Biomedical subjects
Publications and source records attributed to P Ritz.
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This review collates studies of healthy, sick, underweight (BMI < or = 21 kg/m2) and very elderly people (> or = 90 yr), in whom resting energy expenditure (REE) was measured using indirect calorimetry. We have observed the following: (1) REE, when adjusted for differences in both body weight and fat-free mass (FFM), is similar in healthy and in sick elderly people being 20 and 28 kcal/kg of FFM per day, respectively, (2) their nutritional status influences their energy requirements given that weight-adjusted REE increases in line with a decrease in BMI, (3) total energy expenditure is lower in sick elderly people given that their physical activity level, i.e. the ratio of total energy expenditure to REE, is reduced during disease averaging at 1.36, (4) energy intake (EI) being only 1.23 x REE is insufficient to cover energy requirements in sick elderly patients, whereas the EI of healthy elderly people appears sufficient to cover requirements, and finally, (5) gender ceases to be a determinant of REE in people aged 60 yr or over, with the Harris & Benedict equation capable of accurately predicting mean REE in this population, whether healthy or sick.
In doubly labelled water studies, biological sample enrichments are mainly measured using off-line techniques (equilibration followed by dual-inlet introduction) or high-temperature elemental analysis (HT-EA), coupled with an isotope-ratio mass spectrometer (IRMS). Here another continuous-flow method, (CF-EA/IRMS), initially dedicated to water, is tested for plasma and urine analyses. The elemental analyser configuration is adapted for each stable isotope: chromium tube for deuterium reduction and glassy carbon reactor for 18O pyrolysis. Before on-line conversion of water into gas, each matrix is submitted to a short and easy treatment, which is the same for the analysis of the two isotopes. Plasma is passed through centrifugal filters. Urine is cleaned with black carbon and filtered (0.45 microm diameter). Tested between 150 and 300 ppm in these fluids, the D/H ratio response is linear with good repeatability (SD<0.2 ppm) and reproducibility (SD<0.5 ppm). For 18O/16O ratios (from 2000 to 2200 ppm), the same repeatability is obtained with a between-day precision lower than 1.4 ppm. The accuracy on biological samples is validated by comparison to classical dual-inlet methods: 18O analyses give more accurate results. The data show that enriched physiological fluids can be successfully analysed in CF-EA/IRMS.
Resting energy expenditure (REE) is believed to be increased in type 2 diabetes, an increase that is associated with deteriorating glucose tolerance during its development. Meanwhile, insulin resistance, a state linked to obesity and observed in all type 2 diabetic patients, is associated with reduced REE. Our aim was to compare REE in obese patients with and without diabetes. REE, body composition (total body water, density, percentage fat and fat-free mass: 3-compartment model) and metabolic control were assessed in fifty obese Caucasian patients with diabetes (glycated haemoglobin level 7.6 (SD 1.5) %) and fifty obese patients who were non-diabetic. Despite being more overweight and younger, obese non-diabetic patients had an absolute REE (7.73 (SD 1.44) v. 8.12 (SD 1.37) MJ; P=0.17) and percentage fat-free mass similar to those of obese diabetic patients. Even when adjusted for differences in body composition, REE remained similar in both groups. Furthermore, REE (absolute and adjusted) was unaffected by both glucose level and control (glycated haemoglobin), with fat-free mass being the only determinant of REE. We conclude that REE is not necessarily increased by the presence of diabetes in obese people.
AIMS/HYPOTHESIS: Glucocorticoid treatments are associated with increased whole-body oxygen consumption. We hypothesised that an impairment of muscle energy metabolism can participate in this increased energy expenditure. METHODS: To investigate this possibility, we have studied muscle energetics of dexamethasone-treated rats (1.5 mg kg(-1) day(-1) for 6 days), in vivo by (31)P NMR spectroscopy. Results were compared with control and pair-fed (PF) rats before and after overnight fasting. RESULTS: Dexamethasone treatment resulted in decreased phosphocreatine (PCr) concentration and PCr:ATP ratio, increased ADP concentration and higher PCr to gamma-ATP flux but no change in beta-ATP to beta-ADP flux in gastrocnemius muscle. Neither 4 days of food restriction (PF rats) nor 24 h fasting affected high-energy phosphate metabolism. In dexamethasone-treated rats, there was an increase in plasma insulin and non-esterified fatty acid concentration. CONCLUSIONS/INTERPRETATION: We conclude that dexamethasone treatment altered resting in vivo skeletal muscle energy metabolism, by decreasing oxidative phosphorylation, producing ATP at the expense of PCr.
