The habitual degree of weight loss might be associated with specific fat and protein intakes during a period of weight maintenance in athletes used to weight variations: preliminary results from the WAVE study.

Weight variations are common in sporting life, with important inter-individual variability in the degree of an athlete's habitual weight loss. As a part of the WAVE study (NCT04107545), the main objective of this preliminary study was to determine whether the habitual degree of weight loss was associated with anthropometric, body composition, nutritional or psychometric profiles during a period of weight maintenance in athletes accustomed to weight variations. We hypothesized that athletes accustomed to a higher habitual degree of weight loss may have a higher body weight and body fat mass, and may present a more controlled diet regimen and cognitive restriction than athletes with a lower habitual degree of weight loss. During a period of weight maintenance, 62 athletes (24.0 ± 5.3 years; 26 women) completed anthropometry and body composition measurements, a 48-hours food diary and self-reported questionnaires to determine their weight variation practice, nutritional profile and mood state. Athletes were stratified within inter- and intra-quartile groups according to their habitual degree of weight loss. Athletes with a higher habitual degree of weight loss were those who consumed more protein (P < .001) and less fat (P = .01) as a proportion of total energy compared with those losing less weight, without any difference in body composition between the groups. The rapid weight loss score was significantly higher in individuals losing more weight (P < .001) and no difference was observed for the mood state profile. The present results suggest a potential control of nutritional regulation during a period of weight maintenance in order to spare fat-free mass and favor fat mass loss in athletes who are routinely losing more weight. Fat-free mass may be the main nutritional driver due to low body fat mass in athletes, which may limit the "catch-up fat" phenomenon commonly observed in nonathletic population.

Glycaemic Response to a Nut-Enriched Diet in Asian Chinese Adults with Normal or High Glycaemia: The Tu Ora RCT.

Nut-based products are a good source of high-quality plant protein in addition to mono- and polyunsaturated fatty acids, and may aid low-glycaemic dietary strategies important for the prevention of type 2 diabetes (T2D). In particular, they may be advantageous in populations susceptible to dysglycaemia, such as Asian Chinese. The present study aimed to compare effects of a higher-protein nut bar (HP-NB, also higher in total fibre and unsaturated fats, comprising mixed almonds and peanuts) vs. an isoenergetic higher-carbohydrate cereal bar (HC-CB) within the diet of 101 Chinese adults with overweight and normo- or hyperglycaemia. Ectopic pancreas and liver fat were characterised using magnetic resonance imaging and spectroscopy (MRI/S) as a secondary outcome. Participants were randomized to receive HP-NB or HC-CB daily as a 1 MJ light meal or snack replacement, in addition to healthy eating advice. Anthropometry and clinical indicators of T2D risk were assessed fasted and during an oral glucose tolerance test (OGTT), pre- and post-intervention. No significant difference was observed between diet groups for body weight, body mass index, waist or hip circumference, blood pressure, glucoregulatory markers, lipid profile or inflammatory markers over 12 weeks (all, p > 0.05). No difference was observed between glycaemic subgroups or those with normal versus high ectopic organ fat. Although HP-NB can attenuate postprandial glycaemia following a meal, no effects were observed for either fasting or glucose-mediated outcomes following longer-term inclusion in the habitual diet of Chinese adults with overweight, including at-risk subgroups.

Effect of a Higher-Protein Nut versus Higher-Carbohydrate Cereal Enriched Diet on the Gut Microbiomes of Chinese Participants with Overweight and Normoglycaemia or Prediabetes in the Tu Ora Study.

Global increases in metabolic disorders such as type 2 diabetes (T2D), especially within Asian populations, highlight the need for novel approaches to dietary intervention. The Tu Ora study previously evaluated the effects on metabolic health of including a nut product into the diet of a New Zealand cohort of Chinese participants with overweight and normoglycaemia or prediabetes through a 12-week randomised, parallel-group clinical trial. In this current study, we compared the impact of this higher-protein nut bar (HP-NB) versus a higher-carbohydrate cereal bar (HC-CB) on the faecal microbiome by employing both 16S rRNA gene amplicon and shotgun metagenomic sequencing of pre- and post-intervention pairs from 84 participants. Despite the higher fibre, protein, and unsaturated fat content of nuts, there was little difference between dietary groups in gut microbiome composition or functional potential, with the bacterial phylum Firmicutes dominating irrespective of diet. The lack of observed change suggests the dietary impact of the bars may have been insufficient to affect the gut microbiome. Manipulating the interplay between the diet, microbiome, and metabolic health may require a more substantial and/or prolonged dietary perturbation to generate an impactful modification of the gut ecosystem and its functional potential to aid in T2D risk reduction.

