Increased intake of dietary polyunsaturated fat does not promote whole body or preferential abdominal fat mass loss in overweight adults

Metabolomic-based analysis reveals bile acid-mediated ovarian failure induced by low temperature in zebrafish

As ectotherms, fish are highly sensitive to temperature fluctuations, which can profoundly impact their reproductive cycles. In this study, we investigated the fertility and histological characteristics of zebrafish ( Danio rerio) ovaries exposed to a temperature gradient ranging from the thermopreferendum temperature of the species, 27°C, to lower temperatures of 22°C, 20°C, and 13°C over a period of two weeks. Comparative metabolomic (six biological replicates for each temperature) and transcriptomic (four biological replicates for each temperature) analyses were conducted under the four temperature conditions. Results indicated that lower temperatures inhibited oocyte development and differential metabolites were involved in steroid hormone production, antioxidant function, and lipid and protein catabolism. Disrupted reproductive hormones, increased proteolysis, and lipid degradation significantly impeded oocyte development and egg maturation. Notably, a significant increase in bile acid content was noted in the ovaries of the cold-treated fish, indicating that bile acids play a critical role in ovarian failure. Overall, these findings provide valuable insights into the mechanisms governing the reproductive response of fish to cold stress.

Monounsaturated fat-rich diet reduces body adiposity in women with obesity, but does not influence energy expenditure and substrate oxidation: a parallel randomized controlled clinical trial

BACKGROUND

Obesity is an important and growing health problem whose treatment involves dietary changes. In this context, studying the role of macronutrients in weight loss is required in order to understand which strategies may be applied for weight loss. We aimed to evaluate the effects of diets rich in polyunsaturated (PUFAs) and monounsaturated fatty acids (MUFAs) on resting energy expenditure (REE), substrate oxidation, and weight loss in women with obesity.

METHODS

Randomized, controlled, single blind, parallel-group clinical trial was conducted for 60 days. Participants (n = 32) were divided into three groups: G1= normocaloric PUFAs-rich diet (12% of total energy expenditure (TEE), 10% of n-6 and up to 2% of n-3); G2= normocaloric MUFAs-rich diet (15-20% TEE); and G3= maintenance of the usual diet. Anthropometric and metabolic variables (REE and substrate oxidation by indirect calorimetry) were evaluated.

RESULTS

G2 decreased body weight (-1.92 ± 1.99 kg, P = 0.02), body mass index (BMI) (-0.69 ± 0.70 kg/m2; P = 0.02), waist circumference (WC) (-1.91 ± 1.82 cm; P = 0.02), and body fat (-1.14 ± 1.53 kg; P = 0.04).

CONCLUSION

MUFAs-rich diet reduces body weight, BMI, body fat, and WC.

CLINICAL TRIALS

NCT02656940.

CLINICAL TRIAL REGISTRATION

Clinical Trials: NCT02656940.

Sweet Snacks Are Positively and Fruits and Vegetables Are Negatively Associated with Visceral or Liver Fat Content in Middle-Aged Men and Women

BACKGROUND

Visceral adipose tissue (VAT) and hepatic triglyceride content (HTGC) are major risk factors for cardiometabolic diseases.

OBJECTIVE

We aimed to investigate the association of dietary intake of the main food groups with VAT and HTGC in middle-aged men and women.

METHODS

We used data from the Netherlands Epidemiology of Obesity study, a population-based study including 6671 participants aged 45-65 y at baseline. In this cross-sectional analysis, VAT and HTGC were assessed by magnetic resonance imaging and spectroscopy, respectively, as the primary outcomes. Habitual intake of main food groups (dairy, meat, fish, fruits and vegetables, sweet snacks, and fats and oils) was estimated through the use of a food-frequency questionnaire. We examined associations of intake of different food groups with VAT and HTGC by linear regression analysis stratified by sex and adjusted for age, smoking, education, ethnicity, physical activity, basal metabolic rate, energy-restricted diet, menopausal state, and total energy intake.

