The relationship between resting energy expenditure and thyroid hormones in response to short-term weight loss in severe obesity

Weight History Correlates of Resting Energy Expenditure in Women With Bulimia Nervosa

OBJECTIVE

Among those with bulimia nervosa, weight suppression has been associated with illness severity and treatment prognosis. Although significant weight loss is known to reduce metabolic rate, the relation between weight suppression and resting energy expenditure (REE) in bulimia nervosa has not been examined. This study tested the hypothesis of an inverse relation between weight suppression and REE in a sample of women with bulimia nervosa (N = 84).

METHODS

In primary analyses, linear regressions were conducted between weight suppression and REE, corrected for fat-free mass. In follow-up, exploratory analyses, stepwise linear regressions were conducted to explore the main and interaction effects of weight history and weight suppression on REE.

RESULTS

Neither traditional (TWS) nor developmental weight suppression (DWS) correlated with REE. Results from exploratory analyses, however, revealed a medium-to-large inverse relation between several weight history variables and REE (highest past weight, sr2 = 0.05; lowest postmorbid weight, sr2 = 0.07; current weight, sr2 = 0.05). Additionally, DWS interacted with current (sr2 = 0.08) and highest premorbid (sr2 = 0.05) z-BMI to influence REE with a medium-to-large effect. For individuals low in current and premorbid z-BMIs, higher DWS associated with lower REE levels. However, for individuals at higher premorbid z-BMIs, higher DWS unexpectedly associated with greater REE levels.

DISCUSSION

In this sample of women with bulimia nervosa, reduced REE associated with higher weights across all timepoints. If the interaction effect between DWS and z-BMI history persists in future studies, this may indicate unique challenges faced by individuals low in z-BMI and high in DWS related to weight gain and normalization of eating.

Adequacy of basal metabolic rate prediction equations in individuals with severe obesity: A systematic review and meta-analysis

The determination of energy requirements in clinical practice is based on basal metabolic rate (BMR), frequently predicted by equations that may not be suitable for individuals with severe obesity. This systematic review and meta-analysis examined the accuracy and precision of BMR prediction equations in adults with severe obesity. Four databases were searched in March 2021 and updated in May 2023. Eligible studies compared BMR prediction equations with BMR measured by indirect calorimetry. Forty studies (age: 28-55 years, BMI: 40.0-62.4 kg/m2) were included, most of them with a high risk of bias. Studies reporting bias (difference between estimated and measured BMR) were included in the meta-analysis (n = 20). Six equations were meta-analyzed: Harris & Benedict (1919); WHO (weight) (1985); Owen (1986); Mifflin (1990); Bernstein (1983); and Cunningham (1980). The most accurate and precise equations in the overall analysis were WHO (-12.44 kcal/d; 95%CI: -81.4; 56.5 kcal/d) and Harris & Benedict (-18.9 kcal/d; 95%CI -73.2; 35.2 kcal/d). All the other equations tended to underestimate BMR. Harris & Benedict and WHO were the equations with higher accuracy and precision in predicting BMR in individuals with severe obesity. Additional analyses suggested that equations may perform differently according to obesity BMI ranges, which warrants further investigation.

Ultrasound measurement of vastus lateralis and vastus medialis muscle parameters to identify chronic thyrotoxic myopathy

Introduction

Chronic thyrotoxic myopathy (CTM) is a common, easily neglected complication of hyperthyroidism. There are currently no standard diagnostic criteria for CTM, and the ultrasonic characteristics of CTM-affected skeletal muscle remain unclear. Herein, we aimed to evaluate hyperthyroid patients for CTM by ultrasound and identify ultrasonic muscle parameter cutoffs for CTM diagnosis.

Materials and methods

Each participant underwent ultrasonography. The original (muscle thickness (MT), pennation angle (PA), and cross-sectional area (CSA)) and corrected (MT/height (HT), MT/body mass index (BMI), CSA/HT, and CSA/BMI) parameters of the vastus lateralis and vastus medialis (VM) were evaluated. The diagnostic effectiveness of ultrasound for predicting CTM was determined using receiver operating characteristic (ROC) curve analysis. Our study included 203 participants: 67 CTM patients (18 males, 49 females), 67 non-CTM patients (28 males, 39 females) and 69 healthy controls (20 males, 49 females).

