Klaas R. Westerterp

Bio: Klaas R. Westerterp is an academic researcher from Maastricht University Medical Centre. The author has contributed to research in topics: Basal metabolic rate & Resting energy expenditure. The author has an hindex of 87, co-authored 407 publications receiving 27195 citations. Previous affiliations of Klaas R. Westerterp include Katholieke Universiteit Leuven & University of Amsterdam.

How much physical activity is enough to prevent unhealthy weight gain? Outcome of the IASO 1st Stock Conference and consensus statement

Abstract: A consensus meeting was held in Bangkok, 21–23 May 2002, where experts and young scientists in the field of physical activity, energy expenditure and bodyweight regulation discussed the different aspects of physical activity in relation to the emerging problem of obesity worldwide. The following consensus statement was accepted unanimously. ‘The current physical activity guideline for adults of 30 minutes of moderate intensity activity daily, preferably all days of the week, is of importance for limiting health risks for a number of chronic diseases including coronary heart disease and diabetes. However for preventing weight gain or regain this guideline is likely to be insufficient for many individuals in the current environment. There is compelling evidence that prevention of weight regain in formerly obese individuals requires 60–90 minutes of moderate intensity activity or lesser amounts of vigorous intensity activity. Although definitive data are lacking, it seems likely that moderate intensity activity of approximately 45 to 60 minutes per day, or 1.7 PAL (Physical Activity Level) is required to prevent the transition to overweight or obesity. For children, even more activity time is recommended. A good approach for many individuals to obtain the recommended level of physical activity is to reduce sedentary behaviour by incorporating more incidental and leisure-time activity into the daily routine. Political action is imperative to effect physical and social environmental changes to enable and encourage physical activity. Settings in which these environmental changes can be implemented include the urban and transportation infrastructure, schools, and workplaces.’

Physical activity assessment with accelerometers: an evaluation against doubly labeled water

Abstract: This review focuses on the ability of different accelerometers to assess daily physical activity as compared with the doubly labeled water (DLW) technique, which is considered the gold standard for measuring energy expenditure under free-living conditions. The PubMed Central database (U.S. NIH free digital archive of biomedical and life sciences journal literature) was searched using the following key words: doubly or double labeled or labeled water in combination with accelerometer, accelerometry, motion sensor, or activity monitor. In total, 41 articles were identified, and screening the articles' references resulted in one extra article. Of these, 28 contained sufficient and new data. Eight different accelerometers were identified: 3 uniaxial (the Lifecorder, the Caltrac, and the CSA/MTI/Actigraph), one biaxial (the Actiwatch AW16), 2 triaxial (the Tritrac-R3D and the Tracmor), one device based on two position sensors and two motion sensors (ActiReg), and the foot-ground contact pedometer. Many studies showed poor results. Only a few mentioned partial correlations for accelerometer counts or the increase in R(2) caused by the accelerometer. The correlation between the two methods was often driven by subject characteristics such as body weight. In addition, standard errors or limits of agreement were often large or not presented. The CSA/MTI/Actigraph and the Tracmor were the two most extensively validated accelerometers. The best results were found for the Tracmor; however, this accelerometer is not yet commercially available. Of those commercially available, only the CSA/MTI/Actigraph has been proven to correlate reasonably with DLW-derived energy expenditure.

Dietary Protein, Weight Loss, and Weight Maintenance

Abstract: The role of dietary protein in weight loss and weight maintenance encompasses influences on crucial targets for body weight regulation, namely satiety, thermogenesis, energy efficiency, and body composition. Protein-induced satiety may be mainly due to oxidation of amino acids fed in excess, especially in diets with "incomplete" proteins. Protein-induced energy expenditure may be due to protein and urea synthesis and to gluconeogenesis; "complete" proteins having all essential amino acids show larger increases in energy expenditure than do lower-quality proteins. With respect to adverse effects, no protein-induced effects are observed on net bone balance or on calcium balance in young adults and elderly persons. Dietary protein even increases bone mineral mass and reduces incidence of osteoporotic fracture. During weight loss, nitrogen intake positively affects calcium balance and consequent preservation of bone mineral content. Sulphur-containing amino acids cause a blood pressure-raising effect by loss of nephron mass. Subjects with obesity, metabolic syndrome, and type 2 diabetes are particularly susceptible groups. This review provides an overview of how sustaining absolute protein intake affects metabolic targets for weight loss and weight maintenance during negative energy balance, i.e., sustaining satiety and energy expenditure and sparing fat-free mass, resulting in energy inefficiency. However, the long-term relationship between net protein synthesis and sparing fat-free mass remains to be elucidated.