Utilising a Clinical Metabolomics LC-MS Study to Determine the Integrity of Biological Samples for Statistical Modelling after Long Term -80 °C Storage: A TOFI_Asia Sub-Study.

Biological samples of lipids and metabolites degrade after extensive years in -80 °C storage. We aimed to determine if associated multivariate models are also impacted. Prior TOFI_Asia metabolomics studies from our laboratory established multivariate models of metabolic risks associated with ethnic diversity. Therefore, to compare multivariate modelling degradation after years of -80 °C storage, we selected a subset of aged (≥5-years) plasma samples from the TOFI_Asia study to re-analyze via untargeted LC-MS metabolomics. Samples from European Caucasian (n = 28) and Asian Chinese (n = 28) participants were evaluated for ethnic discrimination by partial least squares discriminative analysis (PLS-DA) of lipids and polar metabolites. Both showed a strong discernment between participants ethnicity by features, before (Initial) and after (Aged) 5-years of -80 °C storage. With receiver operator characteristic curves, sparse PLS-DA derived confusion matrix and prediction error rates, a considerable reduction in model integrity was apparent with the Aged polar metabolite model relative to Initial modelling. Ethnicity modelling with lipids maintained predictive integrity in Aged plasma samples, while equivalent polar metabolite models reduced in integrity. Our results indicate that researchers re-evaluating samples for multivariate modelling should consider time at -80 °C when producing predictive metrics from polar metabolites, more so than lipids.

Human Metabolism and Excretion of Kawakawa (Piper excelsum) Leaf Chemicals.

SCOPE: Piper excelsum (kawakawa) has a history of therapeutic use by Maori in Aotearoa New Zealand. It is currently widely consumed as a beverage and included as an ingredient in "functional" food product. Leaves contain compounds that are also found in a wide range of other spices, foods, and medicinal plants. This study investigates the human metabolism and excretion of kawakawa leaf chemicals. METHODS AND RESULTS: Six healthy male volunteers in one study (Bioavailability of Kawakawa Tea metabolites in human volunteers [BOKA-T]) and 30 volunteers (15 male and 15 female) in a second study (Impact of acute Kawakawa Tea ingestion on postprandial glucose metabolism in healthy human volunteers [TOAST]) consume a hot water infusion of dried kawakawa leaves (kawakawa tea [KT]). Untargeted Liquid Chromatography-Tandem Mass spectrometry (LC-MS/MS) analyses of urine samples from BOKA-T identified 26 urinary metabolites that are significantly associated with KT consumption, confirmed by the analysis of samples from the independent TOAST study. Seven of the 26 metabolites are also detected in plasma. Thirteen of the 26 urinary compounds are provisionally identified as metabolites of specific compounds in KT, eight metabolites are identified as being derived from specific compounds in KT but without resolution of chemical structure, and five are of unknown origin. CONCLUSIONS: Several kawakawa compounds that are also widely found in other plants are bioavailable and are modified by phase 1 and 2 metabolism.

Weight regain, body composition, and metabolic responses to weight loss in weight cycling athletes: A systematic review and meta-analyses.

Depending on the nature of their sports, athletes may be engaged in successive weight loss (WL) and regain, conducing to "weight cycling." The aims of this paper were to systematically (and meta-analytically when possible) analyze the post-WL recovery of (i) body weight and (ii) fat mass; fat-free mass; and performance and metabolic responses in weight cycling athletes (18-55 years old, body mass index < 30 kg.m-2 ). MEDLINE, Embase, and SPORTDiscus databases were explored. The quality and risk of bias of the 74 included studies were assessed using the quality assessment tool for quantitative studies. Thirty-two studies were eligible for meta-analyses. Whatever the type of sports or methods used to lose weight, post-WL body weight does not seem affected compared with pre-WL. While similar results are observed for fat-free mass, strength sports athletes (also having longer WL and regain periods) do not seem to fully recover their initial fat mass (ES: -0.39, 95% CI: [-0.77; -0.00], p = 0.048, I2  = 0.0%). Although the methods used by athletes to achieve WL might prevent them from a potential post-WL fat overshooting, further studies are needed to better understand WL episodes consequences on athletes' performance as well as short- and long-term physical, metabolic, and mental health.

