Biomedical subjects
W P James
Publications and source records attributed to W P James.
A simplified approach of assessing adult chronic energy deficiency.
Body mass index (BMI) in conjunction with indices of energy turnover, e.g. physical activity levels (PAL), was recently proposed for classifying adult chronic energy deficiency (CED). Three deprived populations in Africa and Asia were chosen to assess the classification system. Repeated monitoring showed that the combined indicator was affected by instability in PALs and produced implausible discontinuities in the prevalence of different grades of CED. The use of BMI alone produced coherent data with changing BMI distributions, and only 5% of the population would have been wrongly classified as being malnourished, because of being thin but active. The risk of misclassification would be even smaller for populations with BMI distribution shifted towards the right. The prevalence of CED was consistently related within each country to indices of socio-economic status. Yet in Zimbabwe 18% of women and 6% of men had Grade I obesity compared with 11% and 14%, respectively, with CED. Less than 1% Indian and Ethiopian adults were obese but 61% of women and 70% of men were classified as CED in India and 57% and 50%, respectively, in Ethiopia. We propose that adult BMI alone is sufficient to provide important new insights into the problems of food availability and its control in less developed countries.
What is nutritional surveillance?
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Effects of smoking and vitamin E on blood antioxidant status.
Despite similar vitamin E contents, erythrocytes of smokers have an increased tendency (P less than 0.01) to peroxidize in vitro compared with those of nonsmokers. This difference is abolished by vitamin E supplementation (1000 mg alpha-tocopherol acetate/d for 14 d). The increased susceptibility to erythrocyte peroxidation in the smokers may reflect lower glucose-6-phosphate dehydrogenase (P less than 0.02) and glutathione peroxidase (P less than 0.05) activities. Smokers seem to be under a sustained oxidant stress with increased plasma-conjugated dienes (P less than 0.01) and dehydroascorbate (P less than 0.05) and decreased ascorbate (P less than 0.06) concentrations. Additionally, plasma ceruloplasmin in smokers is elevated (P less than 0.01), consistent with an acute-stress response. Plasma total cholesterol is similar in smokers and nonsmokers and is unaffected by vitamin E supplementation. Indices of sustained oxidant stress in smokers are partially ameliorated by vitamin E supplementation.
Concentrations of linoleic acid in adipose tissue differ with age in women but not men.
Samples of adipose tissue, taken post-mortem from the anterior abdominal wall near the umbilicus, were obtained from road-accident victims in the Aberdeen area; subjects were of either sex with a wide age distribution (7-88 years). Similar samples were obtained from elderly females (mean age 77) who had died in Aberdeen Royal Infirmary from a variety of causes. Fatty acid compositions of samples were determined by capillary gas chromatography of methyl esters, which were obtained by direct esterification of the adipose tissue. The mean linoleic acid content for all samples was low compared with published values for similar samples from Europe and North America. Cumulative frequency distribution curves for linoleic acid did not differ with age in males but significant differences (P less than 0.001) occurred in females, with decreased concentrations in those aged over 60 compared to younger groups. Concentrations of trans-unsaturated fatty acids ranged between 2 and 7 per cent but did not differ significantly between groups. Low adipose concentrations of linoleic acid are regarded as a reflection of its reduced long-term dietary intake and as a risk factor for the development of coronary heart disease.
Metabolism and nutritional adaptation to altered intakes of energy substrates.
Adaptive changes in energy expenditure to changes in energy intake are far less than previously believed once changes in body weight and physical activity are taken into account. Alterations in metabolic efficiency of +/- 10% in total energy expenditure are the limits of what can normally be expected on prolonged under- or overfeeding. The supposed twofold variation in energy requirements of adults is based on measurements of food intake, which, despite involving weighted intakes over a week, cannot be considered realistic. Subtle differences in the energetic responses to fat, protein, and carbohydrate signify the different effective energetic contribution of isoenergetic substrates and may account for the propensity to obesity in individuals and societies on a high-fat diet.
Nutrient oxidation patterns and protein metabolism in lean and obese subjects.
