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Abstract Background Protective behaviors were essential for minimizing the spread of the virus during the coronavirus disease 2019 (COVID-19) pandemic. It is often assumed that awareness of bodily sensations (interoception) can improve decision-making and facilitate adaptive behavior. Objective This paper investigates cross-sectional and longitudinal relationships between different aspects of self-reported interoception, trait anxiety, COVID-related worry, and health protective behaviors. Methods The study was conducted on a community sample of 265 adults. The two data collection phases took place online, before (baseline) and during the second wave of the COVID-19 pandemic in Hungary. Results Contrary to our expectations, neither cross-sectional nor longitudinal associations were found between protective behaviors and indicators of self-reported interoception. However, worry at baseline predicted protective behaviors during the second wave, even after controlling for socio-economical characteristics and protective behaviors at baseline. Conclusion Our results highlight the adaptivity of health-related worry when behavioral steps to avoid threats are known and available. Also, higher level of perceived interoception did not appear to be health protective under these circumstances.

Changes in performance caused by positive and negative expectations (i.e., placebo and nocebo responses) were found to play an important role in many aspects of motor performance. This study aimed to test the impact of placebo/nocebo responses and the assumed moderating role of dispositional optimism and anxiety on proprioceptive accuracy, an essential aspect of motor functions. 78 undergraduate university students completed questionnaires assessing dispositional optimism, state anxiety, and motivation to cooperate, then were randomly assigned to three experimental groups. A sham subliminal electric stimulation was applied with claimed positive (placebo group, n = 26), negative (nocebo group, n = 26) or neutral (control group, n = 26) impact on proprioceptive accuracy. Proprioceptive accuracy was measured with active and passive versions of the Joint Position Reproduction task before and after the intervention. Expected and perceived changes in performance were also assessed; changes in state anxiety, optimism, and motivation to cooperate were used as control variables (covariates). Mixed analyses of variance indicated that the experimental manipulation did not affect actual proprioceptive accuracy but impacted expected and perceived performance. Adding the covariates to the models did not substantially change the results. Further, no significant association emerged between actual and perceived change in performance in the active test, and only a weak correlation was found in the passive test. Expected performance did not predict actual performance but predicted perceived performance in both tasks. The results suggest that only perceived (subjective) aspects of proprioceptive accuracy are susceptible to placebo and nocebo interventions.

Abstract Placebo and nocebo effects could influence the perceived, actual, or both postural stabilities. Therefore, this experiment examined whether postural stability is susceptible to placebo and nocebo effects. Driven by expectations, these cognitions could influence the motor stability of people in physical rehabilitation and those with motion instability. We randomly assigned 78 participants to a placebo, nocebo, or control group. Then, we applied a sham sports cream with positive, negative, or neutral instructions about its impact on balance. Next, we tested postural stability with a modified version of the Modified Clinical Test of Sensory Interaction in Balance, including standard, proprioceptive, visual, and vestibular tests before and after the intervention. Further, we measured expected and perceived performance with visual analog scales and assessed trait anxiety, change in state anxiety, optimism, holistic thinking, persistence, and cooperation with questionnaires. The intervention did not affect actual test performances; similarly, trait and state variables and expectations did not have an impact. Furthermore, the experimental manipulation and trait and state variables did not significantly affect perceived performance. However, the association between expectation and perceived performance was strong (ϱ = 0.627, p

