The Nutrition Society Medical Lecture. Obesity: from molecules to man

Global impact on human obesity - A robust non-linear panel data analysis

Purpose: Recent studies in economics showed that humans are bounded rational. This being consumers, they are not perfect judges of what matters for the standard of living. While with a marked increase in economic and social wellbeing, there is a consistent rise in obesity levels, especially in the developed world. Thus, this study intends to explore the empirical and socio-economic antecedents of human obesity across countries using six global indexes. Methods: This study used the data of 40 countries between 1975 to 2018 and used the Panel FGLS Regression with the quadratic specification. Findings: The results showed that health and food indicators increase global human obesity, environment and education indicators decrease global human obesity, and economic and social indicators follow an inverted U-shaped pattern in affecting global human obesity. Originality: Previous studies have used infant mortality and life expectancy as the major health indicator in determining the standard of living while overlooking global human obesity as a major deterrent to welfare. This study has provided a holistic assessment of the causes of obesity in global contexts.

Obesity: considerations about etiology, metabolism, and the use of experimental models

Studies have been conducted in order to identify the main factors that contribute to the development of obesity. The role of genetics has also been extensively studied. However, the substantial augmentation of obesity prevalence in the last 20 years cannot be justified only by genetic alterations that, theoretically, would have occurred in such a short time. Thus, the difference in obesity prevalence in various population groups is also related to environmental factors, especially diet and the reduction of physical activity. These aspects, interacting or not with genetic factors, could explain the excess of body fat in large proportions worldwide. This article will focus on positive energy balance, high-fat diet, alteration in appetite control hormones, insulin resistance, amino acids metabolism, and the limitation of the experimental models to address this complex issue.

S38151 [p-guanidinobenzoyl-[Des-Gly(10)]-MCH(7-17)] is a potent and selective antagonist at the MCH(1) receptor and has anti-feeding properties in vivo

Structure-activity relationships studies have established the minimal sequence of melanin-concentrating hormone (MCH) that retains full agonist potency at the MCH(1), to be the dodecapeptide MCH(6-17). The alpha-amino function is not required for activity since arginine(6) can be replaced by p-guanidinobenzoyl, further improving activity. We report that the deletion of glycine in this short potent agonist (EC(50) 3.4nM) turns it into a potent and new MCH(1) antagonist (S38151, K(B) 4.3nM in the [(35)S]-GTPgammaS binding assay), which is selective versus MCH(2). A compared Ala-scan of the agonist and antagonist sequences reveals major differences in the residues that are mandatory for affinity, including arginine(11) and tyrosine(13) for the agonist and leucine(9) for the antagonist, whereas methionine(8) was necessary for both agonist and antagonist activities. A complete molecular study of the antagonist behavior is described in the present report, with a particular focus on the description of several analogues, attempting to find structure-activity relationships. Finally, S38151 antagonizes food intake when injected intra-cerebroventricularly in the rat. This is in agreement with the in vitro data and with our previous demonstration of a good correlation between in vitro and in vivo data on MCH(1) agonists.

Super CitriMax (HCA-SX) attenuates increases in oxidative stress, inflammation, insulin resistance, and body weight in developing obese Zucker rats

