The relationship between psychological distress and weight maintenance in weight cycling: mediating role of eating behavior.

BACKGROUND: Obesity is a global public health concern. The goal of this study was to see if eating habits could mediate the relationship between psychological distress and weight maintenance in a population with a history of weight cycling. METHODS: A 3-month outpatient intervention consisting of a diet and exercise program was provided to 153 participants. Psychological distress, appetite, and behavior were assessed at the beginning and end of the study. Anthropometric measurements were taken at baseline and six months. RESULTS: After the structural equation model was developed, it was discovered that the psychological status of people with obesity and weight cycling histories correlated with the weight loss outcome effect (three and six months). This effect was mediated by factors related to eating behavior. Associative psychological factors had a direct effect on eating behavior (three months: ß = 0.181, 95% CI: 0.055-0.310; six months: ß = 0.182, 95% CI: 0.039-0.332) and appetite had a direct effect on eating behavior (three months: ß = 0.600, 95% CI: 0.514-0.717; six months: ß = 0.581, 95% CI: 0.457-0.713), both of which were significant (p < 0.01). At three months, psychological distress has a more substantial positive impact on weight change, with eating behavior acting as a partial mediator. At six months, there was no support for appetite's moderating role in eating behavior. CONCLUSIONS: The findings suggest that psychological interventions should be strengthened to improve weight loss effectiveness, particularly in participants with a history of weight cycling, making weight loss more complicated and prone to rebound. CLINICAL TRIAL REGISTRATION: The study has been registered in Clinical Trials (NCT05311462).

Iodine Intakes of <150 µg/day or >550 µg/day are Not Recommended during Pregnancy: A Balance Study.

BACKGROUND: Adequate iodine intake during pregnancy is critical for maintaining maternal and fetal thyroid function and development. There are only limited data from iodine-balance studies to inform iodine requirements during pregnancy. OBJECTIVES: This is an iodine-balance study conducted to explore the associations among iodine intake, excretion, and retention to provide information regarding iodine requirements during pregnancy. METHODS: A 7-d iodine-balance experiment enrolled 93 healthy pregnant Chinese women from Hebei, Tanjin, and Shandong. Duplicates of all foods and beverages consumed were systematically collected and measured for iodine content. Iodine excretion was measured by collecting 24-h urine and feces samples. Simple linear regression models were used to assess relationships between total iodine intake and iodine retention, whereas mixed effect models were used to assess the relationship between daily iodine intake and iodine retention. RESULTS: The mean ± SD age of participating pregnant women was 29 ± 2 y at a median 22 (IQR: 13-30) wk of gestation. The mean 7-d iodine retention was 43.0 ± 1060 µg/7 d. A negative iodine balance was present in 56% of women whereas 44% had a positive balance. Pregnant women with iodine intakes <150 µg/d were in negative balance whereas those with intakes >550 µg/d were in positive balance. The daily iodine intake at zero balance was 343 µg/d, which was higher in women from Shandong (492 µg/d) than in those from Hebei and Tianjin (202 µg/d). CONCLUSIONS: Iodine intake at zero balance determined in pregnant women with adequate iodine nutrition is 202 µg/d, and the calculated recommended nutrient intake (RNI) is 280 µg/d. Iodine intakes of <150 µg/d and >550 µg/d are not recommended during pregnancy. This trial was registered at clinicaltrials.gov as NCT03710148.

New Reference Values for Thyroid Volume and a Comprehensive Assessment for Influencing Factors in Chinese Adults with Iodine Sufficiency.

OBJECTIVES: The reference values for thyroid volume (Tvol) determined by ultrasound require supportive data of normal Tvol from local iodine-sufficient populations. This study aimed to explore new reference values for Tvol in Chinese adults and comprehensively evaluate the factors associated with enlarged Tvol. METHODS: A cross-sectional study was conducted in Tianjin, China. Tvol was measured by ultrasound in adults with long-term iodine sufficiency. Blood and urine samples were collected to evaluate biochemical indexes, thyroid function, and iodine status. RESULTS: A total of 1,991 adults from the urban and suburban areas were analysed. The trend of Tvol increasing with age was observed in men under age 40 years and in women under age 52 years. In the quantile regression analyses, we found that body surface area (BSA) (ß = 7.22, 95% CI: 5.33, 9.12), thyroid-stimulating hormone (TSH) (ß = -1.48, 95% CI: -2.39, -0.57), thyroid nodules (TNs) (ß = 6.70, 95% CI: 2.19, 11.22), and metabolic syndrome (MetS) (ß = 1.40, 95% CI: 0.63, 2.17) had a strong effect on Tvol at higher percentiles in males. The dominant factors influencing Tvol were BSA (ß = 9.64, 95% CI: 2.66, 16.61), TSH (ß = -0.78, 95% CI: -1.16, -0.39), and TNs (ß = 1.11, 95% CI: 0.43, 1.79) in females. The largest reference values for Tvol based on BSA were 20.18 (17.79, 24.32) mL in males and 15.31 (14.05, 16.70) mL in females. CONCLUSIONS: Quantile regression analyses showed that a high BSA index, a decreased TSH level, and the prevalence of TNs were essential factors associated with the enlargement of the thyroid gland. Our findings reported the new reference values for Tvol determined by ultrasound based on gender and BSA in Chinese adults.