Results

The CTM group had lower muscular ultrasonic and anthropometric parameters, higher thyroid hormone and thyroid-stimulating hormone receptor antibody (TRAb) levels, and a longer duration of hyperthyroidism than the non-CTM group (P < 0.05). The VM-PA, VM-CSA, VM-CSA/HT, and VM-CSA/BMI were lower in females than in males (P < 0.05). Free thyroxine (FT4) and TRAb both showed significant negative correlations with VM-MT, VM-MT/HT, VM-CSA, and VM-CSA/HT (P < 0.05). VM-MT/BMI and VM-CSA/HT, respectively, best predicted male and female CTM (AUC = 0.84, 0.85; cutoff ≤ 0.07, < 4.01).

Conclusion

Ultrasound measurement of muscular parameters, especially in the VM, is a valid and feasible way of diagnosing and characterizing possible CTM in hyperthyroidism.

The Effects of Zinc and Selenium Co-Supplementation on Resting Metabolic Rate, Thyroid Function, Physical Fitness, and Functional Capacity in Overweight and Obese People under a Hypocaloric Diet: A Randomized, Double-Blind, and Placebo-Controlled Trial

Evidence of the effectiveness of zinc (Zn) and selenium (Se) on resting metabolic rate (RMR) and physical function parameters in people with overweight and obesity is scarce, while the effects of zinc and selenium on thyroid function and body composition are still a topic of debate and controversy. The aim of this randomized, double-blind, and placebo-controlled trial was to examine the effects of a hypocaloric diet and Se-Zn co-supplementation on RMR, thyroid function, body composition, physical fitness, and functional capacity in overweight or obese individuals. Twenty-eight overweight-obese participants (mean BMI: 29.4 ± 4.7) were randomly allocated (1:1) to the supplementation group (n = 14, 31.1 ± 5.5 yrs, 9 females) and the placebo group (n = 14, 32.1 ± 4.8 yrs, 6 females). The participants received Zn (25 mg of zinc gluconate/day) and Se (200 mcg of L-selenomethionine/day) or placebo tablets containing starch for eight weeks. The participants of both groups followed a hypocaloric diet during the intervention. RMR, thyroid function, body composition, cardiorespiratory fitness (VO₂max), and functional capacity (sit-to-stand tests, timed up-and-go test, and handgrip strength) were assessed before and after the intervention. A significant interaction was found between supplementation and time on RMR (p = 0.045), with the intervention group's RMR increasing from 1923 ± 440 to 2364 ± 410 kcal/day. On the other hand, no interaction between supplementation and time on the thyroid function was found (p > 0.05). Regarding the effects of Zn/Se co-administration on Se levels, a significant interaction between supplementation and time on Se levels was detected (p = 0.004). Specifically, the intervention group's Se serum levels were increased from 83.04 ± 13.59 to 119.40 ± 23.93 μg/L. However, Zn serum levels did not change over time (90.61 ± 23.23 to 89.58 ± 10.61 umol/L). Even though all body composition outcomes improved in the intervention group more than placebo at the second measurement, no supplement × time interaction was detected on body composition (p > 0.05). Cardiorespiratory fitness did not change over the intervention. Yet, a main effect of time was found for some functional capacity tests, with both groups improving similarly over the eight-week intervention period (p < 0.05). In contrast, a supplement x group interaction was found in the performance of the timed up-and-go test (TUG) (p = 0.010), with the supplementation group improving more. In conclusion, an eight-week intervention with Zn/Se co-supplementation combined with a hypocaloric diet increased the RMR, TUG performance, and Se levels in overweight and obese people. However, thyroid function, Zn levels, body composition, and the remaining outcomes of exercise performance remained unchanged.

