A Randomized Controlled Trial Investigating the Impact of a Low-Calorie Dietary Approach to Stop Hypertension (DASH) on Anthropometric and Glycemic Measures in Patients Experiencing Weight Regain 2 Years Post Sleeve Surgery

PURPOSE

To evaluate the effect of a low-calorie dietary approach to stop hypertension (DASH) compared to a low-calorie diet on weight control, body composition and glycemic measures in post sleeve patients with weight regain.

MATERIALS AND METHODS

Participants were randomly allocated to either the low-calorie DASH diet group (intervention) or the low-calorie diet group (control) for a duration of 16 weeks. Both groups had a prescribed caloric intake of 1000-1200 calories. The DASH diet group made dietary adjustments in accordance with the DASH pattern.

RESULTS

At the end of the study, both interventions significantly reduced anthropometric and body composition parameters (P-value < 0.001), with a greater decrease observed in the low-calorie DASH diet group (P-value < 0.001). Insulin levels and homeostatic model assessment for insulin resistance (HOMA-IR) decreased significantly in both groups, but the magnitude of these changes was not statistically different between the two groups. After adjusting for confounders, a significant difference was observed in post-intervention values and changes in weight, body mass index, and fat mass and fat-free mass.

CONCLUSION

In summary, adhering to a calorie-restricted DASH diet for 16 weeks improved weight loss, body mass index, and fat mass reduction in post-bariatric patients who experienced weight regain 2 years after surgery, compared to a calorie-restricted control diet. However, there was no significant difference in the effect on blood glucose, insulin, and HOMA-IR between the two diets.

Food Addiction and Binge Eating Disorder in Relation to Dietary Patterns and Anthropometric Measurements: A Descriptive-Analytic Cross-Sectional Study in Iranian Adults with Obesity

Obesity is associated with maladaptive eating behaviors, including food addiction (FA) and binge eating disorder (BED). However, the key factors influencing the development of maladaptive eating behaviors remain unknown. Adherence to specified dietary patterns has been suspected of making indirect impacts. This study investigates the association of FA and BED with dietary patterns and anthropometric measurements among 400 Iranian adults (aged 18-60; 66.25% women) living with obesity (body mass index [BMI] ≥ 30 kg/m2). The Binge Eating Scale and Yale Food Addiction Scale were used to measure BED and FA. A validated 147-item semi-quantitative food frequency questionnaire underwent principal component analysis and identified three major dietary patterns: mixed, unhealthy, and healthy dietary pattern. After adjusting for confounders, higher adherence to unhealthy dietary patterns was associated with an increased risk of FA, while higher adherence to healthy dietary patterns was associated with a lower risk of FA. Also, those within obesity class III had a significantly higher risk of FA and BED than those in obesity class I. This study suggests that adherence to an unhealthy dietary pattern may be associated with a higher risk of FA. It also highlights the link between higher BMI and maladaptive eating behaviors.

Effect of time restricted feeding on anthropometric measures, eating behavior, stress, serum levels of BDNF and LBP in overweight/obese women with food addiction: a randomized clinical trial

BACKGROUND & AIM

Food addiction (FA) as a specific food-related behavior may play an essential role in the pathogenesis of obesity. Brain-derived neurotrophic factor (BDNF) and gut microbiota (GM) alterations probably through fasting are closely related to brain function, affecting eating behaviors and body weight management. This study aimed to evaluate the effect of time-restricted feeding (TRF) on serum BDNF levels and eating behaviors in overweight and obese women with FA.

METHODS AND DESIGN

This clinical trial was performed with a 2-month follow-up on 56 obese and overweight women with FA. Participants were randomly divided into two groups receiving a low-calorie diet (n = 27) and a group receiving a low-calorie diet with TRF (n = 29). Anthropometric measurements, biochemical markers, eating behavior, and stress were assessed during the study period.

RESULTS

The reductions in weight, body mass index (BMI), waist circumference, and body fat mass were significantly higher in the TRF group compared to the control group at week 8 (P = 0.018, P = 0.015. P = 0.03, and P = 0.036, respectively). The cognitive restriction score was higher in the TRF as compared with the control group (P = 0.002). The food addiction criteria score was significantly reduced in both groups (P < 0.001). Serum levels of BDNF were significantly increased in the TRF group (P < 0.001). In addition, BDNF levels had a positive and significant correlation with the cognitive restriction score (r = 0.468 and P < 0.001), While the correlation with FA was not significant (β = 0.588 and P = 0.618). Lipopolysaccharide binding protein decreased significantly in both groups, but this decrease was significantly higher in the TRF group than in the control group (P < 0.001).

