» Listings for July 2016

1. Calculating energy balance

   Posted on 11:00am Wednesday 20th Jul 2016

   Unless you have been living off-planet for the last 20 years or so, you will be aware that obesity prevalence has risen sharply all across the world. We now view obesity as a greater threat to health than undernutrition and it is implicated in the development of heart disease, type-2 diabetes, several types of cancer and a wide spectrum of other health problems.

   The standard approach to tackling obesity in individuals is to introduce an energy restricted diet to induce a loss of fat mass. To do this we depend upon personalised calculations of actual energy requirements so that we can ensure that the restricted diet delivers energy below requirement, but whilst still maintaining physiological functions.

   Determining energy requirement can be done in a variety of ways, but mostly clinicians rely on predictive equations to determine energy expenditure. These include the Mifflin-St Jeor, Henry, Scholefield, Harris-Benedict, Owen and Katch-McArdle equations. These generally take into account height, weight, age and physical activity levels. All of the equations make assumptions about the individual and are prone to error associated with ethnicity, age and, most importantly, the BMI of the subject. Accuracy tends to be better in lean individuals and the equations lose accuracy with overweight and obesity. Given the importance of estimating energy requirements in order to achieve weight loss in obese individuals, there is a need to identify which equations are most useful for this population.

   Angela Madden (University of Hertfordshire) and colleagues carried out two systematic reviews of the literature (http://onlinelibrary.wiley.com/doi/10.1111/jhn.12355/full ) to consider which predictive equations were the most accurate and precise in estimating resting energy expenditure (REE) and total energy expenditure (TEE) in healthy obese adults. They considered 25 studies which were able to directly compare calculated REE and TEE with measurements made using doubly-labelled water and other techniques. The reviews showed that none of the available equations for measuring TEE were accurate in obese people and as such they cannot be recommended for this purpose.

   Importantly the reviews found that there was considerable variation in accuracy of equations to measure REE, with BMI as the main determinant of that accuracy. The important outcome of the work is that we have some guidance on which equation to choose based upon the body composition of the individual.

   BMI subgroup	Most precise equation	Precision (%)
   >25 kg/m2	Mifflin	65.9
   >30 kg/m2	Mifflin	65.8
   30-39.99 kg/m2	Livingston	75.0
   >40 kg/m2	Mifflin	76.3

   Although a single equation for all individuals is not ideal, Madden and colleagues recognised that in clinical practice, having just one equation for all obese people has greater utility. On this basis they suggest that the Mifflin equation is most appropriate for patients with BMI>25 kg/m².

2. Why do we do research in nutritional sciences?

   Posted on 11:00am Wednesday 6th Jul 2016

   I have a number of different roles as an academic working in nutritional sciences. On the one hand I am responsible for teaching across a number of degree subjects (nutrition, dietetics, nutrition and food science) and on the other I am an active researcher with an interest in pregnancy, infancy and childhood nutrition. On top of these roles I do work outside my University of Nottingham contract as the Editor-in-Chief of the Journal of Human Nutrition and Dietetics.

   Academic journals fill a very important niche, and over a short period of time, their roles have changed. In these modern times of instant information, the journals are far distant from being magazines for only the learned to browse and now act as repositories for research findings, to be searched out by other researchers, students, policy makers and practitioners according to their need.

   As an editor of an academic journal it therefore seems natural, particularly on a horrible, rainy, depressing day, to ponder the nature of why we do research in this discipline. There are of course many reasons, some noble and altruistic, but many of which are quite mundane and unglamorous and perhaps not what you would expect. For some researchers the act of research is driven by the simple need to pay the bills and keep a roof over their heads. Universities value and indeed profit from the research achievements of their academic staff. This inevitably pressurises staff to perform research activities in order to achieve or maintain academic tenure or attain promotion. This is not really the motivation that the general public believes drives the earnest men and women in white coats, but is an important truth. If you see your university lecturers looking a bit tense, remember that there will be people up above pushing them to deliver excellence.

   I have started on a negative there though and there are other reasons why we do research. At the end of the day, I do it simply because I love it. Most, if not all, of my colleagues feel the same. It is the part of my job that gets me up in the morning. To discover something new is the greatest buzz imaginable and to have that work published is an immense pleasure. To put myself at risk of being trite, I'd say if fulfills that basic human instinct to find out, to make a difference and make the world a better place.

   For those of us in the nutrition and dietetics field there are other drivers. Research gives us the ability to formulate the critical knowledge and evidence base that allows public health interventions, dietetic treatment, behavior change strategies, disease prevention, pharmacological treatment and so many other innovations to happen. The nutrition research community is varied. Some of us are practical people, searching for solutions to specific problems. For example, how might we design a school-based intervention to prevent obesity in childhood? Others are less applied and want to understand how things work, to pull apart the systems of the body, uncovering ever-increasing levels of complexity. For example, how do micronutrient influence methylation of DNA, expression of genes and cell proliferation during fetal development?

   Research is the oil that drives the wheels of progress. The work done today will be the basis of the health measures of the 2020s and 2030s. This point cannot be overstated and as a still relatively young man (50ish at any rate) I am amazed by how much of the routine established knowledge of today would have been fantasy in my undergraduate days. Things that we do routinely, for example sequencing genomes or measuring biomarkers of disease, were major challenges or impossible 20 years ago.

   Nutrition is a relatively young science, but sadly has attracted more than its fair share of problems. Bad science, flawed methods, conflated results, incorrect conclusions abound and form a nasty mix with the occasional bit of fraud and fakery and the plethora of quacks out to make a fast buck. Nutrition is however fundamental to understanding of health and disease. The church is broad and the abundance of literature vast. What nutrition and dietetics now needs is a robust underpinning, so that the potential to make a real difference to disease prevention, management and treatment can be delivered. The next generation of nutrition researchers is at university now just waiting for the excitement of novel discovery to sweep them up and carry them along this important path.