Mitochondria are the cells' powerhouse that produce the ubiquitous energy currency (ATP) by consuming oxygen, producing water and building up the proton motive force. Oxygen consumption is a classical means of assessing energy expenditure, one component of energy balance. When energy balance is positive, weight increases. This is observed during the dynamic phase of obesity, and during body composition changes associated with aging. Whether intrinsic defaults in mitochondria occur is the matter of this review. Indeed, the ratio of ATP over oxygen consumed, which is not fixed, is one way of regulating heat release and ATP flux, but can also be the consequence of environmental conditions of mitochondrial work. For example, various hormones (T3, glucocorticoids), changes in lipid membrane composition, changes in food intake and exercise, and various drugs, can modify the ratio of ATP over oxygen consumed. Aging and insulin resistance are other regulators of this ratio. Finally there is a rising body of evidence linking diabetes to mitochondrial functions.
Insulin use is common in type 2 diabetes and is frequently accompanied by weight gain, the composition of which is poorly understood. The present study evaluates insulin-induced body composition changes. Body weight and composition of thirty-two type 2 diabetic patients undergoing their first 12 months of insulin therapy were compared with those observed in thirty-two type 2 diabetic patients previously treated on insulin (minimum 1 year). Body composition was determined by simultaneous body water spaces (bioelectrical impedance analysis) and body density measurements. After 6 months, glycosylated Hb (HbA1c) significantly improved in the newly treated group (P<0.0001), but remained stable in those treated previously. HbA1c did not differ between 6 and 12 months in the two groups. Body weight significantly (P=0.04) changed over 12 months in those newly treated only (+2.8 kg), essentially comprising fat-free mass (P=0.044). Fat mass remained unchanged (P=0.85) as did total body water, while extracellular: total body water ratio tended to increase in those newly treated (P=0.059). Weight changes correlated with HbA1c changes (R2 0.134, P=0.002) in the initial 6 months only. Insulin therapy leads to weight gain (2.8 kg), predominantly fat-free mass, over 12 months. After 6 months, newly treated patients continued gaining weight despite an unchanged HbA1c, suggesting the potential anabolic role of insulin in subsequent gains. Therefore, in the initial 6 months, weight gain can be attributed to a 'glucose control-related effect' and further gain appears to be due to a 'non-glucose control-related' effect of insulin treatment.
In France, indications for bariatric surgery are clearly defined in the recommendations issued by ANAES and medical societies. The number of surgical procedures performed in France, is currently estimated to be 10 to 12.000 per year, with a regular increase of the gastric banding technique, which represents now more than 75% of the procedures. This review presents the main surgical procedures, and particularly, insists on their post-operative complications and their prevention, diagnosis and management.
OBJECTIVE: Insulin is used commonly in Type 2 diabetes and is often accompanied by weight gain. The composition of this weight gain is poorly understood. Predominant increases in fat mass could increase cardiovascular risks. The aim of the study was to evaluate insulin-induced body composition changes. RESEARCH DESIGN AND METHODS: Body weight and composition of 35 Type 2 diabetic patients during their first 6 months of insulin therapy was compared with those in 34 Type 2 diabetic individuals treated with insulin for at least 1 year prior to commencing the study. Body composition was determined by the simultaneous measurement of body water spaces and body density. RESULTS: Over 6 months, glycaemic control improved in the new treatment group only (HbA(1c): 7.26 +/- 0.81 vs. 9.66 +/- 1.60%; P < 0.0001), remaining stable in the previously treated group (7.67 +/- 1.25 vs. 7.76 +/- 1.26%; P = NS). Weight significantly increased over time in the newly treated group (+1.7 kg; P = 0.04), but not in the previously treated group (-0.3 kg). It comprised of both fat (+0.85 kg) and fat-free mass (+0.55 kg). Total body water remained unchanged. Using bioelectrical impedance analysis, the gain in fat mass was +2.2 kg; P = 0.048. CONCLUSIONS: Over 6 months, insulin therapy leads to a weight gain of 1.7 kg because of an increase in both fat and fat-free mass. When body composition is determined by bioelectrical impedance analysis, the results are biased by fluctuations in hydration.