RESULTS

In women, a 100-g/d higher intake of dairy was associated with 2.0 cm2 less VAT (95% CI: -3.4, -0.7 cm2) and a 0.95-fold lower HTGC (95% CI: 0.90-, 0.99-fold). Moreover, a 100-g/d higher intake of fruit and vegetables was associated with 1.6 cm2 less VAT (95% CI: -2.9, -0.2 cm2) in women. Fruit and vegetables were negatively associated (0.95; 95% CI: 0.91, 1.00) with HTGC, and sweet snacks were positively associated (1.29; 95% CI: 1.03, 1.63). Patterns were weaker but similar in men. Fish intake was not associated with VAT or HTGC and plant-based fat and oil intake were only associated with VAT after adjustment for total body fat.

CONCLUSIONS

Despite some variation in the strength of the associations between men and women, dietary intake of sweet snacks was positively associated with HTGC, and fruit and vegetable intake were negatively associated with visceral and liver fat content. Prospective studies are needed to confirm these results. The Netherlands Epidemiology of Obesity study is registered at clinicaltrials.gov with identifier NCT03410316.

Tree Nut Consumption and Adipose Tissue Mass: Mechanisms of Action

There is concern that tree nuts may cause weight gain due to their energy density, yet evidence shows that tree nuts do not adversely affect weight status. Epidemiologic and experimental studies have shown a reduced risk of chronic diseases with tree nut consumption without an increased risk of weight gain. In fact, tree nuts may protect against weight gain and benefit weight-loss interventions. However, the relation between tree nut consumption and adiposity is not well understood at the mechanistic level. This review summarizes the proposed underlying mechanisms that might account for this relation. Evidence suggests that tree nuts may affect adiposity through appetite control, displacement of unfavorable nutrients, increased diet-induced thermogenesis, availability of metabolizable energy, antiobesity action of bioactive compounds, and improved functionality of the gut microbiome. The gut microbiome is a common factor among these mechanisms and may mediate, in part, the relation between tree nut consumption and reduced adiposity. Further research is needed to understand the impact of tree nuts on the gut microbiome and how the gut microbial environment affects the nutrient absorption and metabolism of tree nuts. The evidence to date suggests that tree nut consumption favorably affects body composition through different mechanisms that involve the gut microbiome. A better understanding of these mechanisms will contribute to the evolving science base that addresses the causes and treatments for overweight and obesity.

Dietary fat composition, total body fat and regional body fat distribution in two Caucasian populations of middle-aged and older adult women

OBJECTIVE

We aimed to study whether dietary fat composition (n-3 and n-6 polyunsaturated fatty acids ratio (PUFAs) and PUFAs and saturated fatty acids (SFAs) ratio) is associated with total body fat (TF) and body fat distribution and whether this association was modified by the presence of chronic disease in middle-aged and elderly women in two population-based cohorts in the Netherlands and Australia.

METHODS

The study was performed in the Rotterdam Study (RS), a prospective cohort study among subjects aged 55 years and older (N = 1182 women) and the Calcium Intake Fracture Outcome Study (CAIFOS), a 5-year randomized controlled trial among women age 70+ (N = 891). At baseline, diet (i.e. PUFAs and SFAs) was measured by validated food frequency questionnaires. TF was assessed using Dual-energy X-ray absorptiometry in both studies and android abdominal fat (AF), gynoid fat (GF) and the android/gynoid ratio (A/G ratio) in the RS but not the CAIFOS. Chronic disease was defined as the presence of cardiovascular disease, diabetes mellitus and cancer.