Intra-pancreatic fat is associated with high circulating glucagon and GLP-1 concentrations following whey protein ingestion in overweight women with impaired fasting glucose: A randomised controlled trial.

AIM: Intra-pancreatic fat deposition (IPFD) while hypothesised to impair beta-cell function, its impact on alpha-cells remains unclear. We evaluated the association between IPFD and markers of pancreatic cells function using whey protein. METHODS: Twenty overweight women with impaired fasting glucose (IFG) and low or high IPFD (<4.66% vs ≥4.66%) consumed 3 beverage treatments: 0 g (water control), 12.5 g (low-dose) and 50.0 g (high-dose) whey protein, after an overnight fast, in randomised order. Blood glucose, insulin, C-peptide, glucagon, gastric-inhibitory polypeptide (GIP), glucagon-like peptide-1 (GLP-1) and amylin were analysed postprandially over 4 h. Incremental area-under-the-curve (iAUC), incremental maximum concentration (iCmax), and time to maximum concentration (Tmax) for these were compared between IPFD groups using repeated measures linear mixed models, also controlled for age (pcov). RESULTS: iAUC and iCmax glucose and insulin while similar between the two IPFD groups, high IPFD and ageing contributed to higher postprandial glucagon (iAUC: p = 0.012; pcov = 0.004; iCmax: p = 0.069; pcov = 0.021) and GLP-1 (iAUC: p = 0.006; pcov = 0.064; iCmax: p = 0.011; pcov = 0.122) concentrations. CONCLUSION: In our cohort, there was no evidence that IPFD impaired protein-induced insulin secretion. Conversely, IPFD may be associated with increased protein-induced glucagon secretion, a novel observation which warrants further investigation into its relevance in the pathogenesis of dysglycaemia and type-2 diabetes.

The role of postprandial thermogenesis in the development of impaired glucose tolerance and type II diabetes.

Accounting for 5%-15% of total daily energy expenditure, postprandial thermogenesis (PPT) refers to an acute increase in resting metabolic rate (RMR) in the hours after eating. This is largely explained by the energy costs of processing the macronutrients of a meal. Most individuals spend the majority of the day in the postprandial state, thus over one's lifetime even minor differences in PPT may possess true clinical significance. In contrast to RMR, research indicates that PPT may be reduced in the development of both prediabetes and type II diabetes (T2D). The present analysis of existing literature has found that this impairment may be exaggerated in hyperinsulinemic-euglycemic clamp studies compared with food and beverage consumption studies. Nonetheless, it is estimated that daily PPT following carbohydrate consumption alone is approximately 150 kJ lower among individuals with T2D. This estimate fails to consider protein intake, which is notably more thermogenic than carbohydrate intake (20%-30% vs. 5%-8%, respectively). Putatively, dysglycemic individuals may lack the insulin sensitivity required to divert glucose toward storage-a more energy-taxing pathway. Accordingly, the majority of findings has associated an impaired PPT with a reduced "obligatory" energy output (i.e., the energy costs associated with nutrient processing). More recently, it has been reported that "facultative" thermogenesis [e.g., the energy costs associated with sympathetic nervous system (SNS) stimulation] may also contribute to any impairment in PPT among individuals with prediabetes and T2D. Further longitudinal research is required to truly ascertain whether meaningful changes in PPT manifest in the prediabetic state, before the development of T2D.

Deconstructing interindividual variability in energy metabolism: implications for metabolic health.