CONCLUSION

The results of this study showed that a low-calorie diet with TRF is more effective in weight management than a low-calorie diet alone, probably through further modulating the GM and improving BDNF levels. More effective weight loss in the TRF is probably related to better management of eating behavior than FA.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials identifier: IRCT20131228015968N7.

Effects of probiotic supplementation with weight reducing intervention on anthropometric measures, body composition, eating behavior, and related hormone levels in patients with food addiction and weight regain after bariatric surgery: a study protocol for a randomized clinical trial

BACKGROUND

One of the unfortunate events after bariatric surgery is the weight regain, which occurs in some patients. Food addiction is an eating disorder related to the brain-intestinal axis and can be effective in weight regain after bariatric surgery. In addition, the gut microbiome plays a vital role in eating behaviors, including food addiction. So, this study will aim to evaluate the effects of probiotic supplementation with a weight-reducing diet and cognitive behavioral therapy on anthropometric measures, body composition, eating behavior, and related hormone levels, leptin, oxytocin, and serotonin, in patients with food addiction and weight regain after bariatric surgery.

METHODS

We will carry out a triple-blinded randomized clinical trial for 12 weeks to evaluate the effect of probiotic supplementation with a weight-reducing diet and cognitive behavioral therapy on anthropometric measures, body composition, eating behavior, and related hormone levels including leptin, oxytocin, and serotonin, in patients with food addiction and weight regain after bariatric surgery.

DISCUSSION

Based on the available evidence, probiotic supplementation by modifying the intestinal microbiome can improve food addiction and subsequent weight loss.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials IRCT20220406054437N1 Registered on 2022-06-01.

Sumac (Rhus coriaria L.) powder supplementation has beneficial effects on appetite in overweight/obese women with depression: A randomized controlled trial

BACKGROUND AND PURPOSE

Appetite disturbance is a common problem in obesity and depression. The beneficial effects of polyphenols in promoting satiety have been shown. This study aimed to investigate the effects of sumac supplementation along with calorie restricted diet (CRD) on appetite in overweight and obese women with depression.

MATERIALS AND METHODS

In this trial, 60 overweight and obese women with depression were randomly assigned to receive a CRD plus 3 g/day of either sumac or placebo for 12 weeks. The appetite score, serum levels of leptin, neuropeptide Y (NPY), insulin, fasting blood sugar (FBS), homeostasis model assessment of insulin resistance (HOMA-IR), and quantitative insulin sensitivity check index (QUICKI) were assessed at baseline and at the end of the study.

RESULTS

Sumac supplementation significantly reduced the appetite score (p = 0.02), serum levels of leptin (p = 0.03), NPY (p = 0.01), insulin (p = 0.03), FBS (p = 0.03), and HOMA-IR (p = 0.02) compared to the placebo group. QUICKI increased significantly in the sumac group compared to the placebo group (p = 0.009).

CONCLUSION

Sumac along with a CRD may have some beneficial effects on appetite through possible modulatory effects on leptin resistance, insulin sensitivity, and NPY levels in overweight and obese women with depression.

Dietary acid load and mortality from all causes, CVD and cancer: results from the Golestan Cohort Study