Body mass index is a tool to screen undernourished persons. Cut-off values of 22 or 24 kg/m2 are used for elderly persons. However, standing height cannot be measured in every elderly person. Knee-height has been proposed to estimate standing height, with equations derived from North-American people. The present study analyses the validity of these equations. Standing height and knee-height were measured in 126 elderly persons hospitalized in 6 French geriatrics wards. Consequences of using one of the either height was evaluated on body mass index, body surface area, and total body water as estimated from bioelectrical impedance measurements. Standing height and height derived from knee-height differed significantly by 0.9 cm (P=0.05). This has very limited consequences on the calculation of BMI (0.5 kg/m2), body surface area (0.04 m2) and on total body water (0.2 litres). A regression model was derived from covariates and found the same features as that in the model of Chumlea and Guo. In conclusion, knee-height can be used with sufficient accuracy as a surrogate for standing height in diseased French elderly persons.
There is paramount evidence to suggest the importance of cell volume changes for the regulation of cell function, including protein metabolism. Among many other effects, cell swelling inhibits proteolysis and stimulates protein synthesis. However, most of the data pertinent to this theory relate to in vitro experiments. This paper reviews the evidence about the relevance of cell swelling and changes in water compartments to regulation of metabolism at the whole body level in animals and humans. Protein metabolism is most likely regulated by cellular hydration in health and disease. Cellular hydration appears to bear no effect on energy metabolism. The relationship between cellular hydration and lipolysis deserves to be verified. There appears to be a possible weak effect on glucose metabolism. Further studies are therefore necessary to challenge the cell swelling theory. If confirmed, strategies to modify cellular hydration could be used to improve metabolic orientations especially in the critically ill.
Although the stimulating effect of thyroid hormones on energy metabolism has been recognized for more than a century, the relation between thyroid function and weight control and obesity remains unclear. We review here the effects of thyroid hormones, hyperthyroidism, and hypothyroidism on body composition and the parameters of energy metabolism.
Energy expenditure (or energy needs) corresponds to the energy required for the body to work under all circumstances. This is the energy that should be taken (with food) to maintain energy balance, i.e. the constancy of body weight. Energy is expended at rest (referred to as basal or resting metabolic rate), when food is consumed (diet induced thermogenesis) and with physical activity. In obese people, energy expenditure is increased because of the proportion between body mass and energy expenditure. There is no definite proof that there is a metabolic defect in obese persons by which energy expenditure would be lower than expected for body mass. Hence obesity can only be the result of a positive energy balance. Energy expenditure can be measured by indirect calorimetry or estimated with equations. These equations use factors as weight, age, gender and sometime height. These equations are generally valid although there is a need for more validation studies. This paper also describes in which clinical circumstances the measurement or the estimate of energy expenditure are useful for the care of obese patients.
OBJECTIVE: To test the hypothesis that the increase in fat mass observed with aging might be related to a decrease in whole-body fat oxidation. SUBJECTS AND MEASUREMENTS: Forty volunteers had measurements of sleeping and 24 h substrate oxidation in calorimetric chambers, body composition with the (18)O dilution technique, VO(2)max, and fiber composition analysis from a biopsy of vastus lateralis. They were divided into 10 young women, 10 young men, 10 elderly women and 10 elderly men. RESULTS: Sleeping fat oxidation and 24 h fat oxidation were lower in women than in men and in elderly than in young participants. Sleeping fat oxidation was correlated to fat-free mass and energy balance (multivariate analysis). Twenty four hour fat oxidation was correlated to total energy expenditure and energy balance (multivariate analysis). After adjustment for differences in these factors, sleeping and 24 h fat oxidation were no longer different between age and sex groups. None of the parameters of macronutrient metabolism was correlated with muscle fiber composition. CONCLUSION: Our data suggest that fat oxidation is lower in elderly subjects. This difference could favour fat mass gain if fat intake is not adequately reduced. Differences in fat-free mass and in total energy expenditure appear to participate in the reduction in fat oxidation. International Journal of Obesity (2001) 25, 39-44
OBJECTIVE: Whole body protein turnover (PTO) and resting energy expenditure (REE) are both correlated to fat-free mass (FFM), in young and elderly subjects, and REE is positively correlated to PTO in young adults. Thus, the aim of this study was to compare the energetic cost of PTO in young (n=39, 23.4+/-3.1 y) and elderly (n=41, 67.5+/-3.6 y) healthy volunteers. MEASUREMENTS: REE (indirect calorimetry), PTO ((13)C-leucine isotopic dilution) and body composition (bioelectrical impedance analysis with age-specific equations) were measured in the postabsorptive state. RESULTS: Elderly subjects had a higher fatness (30.5+/-7.1 vs 18.2+/-5.5%, elderly vs young, P<0.001), a similar REE (0.97+/-0.13 vs 1.06+/-0.15 kcal min(-1)), and a lower PTO (1.28+/-0.22 vs 1.44+/-0.18 micromol kg(-1) min(-1), P<0.001). PTO, REE and FFM were significantly correlated and after adjustment for FFM, REE was positively correlated to PTO (r=0.61, P<0.001). The slope of this relationship was the same in both groups, while the adjusted mean REE was lower in elderly subjects (0.97+/-0.09 vs 1.05+/-0.07 kcal min(-1), P<0.01). CONCLUSION: In comparison with young subjects, the energetic cost associated with PTO in elderly subjects is not different, but the proportion of REE not associated with PTO is lower.