A person's metabolic rate corresponds to the whole body level sum of all oxidative reactions occurring on the cellular level. The energy expenditure (EE) can be categorized into various obligatory and facultative processes. In sedentary adults, basal metabolic rate is the largest contributor to total daily EE, and interindividual variability can be significant. Additional EE is required for digesting and metabolizing food, thermoregulatory adaptation to cold, and to support exercise and nonexercise body movements. Interindividual variability also exists for these EE processes, even after controlling for known factors. The complex mechanisms of interindividual variability in EE can have genetic and environmental origins and require further investigation. Exploration of interindividual variability in EE and its underlying factors holds importance to metabolic health, as it may predict disease risk, and be useful in the personalization of preventative and treatment strategies.

Is dieting a risk for higher weight gain in normal-weight individual? A systematic review and meta-analysis.

While there is an increasing prevalence of dieting in the overall population, weight loss (WL) practices could be a risk factor for weight gain (WG) in normal-weight (NW) individuals. The aim of the present work was to systematically review all the studies implicating diet restriction and body weight (BW) evolution in NW people. The literature search was registered in PROSPERO (CRD42021281442) and was performed in three databases from April 2021 to June 2022 for articles involving healthy NW adults. From a total of 1487 records initially identified, eighteen were selected in the systematic review. Of the eight dieting interventional studies, only one found a higher BW after weight recovery, but 75 % of them highlighted metabolic adaptations in response to WL favouring weight regain and persisting during/after BW recovery. Eight of the ten observational studies showed a relationship between dieting and major later WG, while the meta-analysis of observational studies results indicated that 'dieters' have a higher BW than 'non-dieters'. However, considering the high methodological heterogeneity and the publication bias of the studies, this result should be taken with caution. Moreover, the term 'diet' was poorly described, and we observed a large heterogeneity of the methods used to assess dieting status. Present results suggest that dieting could be a major risk factor for WG in the long term in NW individuals. There is, however, a real need for prospective randomised controlled studies, specifically assessing the relationship between WL induced by diet and subsequent weight in this population.

Lightest weight-class athletes are at higher risk of weight regain: results from the French-Rapid Weight Loss Questionnaire.

CONTEXT: Rapid weight loss (RWL) is a common precompetitive strategy used by athletes in weight-class sports and carries with it an increased risk to future cardiometabolic health. The Rapid Weight Loss Questionnaire (RWLQ) is a self-reported tool designed to identify and characterize such weight loss practices. OBJECTIVES: After developing a reliable and reproducible French version of the RWLQ (RWLQ-FR), the present study aims to analyse RWL patterns among French weight-class athletes and to point out potential relationships between such practices and risk of subsequent weight gain. METHODS: A test-retest analysis was performed in 54 athletes to test the questionnaire reproducibility before applying it in a cohort of 168 weight-cycling athletes (23.78 ± 9.25 y, 67.6 ± 12.6 kg, 81 males and 87 females, n = 24 strength sports and n = 144 various combat sports). RESULTS: The test-retest showed good agreement of the RWLQ-FR (Rho = 0.794, [0.696-0.893]). Athletes reported losing an average of 4.1 ± 2.9% of their initial weight in 13.1 ± 9.6 days, with the main methods used being an increase in exercise, training in rubber or plastic suits, and gradual dieting. The average weight recovery in a week was 3.5 ± 2.8% and results showed that the athletes with the lower inter-season weight (weight outside of the training and competition season) regained the more weight (p = 0.025). The average RWLQ-FR score was 31.9 ± 17.3 and athletes who began to lose weight earlier in their competitive carrier had the higher scores (p = 0.032). CONCLUSION: The present study demonstrates relationships between the pattern of RWL practices and potential increased risk of subsequent weight gain in weight-cycling athletes, and the need to better understand the long-term health-related risks.

Exploring the Chemical Space of Kawakawa Leaf (Piper excelsum).

The chemical profiles of kawakawa (Piper excelsum) leaves were analysed through targeted and non-targeted LC-MS/MS. The phytochemical profile was obtained for both aqueous extracts representative of kawakawa tea and methanolic extracts. Sixty-four compounds were identified from eight leaf sources including phenylpropanoids, lignans, flavonoids, alkaloids and amides. Eight of these compounds were absolutely quantified. The chemical content varied significantly by leaf source, with two commercially available sources of dried kawakawa leaves being relatively high in phenylpropanoids and flavonoids compared with field-collected fresh samples that were richer in amides, alkaloids and lignans. The concentrations of pharmacologically active metabolites ingested from the traditional consumption of kawakawa leaf as an aqueous infusion, or from novel use as a seasoning, are well below documented toxicity thresholds.