Background: Proprioceptive accuracy refers to the individual's ability to perceive proprioceptive information, that is, the information referring to the actual state of the locomotor system, which originates from mechanoreceptors located in various parts of the locomotor system and from tactile receptors located in the skin. Proprioceptive accuracy appears to be an important aspect in the evaluation of sensorimotor functioning; however, no widely accepted standard assessment exists. In this systematic review, our goal was to identify and categorize different methods that are used to assess different aspects of proprioceptive accuracy. Methods: A literature search was conducted in 5 different databases (PubMed, SPORTDiscus, PsycINFO, ScienceDirect, and SpringerLink). Results: Overall, 1139 scientific papers reporting 1346 methods were included in this review. The methods assess 8 different aspects of proprioception: (a) the perception of joint position, (b) movement and movement extent, (c) trajectory, (d) velocity, and the sense of (e) force, (f) muscle tension, (g) weight, and (h) size. They apply various paradigms of psychophysics (i.e., the method of adjustment, constant stimuli, and limits). Conclusion: As the outcomes of different tasks with respect to various body parts show no associations (i.e., proprioceptive accuracy is characterized by site-specificity and method-specificity), the appropriate measurement method for the task needs to be chosen based on theoretical considerations and/or ecological validity.

BackgroundYoga based interventions were found to have a positive impact on various indicators of psychological functioning, such as perceived stress, satisfaction with life, positive and negative affectivity. Additionally, such interventions improved bodily or interoceptive awareness and spirituality.MethodsThe present study assessed the effects of a 3-month long complex yoga-based intervention compared to a passive control group in a Hungarian community sample. The final sample consisted of 44 intervention (Mage = 47.5, SD = = 8.76) and 29 control participants (Mage = 47.4, SD = 9.47). The aforementioned constructs were measured 1 week before and after the intervention.ResultsThe intervention reduced participants’ perceived stress (p =

Assessment of the acuity of heartbeat perception, dubbed cardioceptive accuracy, as well as its association with various psychological characteristics are hot topics of interoception research. In this study, we aimed (1) to replicate previously reported findings on the association between the mental tracking task and a novel motor tracking task that eliminates disturbing tactile sensations; and (2) to explore associations between performance in the latter task and indicators of negative affectivity (anxiety, depression, anxiety sensitivity, somatic symptom distress), alexithymia, body focus, and dissatisfaction with body image. 102 young people (age = 20.8±5.08 yrs) participated in the study. Mental tracking score was significantly higher than motor tracking scores, although they were strongly associated. Frequentist correlation analysis showed no significant associations between indicators of cardioceptive accuracy and questionnaire scores; Bayesian analysis indicated the lack of association for the majority of the cases. Similarly, detectors and non-detectors showed no differences in any of the assessed characteristics and Bayesian results typically supported the lack of associations. In conclusion, cardioceptive accuracy, as assessed with different tracking methods, is not associated with the aforementioned self-reported characteristics in young individuals.

This study was performed to investigate further the two-dimensional aspect of passion and its relationship to the risk of exercise addiction (REA) in nine nations and to clarify the unresolved gender differences. The here reported results stem from the reanalysis of data gathered in three previous empirical studies. The analyses demonstrated that harmonious (HP) and obsessive (OP) passion are two independent, non-interacting predictors of the REA, the prevalence of which was 12.1 % in the current sample that included 1448 people (age = 30.49 ± SD = 11.17 years; 55 % men), who exercised at least three hours per week. Furthermore, the results show that HP and OP could co-exist as a single ‘total’ or ‘true’ passion within the individual or in high-low HP and OP proportions, supporting the proposal for one, two-dimensional passion. Indeed, most people at REA demonstrated both high HP and high OP. The weekly amount of exercise was weakly associated with the two dimensions of passion. Relatively specific cultural differences in the REA and OP, but not HP, have emerged. The results also demonstrate that when a minimal weekly volume of training (i.e., 3 h) is a criterion for participant recruitment, no gender differences occur in the REA.