Given the limited studies and controversial results on association between dietary acid load and mortality from CVD and cancers, we aimed to investigate this association in a large population cohort study in Middle East, with a wide range of dietary acid load. The study was conducted on the platform of the Golestan Cohort Study (GCS), which enrolled 50 045 participants in 2004-2008. Dietary intake was assessed using a validated FFQ. Dietary potential renal acid load (PRAL) score was calculated from nutrient intake. Death and its causes were identified and confirmed by two or three physicians. Cox proportional hazards regression was used to estimate hazard ratio (HR) and 95 % CI for total and cause-specific mortalities. Then, the associations were modelled using restricted cubic splines. PRAL range was -57·36 to +53·81 mEq/d for men and -76·70 to +49·08 for women. During 555 142 person-years of follow-up, we documented 6830 deaths, including 3070 cardiovascular deaths, 1502 cancer deaths and 2258 deaths from other causes. For overall deaths, in final model after adjustment for confounders, participants in the first and fifth quintiles of PRAL had a higher risk of mortality compared with the second quintile of PRAL (HR: 1·08; 95 % CI1·01, 1·16 and HR: 1·07; 95 % CI 1·01, 1·15, respectively); Pfor trend < 0·05). Participants in the first and fifth quintiles of PRAL had a 12 % higher risk of CVD mortality compared with the Q2 of PRAL (HR: 1·12; 95 % CI 1·01-1·25 and HR: 1·12; 95 % CI 1·01, 1·26, respectively; Pfor trend < 0·05). We found that all-cause and CVD mortality rates were higher in the lowest and highest PRAL values, in an approximately U-shaped relation (P-values for the overall association and the non-linear association of energy-adjusted PRAL with total mortality were < 0·001 and < 0·001, and with CVD mortality were 0·008 and 0·003, respectively). Our results highlight unfavourable associations of high acidity and alkalinity of diet with the increased total and CVD mortality risk. It may be important to consider a balanced acid-base diet as a protective strategy to prevent pre-mature death, especially from CVD.

Effect of time restricted feeding on anthropometric measures, eating behavior, stress, and brain-derived neurotrophic factor (BDNF) and lipopolysaccharide-binding protein (LBP) levels in women with overweight/obesity and food addiction: a study protocol for a randomized clinical trial

Background

Food addiction is one of the behavioral factors that play an important role in the pathogenesis of obesity. Much evidence is available suggesting intestinal microbiomes can play a role in eating behavior, body composition, and BDNF levels, and they can be modified by time-restricted feeding (TRF). So, this study will aim to evaluate the effect of TRF on anthropometric measures, eating behavior, stress, and serum BDNF and LBP levels in women with overweight/obesity and food addiction.

Methods

We will carry out a randomized clinical trial for 8 weeks to evaluate the effect of a TRF on anthropometric measures, eating behavior, stress level, serum BDNF and LBP levels in women with overweight/obesity and food addiction.

Discussion

Given the effect of BDNF on regulating eating behavior and body weight and the effect of dietary restrictions on BDNF and the gut microbiome, the TRF diet could possibly be a new way to successfully manage weight through modifying BDNF in people with eating disorders, including food addiction.

Trial registration

Iranian Registry of Clinical Trials IRCT20131228015968N7. Registered on 25 October 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06439-x.

Beneficial effects of Se/Zn co-supplementation on body weight and adipose tissue inflammation in high-fat diet-induced obese rats

This research investigated the effect of co-supplementation of selenium with zinc on weight control and the inflammatory and oxidative status in relation to obesity. Male Wistar rats (N = 32) were randomly divided into four groups after induction of obesity model: 1) "Zn" was supplemented with zinc sulfate (15 mg/kg BW), 2) "Se" supplemented with selenium as sodium selenate (0.5 mg/kg BW), 3) "Zn + Se" which received Zn (15 mg/kg BW) + Se (0.5 mg/kg BW), and 4) "HFD" as the control group. The intervention was done for eight weeks. At the end of treatment, serum and tissue level of Zn, Se, SOD, GSH-Px, MDA, leptin, TNF-α, and IL-6 was evaluated. Weight and food intake were significantly reduced in the Se group(p < .001), while in the Zn group, weight gain due to obesity was prevented compared to the control group (p = .48). There was a significant and stronger increase in SOD, GSH-Px levels and a remarkable decrease in MDA, leptin, TNF-α, and IL-6 in the group receiving the combination of two supplements than either alone(p < .001). Leptin had a positive correlation with inflammatory factors and lipid peroxidation marker and showed an inverse relationship with Zn and Se levels and anti-oxidative enzymes(p < .05). The analysis showed the mediating role of leptin in the effects of zinc. Co-supplementation of selenium and zinc may have a synergistic effect in reduction of oxidative and inflammatory markers. Regarding the effect of zinc on inflammatory factors and lipid peroxidation, leptin can play a mediating role.

The combined effects of probiotics and restricted calorie diet on the anthropometric indices, eating behavior, and hormone levels of obese women with food addiction a randomized clinical trial

BACKGROUND AND AIM

Food addiction (FA) is an important contributor to obesity. Alterations in gut microbiota (GM) diversity and composition have also been proposed to play a pivotal role in obesity pathogenesis. This trial aimed to assess the effects of probiotic supplementation on the anthropometric indices, eating behavior, and hormone levels of obese women with FA.