Chemical reactor design and operation

Abstract: Preface to the First Edition Preface to the Second Edition Preface to the Student Edition List of Symbols Chapter I Fundamentals of chemical reactor calculations 1.1 Introduction 1.2 The material, energy and economic balance - Material balance - Energy balance - Economic balance 1.3 Thermodynamic data: heat of reaction and chemical equilibrium - Heat of reaction - Chemical equilibrium 1.4 Conversion rate, chemical reaction rate and chemical reaction rate equations - Influence of temperature on kinetics - Influence of concentration on kinetics 1.5 The degree of conversion - Relation between conversion and concentration expressions 1.6 Selectivity and yield - Selectivity and yield in a reactor section with recycle of non-converted reactant 1.7 Classification of chemical reactors References Chapter II Model reactors: single reactions, isothermal single phase reactor calculations II.1 The well-mixed batch reactor II.2 The continuously operated ideal tubular reactor II.3 The continuously operated ideal tank reactor 11.4 The cascade of tank reactors II.5 The semi-continuous tank reactor II.6 The recycle reactor II.7 A comparison between the different model reactors - Batch versus continuous operation - Tubular reactor versus tank reactor II.8 Some examples of the influence of reactor design and operation on the economics of the process - The use of one of the reactants in excess - Recirculation of unconverted reactant - Maximum production rate and optimum load with intermittent operation References Chapter III Model reactors: multiple reactions, isothermal single phase reactors III.1 Fundamental concepts - Differential selectivity and selectivity ratio - The reaction path III.2 Parallel reactions - Parallel reactions with equal order rate equations - Parallel reactions with differing reaction order rate equations - A cascade of tank reactors III.3 The continuous cross flow reactor system III.4 Consecutive reactions - First order consecutive reactions in a plug flow reactor - First order consecutive reactions in a tank reactor - General discussion III.5 Combination reactions - Graphical methods - Optimum yield in a cascade of tank reactors - Algebraic methods III.6 Autocatalytic reactions - Single biochemical reactions - Multiple autocatalytic reactions References Chapter IV Residence time distribution and mixing in continuous flow reactors IV.1 The residence time distribution (RTD) - The E and the F diagram - The application of the RTD in practice IV.2 Experimental determination of the residence time distribution - Input functions IV.3 Residence time distribution in a continuous plug flow and in a continuous ideally stirred tank reactor. IV.4 Models for intermediate mixing - Model of a cascade of N equal ideally mixed tanks - The axially dispersed plug flow model IV.5 Conversion in reactors with intermediate mixing IV.6 Some data on the longitudinal dispersion in continuous flow systems - Flow through empty tubes - Packed beds - Fluidized beds - Mixing in gas-liquid reactors References Chapter V Influence of micromixing on chemical reactions V.1 Nature of the micromixing phenomena - Macro or gross overall mixing as characterized by the residence time distribution - The state of aggregation of the reacting fluid - The earliness of the mixing V.2 Boundaries to micromixing phenomena - The model tubular and tank reactors - Boundaries for micromixing for reactors with arbitrary RTDs V.3 Intermediate degree of micromixing in continuous stirred tank reactors - Formal models - Agglomeration models - Model for micromixing via exchange of mass between agglomerates and their average' environment, the IEM model V.4 Experimental results on micromixing in stirred vessels V.5 Concluding remarks on micromixing References Chapter VI The role of the heat effect in model reactors VI.1 The energy balance and heat of reaction VI.2 The well-mixed batch reactor - Batch versus semi-batch operation VI.3 The tubular reactor with external heat exchange - Maximum temperature with exothermic reactions para-metric sensitivity VI.4 The continuous tank reactor with heat exchange VI.5 Autothermal reactor operation - The tank reactor - An adiabatic tubular reactor with heat exchange between reactants and products - A multi-tube reactor with internal heat exchange between the reaction mixture and the feed - Determination of safe operating conditions VI.6 Maximum permissible reaction temperatures VI.7 The dynamic behaviour of model reactors - The autothermal tank reactor - Tubular reactor References Chapter VII