A Systematic Review and Meta-Analysis on the Association and Differences between Aerobic Threshold and Point of Optimal Fat Oxidation

Over the past two decades, scientists have attempted to evaluate whether the point of maximal fat oxidation (FATmax) and the aerobic threshold (AerT) are connected. The existence of such a relationship would allow a more tailored training approach for athletes while improving the efficacy of individualized exercise prescriptions when treating numerous health-related issues. However, studies have reported conflicting results, and this issue remains unresolved. This systematic review and meta-analysis aimed: (i) to examine the strength of the association between FATmax and AerT by using the effect size (ES) of correlation coefficient (r) and standardized mean difference (SMD); (ii) to identify potential moderators and their influence on ES variability. This study was registered with PROSPERO (CRD42021239351) and ClinicalTrials (NCT03789045). PubMed and Google Scholar were searched and fourteen articles, consisting of overall 35 ES for r and 26 ES for SMD were included. Obtained ESs were analyzed using a multilevel random-effects meta-analysis. Our results support the presence of a significant association between FATmax and AerT exercise intensities. In conclusion, due to the large ES variance caused by clinical and methodological differences among the studies, we recommend that future studies follow strict standardization of data collection and analysis of FATmax and AerT-related outcomes

Body Composition Impact on Sleep in Young Adults: The Mediating Role of Sedentariness, Physical Activity, and Diet

The authors would like to express their gratitude to Imran Khan for the language and editing assistance.Obesity and sleep disturbances are both related to endocrine and metabolic alterations, cardiovascular disease, and impaired daytime functioning and mood. However, the bidirectional relationship between these conditions and the underlying mechanisms still remain unclear. This study aimed to investigate the potential association of anthropometric and body composition parameters with sleep in young adults, considering the mediating role of sedentariness, physical activity, and diet. A total of 187 adults aged 18–25 (35.29% men) participated in the study. Body mass index (BMI), waist–hip ratio, and waist–height ratio were calculated, and a dual-energy X-ray absorptiometry scanner was used to assess body composition. Sedentary time and physical activity, as well as sleep duration and quality, were objectively and subjectively measured using accelerometry and the Pittsburgh Sleep Quality Index. An inverse association was found between BMI and total sleep time (β = −0.165, p = 0.029). Waist–hip ratio and lean mass index were also negatively associated with total sleep time (β = −0.222, p = 0.007, and β = −0.219, p = 0.004) and sleep efficiency (β = −0.174, p = 0.037, and β = −0.188, p = 0.013). Sedentary time moderated by sex explained the association of BMI with total sleep time such that a high BMI was related to higher sedentariness in men which, in turn, was significantly associated with shorter sleep duration. Sedentary time is, therefore, a link/risk factor mediating the association of high BMI with short sleep duration in healthy young men.Spanish Ministry of Economy and Competitiveness via the Fondo de Investigacion Sanitaria del Instituto de Salud Carlos III PI13/01393Spanish Ministry of Economy and Competitiveness via Retos de la Sociedad DEP2016-79512-RSpanish Ministry of Economy and Competitiveness via European Regional Development Funds (ERDF)Spanish Government FPU16/01093Spanish Ministry of Education and Science (Red EXERNET) DEP2005-00046Fundacion Iberoamericana de Nutricion (FINUT)Redes Tematicas de Investigacion Cooperativa RETIC (Red SAMID) RD16/0022AstraZenecaUniversity of Granada Plan Propio de Investigacion 2016 Excellence actions: Unit of Excellence on Exercise and Health (UCEES)Junta de Andalucia, Consejeria de Conocimiento, Investigacion y Universidades (ERDF) SOMM17/6107/UG

Factors Determining the Agreement between Aerobic Threshold and Point of Maximal Fat Oxidation: Follow-Up on a Systematic Review and Meta-Analysis on Association

