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Query: UMLS:C0028754 (obesity)
 124,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The propensity to obesity in animals and man identifies those individuals who are genetically favoured to survive when food supplies are scarce. Obese subjects are limited in their ability to produce heat, either in a cold environment or after food, because of a reduced activity in skeletal muscle of a "futile" cycle in glucose metabolism. The impaired thermogenesis reduces the maintenance requirement for energy in the pre-obese individual so that a "normal" energy intake can only be balanced by excessive exercise or the expansion of adipocytes. The basal metabolic rate rises as obesity develops and compensates for the impaired thermogenic mechanism.
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PMID:An integrated view of the metabolic and genetic basis for obesity. 6 44

The Zucker (fatty) rat is one of a group of animals that inherit obesity as an autosomal Mendelian recessive trait. These rats are obese, hyperphagic, and hyperinsulinemic, but blood glucose remains at normal levels. Although these rats eat more than normal rats, their response to the addition of adulterants to the food or after exposure to the cold is more like that of normal rats than rats with hypothalamic obesity. The hypertriglyceridemia which characterized these animals is due to the increased hepatic production of a very low density lipoproteins. Adipocytes are increased in size and in number with the subcutaneous fat depot showing the largest increase in the number of fat cells. Lipogenesis from glucose is brisk in the young animals but declines with age. Enzymatic patterns of glycolysis and gluconeogenesis appear to reflect the altered internal milieu rather than specific defects. Endocrine changes in the fatty rat include hyperinsulinemia, reduced levels of glucagon, hypothyroidis, and impaired reproductive function. A model is presented in which the features of the genetically obese (Zucker) fatty rat are compared with those of animals with hypothalamic obesity.
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PMID:The Zucker-fatty rat: a review. 32 51

The metabolic response of one- and two-week-old obese (ob/ob) and lean mice to acute thermal stress, and the influence of maternal diet on body fat and metabolic rates of these mice, were evaluated. Both obese and lean pups increased their rate of oxygen consumption 62 to 67% when exposed to 25 degrees C for 20 minutes rather than to 35 degrees C. Obese pups exposed to an intermediate temperature (30 degrees C), however, increased their rate of oxygen consumption less (35%) than did lean mice (55%) exposed to the same temperature. Reports in the literature suggest that adult obese mice have a markedly reduced ability to increase their oxygen consumption when cold-stressed, but the present results indicate that young obese mice may have less impairment in their capacity to increase oxygen consumption. Two-week-old obese pups contained more fat and consumed less oxygen than lean littermates. The maternal diet was manipulated to increase the body fat content of two-week-old pups to equal that of obese mice, but obese pups still consumed less oxygen than did the lean pups. We, thus, conclude that factors other than differences in body fat content are responsible for the lowered oxygen consumption observed in young obese mice.
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PMID:Influence of acute thermal stress and maternal diet on metabolic rate of obese (ob/ob) and lean mice at two weeks of age. 53 5

Measurement of energy balance during voluntary overeating in rats unequivocally establishes the quantitative importance of diet-induced thermogenesis in energy balance. Like cold-induced thermogenesis, this form of heat production involves changes in the activity of the sympathetic nervous system and brown adipose tissue which suggest that this tissue may determine metabolic efficiency and resistance to obesity.
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PMID:A role for brown adipose tissue in diet-induced thermogenesis. 55 Dec 65

1. The capacity ofr thermoregulation and thermogenesis in lean and genetically obese (ob/ob) mice has been investigated. 2. At 4 degrees C ob/ob mice rapidly die of hypothermia, because of a reduced capacity for cold-induced thermogenesis, but the animals are able to survive if previously adapted to 12 degrees C. 3. At all environmental temperatures between 30 degrees C and 10 degrees C the body temperature of ob/ob mice is 2.0-2.5 degrees C below that of lean animals. This may be due to a lower "setting" for body temperature. 4. At 34 degrees C the oxygen consumption of obese mice is greater than that of the lean animals while at 30 degrees C it is similar. When the environmental temperature is below 30 degrees C the oxygen consumption of the lean mice is greater. The obese animals therefore expend less energy on thermoregulatory thermogenesis. 5. The capacity for non-shivering thermogenesis was measured in lean and obese mice by investigating the effect of an injection of L-nor-adrenaline (1000 microgram/kg body weight) on the metabolic rate at 31 degrees C. Non-shivering thermogenesis was reduced by one-half in the obese animals. 6. One cause of the obesity of the ob/ob mouse is its high metabolic efficiency. We suggest that this high metabolic efficiency is due, at least in part, to less energy being expended on thermoregulatory thermogenesis.
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PMID:Thermoregulation and non-shivering thermogenesis in the genetically obese (ob/ob) mouse. 56 45

1. The body compositions of obob and lean (ob+ and ++) mice at 10, 12, 17 and 28 d of age were investigated using a 'cold stress' test to identify the two groups. 2. At each of these ages the obob mice were found to contain significantly more fat than the lean. At 10 d 20% more fat was present and by 17 d the increase was 72%. The obob mice at 28 d contained nearly three times as much fat as the lean. 3. Carcass energy was significantly higher in obob mice at all ages investigated. 4. Other changes in body composition found in the 28 d obob mice, i.e. a reduction in total carcass nitrogen and water content, were already established in the 17-d-old mice but differences at 10 and 12 d were not apparent. 5. The livers of obob mice were significantly heavier than those from lean control mice at 28 d but no differences were detected at the earlier ages. 6. The results are discussed with reference to the early origin of obesity in obob mice.
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PMID:The development of obesity in preweaning obob mice. 62 27