Multiphase reactors, single reactions VII.1 The role of mass transfer VII.2 A qualitative discussion on mass transfer with homogeneous reaction - Concentration distribution in the reaction phase VII.3 General material balance for mass transfer with reaction VII.4 Mass transfer without reaction - Stagnant film model - Penetration models of Higbie and Danckwerts VII.5 Mass transfer with homogeneous irreversible first order reaction - Penetration models - Stagnant film model - General conclusion on mass transfer with homogeneous irreversible first order reaction - Applications VII.6 Mass transfer with homogeneous irreversible reaction of complex kinetics VII.7 Mass transfer with homogeneous irreversible reaction of order (1.1) with Al " 1 - Slow reaction - Fast reaction - Instantaneous reaction - General approximated solution VII.8 Mass transfer with irreversible homogeneous reaction of arbitrary kinetics with Al "1 VII.9 Mass transfer with irreversible reaction of order (1, 1) for a small Hinterland coefficient VII.10 Mass transfer with reversible homogeneous reactions VII.11 Reaction in a fluid-fluid system with simultaneous mass transfer to the non-reaction phase (desorption) VII.12 The influence of mass transfer on heterogeneous reactions - Heterogeneous reaction at an external surface - Reactions in porous solids VII.13 General criterion for absence of mass transport limitation VII.14 Heat effects in mass transfer with reaction - Mass transfer with reaction in series - Mass transfer with simultaneous reaction in a gas-liquid system - Mass transfer with simultaneous reaction in a porous pellet VII.15 Model reactors for studying mass transfer with chemical reaction in heterogeneous systems - Model reactors for gas-liquid reactions - Model reactors for liquid-liquid reactions - Model reactors for fluid-solid reactions. VII.16 Measurement techniques for mass transfer coefficients and specific contact areas in multi-phase reactors - Measurement of the specific contact area a - Measurement of the product kLa - Measurement of the product kGa - Measurement of mass transfer coefficients kL, kG VII.17 Numerical values of mass transfer coefficients and specific contact areas in multi-phase reactors - Fluid-solid reactors - Fluid-fluid (-solid) reactors References Chapter VIII Multi-phase reactors, multiple reactions VIII.1 Introduction VIII.2 Simultaneous mass transfer of two reactants A and A' with independent parallel reactions A P and A' X (Type I Selectivity) - Mass transfer and reaction in series - Mass transfer and reaction in parallel VIII.3 Mass transfer of one reactant (A) followed by two dependent parallel reactions A(+B) P A(+B,B') X (Type II Selectivity) - Mass transfer and reaction in series - Mass transfer and reaction in parallel VIII.4 Simultaneous mass transfer of two reactants (A and A') followed by dependent parallel reactions with a third reactant: A + B P, A' + B X - Complete mass transfer limitation in non-reaction phase - One reactant mass transfer limited in non-reaction phase - One reaction instantaneous - Both reactions instantaneous - No diffusion limitation of reactant originally present in reaction phase - More complex systems VIII.5 Simultaneous mass transfer of two reactants (A and A') which react with each other VIII.6 Mass transfer with consecutive reactions A P X (Type III Selectivity) - Mass transfer and reaction in series - Mass transfer and reaction in parallel VIII.7 Mass transfer with mixed consecutive parallel reactions - The system: A(1) A(2) A(2) + B(2) P(2) P(2) + B(2) X(2) - The system: A(1) A(2) A(2) + B(2) P(2) A(2) + P(2) X(2) - Complex systems References Chapter IX Heat effects in multi-phase reactors IX.1 Gas-liquid reactors - General - Column reactors - Bubble column reactors - Agitated gas-liquid reactors IX.2 Gas-solid reactors - Single particle behaviour - Catalytic gas-solid reactors - The moving bed gas-solid reactor - Thermal stability and dynamic behaviour of gas solid reactors IX.3 Gas-liquid-solid reactors References Chapter X The optimization of chemical reactors X.1 The object and means of optimization - The objective function - The optimization variables - Relation between technical and economic optima X.2 Optimization by means of temperature - The optimization of exothermic equilibrium reactions - Temperature optimization with complex reaction systems X.3 Some mathematical methods of optimization - Geometric programming - The Lagrange multiplier technique - Numerical search routines - Dynamic programming Pontryagin's maximum principle References Author index Subject Index