The immediate metabolic response to eating has been compared in a group of grossly obese subjects (W/H2 = 45) with that in lean controls (W/H2 = 22). Dietary intake of energy for obese subjects was based on their estimated basal energy expenditure for ideal body weight (given at an hourly rate of 3 X BMR over a 4-h period). Lean subjects were measured twice: control 1 with the same intake of energy as the obese in terms of ideal body weight and control 2 with the same energy intake in relation to each subject's measured resting energy expenditure (2.2 X REE). The changes in energy expenditure and nutrient disposal with the onset of eating have been assessed by a method of combined respiratory gas analysis and intravenous infusion of 13C-labelled leucine. Leucine kinetics were used to quantitate rapid changes in protein oxidation and to assess protein synthesis and degradation. 1) Total energy expenditure was 20-30 per cent greater in obese subjects than lean subjects in fasting and feeding. Energy expenditure expressed per kg fat-free mass, from D2O dilution, was similar in obese and lean subjects in both fasting (5.8 v. 5.5 kJ/kg FFM/h) and feeding [6.7 v. 6.3 (Control 2) kJ/kg FFM/h]. 2) The onset of eating was associated with increased carbohydrate and protein oxidation with decreased fat oxidation in both lean and obese individuals. In obese subjects, however, both the decrease in fat oxidation and the increase in protein oxidation were significantly smaller (P less than 0.05) than the corresponding increments in lean subjects (Control 2). 3) The rate of protein synthesis was significantly (P less than 0.05) higher in obese subjects both in the fasting state (99 v. 84 mumols leucine/kg FFM/h) and in the fed state [94 v. 67 (Control 2) mumols leucine/kg FFM/h]. The rate of protein degradation was also higher in obese individuals in fasting (117 +/- 6 v. 106 +/- 4 mumol leucine/kg FFM/h) and feeding [65 +/- 4 v. 54 +/- 6 (Control 2) mumol leucine/kg FFM/h] though these differences are not statistically significant (P greater than 0.05). 4) The observed differences between obese and lean individuals in protein and energy metabolism in the fasted state and in the immediate response to eating do not support a hypothesis of greater metabolic efficiency in obesity.
Changes in energy expenditure during the menstrual cycle.
1. Eight women were studied under metabolic-ward conditions while consuming a constant diet throughout a single menstrual cycle. Basal body temperature, salivary and urinary hormone concentrations were used in monitoring the cycle and designing the study so that whole-body calorimetry for 36 h was conducted at four phases of the cycle in relation to the time of ovulation. 2. The metabolic rate during sleep showed cyclical changes, being lowest in the late follicular phase and highest in the late luteal phase. The increase amounted to 6.1 (SD 2.7)%. Energy expenditure (24 h) also increased but the change was not statistically significant (P greater than 0.05). Exercise efficiency did not change during the cycle. 3. There were no significant changes in plasma thyroxine, 3,5,3'-triiodothyronine or free 3,5,3'-triiodothyronine concentrations to explain the metabolic rate changes; nor did they relate to urinary luteinizing hormone, pregnanediol-3 alpha-glucuronide or oestrone-3-glucuronide excretion rates. No link with salivary cortisol or progesterone concentrations was observed, but there was a small inverse relation between the individual increase in sleeping metabolic rate and the subjects' falling ratio of urinary oestrone-3-glucuronide: pregnanediol-3 alpha-glucuronide.
Metabolic changes during the menstrual cycle.
1. Eight women maintained on a constant diet throughout a single menstrual cycle were studied for cyclical changes in body-weight, carbohydrate, fat and protein metabolism. 2. A cyclical variation in weight occurred with two phases corresponding to the time of ovulation and menstruation. 3. Creatinine and nitrogen excretion in the urine also tended to be higher in the luteal phase. 4. Analysis of gas exchange in a respiratory chamber for 24 h periods at intervals during the cycle suggested that carbohydrate utilization tended to be less in the early follicular phase. 5. Feeding with a mixed diet produced marked increases in carbohydrate utilization during the day with little change in fat utilization from the fasting state. Carbohydrate utilization was less when fasting at night and tended to be less when fed during the day in the early follicular phase of the menstrual cycle. 6. Weight changes were not readily ascribed to changes in colonic function, or in glycogen or body protein storage.
The role of nutrition and fitness in chronic diseases.
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A European view of nutrition and emerging problems in the Third World.
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The Mediterranean diet: protective or simply non-toxic?
