disease burden costs estimated to be close to half a billion USD by the end of the decade, an in-depth cost analysis for benefits-costs of early detection and treatment or prevention is warranted. Challenge Two. Health messaging and public perception: Prediabetes can revert to normoglycaemia with diet and lifestyle interventions. This, however, is not conveyed well in public health messaging. In addition to public perception about the likelihood of disease progression to T2D, prediabetes is not considered a disease state, which may also influence public perception regarding perceived urgency of treatment and necessity for intervention. Challenge Three. Intervention and treatment: Diet and lifestyle interventions are heralded as best practice when it comes to prediabetes management, and metformin for those at greatest risk of future T2D. Synergistic use of the available novel and promising interventions including low carbohydrate diets, higher protein diets, time restricted feeding, and high intensity interval training may help time-poor individuals achieve improvements in risk-factors including weight loss and glycaemic control (HbA1c and fasting plasma glucose). As large-scale feasibility and adherence are major obstacles to contend with in the rollout of diet and lifestyle interventions, personalised approaches, coupled with counselling based on social cognitive theory, may be increasingly utilised to target specific groups and individuals as programmes can be tailored to meet specific needs and preferences.

Long-Term Space Nutrition: A Scoping Review

This scoping review aimed to identify current evidence and gaps in the field of long-term space nutrition. Specifically, the review targeted critical nutritional needs during long-term manned missions in outer space in addition to the essential components of a sustainable space nutrition system for meeting these needs. The search phrase "space food and the survival of astronauts in long-term missions" was used to collect the initial 5432 articles from seven Chinese and seven English databases. From these articles, two independent reviewers screened titles and abstracts to identify 218 articles for full-text reviews based on three themes and 18 keyword combinations as eligibility criteria. The results suggest that it is possible to address short-term adverse environmental factors and nutritional deficiencies by adopting effective dietary measures, selecting the right types of foods and supplements, and engaging in specific sustainable food production and eating practices. However, to support self-sufficiency during long-term space exploration, the most optimal and sustainable space nutrition systems are likely to be supported primarily by fresh food production, natural unprocessed foods as diets, nutrient recycling of food scraps and cultivation systems, and the establishment of closed-loop biospheres or landscape-based space habitats as long-term life support systems.

Are metabolic adaptations to weight changes an artefact?

BACKGROUND

Adaptive thermogenesis (AT) is currently defined as the fat-free mass (FFM)-independent change in resting energy expenditure (REE) in response to caloric restriction (CR) or overfeeding (OF). So far, the impact of changes in the anatomical and molecular composition of FFM on AT has not been addressed.

OBJECTIVES

To assess the impact of changes in FFM composition on AT.

METHODS

FFM was assessed in 32 healthy young men during controlled 21-d CR and 14 d of subsequent OF. Anatomical (i.e., the organ/tissue level) and molecular (i.e., water, mineral, and protein content and thus body density) composition of FFM were characterized. REE was measured by indirect calorimetry.

RESULTS

With CR, body weight and REE decreased by 4.2 ± 0.9 kg and 173 ± 107 kcal/d, respectively, with corresponding increases of 3.5 ± 1.2 kg and 194 ± 110 kcal/d during OF (P < 0.001 for all changes). Changes in FFM explained 56.7% and 66.7% of weight loss and weight gain, respectively. Weight changes were associated with changes in various anatomical (i.e., masses of skeletal muscle, liver, kidneys, and brain) and molecular components (total body water, protein, and bone minerals) of FFM. After adjustments for changes in FFM only, AT was 116 ± 127 (P < 0.001) and 27 ± 115 kcal/d (NS) with CR and OF, respectively. Adjustments for FFM and its anatomical and molecular composition reduced AT in response to CR to 83 ± 116 and 122 ± 123 kcal/d (P < 0.05 and P < 0.001) whereas during OF, AT became significant at 87 ± 146 kcal/d (anatomical; P < 0.05) and 86 ± 118 kcal/d (molecular; P < 0.001).

CONCLUSIONS

Adjusting changes in REE with under- and overfeeding for the corresponding changes in the anatomical and molecular composition of FFM decreased AT after CR and increased AT after OF, but overall adjusted AT was likely not large enough in magnitude to be able to prevent weight loss or resist weight gain.

