Estimating energy requirements in obese and non-obese patients: a survey of dietetic practice in the United Kingdom

Abstract

Background: Many methods are available to determine energy requirements; however, all have limitations and their use in clinical practice is variable and not universally understood (Green et al., 2008). Estimating energy requirements of obese patients is particularly problematic (Breen et al., 2004). The aim of the current survey was to investigate current practice in the estimation of energy requirements in an obese and non-obese patient in a large cohort of UK dietitians. Methods: A cross-sectional web-based survey of UK Registered Dietitians was performed. An opportunistic sample was recruited via e-mail providing a link to the survey (contact details openly available on NHS Trust websites) and through the online newsletter of the British Dietetic Association. The anonymous online questionnaire was developed specifically for this project by dietitians working in nutrition support and was based on the structure of two previous surveys (Reeves et al., 2003; Green et al., 2008). Respondents were asked to estimate energy requirements using two theoretical case scenarios: one patient was obese and one was not. Demographic information including training, experience and job role were also collected. Data were analysed using SPSS, version 18 (SPSS Inc., Chicago, IL, USA); chi-squared tests for independence, Kruskal–Wallis and Mann–Whitney U-tests were performed. Results: Six hundred and seventy-two responses were received from all areas of the UK. For the non-obese patient, prediction equations and adjustment for metabolic stress and physical activity was used by 90.3% of respondents. The median estimated energy requirement was 8704 kJ (2079 kcal) [interquartile range (IQR): 8122–9295 kJ (1940–2220 kcal)] day−1. The median target volume of feed prescribed was 2000 (IQR: 2000–2000) mL day−1; significantly less than estimated requirements (P 10 years. Respondents used a significantly lower kcal kg−1 for the obese patient (25 (IQR: 20–30) kcal kg−1) compared to the non-obese patient (30 (IQR: 25–35) kcal kg−1) (P = 0.014). Discussion: This survey found the majority of respondents used prediction equations to estimate energy requirements which is similar to the results of previous surveys (Green et al., 2008). Many more respondents used BMR alone in the obese case study compared to the non-obese case study, which may suggest respondents are following published guidelines (Todorovic et al., 2004). This study found that estimated energy requirement using kcal kg−1 method was significantly lower compared to the equations method, which supports results from other studies that have found that kcal kg−1 method tend to underestimate true energy requirements (Reeves et al., 2003). Although many respondents calculated energy requirements above or below 2000 kcal day−1, a large number prescribed 2000 mL day−1 of enteral feed (a significant reduction). Feed prescribed clustered around 500 mL increment points, which may suggest that clinicians choose to feed to the ‘nearest bag’ despite this differing to calculated requirements. This poses the question: if the clinician is to feed to the ‘nearest bag’, is it essential that feeding is tailored to an individual's estimated requirements or could a number of ‘standard’ regimens suffice? Conclusions: The methods used to estimate energy requirements in clinical practice are highly variable, particularly with regards to the treatment of obese patients.