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Biomedical subjects

L Garby

Publications and source records attributed to L Garby.

At least 19 recordsLinked to original sources
PubMed2002

Prediction of body weight changes caused by changes in energy balance.

BACKGROUND: Experimental difficulties have so far restricted knowledge of the effects of energy imbalance on change in body weight. Direct measurement requires that the subjects are kept under dietary supervision for several months while the activity is being measured. MATERIALS AND METHODS: The effects of energy balance can be calculated using a combination of fundamental principles and directly measurable data: the law of energy conservation (increase in combustible energy equals the difference between energy intake and energy expenditure); data on energy expenditure of fat and lean tissues; and data on the composition of added/removed tissue during weight change. RESULTS AND CONCLUSIONS: We obtained an explicit differential equation describing the development of body weight over time, with energy intake and energy expenditure as control variables. Using this model it is possible to isolate and analyse the measured effects of parameters not included in the model, such as age or 'adaptivity' of the body.

Adaptation, Physiological↗
PubMed2000

Iron stores and haemoglobin iron deficits in menstruating women. Calculations based on variations in iron requirements and bioavailability of dietary iron.

BACKGROUND: Iron stores and haemoglobin iron deficits in menstruating women can be calculated from body iron losses and absorption of dietary iron using recently developed methods. OBJECTIVE: To examine iron balance (iron status) expressed as body iron stores or haemoglobin iron deficits in menstruating women from amounts of iron lost (iron requirements) and amounts of dietary iron absorbed. Calculations are made both of stationary states and of the rate of changes in iron stores (iron status) when any of the two main factors determining iron balance are changed. DESIGN: The study is based on (1) previous and new equations describing relationships between iron absorption, iron requirements (losses), iron stores and/or haemoglobin deficits and (2) published data on iron requirements and their variation in menstruating adult women. RESULTS: Both iron stores and haemoglobin iron deficits are strongly related to iron requirements and absorption of dietary iron and follow the same equations during states of iron repletion and iron deficiency. When, for example, increasing or decreasing the bioavailability of the dietary iron, about 90% of the change in iron stores will occur within 1 y. CONCLUSIONS: There are strong relationships between iron requirements, bioavailability of dietary iron and amounts of stored iron. The observations that a reduction in iron stores and a calculated decrease of haemoglobin iron had the same increasing effect on iron absorption suggest that the control of iron absorption is mediated from a common cell, that may register both size of iron stores and hemoglobin iron deficit, eg the hepatocyte. European Journal of Clinical Nutrition (2000) 54, 650-657.

Absorption↗
PubMed1999

Patterns of long-term weight changes in overweight developing Danish men and women aged between 30 and 60 years.

OBJECTIVE: To determine, in a retrospective semi-longitudinal study, the pattern of weight changes over 11 y in a population of subjects who developed their overweight as adults. DESIGN: A randomly selected population of 2436 subjects from the County of Copenhagen with ages 30-60 y was followed by body weight determinations on three occasions between the years 1982-83 and 1993-94. SUBJECTS: At the last examination, 660 subjects had attained a body mass index (BMI) of>/=28 kg/m2. Of these subjects, 341 had a self-reported BMI at 25 y of less than 25 kg/m2. RESULTS: In 1994, average yearly weight changes since 1983 ranged between 0.9 and 1.2 kg in the younger (30-40 y) 0.4 and 1.2 kg in the older (50-60 y) men and women during the preceding 11 y. These changes were similar over the two periods of 5 and 6 y. More than half of the subjects had weight gains between 6 and 21 kg, about equally distributed between the two periods. Women displayed larger and more frequent gains than men, as did the younger compared to the older subjects. CONCLUSIONS: The data show that weight changes to attain overweight are highly variable among subjects. However, in most subjects, the weight changes were so small and continuous that simple theories of control by means of fixed 'set points' cannot explain the results. In fact, the weight changes were generally so small that they are unlikely to be reflected in food consumption studies and in studies of macronutrient metabolism.

Aging↗
PubMed1998

A fast responding combined direct and indirect calorimeter for human subjects.

The construction and performance of a 5.4 m3 combined direct and indirect calorimeter for human subjects is described. The calorimeter was constructed for studies on human subjects primarily undergoing fast alterations in heat production and heat losses, e.g. after a meal or during physical exercise. A heat sink and a heat substitution principle is used to measure sensible heat losses directly. Evaporative heat losses are determined by measuring water vapour input and output. Indirect calorimetry is performed by measuring output air flow and changes in gas composition of the air entering and leaving the calorimeter. The response times (90%) for sensible heat and evaporative heat were found to be 4 min and 34 min, respectively. Three alcohol combustion tests gave a recovery of CO2 and O2 in the range 92-97%. The recovery of water was found to be in the range 56-89%.

Biomedical Engineering↗
PubMed1998

Composition of body weight differences in subjects with the same body height.