Regular exercise at the intensity matching maximal fat oxidation (FATmax) has been proposed as a key element in both athletes and clinical populations when aiming to enhance the body’s ability to oxidize fat. In order to allow a more standardized and tailored training approach, the connection between FATmax and the individual aerobic thresholds (AerT) has been examined. Although recent findings strongly suggest that a relationship exists between these two intensities, correlation alone is not sufficient to confirm that the intensities necessarily coincide and that the error between the two measures is small. Thus, this systematic review and meta-analysis aim to examine the agreement levels between the exercise intensities matching FATmax and AerT by pooling limits of agreement in a function of three parameters: (i) the average difference, (ii) the average within-study variation, and (iii) the variation in bias across studies, and to examine the influence of clinical and methodological inter- and intra-study differences on agreement levels. This study was registered with PROSPERO (CRD42021239351) and ClinicalTrials (NCT03789045). PubMed and Google Scholar were searched for studies examining FATmax and AerT connection. Overall, 12 studies with forty-five effect sizes and a total of 774 subjects fulfilled the inclusion criteria. The ROBIS tool for risk of bias assessment was used to determine the quality of included studies. In conclusion, the overall 95% limits of agreement of the differences between FATmax and AerT exercise intensities were larger than the a priori determined acceptable agreement due to the large variance caused by clinical and methodological differences among the studies. Therefore, we recommend that future studies follow a strict standardization of data collection and analysis of FATmax- and AerT-related outcomes

Does the Time of Day Play a Role in the Acute Effect of p-Synephrine on Fat Oxidation Rate during Exercise in Women? A Randomized, Crossover and Double-Blind Study

p-Synephrine is deemed a safe and effective substance to increase fat utilization during exercise of low-to-moderate intensity in men but not in women. Additionally, the existence of a diurnal variation in substrate utilization has been documented during exercise with enhanced fat oxidation in the evening compared with early morning. However, it remains unknown whether there is an interaction between the effect of p-synephrine and the time of the day on fat oxidation during exercise. This study aimed to evaluate the effect of the acute ingestion of 3 milligram of p-synephrine per kilogram of body mass (mg/kg) on fat oxidation during exercise of increasing intensity when the exercise is performed in the morning vs. the evening. Using a randomized, double-blind, placebo-controlled experimental design, 16 healthy and active women performed four identical exercise trials after the ingestion of 3 mg/kg of p-synephrine and 3 mg/kg of a placebo (cellulose) both in the morning (8-10 am) and in the evening (5-7 pm). In the exercise trials, the substances were ingested 60 min before an incremental test on a cycle ergometer with 3 min stages at workloads from 30 to 80% of maximal oxygen uptake (VO(2)max). Substrate oxidation rates were measured by indirect calorimetry. In each trial, the maximum rate of fat oxidation (MFO) and the intensity that elicited MFO (Fatmax) were measured. A two-way analysis of variance (time-of-the day x substance) was used to detect differences among the trials. With the placebo, MFO was 0.25 +/- 0.11 g/min in the morning and 0.24 +/- 0.07 g/min in the evening. With p-synephrine, MFO was 0.26 +/- 0.09 g/min in the morning and 0.21 +/- 0.07 g/min in the evening. There was no main effect of substance (p = 0.349), time of day (p = 0.186) and the substance x time of day (p = 0.365) on MFO. Additionally, Fatmax was reached at a similar exercise intensity with the placebo (41.33 +/- 8.34% VO(2)max in the morning and 44.38 +/- 7.37% VO(2)max in the evening) and with p-synephrine (43.33 +/- 7.24% VO(2)max in the morning and 45.00 +/- 7.43% VO(2)max in the evening), irrespective of the time of day with no main effect of substance (p = 0.633), time of day (p = 0.191), or interaction (p = 0.580). In summary, the acute intake of 3 mg/kg of p-synephrine before exercise did not increase MFO and Fatmax, independently of the time of day, in female athletes. This indicates that the time of day is not a factor explaining the lack of effectiveness of this substance to enhance fat oxidation during aerobic exercise in women.Francisco de Vitoria University, grant number UFV-18/202

Effect of p-Synephrine on Fat Oxidation Rate during Exercise of Increasing Intensity in Healthy Active Women