Thyroid axis hormones and anthropometric recovery of children/adolescents with overweight/obesity: A scoping review

Introduction

Thyroid hormones exert multiple physiological effects essential to the maintenance of basal metabolic rate (BMR), adaptive thermogenesis, fat metabolism, growth, and appetite. The links between obesity and the hormones of the thyroid axis, i.e., triiodothyronine (T3), thyroxine (T4), and thyrotropin (TSH), are still controversial, especially when considering children and adolescents. This population has high rates of overweight and obesity and several treatment approaches, including nutritional, psychological, and physical exercise interventions have been used. Understanding the importance of the hormones of the thyroid axis in the recovery from overweight and obesity may help directing measures to the maintenance of a healthy body composition. The present scoping review was carried out to analyze studies evaluating these hormonal levels throughout interventions directed at treating overweight and obesity in children and adolescents. The main purpose was to ascertain whether the hormones levels vary during weight loss.

Methods

We selected for analysis 19 studies published between 1999 and 2022.

Results

Most of the studies showed that changes in different anthropometric indicators, in response to the multidisciplinary interventions, correlated positively with free T3 (fT3), total T3 (TT3), and TSH. With respect to free T4 (fT4) and total T4 (TT4).

Discussion

The most common finding was of unchanged levels and, hence, no significant association with weight loss. Moreover, thyroxine supplementation has failed to affect the response to the interventions. Further studies are necessary to elucidate the relevance of the variations in hormone levels to the establishment of overweight/obesity and to the recovery from these conditions in children/adolescents.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42020203359.

Beyond bariatric surgery and weight loss medicaments. A systematic review of the current practice in obesity rehabilitative inpatient programs in adults and pediatrics

Background

Obesity treatment strategies mainly include outpatient lifestyle modification, drugs and bariatric surgery. Voluntary rehabilitative inpatient programs are gaining relevance as potential alternative settings of care that focus on weight loss and prevention of weight regain through a multidisciplinary approach, but their prevalence is still limited due to the high costs.

Aim

Considering the lack of evidence in this area, the objective of this study is to systematically review the currently available literature on non-pharmacological and non-surgical inpatient programs aimed at weight loss, to clarify the efficacy and the characteristics of these interventions.

Methods

Proper English language articles from 2000 to 2022 were searched on relevant databases. Quality assessment was performed by two different authors using ROB2 and robvis tools. Adult and pediatric studies were reviewed separately and their characteristics were systematically displayed.

Results

36 articles were included (20 on adults, 16 on children, and adolescents) for a total of 5,510 individuals. The multidisciplinary approach was mainly comprehensive of a low-calorie diet, scheduled physical activity, and psychological support based on behavioral treatment. Educational and cooking sessions were present at a lower rate. Globally, inpatient weight loss programs showed a consistent efficacy in reducing body weight and inducing beneficial effects on quality of life, psychological well-being, eating behavior, physical performance, and fatigue. Follow-up data were scarce, but with a high percentage of patients regaining weight after a short period.

Conclusion

Weight loss inpatient rehabilitation is a promising area that has evidence of all-rounded success in the amelioration of several aspects related to obesity. Nevertheless, it appears to be quite inconsistent in preserving these benefits after the intervention. This might slow the innovation process in this area and preclude further investments from national healthcare. Personalized and enriched programs could show greater impact when focusing on the behavioral and educational aspects, which are crucial points, in particular in pediatrics, for setting up a long-lasting lifestyle modification. More studies are therefore necessary to evaluate long-term efficacy based on the different work-up models.

Association between High Normal TSH Levels and Obesity in Women with Anti-Thyroid Autoantibodies (ATAs)

A positive correlation between Thyroid-Stimulating Hormone (TSH) and Body Mass Index (BMI) has been reported in many studies, but data on this topic remain controversial, especially when TSH values are in the normal range. Moreover, few studies have evaluated the co-existence of thyroid autoimmunity. This study investigated the role of thyroid autoimmunity in the interconnection between TSH, BMI, and waist circumference (WC) in euthyroid patients with overweight or obesity. We enrolled 902 patients (213 males; mean age ± SD: 45 ± 14 years; mean BMI ± SD: 35.8 ± 6.5 kg/m²), with normal serum TSH concentration; anti-thyroid autoantibodies (ATAs) were evaluated in 752 patients (186 males). Patients were divided into four BMI classes, based on WHO criteria, and the relationship between BMI, WC, and TSH was evaluated in the whole sample and compared to ATAs positivity, observed in 235 patients (44 males). No significant difference was found between TSH levels in the BMI classes. A statistically significant correlation between TSH and BMI was found only in ATAs-positive females (N = 191, Spearman rho: 0.149; p-value: 0.040). However, this finding was not confirmed when considering the WC. Our study shows a positive correlation only between TSH and BMI in obese women with positive ATAs, suggesting that in these patients, the high normal levels of TSH could be attributed to a mild thyroid failure with a possible worsening obesity-related effect, and both need a careful evaluation.