International physical activity questionnaire: 12-country reliability and validity

Abstract: CRAIG, C. L., A. L. MARSHALL, M. SJOSTROM, A. E. BAUMAN, M. L. BOOTH, B. E. AINSWORTH, M. PRATT, U. EKELUND, A. YNGVE, J. F. SALLIS, and P. OJA. International Physical Activity Questionnaire: 12-Country Reliability and Validity. Med. Sci. Sports Exerc., Vol. 35, No. 8, pp. 1381-1395, 2003. Background: Physical inactivity is a global concern, but diverse physical activity measures in use prevent international comparisons. The International Physical Activity Questionnaire (IPAQ) was developed as an instrument for cross-national monitoring of physical activity and inactivity. Methods: Between 1997 and 1998, an International Consensus Group developed four long and four short forms of the IPAQ instruments (administered by telephone interview or self-administration, with two alternate reference periods, either the "last 7 d" or a "usual week" of recalled physical activity). During 2000, 14 centers from 12 countries collected reliability and/or validity data on at least two of the eight IPAQ instruments. Test-retest repeatability was assessed within the same week. Concurrent (inter-method) validity was assessed at the same administration, and criterion IPAQ validity was assessed against the CSA (now MTI) accelerometer. Spearman's correlation coefficients are reported, based on the total reported physical activity. Results: Overall, the IPAQ questionnaires produced repeatable data (Spearman's clustered around 0.8), with comparable data from short and long forms. Criterion validity had a median of about 0.30, which was comparable to most other self-report validation studies. The "usual week" and "last 7 d" reference periods performed similarly, and the reliability of telephone administration was similar to the self-administered mode. Conclusions: The IPAQ instruments have acceptable measurement properties, at least as good as other established self-reports. Considering the diverse samples in this study, IPAQ has reasonable measurement properties for monitoring population levels of physical activity among 18- to 65-yr-old adults in diverse settings. The short IPAQ form "last 7 d recall" is recommended for national monitoring and the long form for research requiring more detailed assessment. Key Words: MEASUREMENT, SURVEILLANCE, EPIDEMIOLOGY

Standards of Medical Care in Diabetes

Abstract: XI. STRATEGIES FOR IMPROVING DIABETES CARE D iabetes is a chronic illness that requires continuing medical care and patient self-management education to prevent acute complications and to reduce the risk of long-term complications. Diabetes care is complex and requires that many issues, beyond glycemic control, be addressed. A large body of evidence exists that supports a range of interventions to improve diabetes outcomes. These standards of care are intended to provide clinicians, patients, researchers, payors, and other interested individuals with the components of diabetes care, treatment goals, and tools to evaluate the quality of care. While individual preferences, comorbidities, and other patient factors may require modification of goals, targets that are desirable for most patients with diabetes are provided. These standards are not intended to preclude more extensive evaluation and management of the patient by other specialists as needed. For more detailed information, refer to Bode (Ed.): Medical Management of Type 1 Diabetes (1), Burant (Ed): Medical Management of Type 2 Diabetes (2), and Klingensmith (Ed): Intensive Diabetes Management (3). The recommendations included are diagnostic and therapeutic actions that are known or believed to favorably affect health outcomes of patients with diabetes. A grading system (Table 1), developed by the American Diabetes Association (ADA) and modeled after existing methods, was utilized to clarify and codify the evidence that forms the basis for the recommendations. The level of evidence that supports each recommendation is listed after each recommendation using the letters A, B, C, or E.