Reproducibility and associations with obesity and insulin resistance of circadian-rhythm parameters in free-living vs. controlled conditions during the PREVIEW lifestyle study

BACKGROUND

Circadian rhythm is altered in individuals with obesity and insulin resistance, showing a smaller amplitude, less stability, and increased intradaily variation.

OBJECTIVE

We compared reproducibility of circadian-rhythm parameters over time and under free-living vs. controlled conditions in participants with obesity and pre-diabetes after 2- and 3-year weight-loss maintenance during the 3-year PREVIEW (PREVention of diabetes through lifestyle intervention and population studies In Europe and around the World) study. Associations of obesity and insulin resistance with circadian-rhythm parameters were assessed.

SUBJECTS AND METHODS

Circadian-rhythm parameters were determined using continuous wrist-temperature measurements in free-living environments at year 2 (n = 24; age 56.8 ± 10.3 y; body mass index (BMI) = 30 ± 3.9 kg/m²; homeostatic model assessment of insulin resistance (HOMA-IR) 2.4 ± 1.1), at year 3 (n = 97; age 61.7 ± 7.8; BMI = 29.7 ± 3.9; HOMA-IR 2.9 ± 2.1), and at year 3 in a controlled condition (n = 38; age 63.4 ± 6.7; BMI = 28.7 ± 3.9; HOMA-IR 3.8 ± 1.4). Reproducibility was assessed by analyzing repeatability coefficients (CR), differences, and associations, over time as well as between conditions. Associations of BMI and HOMA-IR with circadian-rhythm parameters were assessed at y-3 in both conditions using factor analysis, followed by Pearson's correlations.

RESULTS

Reproducibility of circadian-rhythm parameters over time in the free-living environments was high (CR 0.002-5.26; no significant differences; associated amplitudes r = 0.57; p < 0.01). In contrast, reproducibility between different conditions was low (CR 0.02-11.36; significant differences between most parameters (p < 0.05); yet associated amplitudes r = 0.59; p < 0.01). In the controlled vs. free-living condition circadian-rhythm was more stable; BMI and HOMA-IR were associated with the physiological amplitude-related parameters (r = -0.45; p < 0.01; r = -0.33; p < 0.05). In the free-living environment, BMI and behavioral circadian-rhythm parameters indicating circadian alignment, contributed most to the explained variation (47.1%), and were inversely associated (r = -0.22; p < 0.05), while HOMA-IR was inversely associated with stability-related circadian-rhythm parameters (r = -0.21; p < 0.05).

CONCLUSIONS

Circadian rhythm was highly reproducible over time in the free-living environments, yet different under different conditions, being more stable in the controlled condition. BMI may play a significant role in circadian alignment and vice versa in the free-living environment.

Caloric Restriction per se Rather Than Dietary Macronutrient Distribution Plays a Primary Role in Metabolic Health and Body Composition Improvements in Obese Mice

Caloric restriction (CR) is of key importance in combating obesity and its associated diseases. We aimed to examine effects of dietary macronutrient distribution on weight loss and metabolic health in obese mice exposed to CR. Male C57BL/6J mice underwent diet-induced obesity for 18 weeks. Thereafter mice were exposed to a 6-week CR for up to 40% on either low-fat diet (LFD; 20, 60, 20% kcal from protein, carbohydrate, fat), low-carb diet (LCD; 20, 20, 60% kcal, respectively) or high-pro diet (HPD; 35, 35, 30% kcal, respectively) (n = 16 each). Ten mice on the obesogenic diet served as age-matched controls. Body composition was evaluated by tissue dissections. Glucose tolerance, bloods lipids and energy metabolism were measured. CR-induced weight loss was similar for LFD and LCD while HPD was associated with a greater weight loss than LCD. The diet groups did not differ from obese controls in hindlimb muscle mass, but showed a substantial decrease in body fat without differences between them. Glucose tolerance and blood total cholesterol were weight-loss dependent and mostly improved in LFD and HPD groups during CR. Blood triacylglycerol was lowered only in LCD group compared to obese controls. Thus, CR rather than macronutrient distribution in the diet plays the major role for improvements in body composition and glucose control in obese mice. Low-carbohydrate-high-fat diet more successfully reduces triacylglycerol but not cholesterol levels compared to isocaloric high-carbohydrate-low-fat weight loss diets.