Thyroid Function Alteration in Obesity and the Effect of Bariatric Surgery

The most common endocrine disease in obesity is hypothyroidism and secondary endocrine alterations, including abnormal thyroid function, are frequent in obesity. It is unclear whether impaired thyroid function is the cause or the consequence of increased adiposity; furthermore, there are no clear data regarding the best way to dose levothyroxine for patients with both hypothyroidism and obesity, and the effect of bariatric surgery (BS). The aim of the present article is to review some controversial aspects of the relation between obesity and the thyroid: (1) Thyroid function in obesity and the effect of BS (2) Thyroid hormone treatment (THT) in obese patients with hypothyroidism and the effect of BS. In summary: In morbidly obese patients, TSH is moderately increased. Morbid obesity has a mild central resistance to the thyroid hormone, reversible with weight loss. In morbidly obese hypothyroid patients, following weight loss, the levothyroxine dose/kg of ideal weight did not change, albeit there was an increment in the levothyroxine dose/kg of actual weight. From a clinical practice perspective, in morbid obesity, diagnosing mild hypothyroidism is difficult, BS improves the altered thyroid function and THT can be adapted better if it is based on ideal weight.

Adjusted association between type 2 immunity and low risk thyroid nodules: a retrospective cohort study

BACKGROUND

Immune responses, especially type 2 immunity, might be related to the prevalence of thyroid nodules, while the key regulators and potential pathways are remaining largely unknown. In addition, the immune status of individuals could be affected by mixed metabolic background. Herein our aim was to investigate the adjusted association between ultrasound-diagnosed low risk thyroid nodules and immune responses, excluding the interference of metabolic effects on immunity.

METHODS

We retrospectively enrolled 1764 subjects who underwent a thorough thyroid ultrasound examination. To eliminate the interference of confounders, we used propensity score matching (PSM) to match age, gender, cigarette smoking and alcohol drinking, parameters that are related with metabolic syndrome (MetS). Then the potential effectors of immune responses involved in the laboratorial assays were evaluated. Binary logistic regression analysis was used to assess the independent predictors of thyroid nodules in a multivariate manner.

RESULTS

The 1172 subjects were remained after PSM, and differences of demographic background between subjects with and without thyroid nodules were eliminated. Metabolic parameters comprising blood pressure, fasting blood glucose, total cholesterol, triglyceride, high-density lipoprotein, low-density lipoprotein and serum uric acid were shown no significant difference between post-PSM subjects with and without thyroid nodules. Among the biochemistry and hematological parameters, white blood cell count and the positive rate of eosinophil percentage were increased in subjects with thyroid nodules than in those without thyroid nodules. In contrast, the positive rate of basophil percentage was lower in subjects with thyroid nodules than in those without thyroid nodules. In addition, the thyroid function test results showed that subjects with thyroid nodules had higher positive rates of antithyroglobulin antibody (TgAb) and antithyroid peroxidase antibody (TPOAb) than subjects without thyroid nodules. The logistic regression analysis indicated that the positive value of TgAb as well as high level of white blood cell count and BMI could serve as independent risk factors of thyroid nodules.

CONCLUSIONS

The type 2 immune responses mediated by increased level of eosinophils, along with positive value of TgAb and TPOAb were associated with the presence of thyroid nodules. In addition, the potential role of basophils in protecting against thyroid nodules and the pathogenesis of immune-metabolic status remains to be elucidated.

Central Obesity Is Associated with Variations in TSH and ACTH Levels among Euthyroid Obese Individuals

INTRODUCTION

The interactions of central obesity and body composition with thyroid hormones and the hypothalamus-pituitary-adrenal (HPA) axis are unclear; both central obesity and body composition have an impact on energy homeostasis. Our study aimed to investigate the association between body composition and pituitary hormones, including the HPA axis and pituitary-thyroid axis, in a Chinese population of euthyroid overweight and obese individuals.