There is clear evidence that populations living in Mediterranean countries enjoy a longer life expectancy than Northern Europeans. Genetic or racial factors do not explain these societal differences as revealed by migrant studies. The major causes of death in affluent societies, cardiovascular disease, cancers and digestive disorders, show markedly different incidence rates in different European countries. These differences seem to depend on the varied dietary patterns in Europe but the classic lipid hypothesis alone fails to explain the differing rates of coronary heart disease. Limiting the free radical damage to cholesterol thereby reducing the induction of atherosclerosis is a plausible explanation for the finding that some countries, e.g. France as well as Mediterranean countries with their high fruit and vegetable consumption, are well protected against coronary heart disease. The Mediterranean diet is low in saturated fat content but contains either a high or low content of starch and total fat. A high fat diet reveals the genetically determined individual propensity to obesity, e.g. in Greece, but does not predispose to cardiovascular disease or mitigate against the cancer protective properties derived from the vegetable component of the Greek diet. Studies in the Mediterranean area highlight the considerable dietary diversity which is possible for achieving longevity.
Should the national diet be altered to prevent coronary disease?
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Recent progress in studies on energy expenditure: are the new methods providing answers to the old questions?
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Definition of chronic energy deficiency in adults. Report of a working party of the International Dietary Energy Consultative Group.
New criteria are proposed for classifying chronic energy deficiency (CED) in adults. A progressively more precise approach to identifying affected individuals involves measuring body weight and height, then energy intake (or expenditure) and finally the basal metabolic rate (BMR). Three cut-off points for body mass index (BMI) were identified: 18.5, 17.0 and 16.0. A BMI above 18.5 is classified as normal and below 16.0 as grade III CED. A diagnosis of grades I and II CED depends on finding the combination of a BMI of 16.0-16.9 or 17.0-18.4 with a ratio of energy turnover to predicted BMR of less than 1.4. Measuring the individual BMR avoids misclassification and confirms the diagnosis. In groups of African adults 38-63 per cent of each group had a BMI below 18.5 and the majority require studies of their energy turnover before specifying their degree of CED; 3 per cent of Ethiopian women and 24 per cent of a selected male African group had grade III CED. These guidelines can be used when assessing the input of aid programmes and for clinical and other studies.
Inter-individual differences in fasting nutrient oxidation and the influence of diet composition.
The pattern of fasting nutrient oxidation was measured in 11 healthy women of widely different body mass index by measurements of indirect calorimetry and urinary nitrogen excretion on 12 consecutive days. The women were given a diet of normal composition (44.5 per cent energy as carbohydrate; 40.7 per cent energy as fat) for 6 days and a high-carbohydrate diet (54.4 per cent energy as carbohydrate; 30.8 per cent energy as fat) for 6 days, in amounts designed to maintain energy balance for each woman. The differences in fasting respiratory quotient (RQ) between the women on the same diet were highly significant (P less than 0.001). The fasting RQ and the fasting carbohydrate and fat oxidation were significantly different between the two dietary periods, with the average difference in fasting RQ (0.027) being of similar magnitude to the difference in the food quotient (FQ) (0.026) between the two diets. The differences in fasting nutrient oxidation between individuals and between diets suggest differences in the extent of overnight carbohydrate storage as glycogen. There was no evidence that these differences were related to the tendency to gain weight in these subjects.
Healthy nutrition. Preventing nutrition-related diseases in Europe.
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Metabolic effects of isoenergetic nutrient exchange over 24 hours in relation to obesity in women.
Twenty-four hour whole body indirect calorimetry has been used to study the effects of feeding, during a sedentary test day, isoenergetic diets which varied in fat (3 or 40 per cent of total energy) and carbohydrate (82 or 45 per cent) content. Three groups of women were studied: lean, obese and 'post-obese' after slimming. Energy expenditure was greater in absolute terms in the obese women. Twenty-four hour energy expenditure was lower by only 3-7 per cent when fasting compared to that when fed to achieve energy balance. There were no large differences in energy expenditure between the two diets or between the groups but the thermogenic effect of the high carbohydrate diet was significantly greater than that of the high fat diet (5.8 vs 3.5 per cent of energy expenditure: P less than 0.01). The post-obese tended to have lower energy expenditure per kg FFM than controls when fasting and when high-fat fed, but this pattern was not shown by the obese. Sleeping energy expenditure was particularly low in the post-obese group when high-fat fed. Dirunal variations in RQ appear to show more marked rise in morning RQ from the nocturnal minimum in the obese and post-obese, which might be evidence for an energy-saving mechanism through greater availability of stored dietary carbohydrate.