1. Measurements of total heat losses by direct calorimetry, metabolic heat production by indirect calorimetry, body temperatures by thermometry, and thickness of subcutaneous fat with skin-fold calipers were made in four groups of subjects (anorexic, controls, trend to obesity, and obesity) at ambient temperatures of 28 degrees C and 20 degrees C. 2. At 28 degrees C, the four groups of subjects reached thermal equilibrium after 30 min. 3. Both metabolic heat production and total heat losses were lower in the anorexic group than in the control group. 4. Body thermal insulation was not simply related to the thickness of subcutaneous fat (passive insulation), but was actively regulated in such a way that thermal balance was attained by all subjects at 28 degrees C. Body tissues underlying the subcutaneous fat contributed to the thermal insulation of the subjects at both 28 degrees C and 20 degrees C. 5. At 28 degrees C, total body thermal insulation was higher in anorexic subjects than in controls. 6. At 20 degrees C, heat debt was similar in three of the four groups : the anorexic subjects showed a higher debt. 7. A highly significant correlation between subcutaneous fat and weight/area ratio, was found. 8. The heat exchange coefficient of radiation and convection was found to be 6,47 Wm-2 degrees C-1. 9. By combining our measured values with those of various tissue physical characteristics, it was possible to produce a mathematical model. With this model one can calculate the penetration of the thermal gradient into the body, and estimate the mean temperature of each tissue participating in the thermal insulation for moderately cold ambient temperatures.
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PMID:[Heat debt and thermal insulation in women exposed to cold : contribution of direct calorimetry to the study of a mathematical model (author's transl)]. 93 73

The gradient layer direct calorimeter built in Lausanne allows proportionate measurement of respiratory and cutaneous heat losses. The latter consists of evaporative and convective plus radiative heat losses, which are separately measured. Obese subjects had lower heat losses and higher thermal body insulation than controls. The decreased heat loss may contribute to their positive energy balance by decreasing the energy cost of maintaining body temperature during cold exposure. The changes in heat loss during exercise are also illustrated.
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PMID:Direct calorimetry: a new clinical approach for measuring thermoregulatory responses in man. 118 Aug 49

Differential temperature measurement between interscapular brown adipose tissue (BAT, Tbat), rectum (Trect) and a subcutaneous point in the back left of the vertebral column (Tsc) was useful for examination of BAT-thermogenesis in glutamate-induced obese Wistar-rats. Positive temperature gradients Tbat-Tsc pointed to a basal BAT-thermogenesis, whereas negative temperature gradients Tbat-Trect did not indicate that heat production in lean and obese rats. One may conclude from this, that inclusion of subcutaneous points outside the BAT improves sensitivity of differential temperature measurements for BAT-thermogenesis. Basal temperatures Tbat, Trect and Tsc were reduced in obese rats compared to lean rats, although thermoinsulation of obese rats is improved on account of their high fat content. This points to a diminished heat production in obese rats. Cold exposure at 4 degrees C elicited an increase of temperature gradients Tbat-Trect in lean as well as in obese rats, with positive values found only in lean rats. However, positive values Tbat-Tsc were calculated for both groups. Increases were noted only in lean rats. Injection of noradrenaline (0.5 mg/kg i.m.) was followed by positive temperature gradients Tbat-Trect and increased positive values for Tbat-Tsc, pointing to a remarkable activation of BAT-thermogenesis in lean and obese rats. These findings confirm, that glutamate-induced obese rats preserved the ability to activate BAT-thermogenesis. There were, however, hints of reduced heat production in BAT of obese rats, thus contributing to obesity despite normophagia.
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PMID:Examination of brown adipose tissue thermogenesis of glutamate-induced obese rats by differential temperature measurements. 129 79

Whereas short-term cold exposure depletes glycogen reserves, repeated and prolonged moderate exercise in a cold environment creates an energy deficit that is satisfied by an increased metabolism of depot fat. Factors contributing to the fat loss include an exercise-induced hypertrophy of lean tissue, a loss of energy through a cold-induced ketonuria, a stimulation of resting metabolism, increases in the energy cost of movement, and a lower yield of energy per litre of oxygen consumed. Biochemical explanations of the enhanced lipolysis include increased catecholamine secretion, altered sensitivity of catecholamine receptors, and decreases of circulating insulin. The enhanced fat loss with combinations of cold and exercise may be helpful in the therapy of obesity, although the response seems less well developed in women than in men. Moreover, there may be other objections to cold exposure in an older obese population. Short-term glycogen depletion has negative implications for the endurance competitor. Cold acclimation, by favoring an insulative response to cold, reduces glycogen depletion; endurance training may supplement this effect by enhancing the activity of fat-metabolizing enzymes.
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PMID:Fat metabolism, exercise, and the cold. 132 16


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