METHODS

This was a cross-sectional study. Overweight and obese patients who regularly visited the multidisciplinary team (MDT) for obesity at Peking University First Hospital were enrolled in the study. Thyroid function, morning serum ACTH and cortisol levels, thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), body composition, and metabolic indicators, including liver function and the lipid profile, were measured at the first visit. Statistical analysis was performed using SPSS version 21.0 (IBM, USA).

RESULTS

In total, 441 patients with overweight or obesity were enrolled (male/female, 123/318). Patients were assigned to four groups according to the thyroid-stimulating hormone (TSH) level stratified by quartiles, and increased body mass index (BMI) was revealed in the highest TSH quartile group (p=0.002). Hip circumference (HC) of patients in the highest TSH quartile group was significantly increased (p=0.021). Morning ACTH levels and fasting insulin levels were significantly elevated in patients in the highest TSH quartile group (p=0.027 for fasting insulin, p < 0.001 for ACTH). In the female subgroup, patients in the highest TSH quartile group showed increases in BMI (p=0.010), waist circumference (WC) (p=0.007), muscle mass of the lower extremities (p=0.020), fasting C-peptide (p=0.031), and ACTH (p=0.002). In the male subgroup, patients in the highest TSH quartile group exhibited higher BMI (p=0.017), HC (p=0.036), and ACTH (p=0.003). Among patients in the highest ACTH quartile group, there was an elevated proportion of males (p=0.003), and FT3 (p=0.005), fasting insulin (p=0.037), and cortisol (p < 0.001) levels were increased. Weight (p < 0.001), BMI (p < 0.001), WC (p < 0.001), HC (p < 0.001), muscle mass of the upper extremities (p=0.003), muscle mass of the lower extremities (p=0.005), and total muscle mass (p=0.003) were elevated in patients in the highest ACTH quartile group. HC was found to be an independent factor after adjustment for other confounders and was positively associated with the TSH level (p=0.004 for the regression model, B = 0.152, p=0.004).

CONCLUSIONS

BMI is positively correlated with TSH and ACTH levels in both male and female obese individuals. The ACTH level was positively associated with male sex and increased BMI and muscle mass. Hip circumference was an independent factor that was positively related to TSH levels.

The pattern of TSH and fT4 levels across different BMI ranges in a large cohort of euthyroid patients with obesity

PURPOSE

A multifold association relates the hypothalamo-pituitary-thyroid axis to body weight. The potential underlying mechanisms are incompletely understood. Further, the mild severity of obesity and the small proportion of individuals with obesity in so far published cohort studies provide little insights on metabolic correlates of thyroid function in obesity.

METHODS

We retrospectively enrolled 5009 adults with obesity (F/M, 3448/1561; age range, 18-87 years; BMI range, 30.0-82.7 kg/m²), without known thyroid disease in a study on TSH and fT4 levels, lipid profile, glucose homeostasis and insulin resistance, anthropometric parameters including BIA-derived fat mass (%FM) and fat-free mass (FFM).

RESULTS

The overall reference interval for TSH in our obese cohort was 0.58-5.07 mIU/L. As subgroups, females and non-smokers showed higher TSH levels as compared to their counterparts (p<0.0001 for both), while fT4 values were comparable between groups. There was a significant upward trend for TSH levels across incremental BMI classes in females, while the opposite trend was seen for fT4 levels in males (p<0.0001 for both). Expectedly, TSH was associated with %FM and FFM (p<0,0001 for both). TSH and fT4 showed correlations with several metabolic variables, and both declined with aging (TSH, p<0.0001; fT4, p<0.01). In a subgroup undergoing leptin measurement, leptin levels were positively associated with TSH levels (p<0.01). At the multivariable regression analysis, in the group as a whole, smoking habit emerged as the main independent predictor of TSH (β=-0.24, p<0.0001) and fT4 (β=-0.25, p<0.0001) levels. In non-smokers, %FM (β=0.08, p<0.0001) and age (β=-0.05, p<0.001) were the main significant predictors of TSH levels. In the subset of nonsmokers having leptin measured, leptin emerged as the strongest predictor of TSH levels (β=0.17, p<0.01).