OBJECTIVE: To determine the composition of body weight differences in men and women with the same height. DESIGN: A study of a random population sample of Danish subjects, aged 35-65 y. SUBJECTS: An age and sex stratified random sample of 3608 subjects of which 2987 (83%) subjects appeared for study. Of these, 548 men and 498 women were randomly selected for this present work based on their heights. RESULTS: The mean values of the slope of body fat against body fat free mass were 2.88 (s.e.m. = 0.09) in women and 1.84 (s.e.m. = 0.07) in men. There were no significant differences between the different body height classes. CONCLUSIONS: See results.

Adipose Tissue↗
PubMed1998

Iron stores in man in relation to diet and iron requirements.

OBJECTIVE: To calculate iron stores in man and their rates of changes in relation to iron requirements and dietary iron intake and bioavailability. METHOD: Newly established relationships between iron absorption from whole diets and serum ferritin (SF) and between SF and iron stores allow calculations of amounts of stored iron under different conditions (diets, losses) at stationary states when absorption equals losses. Rate of growth of stores can also be calculated. All calculations are based on observations and require no model assumptions. RESULTS: Present calculations of iron stores agree with previously observed phlebotomy values. Differences in intake and bioavailability of dietary iron and in iron requirements had marked effects on amounts of stored iron. A wide range of diets was studied, from a hypothetical high-meat diet typical for early man to diets in developing countries. A new equation is given for the translation of SF into iron stores. Analyses of growth rate of stores under different conditions showed a fast growth from zero iron stores during the first year (reaching about 80% of final amounts) followed by a much slower rate for 2-3 y. A marked inertia was seen in rate of changes in iron stores that was more marked the closer stores were to their stationary states making it difficult to use SF to estimate short term changes in iron absorption in iron replete subjects. CONCLUSIONS: Realistic Western-type diets with good bioavailability can cover iron requirements in most women and can restitute iron stores during lactation. The high prevalence of iron deficiency in menstruating Western women is thus mainly related to a further low bioavailability of iron in present diets. Present analyses also demonstrated an effective control of iron absorption preventing development of iron overload in otherwise healthy subjects even if the diet is fortified with iron and even if meat intake is high.

Absorption↗
PubMed1995

Fat content affects heat capacity: a study in mice.

The specific heat capacity of the human body is a widely used number in calculations related to studies in energy metabolism and temperature regulation. A value of 3.47 kJ kg-1 K-1 has been used during the last century, but there have been no direct studies on the dependence of this value on the body fat content. We present here results of measurements of the specific heat capacity of lean and obese mice. The mice were killed and heated to 40.6 degrees C, transferred to a calorimeter and the specific heat capacity was determined from body mass of the mice and temperature rise of water in the calorimeter. We measured the fat fraction of body mass (mf), fat free body mass and water content of the mice and found a marked dependency of the specific heat capacity (Cp) on body fat. In obese mice (fat content 52.76% body wt) the heat capacity was 2.65 kJ kg-1 K-1 and in lean mice (fat content 7.55% body wt) the heat capacity was 3.66 kJ kg-1 K-1.

Animals↗
PubMed1994

Functional consequences of iron supplementation in iron-deficient female cotton mill workers in Beijing, China.

Eighty iron-deficient, nonpregnant female workers were randomly assigned to ferrous sulphate (60 or 120 mg Fe/d) or placebo treatment for 12 wk. Energy expenditure was estimated during 3 d by heart rate (HR) recording. Production efficiency (PE) was calculated as the ratio of productivity to energy expenditure. In the iron-treated group mean hemoglobin (Hb) increased from 114 to 127 g/L (P < 0.001), mean serum ferritin increased from 9.7 to 30.0 micrograms/L (P < 0.001), and mean free erythrocyte protoporphyrin decreased from 1.01 to 0.49 mumol/L (P < 0.001). Mean HR at work decreased from 95.5 to 91.1 beats/min (P < 0.001), which was inversely correlated with the change in Hb (r = -0.60, P < 0.001). PE increased significantly in the iron-treated group (P < 0.001) and its change paralleled the change in Hb (r = 0.58, P < 0.001). The results show that iron supplementation enabled these women to do the same work at a lower energy cost.

Adult↗
PubMed1994

Between-subjects variation in energy expenditure: estimation of the effect of variation in organ size.

The between-subjects variation in energy expenditure over 24 h at a fixed physical activity and corrected for differences in fat and fat-free mass has recently been determined to be 6-7%. New data on the variation between subjects of the weights of the brain, liver, kidneys, heart and spleen together with estimates of the energy expenditure of these organs were used to calculate the part of the between-subjects variation in energy expenditure at a fixed physical activity that is due to this variation alone. The results show that this variation is close to 5%. Thus, a very considerable part of the total between-subjects variation can be explained by differences in the composition of the fat-free mass.