Evaluation of variation of saliva iodine and recommendations for sample size and sampling time: Implications for assessing iodine nutritional status.

BACKGROUND: Saliva iodine concentration (SIC) has been found to be a good indicator of iodine nutritional status. However, limited information is available regarding saliva iodine characteristics. AIMS: The study aimed to evaluate intra-day, intra-individual, and population SIC variation in order to provide information on optimal sample size and sampling time for assessing iodine nutritional status. METHODS: Twenty-nine healthy school-aged students were recruited. Iodine intake from diet and water, and iodine excretion through urine and feces were assessed over a three-day period. Saliva samples were collected six times a day. RESULTS: Diurnal variations were observed in SIC corresponding to iodine intake. The mean CV in SIC was lower than that for 24-hour urinary iodine concentration (24-h UIC) and 24-hour urinary iodine excretion (24-h UIE) not only at the individual level (42.73% vs. 47.71% and 49.69%) but also at the population level (71.29% vs. 100.43% and 72.49%). The number of saliva samples needed to estimate the iodine level with 95% CI within precision ranges of ±10%, ±20% was 55, 14 in an individual, and 180, 45 in a population. There was a good correlation between post-lunch SIC and total daily iodine intake. CONCLUSIONS: Saliva iodine has utility for evaluating the recent iodine nutrition of individuals and populations. The variation in SIC was lower than that for 24-h UIC and 24-h UIE. Saliva may be preferred over urine because of its ease of collection. Fourteen samples are needed to assess individual iodine status and forty-five saliva samples for assessment of population iodine status with reasonable precision. We recommend that saliva samples be collected after 14:00 in a day.

Saliva Iodine Concentration in Children and Its Association with Iodine Status and Thyroid Function.

CONTEXT: The effectiveness of saliva iodine concentration (SIC) in evaluating iodine status in children is not clear. OBJECTIVE: We aimed to explore associations between SIC and assessed indicators of iodine status and thyroid function. DESIGN: Cross-sectional study. SETTING: Primary schools in Shandong, China. PARTICIPANTS: Local children aged 8 to 13 years with no known thyroid disease were recruited to this study. MAIN OUTCOME MEASURES: Blood, saliva, and urine samples were collected to evaluate thyroid function and iodine status. RESULTS: SIC positively correlated with spot urinary iodine concentration (r = 0.29, P < 0.0001), 24-hour urinary iodine concentration (r = 0.35, P < 0.0001), and 24-hour urinary iodine excretion (r = 0.40, P < 0.0001). The prevalence of thyroid nodules (TN) and goiter showed an upward trend with SIC quantiles (P for trend < 0.05). Children with SIC <105 µg/L had a higher risk of insufficient iodine status (OR = 4.18; 95% CI, 2.67-6.56) compared with those with higher SIC. Those having SIC >273 µg/L were associated with greater risks of TN (OR = 2.70; 95% CI, 1.38-5.26) and excessive iodine status (OR = 18.56; 95% CI, 5.66-60.91) than those with lower SIC values. CONCLUSIONS: There is a good correlation between SIC and urinary iodine concentrations. It is of significant reference value for the diagnosis of iodine deficiency with SIC of less than 105 µg/L and for the diagnosis of iodine excess and TN with SIC of more than 273 µg/L. Given the sanitary nature and convenience of saliva iodine collection, SIC is highly recommended as a good biomarker of recent iodine status in school-aged children.

Intra-individual and inter-individual variations in iodine intake and excretion in adult women: implications for sampling.

Iodine intake and excretion vary widely; however, these variations remain a large source of geometric uncertainty. The present study aims to analyse variations in iodine intake and excretion and provide implications for sampling in studies of individuals or populations. Twenty-four healthy women volunteers were recruited for a 12-d sampling period during the 4-week experiment. The duplicate-portion technique was used to measure iodine intake, while 24-h urine was collected to estimate iodine excretion. The mean intra-individual variations in iodine intake, 24-h UIE (24-h urinary iodine excretion) and 24-h UIC (24-h urinary iodine concentration) were 63, 48 and 55 %, respectively, while the inter-individual variations for these parameters were 14, 24 and 32 %, respectively. For 95 % confidence, approximately 500 diet samples or 24-h urine samples should be taken from an individual to estimate their iodine intake or iodine status at a precision range of ±5%. Obtaining a precision range of ±5% in a population would require twenty-five diet samples or 150 24-h urine samples. The intra-individual variations in iodine intake and excretion were higher than the inter-individual variations, which indicates the need for more samples in a study on individual participants.