RESULTS

No association was found between dietary n-3/n-6 PUFAs ratio or SFA/PUFAs ratio with TF in both cohorts. In the RS, a high n-3/n-6 PUFAs ratio was associated with a higher AF (3rd vs. 2nd tertile (reference): β: 0.15; 95% CI: 0.05, 0.24) but not with the A/G ratio. A low SFA/PUFA ratio was associated with a lower AF (1st vs. 2nd tertile (reference): β: -0.12; 95% CI: -0.22, -0.06) but not with the A/G ratio. Presence of chronic disease was found to be a significant effect modifier in both cohorts with regard to n-3/n-6 PUFAs and TF (P < 0.05). In participants without chronic disease, a higher n-3/n-6 PUFAs ratio was associated with a higher TF in the RS cohort (3rd vs. 2nd tertile (reference): β: 0.94; 95% CI: 0.12, 1.76), but this was not replicated in CAIFOS.

CONCLUSION

These findings do not support the hypothesis that dietary fat composition is consistently associated with TF and body fat distribution in women. Future studies should clarify to what extent these findings may be influenced by the presence of chronic disease.

Saturated fatty acids in human visceral adipose tissue are associated with increased 11- β-hydroxysteroid-dehydrogenase type 1 expression

Background

Visceral fat accumulation is associated with metabolic disease. It is therefore relevant to study factors that regulate adipose tissue distribution. Recent data shows that overeating saturated fatty acids promotes greater visceral fat storage than overeating unsaturated fatty acids. Visceral adiposity is observed in states of hypercortisolism, and the enzyme 11-β-hydroxysteroid-dehydrogenase type 1 (11β-hsd1) is a major regulator of cortisol activity by converting inactive cortisone to cortisol in adipose tissue. We hypothesized that tissue fatty acid composition regulates body fat distribution through local effects on the expression of 11β-hsd1 and its corresponding gene (HSD11B1) resulting in altered cortisol activity.

Findings

Visceral- and subcutaneous adipose tissue biopsies were collected during Roux-en-Y gastric bypass surgery from 45 obese women (BMI; 41 ± 4 kg/m²). The fatty acid composition of each biopsy was measured and correlated to the mRNA levels of HSD11B1. 11β-hsd1 protein levels were determined in a subgroup (n = 12) by western blot analysis. Our main finding was that tissue saturated fatty acids (e.g. palmitate) were associated with increased 11β-hsd1 gene- and protein-expression in visceral but not subcutaneous adipose tissue.

Conclusions

The present study proposes a link between HSD11B1 and saturated fatty acids in visceral, but not subcutaneous adipose tissue. Nutritional regulation of visceral fat mass through HSD11B1 is of interest for the modulation of metabolic risk and warrants further investigation.

Analyzing weight loss intervention studies with missing data: which methods should be used?

OBJECTIVE

Missing data due to study dropout is common in weight loss trials and several statistical methods exist to account for it. The aim of this study was to identify methods in the literature and to compare the effects of methods of analysis using simulated data sets.

METHODS

Literature was obtained for a 1-y period to identify analytical methods used in reporting weight loss trials. A comparison of methods with large or small between-group weight loss, and missing data that was, or was not, missing randomly was conducted in simulated data sets based on previous research.

RESULTS

Twenty-seven studies, some with multiple analyses, were retrieved. Complete case analysis (n = 17), last observation carried forward (n = 6), baseline carried forward (n = 4), maximum likelihood (n = 6), and multiple imputation (n = 2) were the common methods of accounting for missing data. When comparing methods on simulated data, all demonstrated a significant effect when the between-group weight loss was large (P < 0.001, interaction term) regardless of whether the data was missing completely at random. When the weight loss interaction was small, the method used for analysis gave considerably different results with mixed models (P = 0.180) and multiple imputations (P = 0.125) closest to the full data model (P = 0.033).

CONCLUSION

The simulation analysis showed that when data were not missing at random, treatment effects were small, and the amount of missing data was substantial, the analysis method had an effect on the significance of the outcome. Careful attention must be paid when analyzing or appraising studies with missing data and small effects to ensure appropriate conclusions are drawn.