Associations of changes in reported and estimated protein and energy intake with changes in insulin resistance, glycated hemoglobin, and BMI during the PREVIEW lifestyle intervention study

BACKGROUND

Observed associations of high-protein diets with changes in insulin resistance are inconclusive.

OBJECTIVES

We aimed to assess associations of changes in both reported and estimated protein (PRep; PEst) and energy intake (EIRep; EIEst) with changes in HOMA-IR, glycated hemoglobin (HbA1c), and BMI (in kg/m2), in 1822 decreasing to 833 adults (week 156) with overweight and prediabetes, during the 3-y PREVIEW (PREVention of diabetes through lifestyle intervention and population studies In Europe and around the World) study on weight-loss maintenance. Eating behavior and measurement errors (MEs) of dietary intake were assessed. Thus, observational post hoc analyses were applied.

METHODS

Associations of changes in EIEst, EIRep, PEst, and PRep with changes in HOMA-IR, HbA1c, and BMI were determined by linear mixed-model analysis in 2 arms [high-protein-low-glycemic-index (GI) diet and moderate-protein-moderate-GI diet] of the PREVIEW study. EIEst was derived from energy requirement: total energy expenditure = basal metabolic rate × physical activity level; PEst from urinary nitrogen, and urea. MEs were calculated as [(EIEst - EIRep)/EIEst] × 100% and [(PRep - PEst)/PEst] × 100%. Eating behavior was determined using the Three Factor Eating Questionnaire, examining cognitive dietary restraint, disinhibition, and hunger.

RESULTS

Increases in PEst and PRep and decreases in EIEst and EIRep were associated with decreases in BMI, but not independently with decreases in HOMA-IR. Increases in PEst and PRep were associated with decreases in HbA1c. PRep and EIRep showed larger changes and stronger associations than PEst and EIEst. Mean ± SD MEs of EIRep and PRep were 38% ± 9% and 14% ± 4%, respectively; ME changes in EIRep and En% PRep were positively associated with changes in BMI and cognitive dietary restraint and inversely with disinhibition and hunger.

CONCLUSIONS

During weight-loss maintenance in adults with prediabetes, increase in protein intake and decrease in energy intake were not associated with decrease in HOMA-IR beyond associations with decrease in BMI. Increases in PEst and PRep were associated with decrease in HbA1c.This trial was registered at clinicaltrials.gov as NCT01777893.

Efficacy of Dietary and Supplementation Interventions for Individuals with Type 2 Diabetes

The prevalence of Type 2 diabetes (T2D) is increasing, which creates a large economic burden. Diet is a critical factor in the treatment and management of T2D; however, there are a large number of dietary approaches and a general lack of consensus regarding the efficacy of each. Therefore, the purpose of this narrative review is twofold: (1) to critically evaluate the effects of various dietary strategies on diabetes management and treatment, such as Mediterranean diet, plant-based diet, low-calorie and very low-calorie diets, intermittent fasting, low-carbohydrate and very low-carbohydrate diets, and low glycemic diets and (2) to examine several purported supplements, such as protein, branched-chain amino acids, creatine, and vitamin D to improve glucose control and body composition. This review can serve as a resource for those wanting to evaluate the evidence supporting the various dietary strategies and supplements that may help manage T2D.

Dietary carbohydrates and weight loss maintenance

PURPOSE OF REVIEW

Aim of the present review is to provide an overview of the effect of manipulating dietary carbohydrates (content, type) after a period of weight loss on weight loss maintenance and its potential underlying mechanisms.

RECENT FINDINGS

Few recent studies directly tested whether lower carbohydrate/glycaemic load or higher fibre diets help to limit weight regain after weight loss and they did not provide evidence supporting a role of a reduction of the carbohydrate or an increase of the fibre content of the diet in the prevention of weight regain after weight loss. Some evidence is emerging that personal characteristics (gut microbiota, glycaemia) may interact with diet composition. but randomized clinical trials are needed to substantiate these claims.

SUMMARY

There is currently no convincing evidence that lowering dietary carbohydrates has a clinically relevant effect on weight regain after weight loss, unless there is an increase in protein intake at the same time. Further randomized trials are needed to investigate potential interactions with personal characteristics while improving strategies for long-term adherence.