CONCLUSIONS

Our study provides evidence of a gender- and smoking-dependent regulation of TSH levels in obesity.

Daily intake of yogurt drink fortified either with vitamin D alone or in combination with added calcium causes a thyroid-independent increase of resting metabolic rate in adults with type 2 diabetes: a randomized double blind clinical trial

We investigated the effect of daily intake of yogurt drink fortified with either vitamin D alone or with added calcium on resting metabolic rate (RMR), thyroid hormones and homeostatic model assessment for insulin resistance (HOMA-IR) in subjects with type 2 diabetes (T2D). A total of 75 adult subjects with T2D were randomly assigned to one of the three groups to receive either D-fortified yogurt drink (DY; 1000 IU vitamin D/d), Ca-D-fortified yogurt drink (CDY; 1000 IU vitamin D plus 500 mg calcium), or plain yogurt drink (PY) for 12 weeks. All assessments were done at the baseline and after the intervention. The concentrations of anti-thyroid peroxidase antibody (anti-TPO-Ab), intact parathyroid hormone (iPTH) and thyroid stimulating hormone (TSH) had significant decline compared with baseline values only in CDY group. The mean RMR increased in both DY and CDY groups (p<0.001 for both). Also, changes of serum concentrations of 25(OH)D (B= 2.96, 95%CI= 1.3- 4.6, p=0.001) and iPTH (B= -2.41, 95%CI= -4.5- -0.31, p=0.025) remained significant predictors of RMR changes even after adjustment for changes of serum concentrations of TSH (B= -18.2, 95%CI= -61.7- 25.2, p=0.406). Daily intake of vitamin D together with calcium at physiological doses has attenuating effect on anti-TPO-Ab and TSH. Also, vitamin D with or without added calcium causes a significant thyroid-independent increase in RMR in euthyroid subjects with T2D. Registered at clinicaltrials.gov as NCT01229891. Novelty: Daily intake of vitamin D with calcium at physiological doses has attenuating effect on anti-TPO-Ab and TSH. Vitamin D with or without added calcium causes a thyroid-independent increase in RMR in euthyroid subjects with T2D.

Variation in Normal Range Thyroid Function Affects Serum Cholesterol Levels, Blood Pressure, and Type 2 Diabetes Risk: A Mendelian Randomization Study

Background: Observational studies have demonstrated that variation in normal range thyroid function is associated with major cardiovascular risk factors, including dyslipidemia, hypertension, type 2 diabetes (T2D), and obesity. As observational studies are prone to residual confounding, reverse causality, and selection bias, we used a Mendelian randomization (MR) approach to investigate whether these associations are causal or not. Methods: Two-sample MR analysis using data from the largest available genome-wide association studies on normal range thyrotropin (TSH) and free thyroxine (fT4) levels, serum lipid levels, blood pressure measurements, T2D, and obesity traits (body mass index [BMI] and waist/hip ratio). Results: A one standard deviation (SD) increase in genetically predicted TSH levels was associated with a 0.037 SD increase in total cholesterol levels (p = 3.0 × 10-4). After excluding pleiotropic instruments, we also observed significant associations between TSH levels and low-density lipoprotein levels (β = 0.026 SD, p = 1.9 × 10-3), pulse pressure (β = -0.477 mmHg, p = 7.5 × 10-10), and T2D risk (odds ratio = 0.95, p = 2.5 × 10-3). While we found no evidence of causal associations between TSH or fT4 levels and obesity traits, we found that a one SD increase in genetically predicted BMI was associated with a 0.075 SD decrease in fT4 levels (p = 3.6 × 10-4). Conclusions: Variation in normal range thyroid function affects serum cholesterol levels, blood pressure, and T2D risk.

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.