Super CitriMax (HCA-SX) is a novel calcium/potassium salt of (-)-hydroxycitric acid extracted from the dried fruit rind of the plant Garcinia cambogia, and commonly consumed as weight loss dietary supplement. In the present study, we investigated the effect of HCA-SX on inflammation, oxidative stress and insulin resistance in developing obese Zucker rats, an animal model of type II diabetes associated with inflammation and oxidative stress. Male Zucker rats (5-week old) were supplemented with vehicle (control) and HCA-SX in drinking water for 7 weeks. Oxidative stress markers, including malondialdehyde (MDA), protein carbonyl (DNPH), and protein tyrosine nitration (tyr-NO(2)) were measured in the liver and kidney tissues using biochemical and immunoblotting techniques. Compared to controls, the levels of MDA, DNPH and tyr-NO(2) were lower in the liver and kidney of HCA-SX-treated animals. Furthermore, the levels of C-reactive protein and interleukin-6, markers of inflammation measured by ELISA, were lower in the plasma of HCA-SX-supplemented animals compared to controls, as were levels of fasting plasma insulin, glucose, and triglycerides. Interestingly, insulin resistance did not develop in HCA-SX-supplemented rats. Food-intake and body weight gain was also lower in rats supplemented with HCA-SX compared to their control counterparts. These results suggest that HCA-SX supplementation in obese Zucker rats reduces food-intake, body weight gain, and also attenuates the increases in inflammation, oxidative stress, and insulin resistance observed in untreated animals. Therefore, HCA-SX may be used as an intervention to overcome obesity-related complications, including inflammation, oxidative stress, and insulin resistance.

Fat nation: deciphering the distinctive geographies of obesity in England

Much attention is focused on obesity by both the media and by public health. As a health risk, obesity is recognised as a contributing factor to numerous health problems. Recent evidence points to a growth in levels of obesity in many countries and particular attention is usually given to rising levels of obesity among younger people. England is no exception to these generalisations with recent studies revealing a clear geography to what has been termed an 'obesity epidemic.' This paper examines the complexities inherent in the geography of adult obesity in England. Existing knowledge about the sub-national geography of obesity is examined and assessed. Multilevel synthetic estimation is then used to construct an age-sex-ethnicity disaggregated geography of obesity. These differing geographies are compared and contrasted with pre-existing findings and explored at multiple scales. A complex picture of the geography of obesity in England is revealed.

Apparent low frequency of undernutrition in Dublin hospital in-patients: should we review the anthropometric thresholds for clinical practice?

Protein–energy undernutrition, or the possibility of its development, has been documented to occur frequently in patients on admission to hospital. Deterioration in nutritional status is known to occur in hospital. In a prospective study of 594 sequential hospital admissions, we aimed to assess the prevalence of undernutrition among patients on admission to two acute teaching hospitals in Dublin, Republic of Ireland using the widely-accepted anthropometric criteria applied in a large study from Dundee, Scotland, UK () and to determine changes in nutritional status in hospital. The mean prevalence of undernutrition (11 %) was considerably lower than was reported from Dundee (40 %). Unintentional weight loss before admission and functional impairment on admission occurred to a similar extent in both centres. Weight loss in hospital occurred in the same proportion of patients, but less frequently among those undernourished on admission to hospital, in Dublin compared with Dundee. The patients found to be undernourished on admission in this study had a mortality rate in hospital (6·5 %) over three times that of the adequately nourished group (2 %). The magnitude of the difference in prevalence of undernutrition between the two centres cannot be explained by ethnicity, case-mix or age distribution. With the secular increase in BMI in the population, the thresholds for classifying patients as undernourished or at risk of nutritional deterioration may need to be reviewed. For clinical use, recent weight loss and functional status may be more appropriate variables to use in the evaluation of nutritional status on admission to hospital.

Some mathematical and technical issues in the measurement and interpretation of open-circuit indirect calorimetry in small animals