Fatty Pancreas and Cardiometabolic Risk: Response of Ectopic Fat to Lifestyle and Surgical Interventions.

Ectopic fat accumulation in non-adipose organs, such as the pancreas and liver, is associated with an increased risk of cardiometabolic disease. While clinical trials have focused on interventions to decrease body weight and liver fat, ameliorating pancreatic fat can be crucial but successful intervention strategies are not yet defined. We identified twenty-two published studies which quantified pancreatic fat during dietary, physical activity, and/or bariatric surgery interventions targeted at body weight and adipose mass loss alongside their subsequent effect on metabolic outcomes. Thirteen studies reported a significant decrease in body weight, utilising weight-loss diets (n = 2), very low-energy diets (VLED) (n = 2), isocaloric diets (n = 1), a combination of diet and physical activity (n = 2), and bariatric surgery (n = 5) including a comparison with VLED (n = 1). Surgical intervention achieved the largest decrease in pancreatic fat (range: -18.2% to -67.2%) vs. a combination of weight-loss diets, isocaloric diets, and/or VLED (range: -10.2% to -42.3%) vs. diet and physical activity combined (range: -0.6% to -3.9%), with a concurrent decrease in metabolic outcomes. While surgical intervention purportedly is the most effective strategy to decrease pancreas fat content and improve cardiometabolic health, the procedure is invasive and may not be accessible to most individuals. Given that dietary intervention is the cornerstone for the prevention of adverse metabolic health, the alternative approaches appear to be the use of weight-loss diets or VLED meal replacements, which are shown to decrease pancreatic fat and associated cardiometabolic risk.

Acute Effects of Kawakawa (Piper excelsum) Intake on Postprandial Glycemic and Insulinaemic Response in a Healthy Population.

Background: Piper excelsum (kawakawa) is an endemic shrub of Aotearoa, New Zealand, of cultural and medicinal importance to Maori. Its fruits and leaves are often consumed. These tissues contain several compounds that have been shown to be biologically active and which may underpin its putative health-promoting effects. The current study investigates whether kawakawa tea can modulate postprandial glucose metabolism. Methods: We report a pilot three-arm randomized crossover study to assess the bioavailability of kawakawa tea (BOKA-T) in six male participants with each arm having an acute intervention of kawakawa tea (4 g/250 mL water; 1 g/250 mL water; water) and a follow-up two-arm randomized crossover study to assess the impact of acute kawakawa tea ingestion on postprandial glucose metabolism in healthy human volunteers (TOAST) (4 g/250 mL water; and water; n = 30 (15 male and 15 female)). Participants consumed 250 mL of kawakawa tea or water control within each study prior to consuming a high-glycemic breakfast. Pre- and postprandial plasma glucose and insulin concentrations were measured, and the Matsuda index was calculated to measure insulin sensitivity. Results: In the BOKA-T study, lower plasma glucose (p < 0.01) and insulin (p < 0.01) concentrations at 60 min were observed after consumption of a high-dose kawakawa tea in comparison to low-dose or water. In the TOAST study, only plasma insulin (p = 0.01) was lower at 60 min in the high-dose kawakawa group compared to the control group. Both studies showed a trend towards higher insulin sensitivity in the high-dose kawakawa group compared to water only. Conclusions: Consuming kawakawa tea may modulate postprandial glucose metabolism. Further investigations with a longer-term intervention study are warranted.

The Role of Bovine and Non-Bovine Milk in Cardiometabolic Health: Should We Raise the "Baa"?