IEI-EMF refers to an environmental illness whose primary feature is the occurrence of symptoms that are attributed to exposure to weak electromagnetic fields (EMFs). There is a growing evidence that this condition is characterized by marked individual differences thus a within-subject approach might add important information beyond the widely used nomothetic method. A mixed qualitative/quantitative idiographic protocol with a threefold diagnostic approach was tested with the participation of three individuals with severe IEI-EMF. In this qualitative paper, the environmental, psychosocial, and clinical aspects are presented and discussed (results of ecological momentary assessment are discussed in Part II of this study). For two participants, psychopathological factors appeared to be strongly related to the condition. Psychological assessment indicated a severe pre-psychotic state with paranoid tendencies, supplemented with a strong attentional focus on bodily sensations and health status. The psychological profile of the third individual showed no obvious pathology. Overall, the findings suggest that the condition might have uniformly been triggered by serious psychosocial stress for all participants. Substantial aetiological differences among participants with severe IEI-EMF were revealed. The substantial heterogeneity in the psychological and psychopathological profiles associated with IEI-EMF warrants the use of idiographic multimodal assessments in order to better understand the different ways of aetiology and to facilitate person-taylored treatments.

IEI-EMF refers to a self-reported sensitivity characterized by attribution of non-specific physical symptoms to exposure to weak EMFs. The majority of empirical results do not support the existence of a causal relationship between EMF and IEI-EMF. However, this conclusion was drawn from environmental and experimental studies that are not without methodological limitations. In the current study, as part of a complex biopsychosocial approach, an ecological momentary assessment (EMA) protocol was applied for the investigation of the temporal relationship between actual radio frequency (RF) EMF exposure and IEI-EMF, at the individual level. Continuous measurement of autonomic variables by holter electrocardiogram (ECG) monitors and the ambient RF EMF by personal dosimeters, as well as repeated (8/day) paper-and-pencil assessments of momentary internal states (symptoms, mood, perceived EMF intensity) and situational factors was conducted for 21 days with the participation of three individuals with severe IEI-EMF. Temporal relationships were examined by time series analyses. For two participants, the results did not support the association between the suspected EMF frequency range(s) and symptom reports. Nevertheless, the results revealed a reverse association with respect to another frequency range (GSM900 downlink), which contradicts the IEI-EMF condition. Autonomic activation related findings were inconsistent. For the third participant, the claimed association was partly supported, both for symptom reports and autonomic reactions (UMTS downlink, total RF; RMS values). The findings of this study suggest that IEI-EMF does not have a unitary aetiology. For certain individuals, a biophysical background cannot be excluded, whereas no such underlying factor appears to be at work for others. EMA is a useful method for the investigation of the aetiology of IEI-EMF.

Laughter yoga is claimed to have similar psychological and physiological effects to exercising. The objectives of the two studies reported here were to examine the visual and practice effects of laughter yoga in women. Study 1 was performed with 13 young women (mean age =21.92 ± SD = 1.66 years) who only experienced laughter yoga visually. Study 2 investigated 25 older women (mean age = 63.83 ± SD = 11.91 years) during an in-situ laughter yoga class. There was no relationship between the humor styles, expectancy, and the magnitude of change in psychological measures, neither in visual nor in the practice experience of laughter yoga. In Study 1, negative affect decreased while feeling states, heart rate, and respiration rate increased because of watching laughter yoga. In Study 2, feeling states, felt arousal, positive affect, and negative affect improved after the class. Even more intriguingly, heart rate also increased, and the basic metabolic rate during the class was comparable to that of light to moderate physical activity. As laughter yoga is characterized by positive psychological and cardiometabolic changes, it could represent a pleasurable, healthy, and secure form of recreation for all, but based on the current results, especially for older women. Keywords: affect, exercise, humor, recreation, social.

There are a number of questionnaires assessing the self-reported trait-like aspect of interoception, also called interoceptive sensibility (ISb). Based on the varying purposes of their development and characteristics, however, it is not likely that they assess exactly the same construct. In a community sample of 265 adults, we examined this assumption for three commonly used questionnaires of ISb, namely the Body Awareness subscale of the Body Perception Questionnaire (BPQ-BA), the Body Awareness Questionnaire (BAQ), and the eight subscales of Multidimensional Assessment of Interoceptive Awareness (MAIA). We investigated their associations, and their relation to positive and negative affect and somatosensory amplification. According to the results of correlation analysis, BPQ-BA, BAQ and MAIA were partly unrelated to each other, partly showed weak to moderate positive associations. Also, differences with respect to their association with positive and negative affect were found. These findings suggest that the investigated questionnaires cannot be used interchangeably to assess the subjective aspect of interoception, and the term ISb is not appropriately defined.