Indirect calorimetry is increasingly used to investigate why compounds or genetic manipulations affect body weight or composition in small animals. This review introduces the principles of indirect (primarily open-circuit) calorimetry and explains some common misunderstandings. It is not widely understood that in open-circuit systems in which carbon dioxide (CO2) is not removed from the air leaving the respiratory chamber, measurement of airflow out of the chamber and its oxygen (O2) content paradoxically allows a more reliable estimate of energy expenditure (EE) than of O2 consumption. If the CO2 content of the exiting air is also measured, both O2 consumption and CO2 production, and hence respiratory quotient (RQ), can be calculated. Respiratory quotient coupled with nitrogen excretion allows the calculation of the relative combustion of the macronutrients only if measurements are over a period where interconversions of macronutrients that alter their pool sizes can be ignored. Changes in rates of O2 consumption and CO2 production are not instantly reflected in changes in the concentrations of O2 and CO2 in the air leaving the respiratory chamber. Consequently, unless air-flow is high and chamber size is small, or rates of change of O2 and CO2 concentrations are included in the calculations, maxima and minima are underestimated and will appear later than their real times. It is widely appreciated that bigger animals with more body tissue will expend more energy than smaller animals. A major issue is how to compare animals correcting for such differences in body size. Comparison of the EE or O2 consumption per gram body weight of lean and obese animals is misleading because tissues vary in their energy requirements or in how they influence EE in other ways. Moreover, the contribution of fat to EE is lower than that of lean tissue. Use of metabolic mass for normalisation, based on interspecific scaling exponents (0.75 or 0.66), is similarly flawed. It is best to use analysis of covariance to determine the relationship of EE to body mass or fat-free mass within each group, and then test whether this relationship differs between groups.

High dose of Garcinia cambogia is effective in suppressing fat accumulation in developing male Zucker obese rats, but highly toxic to the testis

We investigated the ability of Garcinia cambogia extract containing (-)-hydroxycitric acid (HCA) to suppress body fat accumulation in developing male Zucker obese (fa/fa) rats. We also examined histopathologically the safety of its high doses. Diets containing different levels of HCA (0, 10, 51, 102 and 154 mmol/kg diet) were fed to 6-week-old rats for 92 or 93 days. Each diet group was pair-fed to the 154 mmol HCA/kg diet group. Epididymal fat accumulation and histopathological changes in tissues were observed. The highest dose of HCA-containing Garcinia cambogia (154 mmol HCA/kg diet) showed significant suppression of epididymal fat accumulation in developing male Zucker obese rats, compared with the other groups. However, the diets containing 102 mmol HCA/kg diet and higher (778 and 1244 mg HCA/kg BW/d, respectively) caused potent testicular atrophy and toxicity, whereas diets containing 51 mmol HCA/kg diet (389 mg HCA/kg BW/d) or less did not. Accordingly, 51 mmol HCA/kg diet (389 mg HCA/kg BW/d) was deemed to be the no observed adverse effect level (NOAEL).

Pregnancy weight gain from 1960s to 2000 in Finland

OBJECTIVE

To study secular trends in average pregnancy weight gain between the 1960s and 2000 in Finland, and whether the changes were related to body mass index (BMI), age or parity.

DESIGN

Three cross-sectional population surveys in Finland from three different periods.

SUBJECTS

Women who were pregnant in Helsinki in the period 1954-1963 (N=2262), or in Tampere in the period 1985-1986 (N=1771) or in 2000-2001 (N=371).

MEASUREMENTS

Pregnancy weight gain was determined from self-reported prepregnancy weight and measured weights during pregnancy.

RESULTS

The mean age and prepregnancy BMI of all pregnant women increased between the 1960s and 2000 (from 26.5 to 29.6 y, from 21.9 to 23.7 kg/m(2)). The mean pregnancy weight gain, adjusted for mother's age, BMI and parity, increased from the 1960s to the mid-1980s from 13.2 to 14.3 kg. The increase was observed in all BMI categories. Compared to the 1960 cohort, the proportion of women with a pregnancy weight gain of less than 10 kg decreased and the proportion of women with a weight gain of 15 kg or more increased in the 1980 cohort. After the mid-1980s, the average pregnancy weight gain remained the same. In all cohorts, overweight women gained least weight during pregnancy, but age and parity were not associated with BMI and parity-/age-adjusted pregnancy weight gain. Higher pregnancy weight gain was associated with higher mean child's birthweight and higher proportion of high birthweight babies in all cohorts.

CONCLUSIONS

The mean pregnancy weight gain has increased since the 1960s, which may be of importance with regard to the development of later obesity. Factors other than changes in prepregnancy BMI, age and parity must explain the increased pregnancy weight gain over time.