A High-Protein, Low Glycemic Index Diet Suppresses Hunger but Not Weight Regain After Weight Loss: Results From a Large, 3-Years Randomized Trial (PREVIEW)

Background: Previous studies have shown an increase in hunger during weight-loss maintenance (WLM) after diet-induced weight loss. Whether a combination of a higher protein, lower glycemic index (GI) diet and physical activity (PA) can counteract this change remains unclear. Aim: To compare the long-term effects of two diets [high protein (HP)-low GI vs. moderate protein (MP)-moderate GI] and two PA programs [high intensity (HI) vs. moderate intensity (MI)] on subjective appetite sensations during WLM after ≥8% weight loss (WL). Methods: Data derived from the 3-years PREVIEW randomized intervention study. An 8-weeks WL phase using a low-energy diet was followed by a 148-weeks randomized WLM phase. For the WLM phase, participants were assigned to one of the four groups: HP-MI, HP-HI, MP-MI, and MP-HI. Available data from 2,223 participants with overweight or obesity (68% women; BMI ≥ 25 kg/m²). Appetite sensations including satiety, hunger, desire to eat, and desire to eat something sweet during the two phases (at 0, 8 weeks and 26, 52, 104, and 156 weeks) were assessed based on the recall of feelings during the previous week using visual analogue scales. Differences in changes in appetite sensations from baseline between the groups were determined using linear mixed models with repeated measures. Results: There was no significant diet × PA interaction. From 52 weeks onwards, decreases in hunger were significantly greater in HP-low GI than MP-moderate GI (P _{time × diet} = 0.018, P _dietgroup = 0.021). Although there was no difference in weight regain between the diet groups (P _{time × diet} = 0.630), hunger and satiety ratings correlated with changes in body weight at most timepoints. There were no significant differences in appetite sensations between the two PA groups. Decreases in hunger ratings were greater at 52 and 104 weeks in HP-HI vs. MP-HI, and greater at 104 and 156 weeks in HP-HI vs. MP-MI. Conclusions: This is the first long-term, large-scale randomized intervention to report that a HP-low GI diet was superior in preventing an increase in hunger, but not weight regain, during 3-years WLM compared with a MP-moderate GI diet. Similarly, HP-HI outperformed MP-HI in suppressing hunger. The role of exercise intensity requires further investigation. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT01777893.

Does adaptive thermogenesis occur after weight loss in adults? A systematic review

Adaptive thermogenesis (AT) has been proposed to be a compensatory response that may resist weight loss (WL) and promote weight regain. This systematic review examined the existence of AT in adults after a period of negative energy balance (EB) with or without a weight stabilisation phase. Studies published until 15 May 2020 were identified from PubMed, Cochrane Library, EMBASE, MEDLINE, SCOPUS and Web of Science. Inclusion criteria included statistically significant WL, observational with follow-up or experimental studies, age > 18y, sample size ≥10 participants, intervention period ≥ 1week, published in English, objective measures of total daily energy expenditure (EE) (TDEE), resting EE (REE) and sleeping EE(SEE). The systematic review was registered at PROSPERO (2020 CRD42020165348). A total of thirty-three studies comprising 2528 participants were included. AT was observed in twenty-seven studies. Twenty-three studies showed significant values for AT for REE (82·8 %), four for TDEE (80·0 %) and two for SEE (100 %). A large heterogeneity in the methods used to quantify AT and between subjects and among studies regarding the magnitude of WL and/or of AT was reported. Well-designed studies reported lower or non-significant values for AT. These findings suggest that although WL may lead to AT in some of the EE components, these values may be small or non-statistically significant when higher-quality methodological designs are used. Furthermore, AT seems to be attenuated, or non-existent, after periods of weight stabilisation/neutral EB. More high-quality studies are warranted not only to disclose the existence of AT but also to understand its clinical implications on weight management outcomes.