Although causality is yet to be confirmed, a considerable volume of research has explored the relationships between cow milk consumption, type II diabetes, and cardiovascular disease. Contrastingly, it has not been comprehensively examined whether milk of non-bovine origin can provide cardiometabolic protection. This narrative review outlines the marked differences in macronutrient composition, particularly protein and lipid content, and discusses how whole milk product (and individual milk ingredients) from different species could impact cardiometabolic health. There is some data, although primarily from compositional analyses, animal studies, and acute clinical trials, that non-bovine milk (notably sheep and goat milk) could be a viable substitute to cow milk for the maintenance, or enhancement, of cardiometabolic health. With a high content of medium-chain triglycerides, conjugated linoleic acid, leucine, and essential minerals, sheep milk could assist in the prevention of metabolic-related disorders. Similarly, albeit with a lower content of such functional compounds relative to sheep milk, goat and buffalo milk could be plausible counterparts to cow milk. However, the evidence required to generate nutritional recommendations for 'non-bovine milk' is currently lacking. Longer-term randomised controlled trials must assess how the bioactive ingredients of different species' milks collectively influence biomarkers of, and subsequently incidence of, cardiometabolic health.

Objectively Measured Physical Activity Is Associated With Body Composition and Metabolic Profiles of Pacific and New Zealand European Women With Different Metabolic Disease Risks.

Objective: To assess associations between physical activity (PA), body composition, and biomarkers of metabolic health in Pacific and New Zealand European (NZE) women who are known to have different metabolic disease risks. Methods: Pacific (n = 142) or NZE (n = 162) women aged 18-45 years with a self-reported body mass index (BMI) of either 18.5-25.0 kg⋅m-2 or ≥30.0 kg⋅m-2 were recruited and subsequently stratified as either low (<35%) or high (≥35%) BF%, with approximately half of each group in either category. Seven-day accelerometery was used to assess PA levels. Fasting blood was analysed for biomarkers of metabolic health, and whole body dual-energy X-ray absorptiometry (DXA) was used to estimate body composition. Results: Mean moderate-to-vigorous physical activity (MVPA; min⋅day-1) levels differed between BF% (p < 0.05) and ethnic (p < 0.05) groups: Pacific high- 19.1 (SD 15.2) and low-BF% 26.3 (SD 15.6) and NZE high- 30.5 (SD 19.1) and low-BF% 39.1 (SD 18.4). On average Pacific women in the low-BF% group engaged in significantly less total PA when compared to NZE women in the low-BF% group (133 cpm); no ethnic difference in mean total PA (cpm) between high-BF% groups were observed: Pacific high- 607 (SD 185) and low-BF% 598 (SD 168) and NZE high- 674 (SD 210) and low-BF% 731 (SD 179). Multiple linear regression analysis controlling for age and deprivation showed a significant inverse association between increasing total PA and fasting plasma insulin among Pacific women; every 100 cpm increase in total PA was associated with a 6% lower fasting plasma insulin; no significant association was observed in NZE women. For both Pacific and NZE women, there was an 8% reduction in fasting plasma insulin for every 10-min increase in MVPA (p ≤ 0.05). Conclusion: Increases in total PA and MVPA are associated with lower fasting plasma insulin, thus indicating a reduction in metabolic disease risk. Importantly, compared to NZE, the impact of increased total PA on fasting insulin may be greater in Pacific women. Considering Pacific women are a high metabolic disease risk population, these pre-clinical responses to PA may be important in this population; indicating promotion of PA in Pacific women should remain a priority.

Adaptive Thermogenesis Driving Catch-Up Fat Is Associated With Increased Muscle Type 3 and Decreased Hepatic Type 1 Iodothyronine Deiodinase Activities: A Functional and Proteomic Study.