AH. Obesidade: hábitos nutricionais, sedentarismo e resistência à insulina

A obesidade já é considerada uma epidemia mundial independente de condições econômicas e sociais. O risco aumentado de mortalidade e morbidade associado à obesidade tem sido alvo de muitos estudos que tentam elucidar os aspectos da síndrome X como conseqüência da obesidade. Esta síndrome é caracterizada por algumas doenças metabólicas, como resistência à insulina, hipertensão, dislipidemia. Está bem estabelecido que fatores genéticos têm influência neste aumento dos casos de obesidade. No entanto, o aumento significativo nos casos de obesidade nos últimos 20 anos dificilmente poderia ser explicado por mudanças genéticas que tenham ocorrido neste espaço de tempo. Sendo assim, os principais fatores envolvidos no desenvolvimento da obesidade têm sido relacionados com fatores ambientais, como ingestão alimentar inadequada e redução no gasto calórico diário. Na tentativa de desencadear obesidade em animais e permitir o estudo desta doença de maneira mais completa, diversos modelos experimentais de obesidade têm sido desenvolvidos. Ainda que não possam ser considerados exatamente iguais aos modelos de obesidade humana, são de grande valor no estudo dos diversos aspectos que contribuem para este excessivo acúmulo de adiposidade e suas conseqüências.

11Beta-hydroxysteroid dehydrogenase type 1 in differentiating omental human preadipocytes: from de-activation to generation of cortisol

In humans, glucocorticoids are important regulators of adipose tissue distribution and function but circulating cortisol concentrations are normal in most patients with obesity. However, intracellular glucocorticoid levels can be modified by a microsomal enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) expressed mainly in the liver and adipose tissue. Locally generated cortisol within human adipose tissue can induce preadipocyte differentiation, but the relationship between 11beta-HSD1 expression and adipogenesis is unknown. Our present study has shown that in intact, undifferentiated omental (OM) but not subcutaneous (SC) preadipocytes, 11beta-HSD1 acts primarily as a dehydrogenase inactivating cortisol to cortisone. When preadipocytes become "committed" to adipocyte differentiation, oxo-reductase activity predominates generating cortisol. Since glucocorticoids are not only essential for OM preadipocyte differentiation but also inhibit cell proliferation, we postulate that 11beta-HSD1 dehydrogenase activity in "uncommitted" OM preadipocytes may provide an autocrine mechanism to protect preadipocytes from differentiation, in turn facilitating their proliferation. Once early differentiation is initiated, a "switch" to 11beta-HSD1 oxo-reductase activity generates cortisol, thus promoting adipogenesis. The differences in set-point of 11beta-HSD1 activity between OM and SC human adipose tissue may be an important factor in the pathogenesis of visceral obesity.

Lessons in obesity from transgenic animals

Many genetic manipulations have created models of obesity, leanness or resistance to dietary obesity in mice, often providing insights into molecular mechanisms that affect energy balance, and new targets for anti-obesity drugs. Since many genes can affect energy balance in mice, polymorphisms in many genes may also contribute to obesity in humans, and there may be many causes of primary leptin resistance. Secondary leptin resistance (due to high leptin levels) can be investigated by combining the ob mutation with other obesity genes. Some transgenic mice have failed to display the expected phenotype, or have even been obese when leanness was expected. Compensatory changes in the expression of other genes during development, or opposing influences of the gene on energy balance, especially in global knockout mice, may offer explanations for such findings. Obesity has been separated from insulin resistance in some transgenic strains, providing new insights into the mechanisms that usually link these phenotypes. It has also been shown that in some transgenic mice, obesity develops without hyperphagia, or leanness without hypophagia, demonstrating that generalised physiological explanations for obesity in individual humans may be inappropriate. Possibly the most important transgenic model of obesity so far created is the Type 1 11beta-hydroxysteroid dehydrogenase over-expressing mouse, since this models the metabolic syndrome in humans. The perspectives into obesity offered by transgenic mouse models should assist clinical researchers in the design and interpretation of their studies in human obesity.