There are a number of questionnaires assessing the self-reported trait-like aspect of interoception, also called interoceptive sensibility (ISb). Based on the varying purposes of their development and characteristics, however, it is not likely that they assess exactly the same construct. In a community sample of 265 adults, we examined this assumption for three commonly used questionnaires of ISb, namely the Body Awareness subscale of the Body Perception Questionnaire (BPQ-BA), the Body Awareness Questionnaire (BAQ), and the eight subscales of Multidimensional Assessment of Interoceptive Awareness (MAIA). We investigated their associations, and their relation to positive and negative affect and somatosensory amplification. According to the results of correlation analysis, BPQ-BA, BAQ and MAIA were partly unrelated to each other, partly showed weak to moderate positive associations. Also, differences with respect to their association with positive and negative affect were found. These findings suggest that the investigated questionnaires cannot be used interchangeably to assess the subjective aspect of interoception, and the term ISb is not appropriately defined.

Beneficial physical and physiological health outcomes of yoga practice are well-supported by empirical data. However, whether weekly frequency of training is sufficient to evoke positive changes, is still an open question. The present intervention study investigated the effects of 10 weekly sessions of beginner level hatha yoga with respect to indicators of physical fitness and physiological markers. 82 young women (mean age of 22.0 ± 3.83 years) participated in the study. The yoga group (N = 49) attended a yoga course consisting of 10 sessions (1.5 h each) on a weekly basis. The control group (N = 33) did not receive any intervention. BMI, body fat percentage, balance (one-leg-stand test with open and closed eyes, functional reach test), flexibility (side bend test, modified sit and reach test) core muscle strength (plank test) as well as resting heart rate (HR), and heart rate variability (HRV) were assessed 1 week before and after the course. Both frequentist and Bayesian analysis showed an improvement in flexibility and balance in the yoga group compared to the control group. The yoga group showed also increased core muscle strength. No changes with respect to BMI, body fat percentage, resting HR and HRV were found. Ninety minute beginner level hatha yoga classes were characterized by 93.39 HR and 195 kcal energy consumption on average. The present findings suggest that weekly setting of a 10-session long hatha yoga training leads to improvements in balance, flexibility and core muscle strength among healthy young women. However, for changes in BMI, body fat percentage, resting HR and HRV longer, and/or more intense interventions are needed.

ObjectiveBoth yoga practice and spirituality are associated with beneficial mental health outcomes. Within yoga research, however, spirituality is still a widely neglected area. The present systematic review aims to explore empirical studies, which do, in fact, investigate the relationship between yoga and spirituality in order to provide an overview and future directions for research on this topic. The review examines whether available empirical research supports an association between yoga practice and spirituality and, if so, which specific aspects of spirituality are associated with yoga practice.MethodsThe systematic review followed the PRISMA guideline (Prospero registration number: CRD42020155043). Empirical studies written in English, German, or Hungarian language were selected from a database search in Google Scholar, PsycINFO, and Science Direct. A total of 30 studies met the final inclusion criteria.ResultsAccording to the quantitative and qualitative studies reviewed, yoga practice seems to be positively associated with spirituality. This association concerns various aspects of spirituality, such as spiritual aspirations, a search for insight/wisdom, an integrative worldview, a sense of meaning and peace, faith, hope, compassion, and happiness within. To harness the potential spiritual benefits of yoga, regular practice appears to be essential. Yoga practitioners seem to have both physical and spiritual motives for practicing. At least in Western societies, however, physical intentions are more prevalent than spiritual ones. The meaning of spirituality for yoga practitioners is also discussed. Due to risk of bias of the majority of the reviewed studies, however, outcomes must be taken with caution.ConclusionYoga practice may be positively associated with several aspects of spirituality. For more evidence, further investigation of the topic is suggested. Particularly, we propose the inclusion of holistic forms of yoga practice and a comparison of Eastern and Western approaches to yoga.

