Diet and Weight Loss

Tb, Van Itallie; Mu, Yang

doi:10.1056/nejm197711242972106

Cited by 54 publications

(8 citation statements)

References 7 publications

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“…Body fluid depletion during RF may also be due to caloric restriction and decreased gly cogen metabolism. Van Itallie and Yang [20] have shown that during caloric restriction, weight loss in the early stages was composed of 66% water that is liberated for each gram of glycogen metabolized. Although we did not 208 Ramadan/Mousa/T x 140-130- document any change in hematocrit, the small but significant increase in plasma constitu ents and osmolarity may indicate a slight decrease in total body water.…”

Section: Discussionmentioning

confidence: 99%

Effect of Ramadan Fasting on Physical Performance, Blood and Body Composition

1994

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In order to understand the physiological adaptations during Ramadan fasting (RF), we studied the body composition, electrolyte balance, hematological response and physical performance in 15 healthy male Kuwaitis (mean age 37 years). Body composition, biochemical analysis, hematological count and exercise performance were evaluated on four occasions: 1 week before RF, 2 weeks during RF, during the last 4 days of RF, and 1 week to 10 days after RF. Cardiopulmonary exercise was performed on a Monark bicycle ergometer at 100 W for 6–8 min. Body composition was obtained using the skin-fold technique, and biochemical and hematological analyses were done using established standard techniques. Subjects lost 1.2% of their total body weight and 5 % of their body fat weight within 2 weeks of RF (p < 0.05). Total serum proteins, albumin and osmolarity significantly increased (p < 0.05) at the end of RF. White blood cells, platelets and serum iron were significantly decreased at the end of RF (p < 0.05). There was no significant change in red blood cell count and hematocrit during RF. Submaximal heart rate was significantly decreased (p < 0.05) by 5.4% whereas submaximal oxygen uptake increased by 12.7% at the end of RF. There was no significant difference in submaximal minute ventilation during the study period. It is concluded that RF is associated with metabolic, hematologic and cardiopulmonary adaptations which are of paramount importance in this period of restricted fluid, mineral and food intake.

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Section: Discussionmentioning

confidence: 99%

Effect of Ramadan Fasting on Physical Performance, Blood and Body Composition

1994

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“…31 Reduced intravascular fluid volume may cause the initial blood pressure fall by reducing venous return and cardiac output. Under such circumstances it is possible that unloading of arterial or low-pressure receptors would activate the sympathetic vasoconstrictor system as a compensatory mechanism to preserve blood pressure.…”

Section: Effects Of Semistarvationmentioning

confidence: 99%

“…4 As mentioned above, reduced intravascular fluid volume may contribute to the fall in blood pressure during severe short-term energy restriction. 31 However, several reports 42 -44 indicate that also after long-term negative energy balance, weight loss re-suits in a contracted blood volume, leading to a decreased cardiac output and lowered blood pressure. We failed to show any contraction of plasma volume in spite of a reduced blood pressure.…”

Section: Effects Of Long-term Energy Restrictionmentioning

confidence: 99%

Effect of energy-restricted diet on sympathetic muscle nerve activity in obese women.