Leptin: a review of its peripheral actions and interactions

Following the discovery of leptin in 1994, the scientific and clinical communities have held great hope that manipulation of the leptin axis may lead to the successful treatment of obesity. This hope is not yet dashed; however the role of the leptin axis is now being shown to be ever more complex than was first envisaged. It is now well established that leptin interacts with pathways in the central nervous system and through direct peripheral mechanisms. In this review, we consider the tissues in which leptin is synthesized and the mechanisms which mediate leptin synthesis, the structure of leptin and the knowledge gained from cloning leptin genes in aiding our understanding of the role of leptin in the periphery. The discoveries of expression of leptin receptor isotypes in a wide range of tissues in the body have encouraged investigation of leptin interactions in the periphery. Many of these interactions appear to be direct, however many are also centrally mediated. Discovery of the relative importance of the centrally mediated and peripheral interactions of leptin under different physiological states and the variations between species is beginning to show the complexity of the leptin axis. Leptin appears to have a range of roles as a growth factor in a range of cell types: as be a mediator of energy expenditure; as a permissive factor for puberty; as a signal of metabolic status and modulation between the foetus and the maternal metabolism; and perhaps importantly in all of these interactions, to also interact with other hormonal mediators and regulators of energy status and metabolism such as insulin, glucagon, the insulin-like growth factors, growth hormone and glucocorticoids. Surely, more interactions are yet to be discovered. Leptin appears to act as an endocrine and a paracrine factor and perhaps also as an autocrine factor. Although the complexity of the leptin axis indicates that it is unlikely that effective treatments for obesity will be simply derived, our improving knowledge and understanding of these complex interactions may point the way to the underlying physiology which predisposes some individuals to apparently unregulated weight gain.

Hydroxycitrate has long-term effects on feeding behavior, body weight regain and metabolism after body weight loss in male rats

We examined the long-term effect of hydroxycitrate (HCA) on food intake, meal patterns, body weight regain and energy conversion ratio as well as on different blood and liver variables in rats after substantial body weight loss. Rats were fed a 1% (g/100 g) fat diet (81% carbohydrate, 10% protein, 1% fat) or a 12% (g/100 g) fat diet (76% carbohydrate, 9% protein, 12% fat) in two separate experiments. Supplementing both diets with 3% HCA after 10 d of restrictive feeding reduced body weight regain over the whole subsequent period of ad libitum consumption (22 d) and decreased the energy conversion ratio [body weight regain (g)/energy intake (MJ)] at the end of the experiment. Only in rats fed the 12% fat diet, HCA had a long-term suppression of food intake. The anorectic effect occurred predominately during the light phase, and was due mainly to a reduction in numbers of meals. In rats fed the 12% fat diet, HCA had no effect on plasma beta-hydroxybutyrate (BHB), but reduced plasma triacylglycerol and increased liver fat concentration. In rats fed the 1% fat diet, HCA did not affect any metabolic variable examined. Thus, the suppressive effect of HCA on body weight regain, which was maintained for at least 3 wk, appears to be independent of the dietary fat content. Yet, the fat content of the diet seemed to be important for the long-term suppressive effect of HCA on feeding. The fact that HCA did not change plasma BHB concentration does not support a role for increased hepatic fatty acid oxidation in the anorectic effect of HCA.