Accuracy of the Resting Energy Expenditure Estimation Equations for Healthy Women

Background: There exist several prediction equations for the estimation of resting energy expenditure (REE). However, none of these equations have been validated in the Chilean female population yet. The aims of this study are (1) to determine the accuracy of existing equations for prediction of REE and (2) to develop new equations in a sample of healthy Chilean women. Methods: A cross-sectional descriptive study was carried out on 620 Chilean women. The sample showed an age range between 18 and 73 years, a body mass index average of 28.5 ± 5.2 kg/m², and a prevalence of overweight and obesity of 41% and 33.2%, respectively. REE was measured by indirect calorimetry (REE_IC), which was used as the gold standard to determine the accuracy of twelve available REE prediction equations and to calculate alternative formulas for estimation of REE. Paired t-tests and Bland–Altman plots were used to know the accuracy of the estimation equations with REE_IC. At the same time, multiple linear regressions were performed to propose possible alternative equations. The analyses were carried out by age groups and according to nutritional status. Results: All the equations showed a tendency to overestimate REE, regardless of age or nutritional status. Overall, the Ireton-Jones equation achieved the highest mean percentage difference from REE_IC at 67.1 ± 31%. The alternative new equations, containing variables of body composition, reached a higher percentage of classification within ±10% of REE_IC. Conclusions: The available equations do not adequately estimate REE in this sample of Chilean women. Although they must be validated, the new formulas proposed show better adaptation to this Chilean sample.

Irisin levels in genetic and essential obesity: clues for a potential dual role

Irisin is conventionally regarded as a myokine involved in the browning of white adipose tissue, energy expenditure and glucose tolerance. Its potential link to fat accumulation and metabolic dysfunction is debated. We sought to explore the relationship between circulating irisin and components of body composition in two different phenotypes of severe obesity. For this purpose, 30 obese adults with Prader-Will syndrome (PWS) (age 35.7 ± 1.5 y, BMI 45.5 ± 1.5 kg/m²) and 30 adult controls with common obesity (age 34.9 ± 1.7 y, BMI 46.8 ± 1.4 kg/m²) underwent analysis of irisin levels, metabolic profile, body composition and resting energy expenditure (REE). Normal irisin levels were obtained from a group of 20 lean donors (age 32.4 ± 1.5 y, BMI 23.8 ± 0.8 kg/m²). Expected differences in body composition and metabolic profile existed between study groups. PWS exhibited lower muscle mass (p < 0.001), FFM (p < 0.001), REE (p < 0.001), as well as insulin (p < 0.05), HOMA-IR (p < 0.05) and triglycerides levels (p < 0.05) than controls with common obesity. In PWS, irisin levels were significantly lower and overall less dispersed than in controls with common obesity (p < 0.05), while being similar to values recorded in lean subjects. To explore the relation between irisin and body composition in obesity, univariate correlation analysis in the obese populations as a whole showed positive associations between irisin and muscle mass (p = 0.03) as well as REE (p = 0.01), which disappeared when controlled for the PWS status. Noticeably, a positive association became evident between irisin and %FM after controlling for the PWS status (p = 0.02). Also positive were associations between irisin and insulin (p = 0.02), HOMA-IR (p = 0.02) and triglycerides (p = 0.04). In stepwise multivariable regression analysis, irisin levels were independently predicted by the PWS status (p = 0.001), %FM (p = 0.004) and triglycerides (p = 0.008). Current results suggest that obese adults with PWS harbor lower irisin levels than individuals with common obesity. The divergent models of obesity herein studied suggest a potential link between circulating irisin and muscle mass and metabolic dysfunction relating to adiposity.

Levothyroxine Replacement in Obese Adults: The Role of Metabolic Variables and Aging on Thyroid Testing Abnormalities

CONTEXT

General rates of over- and underreplacement in levothyroxine (LT4) users with primary hypothyroidism are variably high. No information on LT4 adequacy exists in obesity.

OBJECTIVE

We explored rates and factors relating to LT4 adequacy in obese patients with primary hypothyroidism.

SETTING

Tertiary care center.

DESIGN

Among 4954 consecutive obese patients admitted between 2011 and 2014, 691 hypothyroid patients receiving LT4 therapy and 691 body mass index (BMI)-, age-, and sex-matched euthyroid controls underwent analysis of thyroid function, glucolipid profile, body composition, and indirect calorimetry. LT4 users were classified into low TSH (<0.27 mU/L), euthyroid (0.27 to 4.2 mU/L), and high TSH (>4.2 mU/L).