METHODS

This randomized, double-blind, placebo-controlled clinical trial was conducted among obese women with FA. Participants (n = 62) received a restricted calorie diet (RCD) plus either probiotic, or placebo for 12 weeks. Anthropometric measurements, biochemical markers, eating behavior and appetite were assessed during the study period.

RESULTS

Probiotics administration significantly reduced weight, body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR), body fat percentage (BFP), and trunk fat percentage (TFP) compared to the placebo group (p < 0.001). Also, a significant improvement was observed in eating behavior in the probiotic group compared to the placebo group (p < 0.001).Serum levels of oxytocin increased and NPY decreased significantly in the probiotic group compared to the placebo group (p = 0.02, p = 0.002, respectively). Moreover, leptin level significantly decreased in the probiotic group compared to the baseline values (p < 0.001), while probiotics did not cause a greater significant reduction in leptin level, compared to the placebo group.

CONCLUSION

Multi-probiotic supplementation may have beneficial effects on anthropometric indices, eating behavior, and some appetite-regulating hormones in obese women with FA.Trial registration: Iranian Registry of Clinical Trials identifier: IRCT20131228015968N5.

Grape seed extract supplementation along with a restricted-calorie diet improves cardiovascular risk factors in obese or overweight adult individuals: A randomized, placebo-controlled trial

Grape seed extract (GSE) is a flavonoid-rich supplement, recently discussed as a potential moderator of inflammation and obesity. In this study, we aimed to investigate the effects of GSE supplementation along with a restricted-calorie diet (RCD), on changes in blood lipid profile, visceral adiposity index (VAI), and atherogenic index of plasma (AIP). We designed a randomized, double-blinded, placebo-controlled clinical trial. Forty obese or overweight individuals (25 ≤ body mass index < 40 kg/m² ) were randomly assigned to receive GSE (300 mg/day) or placebo, plus RCD, for 12 weeks. We studied the anthropometric measures, biochemical biomarkers and dietary intake within the study timelines. Levels of high-density lipoprotein cholesterol (HDL-C) and HDL-C/low-density lipoprotein cholesterol (LDL-C) significantly increased in the GSE group as compared with the placebo group at week 12 (p = .03 and .008, respectively, adjusted for age, sex, energy and saturated fatty acid intake). We also observed a significant reduction in LDL-C following GSE supplementation in comparison to placebo (adjusted for age, sex and energy intake, p = .04). VAI, AIP, total cholesterol and triglyceride significantly decreased in the GSE group compared with the baseline (p = .04, .02, .01, and .02, respectively). GSE supplementation may have a modulatory role in improving blood lipid profile in obese or overweight individuals, when accompanied by RCD.

The effects of royal jelly and tocotrienol-rich fraction on impaired glycemic control and inflammation through irisin in obese rats

The effects of royal jelly (RJ) and tocotrienol-rich fraction (TRF) on obesity-induced glucose intolerance and inflammation were assessed in the current study. Regarding irisin as an important adipomyokine that attenuates obesity-induced disorders, we evaluated whether RJ and TRF could exert their metabolism regulatory effects through irisin. Obese rats were fed a high-fat diet (HFD) with or without supplementation of RJ, TRF, or both, for 8 weeks. At the end of the intervention, weight, irisin, glycemic, and inflammatory indices were measured. The weight of the rats did not remarkably reduce in any of the groups. Glucose homeostasis and inflammation were improved when we added RJ and TRF to HFD. RJ elevated irisin concentration, but the effect of TRF on irisin was not noticeable. Our results indicated that, despite the lack of significant weight loss, RJ and TRF promoted healthy obesity. This improvement was mediated by irisin in RJ consuming rats. PRACTICAL APPLICATIONS: Obesity is a public health concern associated with several chronic disorders. The beneficial effects of irisin on obesity-related disorders are well-established. It is the first study assessing the effect of RJ and TRF as functional foods, with pharmacological and nutritional activities on obesity complications, through irisin mediation. Our study demonstrated that RJ exerts its metabolic regulatory effects by irisin as a mediator. Our investigation makes a remarkable contribution to the literature, because it suggests a new mechanism for the anti-obesity properties of RJ and TRF.