A switch in dehydrogenase to reductase activity of 11 beta-hydroxysteroid dehydrogenase type 1 upon differentiation of human omental adipose stromal cells

As exemplified in patients with Cushing's syndrome, glucocorticoids play an important role in regulating adipose tissue distribution and function, but circulating cortisol concentrations are normal in most patients with obesity. However, human omental adipose stromal cells (ASCs) can generate glucocorticoid locally through the expression of the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) type 1 (11 beta-HSD1), which, in intact cells, has been considered to be an oxoreductase, converting inactive cortisone (E) to cortisol (F). Locally produced F can induce ASC differentiation, but the relationship between 11 beta-HSD1 expression and adipocyte differentiation is unknown. Primary cultures of paired omental (om) and sc ASC and adipocytes were prepared from 17 patients undergoing elective abdominal surgery and cultured for up to 14 d. Expression and activity of 11 beta-HSD isozymes were analyzed together with early (lipoprotein lipase) and terminal (glycerol 3 phosphate dehydrogenase) markers of adipocyte differentiation. On d 1 of culture, 11 beta-HSD1 activity in intact om ASCs exceeded oxoreductase activity in every patient (78.9 +/- 24.9 vs. 15.8 +/- 3.7 [mean +/- SE] pmol/mg per hour, P < 0.001), and in sc ASCs, relative activities were similar (40.6 +/- 12.2 vs. 36.9 +/- 8.8). Conversely, in freshly isolated om adipocytes, reductase activity exceeded dehydrogenase activity (23.6 +/- 1.5 vs. 6.2 +/- 0.8 pmol/mg per hour, P < 0.01). Following 14 d of culture in serum-free conditions with addition of 10 nM insulin (Ctr) or insulin with 100 nM F (+F), lipoprotein lipase/18S RNA levels increased in both the Ctr- and +F-treated ASCs, but glycerol 3 phosphate dehydrogenase increased only in the +F cultures. In both cases, however, 11 beta-HSD1 oxoreductase activity exceeded dehydrogenase activity (Ctr: 53.3 +/- 9.0 vs. 32.4 +/- 10.5, P < 0.05; +F: 65.6 +/- 15.6 vs. 37.1 +/- 11.5 pmol/mg per hour, P < 0.05), despite no significant changes in 11 beta-HSD1 mRNA levels. In sc ASCs, dehydrogenase activity was similar to reductase activity in both Ctr- and +F-treated cells. Type 2 11 beta-HSD expression was undetectable in each case. These data show that in intact, undifferentiated om ASCs, 11 beta-HSD1 acts primarily as a dehydrogenase, but in mature adipocytes oxoreductase activity predominates. Because glucocorticoids inhibit cell proliferation, we postulate that 11 beta-HSD1 activity in uncommitted ASCs may facilitate proliferation rather than differentiation. Once early differentiation is initiated, a "switch" to 11 beta-HSD1 oxoreductase activity generates F, thus promoting adipogenesis. Site-specific regulation of the set-point of 11 beta-HSD1 activity may be an important mechanism underpinning visceral obesity.

Effect of hydroxycitrate on food intake and body weight regain after a period of restrictive feeding in male rats

We examined whether dietary supplementation of hydroxycitrate (HCA), a competitive inhibitor of the extramitochondrial enzyme ATP-citrate-lyase, which inhibits lipogenesis, reduces food intake and body weight regain in rats after 10-15% weight loss. In four experiments, 24 male rats were fed restrictively (10 g/day) for 10 days and then given ad lib access to one of four different diets (HI-Suc=high sucrose; HI-Glu=high glucose; Chow=grounded standard rat chow; HI-Glu+Fat=high glucose+fat) varying in the content of fat and low molecular carbohydrates for the following 10 days. For half of the rats (n=12), the ad lib diet was supplemented with 3% (w/w) HCA. HCA reduced body weight regain with all diets except Chow. HCA also reduced food intake temporarily with three of the four tested diets. The suppressive effect of HCA on food intake was particularly strong with the HI-Glu+Fat diet (fat=24% of energy). With Diet HI-Glu and HI-Glu+Fat HCA reduced the feed conversion efficiency (cumulative body weight regain (g)/cumulative food intake (MJ)) during the 10 ad lib days, suggesting that it also increased energy expenditure. This effect seemed to be positively related to the glucose content of the diet. All in all, HCA reduced body weight regain after substantial body weight loss, and the effects are presumably linked to its inhibiting effect on lipogenesis, but the exact mechanism still has to be determined.