Dietary interventions for obesity: clinical and mechanistic findings

Dietary modification is central to obesity treatment. Weight loss diets are available that include various permutations of energy restriction, macronutrients, foods, and dietary intake patterns. Caloric restriction is the common pathway for weight reduction, but different diets may induce weight loss by varied additional mechanisms, including by facilitating dietary adherence. This narrative Review of meta-analyses and select clinical trials found that lower-calorie diets, compared with higher-calorie regimens, reliably induced larger short-term (<6 months) weight losses, with deterioration of this benefit over the long term (>12 months). Few significant long-term differences in weight loss were observed for diets of varying macronutrient composition, although some regimens were found to have short-term advantages (e.g., low carbohydrate versus low fat). Progress in improving dietary adherence, which is critical to both short- and long-term weight loss, could result from greater efforts to identify behavioral and metabolic phenotypes among dieters.

Role of Endocannabinoids in Energy-Balance Regulation in Participants in the Postobese State-a PREVIEW Study

CONTEXT

Endocannabinoids are suggested to play a role in energy balance regulation.

OBJECTIVE

We aimed to investigate associations of endocannabinoid concentrations during the day with energy balance and adiposity and interactions with 2 diets differing in protein content in participants in the postobese phase with prediabetes.

DESIGN AND PARTICIPANTS

Participants (n = 38) were individually fed in energy balance with a medium protein (MP: 15:55:30% of energy from protein:carbohydrate:fat) or high-protein diet (HP: 25:45:30% energy from P:C:F) for 48 hours in a respiration chamber.

MAIN OUTCOME MEASURES

Associations between energy balance, energy expenditure, respiratory quotient, and endocannabinoid concentrations during the day were assessed.

RESULTS

Plasma-concentrations of anandamide (AEA), oleoylethanolamide (OEA), palmitoyethanolamide (PEA), and pregnenolone (PREG) significantly decreased during the day. This decrease was inversely related to body mass index (AEA) or body fat (%) (PEA; OEA). The lowest RQ value, before lunch, was inversely associated with concentrations of AEA and PEA before lunch. Area under the curve (AUC) of concentrations of AEA, 2-AG, PEA, and OEA were positively related to body fat% (P < .05).The HP and MP groups showed no differences in concentrations of AEA, OEA, PEA, and PREG, but the AUC of 2-arachidonoylglycerol (2-AG) was significantly higher in the HP vs the MP group.

CONCLUSIONS

In energy balance, only the endocannabinoid 2-AG changed in relation to protein level of the diet, whereas the endocannabinoid AEA and endocannabinoid-related compounds OEA and PEA reflected the gradual energy intake matching energy expenditure during the day.

Effects of a High-Protein Diet on Cardiometabolic Health, Vascular Function, and Endocannabinoids-A PREVIEW Study

An unfavorable lipid profile and being overweight are known mediators in the development of cardiovascular disease (CVD) risk. The effect of diet, particularly high in protein, remains under discussion. Therefore, this study examines the effects of a high-protein (HP) diet on cardiometabolic health and vascular function (i.e., endothelial function, arterial stiffness, and retinal microvascular structure), and the possible association with plasma endocannabinoids and endocannabinoid-related compounds in overweight participants. Thirty-eight participants (64.5 ± 5.9 (mean ± SD) years; body mass index (BMI) 28.9 ± 4.0 kg/m²) were measured for 48 h in a respiration chamber after body-weight maintenance for approximately 34 months following weight reduction. Diets with either a HP (n = 20) or moderate protein (MP; n = 18) content (25%/45%/30% vs. 15%/55%/30% protein/carbohydrate/fat) were provided in energy balance. Validated markers for cardiometabolic health (i.e., office blood pressure (BP) and serum lipoprotein concentrations) and vascular function (i.e., brachial artery flow-mediated vasodilation, pulse wave analysis and velocity, and retinal microvascular calibers) were measured before and after those 48 h. Additionally, 24 h ambulatory BP, plasma anandamide (AEA), 2-arachidonoylglycerol (2-AG), oleoylethanolamide (OEA), palmitoylethanolamide (PEA), and pregnenolone (PREG) were analyzed throughout the day. Office and ambulatory BP, serum lipoprotein concentrations, and vascular function markers were not different between the groups. Only heart rate (HR) was higher in the HP group. HR was positively associated with OEA, while OEA and PEA were also positively associated with total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol concentrations. Vascular function markers were not associated with endocannabinoids (or endocannabinoid-related substances). In conclusion, the HP diet did not affect cardiometabolic health and vascular function in overweight participants after completing a weight-loss intervention. Furthermore, our data indicate a possible association between OEA and PEA with TC and LDL cholesterol.