The effect of royal jelly and tocotrienol-rich fraction along with calorie restriction on hypothalamic endoplasmic reticulum stress and adipose tissue inflammation in diet-induced obese rats

Objectives

Endoplasmic reticulum (ER) stress causes adipose tissue dysfunction and chronic inflammation in obesity. Royal jelly (RJ) and tocotrienol-rich fraction (TRF) are reported to ameliorate inflammation. However, the improving effects of RJ and TRF on inflammation from ER stress modulating view have not been assessed so far. Hence, we investigated the effect of RJ and TRF on ER stress and some adipose tissue-derived inflammatory markers in the high-fat diet (HFD)-induced obesity. Wistar obese rats randomly allocated into 5 groups: HFD, calorie restriction diet (CRD), RJ + CRD, TRF + CRD, RJ + TRF + CRD. After 8-week intervention, adipose tissues and hypothalamus were dissected and serum was collected.

Results

RJ reduced glucose-regulated protein-78 (GRP78) expression as ER stress indicator in WAT and hypothalamus compared to CRD. Besides, RJ diminished the expression of inflammatory markers in white adipose tissue (WAT) and also decreased the serum concentration of them. TRF reduced inflammatory markers in the serum without remarkable effects on ER stress. Overall, RJ has protective effect against adipose tissue dysfunction and inflammation then suggested as a therapeutic approach to reduce some obesity-related complications. The impact of TRF in this regard is lower than RJ and limited to systemic inflammation improvement without remarkable changes in adipose tissue inflammation.

Association of dietary intake of fruit and green vegetables with PTEN and P53 mRNA gene expression in visceral and subcutaneous adipose tissues of obese and non-obese adults

OBJECTIVE

The present study investigates the association of dietary intake of fruit and green Vegetables with PTEN and P53 mRNA gene expression in visceral (VAT) and subcutaneous adipose tissues (SAT) of obese and non-obese adults.

METHODS

VAT and SAT were obtained from 151 individuals, aged ~40 years, who had undergone elective abdominal surgery. The participants were grouped according to their body mass index (BMI), as obese (BMI > 30 kg/m²) and non-obese (BMI = 18.5-30 kg/m²). Dietary intakes were obtained using a valid and reliable food-frequency questionnaire (FFQ). Real-time PCR was carried out for PTEN and P53 mRNA expressions. Associations between expression levels and dietary parameters were analyzed.

RESULTS

P53 mRNA expression of obese participants was significantly higher than the non-obese, only in VAT (p < 0.001). After adjusting for total energy intake, age and BMI, fruit intake was inversely associated with P53 gene expression in both VAT (β = -0.38, P = 0.01) and SAT (β = -0.35, P = 0.03) among non-obese participants. Furthermore, fruit consumption was inversely associated with P53 gene expression in obese individuals, only in VAT (β = -0.21, P = 0.05). More so, intake of green vegetables in obese subjects was negatively associated with P53 gene expression in VAT (β = -0.27, P = 0.01) and SAT (β = -0.28, P < 0.001). On the other hand, after adjustment for total energy intake, age and BMI, a positive association was observed between fruit intake and PTEN in VAT (β = 0.27, P = 0.01) and SAT (β = 0.34, P < 0.001) among obese participants. In addition, dietary consumption of fruits in non-obese individuals was negatively associated withPTEN expression in SAT (β = -0.48, P < 0.001).

CONCLUSION

Dietary intake of fruit and green vegetables was associated with P53 gene expression in VAT and SAT of obese participants, suggesting their protective role in regulating P53 mRNA expression in adipose tissue. Furthermore, higher fruit intake was inversely associated with PTEN mRNA levels in non-obese participants, implying the anti-adipogenic role of PTEN gene expression.

The prevalence of food addiction and its associations with plasma oxytocin level and anthropometric and dietary measurements in Iranian women with obesity