Physical Activity and Public Health Updated Recommendation for Adults From the American College of Sports Medicine and the American Heart Association

Abstract: Summary—In 1995 the American College of Sports Medicine and the Centers for Disease Control and Prevention published national guidelines on Physical Activity and Public Health The Committee on Exercise and Cardiac Rehabilitation of the American Heart Association endorsed and supported these recommendations The purpose of the present report is to update and clarify the 1995 recommendations on the types and amounts of physical activity needed by healthy adults to improve and maintain health Development of this document was by an expert panel of scientists, including physicians, epidemiologists, exercise scientists, and public health specialists This panel reviewed advances in pertinent physiologic, epidemiologic, and clinical scientific data, including primary research articles and reviews published since the original recommendation was issued in 1995 Issues considered by the panel included new scientific evidence relating physical activity to health, physical activity recommendations by various organizations in the interim, and communications issues Key points related to updating the physical activity recommendation were outlined and writing groups were formed A draft manuscript was prepared and circulated for review to the expert panel as well as to outside experts Comments were integrated into the final recommendation Primary Recommendation—To promote and maintain health, all healthy adults aged 18 to 65 yr need moderate-intensity aerobic (endurance) physical activity for a minimum of 30 min on five days each week or vigorous-intensity aerobic physical activity for a minimum of 20 min on three days each week [I (A)] Combinations of moderate- and vigorous-intensity activity can be performed to meet this recommendation [IIa (B)] For example, a person can meet the recommendation by walking briskly for 30 min twice during the week and then jogging for 20 min on two other days Moderate-intensity aerobic activity, which is generally equivalent to a brisk walk and noticeably accelerates the heart rate, can be accumulated toward the 30-min minimum by performing bouts each lasting 10 or more minutes [I (B)] Vigorous-intensity activity is exemplified by jogging, and causes rapid breathing and a substantial increase in heart rate In addition, every adult should perform activities that maintain or increase muscular strength and endurance a minimum of two days each week [IIa (A)] Because of the dose-response relation between physical activity and health, persons who wish to further improve their personal fitness, reduce their risk for chronic diseases and disabilities or prevent unhealthy weight gain may benefit by exceeding the minimum recommended amounts of physical activity [I (A)] (Circulation 2007;116:1081-1093)

Exercise and physical activity for older adults

Abstract: The purpose of this Position Stand is to provide an overview of issues critical to understanding the importance of exercise and physical activity in older adult populations. The Position Stand is divided into three sections: Section 1 briefly reviews the structural and functional changes that characterize normal human aging, Section 2 considers the extent to which exercise and physical activity can influence the aging process, and Section 3 summarizes the benefits of both long-term exercise and physical activity and shorter-duration exercise programs on health and functional capacity. Although no amount of physical activity can stop the biological aging process, there is evidence that regular exercise can minimize the physiological effects of an otherwise sedentary lifestyle and increase active life expectancy by limiting the development and progression of chronic disease and disabling conditions. There is also emerging evidence for significant psychological and cognitive benefits accruing from regular exercise participation by older adults. Ideally, exercise prescription for older adults should include aerobic exercise, muscle strengthening exercises, and flexibility exercises. The evidence reviewed in this Position Stand is generally consistent with prior American College of Sports Medicine statements on the types and amounts of physical activity recommended for older adults as well as the recently published 2008 Physical Activity Guidelines for Americans. All older adults should engage in regular physical activity and avoid an inactive lifestyle.