Adolescent↗
PubMed1993

Prevalence and type of anaemia in female cotton mill workers in Beijing, China.

The present study investigates the prevalence and type of anaemia in Chinese female cotton mill workers. The prevalence of anaemia is reported in 447 non-pregnant female workers aged between 19 and 45 years. The mean value for haemoglobin (Hb) was 123 (SD 15) g/l and 150 of the total 447 subjects had Hb values below 120 g/l; thus 34% of the population was anaemic according to World Health Organization (WHO, 1975) criteria. The mean value for free erythrocyte protoporphyrin (FEP) was 419 (SD 215) micrograms/l; 55% of the total population had FEP values higher than 350 micrograms/l and 72% among the anaemic subjects. Serum ferritin (SF) was tested in all the women with a Hb value less than 120 g/l and 71% of them had SF values below 12.0 micrograms/l. Eighty women diagnosed as either Fe deficient or with Fe-deficient anaemia were selected for a diagnostic supplementation trial. They were randomly assigned to FeSO4 (60 or 120 mg Fe/d) or placebo treatment for 12 weeks. Fe supplementation increased mean Hb values from 114 to 127 g/l (P < 0.001) and SF levels from 9.7 to 30.0 micrograms/l (P < 0.001), and decreased mean FEP values from 570 to 277 micrograms/l (P < 0.001). The response rate of Hb in the whole Fe-treated group or Fe-treated subjects with an Hb level less than 120 g/l was 90% or 92% respectively. These findings indicate that the type of anaemia in this population was mainly Fe deficiency. It was also found that in this population the severity of anaemia, not the prevalence, was significantly related to the use of intra-uterine devices (IUD).

Adult↗
PubMed1991

Within-subjects variation over 10 months in 24-hour energy expenditure at a fixed physical activity programme.

In order to estimate within-subjects variability in 24-hour energy expenditure at a fixed physical activity programme with a physical activity index of 1.30, this quantity was measured in four apparently healthy subjects once a month over 10 months. The coefficient of variation of the measurements was found to be between 2.7 and 4 per cent and in agreement with previously published data.

Adipose Tissue↗
PubMed1990

Metabolic adaptation to decreases in energy intake due to changes in the energy cost of low energy expenditure regimen.

(1) The energy content in food is used in the human body for three main purposes. The first is to maintain the dissipative structures. Most of the structures of the body are of this kind, i.e. they represent stationary non-equilibrium states, or (generalized) stationary potentials, and are inherently unstable. The second is to maintain a body temperature independent of and usually higher than that of the surroundings. The third is to provide energy for performance of external work. The functional structure of the system providing these results consists of a large number of coupled processes (chemical reactions and translocations), in series and in parallel, whose general nature is well understood but whose quantitative extents are mainly unknown. The coupled processes are driven by the spontaneous reaction of the main substrates with oxygen. Energy flows through the system and is converted to heat (and external work) with simultaneous creation of stationary generalized potentials. For each potential there is an associated flow of energy and the relation between the two is an expression of the efficiency with which the potential is maintained. The processes giving rise to the potentials are likely to be controlled with respect to the efficiency with which the potentials are maintained. The control is partly provided through feedback from the potentials themselves: the potentials are regulated. In this way, the system can respond in a non-linear fashion to perturbations in the energy intake (or energy expenditure): the potentials are maintained at constant, or nearly constant, values. The concept of metabolic adaptation implies that control of the efficiency by feedback from the potentials is an important element in the overall regulation of the potentials, including that of the body temperature. (2) The concept of metabolic adaptation can be framed in such a way that it becomes operational. Quantities such as maintained potentials and efficiency can be revealed in terms of their external manifestations: performance of tasks and associated costs (energy expenditure). A change in efficiency is defined as a change in cost for given tasks. Performances can be defined such that they are both reproducible and of physiological relevance and costs can be measured. There are several complications associated with this approach to operational definition, the most important being the effect on energy expenditure of changes (or differences) in body composition. (3) The FAO approach to estimation of prevalence of undernutrition is based on measurements of energy expenditure for given tasks. This approach requires knowledge of the extent of metabolic adaptation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗
PubMed1990

The effect of a soluble dietary fibre supplement on 24-hour energy expenditure during a standardized physical activity programme.

Twenty-four hour energy expenditure during a standard physical activity programme was investigated in 19 healthy volunteers in a randomized, double-blind, cross-over design, after supplementation with a soluble dietary fibre amounting 7 g/day for 2 weeks. Energy intake and food fibre intake were kept constant during the treatment period. Twenty-four hour energy expenditure decreased insignificantly during fibre treatment (1.3 +/- 1.7 per cent). The dietary fibre supplement also had no significant effect on body weight, faecal energy loss or heart rate. Systolic blood pressure was insignificantly reduced during both placebo and fibre treatment (P = 0.09). There was, however, no difference between the groups after treatment.

Adolescent↗