Obesity is a prevalent public health problem, and food addiction (FA) is one of the most controversial factors in its management. Therefore, this study was designed to validate an FA questionnaire for Iranian women with obesity and to determine the prevalence of FA and its associations with plasma oxytocin (OT) levels as well as anthropometric and dietary measurements. In this descriptive-analytical study, 450 adult women with obesity were included. The prevalence of FA was determined with a valid Yale food addiction scale (YFAS). Macronutrient intakes were measured by a valid semi-quantitative food frequency questionnaire (FFQ). In addition, plasma OT was measured after eight hours of fasting. In this study, the prevalence of FA was 26.2% in women with obesity. In comparison with class I obesity, the odds ratios (95% CI) of FA for class II and class III obesity were 2.5 (CI: 1.29-5.09) and 3.3 (CI: 1.69-6.4) respectively. Dietary intakes of energy, protein, carbohydrate, fat, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, and cholesterol were significantly higher in food-addicted (FAD) women compared to non-food-addicted (NFA) ones (p < 0.001). Moreover, plasma OT level was lower in FAD women with obesity than in NFA subjects (p = 0.02). In conclusion, the results of this study indicate that FA is prevalent in Iranian women with obesity. In addition, FA is related to obesity severity, dietary intakes of energy, carbohydrate, protein, fat, cholesterol, and plasma OT level.

Zinc supplementation improves body weight management, inflammatory biomarkers and insulin resistance in individuals with obesity: a randomized, placebo-controlled, double-blind trial

BACKGROUND

The present study was designed to determine whether zinc supplementation would increase the effects of restricted calorie diet (RCD) on obesity.

METHODS AND MATERIALS

A randomized, double-blind clinical trial was performed on 40 obese subjects who were randomly assigned to receive zinc supplements (30 mg/day) or placebo for a period of 15-weeks. Both groups were under a restricted calorie diet (~ 300 kcal lower than the estimated energy requirement). Anthropometric measurements, biochemical markers, appetite, and dietary intakes were determined during the study period.

RESULTS

The reductions of body weight, body mass index, waist circumference, and hip circumference were significantly higher in the zinc group compared to the placebo group (P = 0.032, 0.025, 0.003, and 0.0001, respectively). Lower levels of high sensitivity C-reactive protein, apelin, homeostatic model assessment of insulin resistance (HOMA-IR), and appetite score were observed in the zinc group in comparison with the placebo group (P = 0.0001, 0.001, 0.031 and 0.001 respectively).

CONCLUSION

This study indicates that Zn supplementation with a restricted calorie diet has favorable effects in reducing anthropometric measurements, inflammatory markers, insulin resistance and appetite in individuals with obesity, and may play an effective role in the treatment of obesity.Trial registration This clinical trial was registered at clinicaltrials.gov at the U.S. National Library of Medicine (NCT02516475).

PI3K/AKT and Mdm2 activation are associated with inhibitory effect of cAMP increasing agents on DNA damage-induced cell death in human pre-B NALM-6 cells

DNA damage response (DDR) consists of both proapoptotic and prosurvival signaling branches. Superiority of each signaling branch determines the outcome of DNA damage: death or allowing the repair. The present authors have previously shown that an increased intracellular level of cAMP disrupts p53-mediated apoptosis in human pre-B NALM-6 cells and inhibition of NF-κB prevents prosurvival effect of cAMP during DNA damage. AKT/PKB (protein kinase B) is a general mediator of survival signaling. AKT signaling inhibits p53-mediated transcription and apoptosis. The results of present study showed that cAMP disrupted DNA damage/p53-mediated apoptosis through AKT and subsequent NF-κB activation. These results suggested that AKT may be found as part of a complex with scaffolding proteins, beta-arrestins and PDE4D. cAMP disarticulated the complex through binding to PDE4D compartment. It seems that release of AKT protein potentiated DDR activated pro-survival AKT in NALM-6 cells. Taken together, the present data indicated that regulation of AKT signaling may determine the fate of cells exposed to genotoxic stress.

Fish oil and olive oil can modify insulin resistance and plasma desacyl-ghrelin in rats

BACKGROUND

Evidence exists for reciprocal effects of insulin and desacyl-ghrelin (DAG) concentration, but the association between different fatty acid saturation in high fat diet (HFD) and these hormones remain to be established. To evaluate the impact of different sources of dietary fat and the level of fatty acid saturation on plasma insulin and DAG levels and also the association of DAG with insulin action this study was carried out.

METHODS

Male weaning Wistar rats were randomly divided into four groups of HFDs, high fat butter (HF-B), high fat soy (HF-S), high fat olive (HF-O), high fat fish (HF-F), and a group of standard diet (SD). Blood samples were collected after 8 weeks and after they were fasted for 24 h. Body weight, food intake, plasma glucose, insulin, DAG and insulin resistance (HOMA-IR) were measured.