Pain perception is influenced by several factors, and among them, affect, sex, and perception of bodily signals are assumed to play a prominent role. The aim of the present study is to explore how sex, cardiac interoceptive accuracy, and the interaction of the latter two influence the perception of experimentally induced pain. We investigated a large sample of young adults (n = 159, 50.9% female, age: 23.45, SD = 3.767), assessing current positive and negative affective state with the Positive and Negative Affect Schedule (both involved as control variables), cardiac interoceptive accuracy with the mental heartbeat tracking task, and pain sensitivity with electrical stimulation on the back of the dominant hand, applying a repeated-measures staircase protocol. Males showed a significantly higher pain threshold and tolerance level than females, whereas cardiac interoceptive accuracy was not associated with pain sensitivity. The impact of sex × cardiac interoceptive accuracy interaction was significant for pain threshold only, while pain tolerance was predicted only by sex. According to these findings, the associations between pain sensitivity, cardiac IAc, and sex might be more complicated than it was supposed in previous studies. Interactions between factors impacting pain perception appear worthy of further investigation.

Interoception in the broader sense refers to the perception of internal states, including the perception of the actual state of the internal organs (visceroception) and the motor system (proprioception). Dimensions of interoception include (1) interoceptive accuracy, i.e., the ability to sense internal changes assessed with behavioral tests, (2) confidence rating with respect to perceived performance in an actual behavioral test, and (3) interoceptive sensibility, i.e., the self-reported generalized ability to perceive body changes. The relationship between dimension of cardioceptive and proprioceptive modalities and their association with affect are scarcely studied. In the present study, undergraduate students (N = 105, 53 males, age: 21.0 ± 1.87 years) filled out questionnaires assessing positive and negative affect (Positive and Negative Affect Schedule), interoceptive sensibility (Body Awareness Questionnaire), and body competence (Body Competence Scale of the Body Consciousness Questionnaire). Following this, they completed a behavioral task assessing cardioceptive accuracy (the mental heartbeat tracking task by Schandry) and two tasks assessing proprioceptive accuracy with respect to the tension of arm flexor muscles (weight discrimination task) and the angular position of the elbow joint (joint position reproduction task). Confidence ratings were measured with visual analog scales after the tasks. With the exception of a weak association between cardioceptive accuracy and the respective confidence rating, no associations between and within modalities were found with respect to various dimensions of interoception. Further, the interoceptive dimensions were not associated with state and trait positive and negative affect and perceived body competence. In summary, interoceptive accuracy scores do not substantially contribute to conscious representations of cardioceptive and proprioceptive ability. Within our data, non-pathological affective states (PANAS) are not associated with the major dimensions of interoception for the cardiac and proprioceptive modalities.

Verbal instructions provided during yoga classes can differ substantially. Yoga instructors might choose to focus on the physical aspects of yoga (e.g., by emphasizing the characteristics of the poses), or they might take a more spiritual approach (e.g., by mentioning energy flow and chakras). The present study investigated the effects of verbal cues during yoga practice on various psychological measures. Eighty-four female students (22.0 ± 3.80 years) participated in the study. Two groups attended a beginner level hatha yoga course in which physically identical exercise was accompanied by different verbal cues. The so-called “Sport group” (N = 27) received instructions referring primarily to the physical aspects of yoga practice, while the “Spiritual group” (N = 23) was additionally provided with philosophical and spiritual information. A control group (N = 34) did not receive any intervention. Mindfulness, body awareness, spirituality, and affect were assessed 1 week before and after the training. 2 × 3 mixed (time × intervention) ANOVAs did not show an interaction effect for any of the variables. However, when the two yoga groups were merged and compared to the control group, we found that spirituality increased, and negative affect decreased among yoga participants. In conclusion, yoga practice might influence psychological functioning through its physical components, independent of the style of verbal instructions provided.