OBJECTIVES: (i) to describe energy and macronutrient requirements in healthy and diseased elderly patients from knowledge acquired about the age-related changes in energy balance (ii) to describe changes in body composition and the consequences of physical activity and exercise programs. RESULTS: Aging in individuals considered healthy is associated with a reduction in muscle mass and strength (with consequences on autonomy), and an increase in fat mass mainly in the central area, the latter might increase the risk of cardiovascular disease. Body composition changes can be seen as a positive energy (fat) balance. The reduced fat-free mass is responsible for a low resting metabolic rate. Therefore, energy requirements are reduced all the more since physical activity is decreased. A simple means for calculating individuals' energy requirements from estimated resting metabolic rate and physical activity is not yet available in a validated form and is much required. Protein requirements are still debated. Exercise programs can be implemented for increasing muscle mass and strength (resistance training) or for improving aerobic fitness and reducing fat mass (endurance exercise). It is not yet clear whether structured exercise programs or spontaneous physical activity have similar advantages. It is not known in which cases resistance, endurance, or a combination of both exercises should be recommended. The consequences of physical activity and exercise programs on energy and macronutrient requirements is not clear. Diseased elderly persons are prone to malnutrition which impairs clinical and functional outcome. Malnutrition is the result of an energy intake inadequate to match energy requirements. Literature is very short of data on energy requirements in diseased elderly persons, who are under the complex influences of stress (increasing resting energy requirements), reduced body mass and physical activity (reducing energy requirements), plus potential effects of drugs. Almost nothing is known about macronutrient requirements. CONCLUSIONS: Further studies are required to enable calculations of energy and macronutrient requirements of individuals, especially diseased. More work has to be done to understand the energy imbalance in the elderly (healthy and diseased). Careful evaluations of physical activity and exercise programs are necessary.
BACKGROUND: This study validates, in geriatric patients, bioelectrical impedance analysis (BIA) equations that had been derived to estimate total body water (TBW) and extracellular water (ECW) in healthy elderly subjects. METHODS: We performed a multicentric trial in six geriatric wards. We studied 169 patients with varying degrees of hydration: dehydrated, euvolemic, and overhydrated. BIA estimates of TBW and of ECW were compared with the measurement of TBW with (18)O dilution and of ECW with bromide (Br) dilution. RESULTS: BIA estimated TBW with a difference of 0.48 +/- 2.3 l (mean +/- SD) (50 kHz; p = .01) and 0.69 +/- 2.2 l (100 kHz; p < 0.001) compared with (18)O dilution. The difference was not affected by the hydration status. Estimates of ECW with BIA were systematically biased compared with Br dilution: 4.6 +/- 3.1 l (equation from Segal and colleagues; p < .001) and 3.4 +/- 2.9 l (equation from Visser and colleagues; p < .001). We propose a new, cross-validated equation. Conclusions. Body water spaces can be estimated accurately in geriatric patients with BIA.
BACKGROUND: As a reduction of water spaces is expected in the elderly because of fat-free mass loss, disease is often associated with increased hydration. The present study compared water spaces and cellular hydration in adults, healthy and diseased aged patients. METHODS: An open study was conducted in 6 geriatric wards and a nutrition laboratory involving 85 aged diseased persons, 68 healthy elderly adults, and 35 adults. Total body water (TBW, H(2)(18)O dilution), extracellular water (ECW, Bromide dilution), and fat-free mass (FFM, body density and Siri's equation) were measured directly whereas intracellular water (ICW = TBW - ECW) and body cell mass (FFM - ECW) were obtained by calculations. RESULTS: FFM, TBW, and ICW were higher in adults than in the 2 other groups and in the elderly than in aged patients. ECW was higher in aged patients than in healthy elderly participants. The proportion of TBW made of ECW or ICW was the same in adults and in healthy elderly persons. A higher proportion of TBW was composed of ECW, and a lower proportion of TBW was composed of ICW, in diseased patients compared with the 2 other groups. The proportion of ICW in body cell mass was also lower in diseased patients. CONCLUSIONS: Diseased elderly persons display reduced ICW and expanded ECW. A cellular dehydration is suggested.