RESULTS

Plasma insulin levels at fed and fasted status, were significantly higher in rats on HF-B compared to those on SD, HF-F and HF-O diets (P<0.05). Insulin concentration in rats on HF-S was also higher than those on SD, HF-F and HF-O diets (P<0.05), in the feeding status. Insulin resistance was significantly higher in rats on HF-B, compared to those on SD, HF-F and HF-O (P<0.05). Rats that were fed with HF-B diet had lower fasting plasma DAG levels than the SD, HF-F and HF-O groups (P<0.05); furthermore, the HF-F group had significantly higher DAG level than the HF-S groups (P<0.05).

CONCLUSIONS

Fish and olive oils may hence contribute to lower insulin level and HOMA-IR by increasing DAG concentration and may have more health benefits than other fat sources in diets.

Perceived depth of 3-D objects in 3-D scenes

Effects of information specifying the position of an object in a 3-D scene were investigated in two experiments with twelve observers. To separate the effects of the change in scene position from the changes in the projection that occur with increased distance from the observer, the same projections were produced by simulating (a) a constant object at different scene positions and (b) different objects at the same scene position. The simulated scene consisted of a ground plane, a ceiling plane, and a cylinder on a pole attached to both planes. Motion-parallax scenes were studied in one experiment; texture-gradient scenes were studied in the other. Observers adjusted a line to match the perceived internal depth of the cylinder. Judged depth for objects matched in simulated size decreased as simulated distance from the observer increased. Judged depth decreased at a faster rate for the same projections shown at a constant scene position. Adding object-centered depth information (object rotation) increased judged depth for the motion-parallax displays. These results demonstrate that the judged internal depth of an object is reduced by the change in projection that occurs with increased distance, but this effect is diminished if information for change in scene position accompanies the change in projection.

Age-related differences in collision detection during deceleration

Observers were presented with displays simulating a 3-D environment with obstacles in the path of motion. During the trial, observer motion decelerated at a constant rate and was followed by a blackout prior to the end of the display. On some trials the rate of deceleration resulted in stopping before the collision, whereas on other trials the rate of deceleration resulted in a collision with the obstacles. The observer's task was to detect which trials simulated an impending collision. Proportion of collision judgments was greater for older as compared with younger observers when a collision was not simulated. Older observers showed less sensitivity to detect collisions than younger observers did, particularly at high speeds. The age-dependent results are discussed in terms of analyses based on tau and constant deceleration. The results suggest that increased accident rates for older drivers may be due to an inability to detect collisions at high speeds.

Age-related differences in collision detection during deceleration

Observers were presented with displays simulating a 3-D environment with obstacles in the path of motion. During the trial, observer motion decelerated at a constant rate and was followed by a blackout prior to the end of the display. On some trials the rate of deceleration resulted in stopping before the collision, whereas on other trials the rate of deceleration resulted in a collision with the obstacles. The observer's task was to detect which trials simulated an impending collision. Proportion of collision judgments was greater for older as compared with younger observers when a collision was not simulated. Older observers showed less sensitivity to detect collisions than younger observers did, particularly at high speeds. The age-dependent results are discussed in terms of analyses based on tau and constant deceleration. The results suggest that increased accident rates for older drivers may be due to an inability to detect collisions at high speeds.

Effects of collimation on perceived layout in 3-D scenes

The effect of varying information for overall depth in a simulated 3-D scene on the perceived layout of objects in the scene was investigated in two experiments. Subjects were presented with displays simulating textured surfaces receded in depth. Pairs of markers were positioned at equal intervals within the scenes. The subject's task was to judge the depth between the intervals. Overall scene depth was varied by viewing through either a collimating lens or a glass disk. Judged depth for equal depth intervals decreased with increasing distance of the interval from the front of the scene. Judged depth was greater for collimated than for non-collimated viewing. Interestingly, collimated viewing resulted in a uniform rescaling of the perceived depth intervals.

The perception of depth and slant from texture in three-dimensional scenes

The perception of depth and slant in three-dimensional scenes specified by texture was investigated in five experiments. Subjects were presented with computer-generated scenes of a ground and ceiling plane receding in depth. Compression, convergence, and grid textures were examined. The effect of the presence or absence of a gap in the center of the display was also assessed. Under some conditions perceived slant and depth from compression were greater than those found with convergence. The relative effectiveness of compression in specifying surface slant was greater for surfaces closer to ground planes (80 degrees slant) than for surfaces closer to frontal parallel planes (40 degrees slant). The usefulness of compression was also observed with single-plane displays and with displays with surfaces oriented to reduce information regarding the horizon.

