Nutritional status and body habitus are closely related throughout the lifespan and generally follow a standard trajectory. Both can be modified, primarily due to the life style of an individual, and fluctuations in body weight are frequently observed in the modern era. These mostly occur in cycles of weight gain, followed by voluntary weight loss because of aesthetic reasons. In the elderly and patients with chronic disease, however, weight loss generally is not a good sign; in fact, the contrary is true and the so-called obesity paradox with reverse epidemiology is an established term [1–4].

Although weight loss is common and frequently reported in clinical medicine, there is a considerable diversity in terminology as used in clinical practice and even among researchers to describe the patient body habitus and nutritional status [5]. It is therefore not surprising that many misbeliefs and misconceptions are present in the field. Seen from the evolutionary perspective, a default presumption is that true beliefs are adaptive and misbeliefs maladaptive [6]. The question therefore is, why people make exceptions to true beliefs and why misbeliefs are present and even so frequent. Generally, there are two types of misbelief: they can be due to a breakdown in the normal functioning of the belief formation system (e. g. delusions) or they can arise due to incomplete or inaccurate information (but with a normal course of the belief formation system). The latter can definitely be observed in the literature and in clinical practice [1, 5, 7]. This can in part be due to lack of gold standards for many definitions in the fields of nutrition, body composition and body habitus as criteria are often descriptive and arbitrary. Terms such as “anorexia”, “malnutrition/undernutrition”, “sarcopenia”, “cachexia” and even “frailty” are commonly used as synonyms, even by the experts in the field [5]. One can argue that all are mostly associated with weight change but this is not necessarily true, e. g. in sarcopenia; some of them look beyond nutrition itself as they also consider patient performance (frailty, sarcopenia) [2, 8]. Evidently, there is some overlap between them and some per definition coexist (malnutrition and cachexia) in the same patient. There are pathophysiological grounds for this as several mechanisms are shared and perpetuate each other [7, 9–11]. It is therefore of utmost importance that uniform terminology is used for research and clinical practice and that comparable methods are used to assess the patient’s nutritional status and performance (Fig. 1). In this issue of the Journal, several papers have touched on these issues and they elegantly demonstrate that significant inconsistency persists in the field, both in general terms and in geriatrics [12–14]. This is why the recent publications of the European Society of Parenteral and Enteral Nutrition (ESPEN) are so important to minimize or even abolish the heterogeneity in the field [15, 16]. Once such a consensus is reached, research activity and yield across the field should increase, as should the investigator and industry-driven research. From the clinical point of view, it is also important to evaluate nutritional risks so patient risks can be stratified better and managed if evidence-based therapy exists [17–23]. Some nutritional problems can easily be treated and those are mostly linked to malnutrition/undernutrition and micronutrient abnormalities. As nutritional issues commonly go hand in hand with chronic disease, certain caveats regarding the pharmacotherapy exist. Drug pharmacokinetics depend on body composition and organ function that can be altered due to nutritional disorders with or without chronic disease thus caution or referral to a clinical pharmacist should be considered [24, 25].

Fig. 1
figure 1

Nutritional evaluation and nutritional profiles

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In pursuit of better patient assessment (Fig. 1), existing evidence from large epidemiological databases should be examined in detail. The nutritionDay, a multinational cross-sectional snapshot survey, definitely holds a wealth of information that is relevant and can identify processes that can easily be addressed [26, 27]. Generally, a golden hour for nutritional assessment is during hospitalization when patients are available for several days and are more susceptible to potential interventions. The real world is certainly not meeting this challenge as such services could be delivered in less than half of the participating hospitals in the nutritionDay survey. Nutritional status assessment and risk stratification are evidently insufficient but area necessary step to appreciate the magnitude of the problem. The next and maybe even greater challenge is the sustainable system to deliver appropriate management if evidence is available. The latter is still largely lacking thus sufficiently powered and well-designed interventional studies using nutritional support are crucial to close the loop [28].