et al. 1991

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Twenty obese women aged 45-65 years with borderline hypertension were allocated randomly to either a group with an energy-restricted diet or to a control group. Body weight, blood pressure, urinary sodium, and urinary excretion of norepinephrine and plasma volume were recorded. Resting muscle sympathetic nerve activity was measured in the peroneal nerve by tungsten microelectrodes and expressed as bursts per minute. These measurements were repeated after 3 days of semistarvation and after a body weight reduction of 7% while each patient's weight was in a steady state. After 3 days of semistarvation, only body weight was reduced, whereas after the long-term energy intake restriction, there were reductions of body weight (79.9±3.4 versus 74.1±3.4 kg;p<0.001), diastolic blood pressure (93+3 versus 86±4 mm Hg; p=0.01), and muscle sympathetic nerve activity (49±2 versus 42±3 bursts/min; p<0.05). Other variables were unchanged. There were no changes in body weight, blood pressure, or muscle sympathetic nerve activity in the control group. We conclude that body weight decrease in obesity results in a reduction of blood pressure that is at least partially caused by a reduction of sympathetic vasoconstrictor activity. (Hypertension 1991;18:783-789) M any studies have shown that a decrease in body weight in hypertensive patients with moderate-to-severe obesity is associated with a fall in blood pressure. 1 -2 The mechanisms behind the blood pressure reduction are only partially understood. Some authors have suggested that a restricted sodium intake 34 contributes to the blood pressure decrement; others have found a fall in blood pressure without a concomitant decrease of sodium intake.5 Based on measurements of circulating norepinephrine concentrations, it has also been proposed that both the acute and the long-term reduction of blood pressure are due to a reduced sympathetic vasoconstrictor drive. In a previous study 13 of obese borderline hypertensive women who had been fasting for 48 hours, we made direct recordings of sympathetic neural outflow to the vascular bed of skeletal muscle and found an essentially unchanged nerve traffic in spite of a significant blood pressure reduction. The patients were energy and sodium restricted. It has been suggested previously 1415 that salt and energy intake restriction have opposite effects on sympathetic nervous activity so that the net effect of a markedly reduced sodium intake combined with a negative energy balance may be no change or even an increased sympathetic drive (expressed as increased levels of plasma norepinephrine). Our previous results are compatible with this hypothesis.The aim of the present study was to clarify the effect of calorie restriction on sympathetic nerve activity by measuring efferent muscle sympathetic activity in a group of obese and borderline hypertensive women before and after a short-term sodiumsupplemented period of fasting and also to assess the effects of a long-term negative energy balance on plasma volume, blood pressure, and efferent vasoco...

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“…That is, greater clarity on the effects of weight changes on health risks and mortality may be produced by separately considering the differential effects of weight change per se vs changes in the degree of fatness. Van Itallie and Yang 14 suggested that the degree of health bene®t achieved from weight loss is likely to be dependent on the degree to which the weight is lost as fat and lean mass is preserved.…”

Section: Introductionmentioning

confidence: 99%

Weight loss increases and fat loss decreases all-cause mortality rate: results from two independent cohort studies

et al. 1999

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OBJECTIVE: In epidemiological studies, weight loss is usually associated with increased mortality rate. Contrarily, among obese people, weight loss reduces other risk factors for disease and death. We hypothesised that this paradox could exist because weight is used as an implicit adiposity index. No study has considered the independent effects of weight loss and fat loss on mortality rate. We studied mortality rate as a function of weight loss and fat loss. DESIGN: Analysis of`time to death' in two prospective population-based cohort studies, the Tecumseh Community Health Study (1890 subjects; 321 deaths within 16 y of follow-up) and the Framingham Heart Study (2731 subjects; 507 deaths within 8 y of follow-up), in which weight and fat (via skinfolds) loss were assessable. RESULTS: In both studies, regardless of the statistical approach, weight loss was associated with an increased, and fat loss with a decreased, mortality rate (P`0.05). Each standard deviation (s.d.) of weight loss (4.6 kg in Tecumseh, 6.7 kg in Framingham) was estimated to increase the hazard rate by 29% (95% con®dence interval CI), (14%, 47%, respectively) and 39% (95% CI, 25%, 54% respectively), in the two samples. Contrarily, each s.d. of fat loss (10.0 mm in Tecumseh, 4.8 mm in Framingham) was estimated to reduce the hazard rate 15% (95% CI, 4%, 25%) and 17% (95% CI, 8%, 25%) in Tecumseh and Framingham, respectively. Generalisability of these results to severely (that is, body mass index BMI) ! 34) obese individuals is unclear. CONCLUSIONS: Among individuals that are not severely obese, weight loss is associated with increased mortality rate and fat loss with decreased mortality rate.

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Diet and Weight Loss

Cited by 54 publications

References 7 publications

Effect of Ramadan Fasting on Physical Performance, Blood and Body Composition

Effect of Ramadan Fasting on Physical Performance, Blood and Body Composition

Effect of energy-restricted diet on sympathetic muscle nerve activity in obese women.

Weight loss increases and fat loss decreases all-cause mortality rate: results from two independent cohort studies

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