Speed, size, and edge-rate information for the detection of collision events

In the present study an alternative analysis to tau was considered that was based on perceived speed and size and that assumed constant deceleration for the detection of collision events. Observers were presented with displays simulating a 3-D environment with obstacles in the path of observer motion. During the trial, observer motion decelerated at a constant rate and was followed by a blackout prior to the end of the display. Observers had to detect which trials resulted in a collision. The results indicate that collision detection varied as a function of the size of the obstacles, observer speed, and edge rate--findings not predicted by an analysis of tau. The results suggest that observers use an analysis based on speed and size information. A model that assumes constant deceleration is proposed for braking control.

Speed, size, and edge-rate information for the detection of collision events

In the present study an alternative analysis to tau was considered that was based on perceived speed and size and that assumed constant deceleration for the detection of collision events. Observers were presented with displays simulating a 3-D environment with obstacles in the path of observer motion. During the trial, observer motion decelerated at a constant rate and was followed by a blackout prior to the end of the display. Observers had to detect which trials resulted in a collision. The results indicate that collision detection varied as a function of the size of the obstacles, observer speed, and edge rate--findings not predicted by an analysis of tau. The results suggest that observers use an analysis based on speed and size information. A model that assumes constant deceleration is proposed for braking control.

Interpolation across surface discontinuities in structure from motion

Interpolation across orientation discontinuities in simulated three-dimensional (3-D) surfaces was studied in three experiments with the use of structure-from-motion (SFM) displays. The displays depicted dots on two slanted planes with a region devoid of dots (a gap) between them. If extended through the gap at constant slope, the planes would meet at a dihedral edge. Subjects were required to place an SFM probe dot, located within the gap, on the perceived surface. Probe dot placements indicated that subjects perceived a smooth surface connecting the planes rather than a surface with a discontinuity. Probe dot placements varied with slope of the planes, density of the dots, and gap size, but not with orientation (horizontal or vertical) of the dihedral edge or of the axis of rotation. Smoothing was consistent with models of 2-D interpolation proposed by Ullman (1976) and Kellman and Shipley (1991) and with a model of 3-D interpolation proposed by Grimson (1981).

Interpolation in structure from motion

We investigated surface interpolation in displays of structure from motion (SFM). To do so, we introduced a new method for measuring surface perception in dynamic displays--the SFM probe. An SFM probe is a dot that moves rigidly with the dots on a simulated surface, and whose distance from that surface can be adjusted with a joystick or similar control. The displays we studied were random-dot cylinders containing a vertical strip devoid of feature points (the gap). Subjects adjusted an SFM probe, presented in the gap, until the probe dot appeared to be on the surface. Variability in probe-dot placement decreased with increasing texture density on the cylinder and increased with increasing gap width. Subjects showed a consistent bias to place the probe dot outside the cylinder. This bias increased with increasing texture density for the SFM displays. (The opposite bias was found in a static two-dimensional interpolation task with an arc whose curvature matched that of the cylinder: Subjects placed the probe dot inside the arc.) This outside bias is inconsistent with several theoretical approaches to surface interpolation.

Parts of visual objects: an experimental test of the minima rule

Three experiments were conducted to test Hoffman and Richards's (1984) hypothesis that, for purposes of visual recognition, the human visual system divides three-dimensional shapes into parts at negative minima of curvature. In the first two experiments, subjects observed a simulated object (surface of revolution) rotating about a vertical axis, followed by a display of four alternative parts. They were asked to select a part that was from the object. Two of the four parts were divided at negative minima of curvature and two at positive maxima. When both a minima part and a maxima part from the object were presented on each trial (experiment 1), most of the correct responses were minima parts (101 versus 55). When only one part from the object--either a minima part or a maxima part--was shown on each trial (experiment 2), accuracy on trials with correct minima parts and correct maxima parts did not differ significantly. However, some subjects indicated that they reversed figure and ground, thereby changing maxima parts into minima parts. In experiment 3, subjects marked apparent part boundaries. 81% of these marks indicated minima parts, 10% of the marks indicated maxima parts, and 9% of the marks were at other positions. These results provide converging evidence, from two different methods, which supports Hoffman and Richard's minima rule.