p-Synephrine is the principal alkaloid of bitter orange (Citrus aurantium). Several recent investigations have found that the intake of 2-3 mg/kg of p-synephrine raises fat oxidation rate during exercise of low-to-moderate intensity. However, these investigations have been carried out only with samples of male participants or mixed men/women samples. Therefore, the aim of this investigation was to study the effect of p-synephrine intake on fat oxidation during exercise of increasing intensity in healthy women. Using a double-blind, randomized experiment, 18 healthy recreationally active women performed two identical exercise trials after the ingestion of (a) 3 mg/kg of p-synephrine and (b) 3 mg/kg of a placebo (cellulose). The exercise trials consisted of a ramp test (from 30 to 80% of maximal oxygen uptake; VO(2)max) on a cycle ergometer while substrate oxidation rates were measured at each workload by indirect calorimetry. In comparison to the placebo, the intake of p-synephrine increased resting tympanic temperature (36.1 +/- 0.5 vs. 36.4 +/- 0.4 degrees C p = 0.033, d = 0.87) with no effect on resting heart rate (p = 0.111) and systolic (p = 0.994) and diastolic blood pressure (p = 0.751). During exercise, there was no significant effect of p-synephrine on fat oxidation rate (F = 0.517; p = 0.484), carbohydrate oxidation rate (F = 0.730; p = 0.795), energy expenditure rate (F = 0.480; p = 0.833), heart rate (F = 4.269; p = 0.068) and participant's perceived exertion (F = 0.337; p = 0.580). The maximal rate of fat oxidation with placebo was 0.26 +/- 0.10 g/min and it was similar with p-synephrine (0.28 +/- 0.08 g/min, p = 0.449, d = 0.21). An acute intake of 3 mg/kg of p-synephrine before exercise did not modify energy expenditure and substrate oxidation during submaximal aerobic exercise in healthy active women. It is likely that the increase in resting tympanic temperature induced by p-synephrine hindered the effect of this substance on fat utilization during exercise in healthy active women.Francisco de Vitoria University UFV-18/202

A Atividade Seguradora e o Estilo de Vida em Portugal - o Incentivo como Estímulo para a Mudança: Uma Abordagem Atuarial

Os gastos com os cuidados de saúde têm vindo a aumentar e estima-se que, mantendo-se esta tendência, em 2050 a maioria dos países da OCDE despendam mais de 20 porcento do PIB com a saúde. A principal causa de mortalidade e morbilidade na generalidade dos países são as doenças crónicas (diabetes, obesidade, cancro, hipertensão, entre outras) que, por sua vez, podem ser o resultado de um estilo de vida pouco saudável por parte da população. Por estes motivos, torna-se imprescindível a tomada de medidas que promovam uma mudança comportamental nos hábitos de vida de forma a controlar estas doenças e, por conseguinte, reduzir os custos com a saúde. Em alguns países como África do Sul, Estados Unidos e Reino Unido, a indústria seguradora tem tomado iniciativas no sentido de promover a prática de hábitos de vida saudáveis através de um programa de recompensas como incentivo àmudança, no entanto tais medidas não são verificadas em Portugal. Estas recompensas consistem na oferta de descontos em lojas e descontos no prémio do seguro. Na presente dissertação pretende estudar-se a possibilidade de implementação de um programa de incentivos em Portugal e analisar, do ponto de vista atuarial, o comportamento de uma carteira. Para tal, é simulada uma carteira admitindo diferentes cenários para o estado de saúde dos elementos da carteira. A esta carteira são aplicados conceitos teóricos acerca dos Sistemas de Bonus Malus, considerando-se tanto uma carteira fechada (Modelo Clássico) como uma carteira aberta (Modelo Vórtices Estocásticos)

Body Composition Impact on Sleep in Young Adults: The Mediating Role of Sedentariness, Physical Activity, and Diet

Obesity and sleep disturbances are both related to endocrine and metabolic alterations, cardiovascular disease, and impaired daytime functioning and mood. However, the bidirectional relationship between these conditions and the underlying mechanisms still remain unclear. This study aimed to investigate the potential association of anthropometric and body composition parameters with sleep in young adults, considering the mediating role of sedentariness, physical activity, and diet. A total of 187 adults aged 18–25 (35.29% men) participated in the study. Body mass index (BMI), waist–hip ratio, and waist–height ratio were calculated, and a dual-energy X-ray absorptiometry scanner was used to assess body composition. Sedentary time and physical activity, as well as sleep duration and quality, were objectively and subjectively measured using accelerometry and the Pittsburgh Sleep Quality Index. An inverse association was found between BMI and total sleep time (β = −0.165, p = 0.029). Waist–hip ratio and lean mass index were also negatively associated with total sleep time (β = −0.222, p = 0.007, and β = −0.219, p = 0.004) and sleep efficiency (β = −0.174, p = 0.037, and β = −0.188, p = 0.013). Sedentary time moderated by sex explained the association of BMI with total sleep time such that a high BMI was related to higher sedentariness in men which, in turn, was significantly associated with shorter sleep duration. Sedentary time is, therefore, a link/risk factor mediating the association of high BMI with short sleep duration in healthy young men