Refeeding after caloric restriction induces weight regain and a disproportionate recovering of fat mass rather than lean mass (catch-up fat) that, in humans, associates with higher risks to develop chronic dysmetabolism. Studies in a well-established rat model of semistarvation-refeeding have reported that catch-up fat associates with hyperinsulinemia, glucose redistribution from skeletal muscle to white adipose tissue and suppressed adaptive thermogenesis sustaining a high efficiency for fat deposition. The skeletal muscle of catch-up fat animals exhibits reduced insulin-stimulated glucose utilization, mitochondrial dysfunction, delayed in vivo contraction-relaxation kinetics, increased proportion of slow fibers and altered local thyroid hormone metabolism, with suggestions of a role for iodothyronine deiodinases. To obtain novel insights into the skeletal muscle response during catch-up fat in this rat model, the functional proteomes of tibialis anterior and soleus muscles, harvested after 2 weeks of caloric restriction and 1 week of refeeding, were studied. Furthermore, to assess the implication of thyroid hormone metabolism in catch-up fat, circulatory thyroid hormones as well as liver type 1 (D1) and liver and skeletal muscle type 3 (D3) iodothyronine deiodinase activities were evaluated. The proteomic profiling of both skeletal muscles indicated catch-up fat-induced alterations, reflecting metabolic and contractile adjustments in soleus muscle and changes in glucose utilization and oxidative stress in tibialis anterior muscle. In response to caloric restriction, D3 activity increased in both liver and skeletal muscle, and persisted only in skeletal muscle upon refeeding. In parallel, liver D1 activity decreased during caloric restriction, and persisted during catch-up fat at a time-point when circulating levels of T4, T3 and rT3 were all restored to those of controls. Thus, during catch-up fat, a local hypothyroidism may occur in liver and skeletal muscle despite systemic euthyroidism. The resulting reduced tissue thyroid hormone bioavailability, likely D1- and D3-dependent in liver and skeletal muscle, respectively, may be part of the adaptive thermogenesis sustaining catch-up fat. These results open new perspectives in understanding the metabolic processes associated with the high efficiency of body fat recovery after caloric restriction, revealing new implications for iodothyronine deiodinases as putative biological brakes contributing in suppressed thermogenesis driving catch-up fat during weight regain.

Weight cycling practices in sport: A risk factor for later obesity?

Weight cycling, repeated cycles of weight loss and weight regain over time, is commonplace amongst many population groups. Although the effect of weight cycling on future obesity and cardiometabolic risk is still hotly debated, evidence does indicate that individuals who were normal weight prior to weight cycling are more susceptible to its adverse consequences than those who were overweight or with obesity. Athletes, and particularly those who compete in the so-called weight-sensitive sports, are prone to dieting and weight cycling practice owing to the competitive advantage to be gained from manipulating their body weight. However, in comparison with the general population, athletes tend to be leaner and weight loss phases more rapid and superimposed on a background of a high level of physical activity. In this context, it can be questioned whether weight cycling in this subpopulation will indeed increase risk for future obesity. It is perhaps surprising that despite recognition that athletes commonly partake in weight cycling during their career, studies are scarce and firm conclusions regarding the effect of this practice on future cardiometabolic risk remain to be drawn. In this review, we examine weight cycling prevalence and strategies in athletes and the current evidence relating to its short- and long-term consequences. In addition, a conceptual framework relating the dynamics of weight loss and recovery to athlete characteristics will be discussed, highlighting the need for well-controlled, prospective studies in this specific subpopulation.

Low 24-hour core body temperature as a thrifty metabolic trait driving catch-up fat during weight regain after caloric restriction.

The recovery of body weight after substantial weight loss or growth retardation is often characterized by a disproportionately higher rate of fat mass vs. lean mass recovery, with this phenomenon of "preferential catch-up fat" being contributed by energy conservation (thrifty) metabolism. To test the hypothesis that a low core body temperature (Tc) constitutes a thrifty metabolic trait underlying the high metabolic efficiency driving catch-up fat, the Anipill system, with telemetry capsules implanted in the peritoneal cavity, was used for continuous monitoring of Tc for several weeks in a validated rat model of semistarvation-refeeding in which catch-up fat is driven solely by suppressed thermogenesis. In animals housed at 22°C, 24-h Tc was reduced in response to semistarvation (-0.77°C, P < 0.001) and remained significantly lower than in control animals during the catch-up fat phase of refeeding (-0.27°C on average, P < 0.001), the lower Tc during refeeding being more pronounced during the light phase than during the dark phase of the 24-h cycle (-0.30°C vs. -0.23°C, P < 0.01) and with no between-group differences in locomotor activity. A lower 24-h Tc in animals showing catch-up fat was also observed when the housing temperature was raised to 29°C (i.e., at thermoneutrality). The reduced energy cost of homeothermy in response to caloric restriction persists during weight recovery and constitutes a thrifty metabolic trait that contributes to the high metabolic efficiency that underlies the rapid restoration of the body's fat stores during weight regain, with implications for obesity relapse after therapeutic slimming and the pathophysiology of catch-up growth.