Changes in body mass index around menopause: a population study of Chilean woman

OBJECTIVE

To evaluate the influence of menopause and hormone replacement therapy (HRT) on weight and the effect of weight gain on coronary risk factors.

DESIGN

From 1991 to 1992 cardiovascular risk factors were assessed in 271 premenopausal women between the ages of 40 and 53 years. The women were not receiving HRT at that time. Five years later, these women were reevaluated.

RESULTS

Weight and body mass index (BMI) increased steadily with age. During the observation period there was an average increase of 4.0 kg +/- 4.6 (p < 0.0001). Women who experienced menopause and those who did not experience menopause had a similar weight increase (3.8 +/- 4.4 kg vs. 4.3 +/- 4.8, p = 0.37). Likewise, weight gain was similar in those who did or did not use HRT (nonusers, 4.3 +/- 4.6 kg; users, 3.5 +/- 3.7 kg; ex-users, 3.4 +/- 5.8 kg). At their first checkups, overweight women and obese women already had significant differences in their risk factors, including higher systolic pressure (p < 0.02), diastolic pressure (p < 0.01), glucose (p < 0.02) and triglycerides (p < 0.0001), and lower high-density lipoprotein cholesterol (p < 0.004) as compared with women of normal weight. Unexpectedly, women of normal weight who became overweight or obese during the monitoring period did not show any deterioration in their risk factors.

CONCLUSIONS

During the perimenopausal period there is a weight gain that does not seem to depend on the menopause or HRT. Being overweight or obese during the menopausal transition is not necessarily associated with deterioration in coronary risk factors. This seems to imply the existence of different metabolic populations within this group of women.

Protein-energy undernutrition in hospital in-patients

Impaired nutritional status has been frequently reported in surveys estimating its prevalence amongst patients in hospital. While there is no doubt that protein-energy undernutrition has serious implications for health, recovery from illness or surgery and hospital costs, lack of nationally or internationally accepted cut-off points and guidelines for most nutrition-related variables make nutritional assessment difficult and proper comparisons between studies impossible. In reviewing published work in which the prevalence of undernutrition has been assessed, it can be seen that each study defined undernutrition, or nutritional risk, using different methodology. This present review aims to highlight the problems which arise when deciphering these studies, and the resulting difficulty in determining the true prevalence of undernutrition and nutritional risk, amongst both general and specific groups of hospital in-patients. It is widely agreed that routine hospital practices can further adversely affect the nutritional status of sick patients in hospital. How this occurs, and the potential effects of impaired nutritional status on clinical outcome are examined. The methods currently available to assess nutritional status are evaluated in the knowledge that such assessments are difficult in clinical practice. The review concludes by proposing that if we want the medical and nursing professions to consider the nutritional status of hospital patients seriously, definitions of undernutrition and nutritional risk, and cut-off values for the nutritional variables measured must be agreed to allow evidence-based practice. Outcome measures which allow clear comparisons between groups and treatments must be used in studies assessing the effects of nutritional interventions.

Pre-operative nutritional assessment

Protein-energy undernutrition, or the possibility of its development, has been documented to occur frequently in surgical patients admitted to hospital. Nutritional status is known to deteriorate over the course of the hospital stay, with poor awareness by medical and nursing staff as to the deleterious effects of impaired nutritional status on clinical outcome and hospital costs. While there is no consensus on the best method for assessment of the nutritional status of surgical patients pre-operatively, there are a number of techniques available. These techniques can be divided into two types, those suitable for screening for nutrition risk on admission to hospital and those used to fully assess nutritional status. Both techniques have their limitations, but if used correctly, and their limitations recognized, should identify the appropriate degree of nutritional intervention for an individual patient in a timely and cost-effective manner. The techniques currently available for nutritional screening and nutritional assessment are reviewed, and their applicability to the Irish setting are discussed in the present paper.