[Background] Objectification theory assumes that individuals with low level of interoceptive accuracy may develop an external orientation for information concerning their body. Past research has found associations between interoceptive accuracy and body image concerns. We aimed to explore temporal relationships between the tendency to monitor one's body from a third-party perspective, body image dissatisfaction, and interoceptive accuracy. [Method] In a short longitudinal research, 38 Hungarian and 59 Norwegian university students completed the Schandry heartbeat tracking task and filled out baseline and follow-up questionnaires assessing private body consciousness, body surveillance, and body image dissatisfaction 8 weeks apart. [Results] Interoceptive accuracy and indicators of external body orientation did not predict body image dissatisfaction after controlling for gender, nationality, and body image dissatisfaction at baseline. Similarly, body surveillance was not predicted by baseline levels of interoceptive accuracy and body image dissatisfaction. [Conclusion] Contrary to the tenets of objectification theory, body image dissatisfaction and body surveillance are not predicted by interoceptive accuracy over a short period of time among young individuals.

[Background] Idiopathic Environmental Intolerance attributed to Electromagnetic Fields (IEI-EMF) is a self-reported condition where non-specific symptoms are attributed to weak non-ionizing electromagnetic fields. Despite its expanding prevalence, there is no generally accepted diagnostic procedure or definition to identify patients with this condition, thus studies usually apply only one question as inclusion criterion. The aim of our study was to demonstrate the heterogeneity of a self-reported IEI-EMF group and to identify further self-report questions that could be applied as inclusion criteria. [Method] Cross-sectional on-line survey study was carried out with 473 participants (76.3% women; age: 35.03 ± 13.24 yrs). Self-diagnosed IEI-EMF (as assessed with a yes-or-no question), frequency of EMF-related symptom and severity of the condition were assessed, as well as somatic symptom distress (Patient Health Questionnaire Somatic Symptom Severity Scale, PHQ-15). [Results] 72 (15.2%) individuals labelled themselves as IEI-EMF, however only 61% of them remained in the IEI-EMF group after the use of three inclusion criteria instead of one. 21% of the individuals labelling themselves as IEI-EMF reported neither symptoms nor any negative impact on their daily life. [Conclusion] A minimum of two questions appear to be necessary as inclusion criteria for IEI-EMF in empirical research. Instead of the widely used yes-or-no question on accepting the IEI-EMF label, occurrence of symptoms attributed to EMF on a regular basis and at least a slight negative impact on daily life are required.

Background. Aikido is a philosophy and an Eastern martial-art which is conjectured to have many positive effects on mind and body. At this time there is limited, but growing research on this topic. The objective of the current work was to examine for the first time the hypothesis that aikido training, like many other western forms of organized physical activities, has acute psychological benefits as manifested via favourable changes in affect and the flow experience. Methods. Aikidokas (N = 53) took part in an in-situ investigation in which they completed the Positive Affect Negative Affect Schedule (PANAS) on at least three different occasions before and after their practice. They also completed a flow questionnaire at least on three occasions after their practice. Results. The results indicated that positive affect increased, and negative affect decreased (p < .001) from pre- to post-practice. Aikidokas reported flow experience that on the average was not greater than that reported for other exercises; however it was greater than that reported after video-sport games. The reported flow was independent of the magnitude of change in positive and/or negative affect. The more experienced aikidokas experienced greater skill-challenge harmony, but not oneness with the experience, which are two constructs in flow, than less experienced practitioners. Conclusion. These findings reveal relatively clearly for the very first time in the literature that aikido practice has acute, or immediate, psychological benefits akin to other martial arts and exercises.