RESULTS

LT4 users constituted 13.9% of the incident population. TSH was low in 7.5%, high in 17.2%, and normal in 75.2% of LT4 users. Overtreatment decreased with aging and more LT4 users ≥65 years of age had normal TSH than those <65 years of age (P < 0.05). Compared with the euthyroid obese group, LT4 users showed higher adiposity, similar insulin resistance, but a healthier lipid profile. In multivariable analyses, LT4 dose was predicted by fat-free mass, hypothyroidism cause, and sex (P < 0.0001 to < 0.05). Risk of LT4 overreplacement increased with younger age (OR 0.96; 95% CI 0.94 to 0.99), higher LT4 dose (OR 2.98; 95% CI 1.44 to 6.14), and lower BMI (OR 0.93; 95% CI 0.88 to 0.99). Male sex increased the likelihood of LT4 underreplacement (OR 2.37; 95% CI 1.10 to 5.11).

CONCLUSIONS

Obesity is associated with milder rates of inadequate LT4 treatment compared with nonobese populations. LT4 adequacy increases with aging. Age, body composition, and sex are main determinants of LT4 requirements in obesity.

Effect of Weight Loss after Bariatric Surgery on Thyroid-Stimulating Hormone Levels in Euthyroid Patients with Morbid Obesity

Obesity is associated with several endocrine abnormalities, including thyroid dysfunction. The objective of this study was to investigate the effect of weight loss after bariatric surgery on thyroid-stimulating hormone (TSH) levels in euthyroid patients with morbid obesity. We performed an observational study, evaluating patients with morbid obesity submitted to bariatric surgery. We included 129 patients (92 women) and 31 controls (21 women). Clinical, anthropometric, biochemical, and hormonal parameters were evaluated. The primary endpoint was circulating TSH (µU/mL). Fasting TSH levels were higher in the obese group (3.3 ± 0.2) than in the control group (2.1 ± 0.2). The mean excessive body mass index (BMI) loss (EBMIL) 12 months after bariatric surgery was 72.7 ± 2.1%. TSH levels significantly decreased in the obese patients after surgery; 3.3 ± 0.2 vs. 2.1 ± 0.2 before and 12 months after surgery, respectively. Free thyroxine (T4) (ng/dL) levels significantly decreased in the obese patients after surgery; 1.47 ± 0.02 vs. 1.12 ± 0.02 before and 12 months after surgery, respectively. TSH decreased significantly over time, and the decrement was associated with the EBMIL. In euthyroid patients with morbid obesity, weight loss induced by bariatric surgery promotes a significant decline of the increased TSH levels. This decrement of TSH is progressive over time after surgery and significantly associated with excess BMI loss.

Effects of a diet plus exercise program on thyroid function in patients with obesity

Background

Studies of thyroid function after diet-induced weight loss in patients with obesity have yielded conflicting results. It is not known whether adding exercise to diet affects thyroid function in this patient population. The aim of the study was to prospectively evaluate the effects of a rehabilitation program on weight, body composition and thyroid function in euthyroid patients with obesity.

Methods

Serum levels of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) in euthyroid patients with severe obesity were analyzed before and at the end of a 3-month rehabilitation program. Relationships between body weight or composition and changes in thyroid function were also investigated. Each study participant acted as his/her own control.

Results

The study population consisted of 34 euthyroid patients with obesity (18 men and 16 women; mean ± SD age: 51 ± 12). The mean BMI was 49.3 ± 12.4 kg/m² before the program and 46 ± 10.8 (p < 0.005) at the end, with a mean body weight loss of 11 kg (p < 0.05) and a mean fat mass loss of 6.8 kg (p < 0.05). The weight and fat mass losses were not significantly correlated with the serum concentrations of TSH, FT3 and FT4 measured at the end of the program.

Conclusion

A 3-month rehabilitation program combining diet and exercise produced weight and fat mass losses without inducing thyroid dysfunction in patients with obesity.

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Obesity is closely linked to thyroid dysfunction.

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Weight change interventions on thyroid function yielded mixed results.

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A normal calorie diet plus exercise improve body composition and insulin resistance.

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Maintenance of protein and nutritional status has beneficial effects on thyroid function.