Worries about possible harmful effects of new technologies (modern health worries) have intensely been investigated in the last decade. However, the comparability of translated self-report measures across countries is often problematic. This study aimed to overcome this problem by developing psychometrically sound brief versions of the widely used 25-item Modern Health Worries Scale (MHWS) suitable for multi-country use. Based on data of overall 5,176 individuals from four European countries (England, Germany, Hungary, Sweden), Ant Colony Optimization was used to identify the indicators that optimize model fit and measurement invariance across countries. Two scales were developed. A short (12-item) version of the MHWS that represents the four-factor structure of the original version and an ultra-short (4-item) scale that only measures the general construct. Both scales show that overall levels of health worries were highest in England and Hungary, but that the main reason for concern (e.g. electromagnetic radiation or food related fears) differs considerably between these countries. This study also shows that even if measurement invariance of translated self-report instruments across countries is problematic, it can be optimized by using adequate item selection procedures. Differences of modern health worries across countries and recommendations for cross-cultural research are discussed.

Objective: The term interoception refers to the perception of bodily cues. In empirical studies, it is assessed using heartbeat detection or tracking tasks, often with the implicit assumption that cardioception reflects general interoceptive ability. Studies that applied a multichannel approach measured only a limited number of modalities. In the current study, six modalities were assessed to gain a deeper understanding of the relationship between the different sensory channels of interoception.Methods: For 118 university students (53% male) gastric perception (water load test), heartbeat perception (Schandry task), proprioception (elbow joint), ischemic pain (tourniquet technique), balancing ability (one leg stand), and perception of bitter taste were measured. Pair-wise correlation analysis and exploratory factor analyses (principal component analysis (PCA) and maximum likelihood (ML) extraction with oblimin rotation) were then carried out with a three-factor solution to investigate the underlying associations.Results: Correlation analysis only revealed significant associations between variables belonging to the same sensory modality (gastric perception, pain, bitter taste). Similarly, the three factors that consistently emerged in the factor analyses represented the three aforementioned modalities.Discussion: Interoceptive sensitivity assessed by using one channel only cannot be generalized. Interoceptive modalities carrying crucial information for survival are not integrated with other channels.

Background. Fish oil contains essential fatty acids that are linked to better cardiovascular health and even the prevention of sudden cardiac death in athletes. The purpose of this work was to examine the effects of 90 days of fish oil supplementation in elite-, leisure-, and non-athletes on body fat percent, body mass index (BMI), blood cholesterol and triglycerides, heart rate and blood pressure, and on exercise performance. Method. Three groups of participants were tested with 12 equally distributed men and women in each: elite- athletes, leisure-athletes, and non-athletes. Participants received body weight-adjusted commercially available fish oil over 90 days. These nutritional supplements were taken in the morning, immediately following breakfast. Results. The findings revealed that compared to the baseline, body fat percent decreased in all the three groups (p = .034), however, blood cholesterol and the cholesterol/high density lipoprotein (HDL) ratio increased (p < .05), with the elite-athletes showing the largest increase. Exercise performance, in terms of the time of running to voluntary exhaustion, increased (p = .05), but the largest benefits were observed in non-athletes (22%) in contrast to leisure- athletes (4%) and elite-athletes (1%), which could be linked to a ceiling effect. No statistically significant changes were observed in any other anthropometric, physiological, or biochemical measures. Conclusion. These findings suggest that 90 days of fish oil supplementation may benefit body composition and increase exercise performance, especially in non-athletes, and increases cholesterol, as well as cholesterol/HDL ratio levels, primarily in elite-athletes. Based on these results, it appears that fish oil supplementation yields greater benefits in non-athletes than in athletes. Keywords: anthropometric measures, biochemical measures, body composition, in-situ, real life setting.