Rate Of Fat Loss Research Articles

Measuring breath acetone for monitoring fat loss: Review.

ObjectiveEndogenous acetone production is a by‐product of the fat metabolism process. Because of its small size, acetone appears in exhaled breath. Historically, endogenous acetone has been measured in exhaled breath to monitor ketosis in healthy and diabetic subjects. Recently, breath acetone concentration (BrAce) has been shown to correlate with the rate of fat loss in healthy individuals. In this review, the measurement of breath acetone in healthy subjects is evaluated for its utility in predicting fat loss and its sensitivity to changes in physiologic parameters.ResultsBrAce can range from 1 ppm in healthy non‐dieting subjects to 1,250 ppm in diabetic ketoacidosis. A strong correlation exists between increased BrAce and the rate of fat loss. Multiple metabolic and respiratory factors affect the measurement of BrAce. BrAce is most affected by changes in the following factors (in descending order): dietary macronutrient composition, caloric restriction, exercise, pulmonary factors, and other assorted factors that increase fat metabolism or inhibit acetone metabolism. Pulmonary factors affecting acetone exchange in the lung should be controlled to optimize the breath sample for measurement.ConclusionsWhen biologic factors are controlled, BrAce measurement provides a non‐invasive tool for monitoring the rate of fat loss in healthy subjects.

Differential Loss of Fat and Lean Mass in the Morbidly Obese After Bariatric Surgery

Bariatric surgery has become a common treatment for morbid obesity. The relative changes in body tissue that comprise the substantial weight loss over time are not completely understood. We evaluated the differential rates of fat and lean tissue losses in morbidly obese patients who underwent Roux-en-Y gastric bypass surgery. Body composition was assessed using whole-body dual energy X-ray absorptiometry (DXA) performed at two timepoints in the postoperative period. Patients were stratified by the tertile of rapidity of weight loss expressed as percent reduction in body mass index per month. Thirty two patients (25 women, 7 men) with a mean age of 46.7 +/- 10.4 years and an average initial body weight of 141.4 +/- 29.4 kg experienced a 52.3 +/- 16.6 kg (36.5 +/- 5.5%) weight loss over 13.9 +/- 6.0 months. The incremental rates of lean body mass loss by tertiles were 0.3 +/- 0.6, 0.5 +/- 0.2, and 1.0 +/- 0.8 kg/month (P = 0.02), whereas the rates of fat loss were 1.2 +/- 0.9, 1.8 +/- 0.4, and 2.9 +/- 1.0 kg/month (P = 0.0001). The ratios for lean to fat loss among the respective tertiles were 1:4.0, 1:3.6, and 1:3.0. The correlation between rates of lean and fat mass loss was r = 0.37 (P = 0.04). Only three of the 32 patients (9.4%) patients maintained or gained lean mass following Roux-en-Y gastric bypass surgery. After bariatric surgery, those patients losing weight at the greatest rate appear to have accelerated losses of both lean and fat mass. Few patients maintain lean body mass after bariatric surgery, despite self-reported participation in conventional exercise programs. These data suggest the need for more aggressive interventions to preserve lean body mass during the weight loss phase after Roux-en-Y gastric bypass surgery.

A “mini-fast with exercise” protocol for fat loss

From the standpoint of promoting leanness, exercise is of most value if oxidation of stored fat is maximized during and following the exercise sessions. Bahadori has proposed that this can best be achieved if prolonged exercise of moderate intensity is performed during a 12-14 h "mini-fast" that entails skipping a meal; if subsequent food consumption features low-fat foods, the fat stores expended during and after the exercise will not be fully repleted by dietary fat. Thus, prolonged compliance with such a regimen should lead to steady loss of body fat until a much leaner equilibrium body composition is attained. The feasibility and efficacy of this strategy has been examined in an open pilot study. Participants were asked to perform prolonged, moderate-intensity aerobic exercise at least 3-5 times weekly, nesting each exercise session within a 12-14 h mini-fast. No restrictions were placed on daily calorie consumption, but low-fat, low-glycemic-index food choices were recommended. Of the 34 subjects originally enrolled, 27 returned for follow-up evaluations at 6 and 12 weeks. During the 12 week study, the average fat loss in these 27 subjects - 7.4 kg - corresponded to one-quarter of their baseline fat mass. Fasting insulin levels likewise fell by 25%. The rate of fat loss was at least as great in the second 6 weeks as in the first, suggesting that fat loss might have persisted for some time if the study had been prolonged. This protocol, combining elements of exercise training, fasting, and low-fat eating, is both sustainable and healthful, and in reasonably compliant subjects may have considerable potential for promoting and maintaining leanness and insulin sensitivity.

Conjugated linoleic acid reduces body fat and prevents seasonal weight gain among overweight adults

Conjugated linoleic acid (CLA) supplementation has been shown to reduce fat mass in animals, but results in humans have been inconsistent. To further test the effect of CLA on body composition, we conducted a randomized, double-blind study in 40 overweight adults. For six months including the holiday season, 22 subjects took 3.2 g/d of a 50:50 mixture of cis-9, trans-11 and trans-10, cis-12 isomers of CLA and 18 subjects took a safflower oil placebo. Using the 4-compartment model, we found a decrease in body fat with CLA (P = 0.02): while CLA reduced body fat (1.0 ± 2.2 kg, P = 0.05), placebo tended to increase (0.7 ± 3.0 kg, P = NS). CLA also reduced body weight vs. placebo (P = 0.04). Specifically, CLA attenuated weight gain during the holiday season (P = 0.01). To compare our results with previous studies, we performed a meta-analysis on the rate of fat loss with CLA vs. placebo, which averaged −80 g/wk (P = 0.01). Power analysis indicated that most studies reporting no significant effect of CLA on fat mass were underpowered or of insufficient duration. In conclusion, CLA reduced body fat over six months and prevented weight gain during the holiday season in overweight adults. Research has shown that holiday weight gain contributes to annual weight gain and that overweight individuals are susceptible to greater holiday gains. CLA may aid in reducing these gains, particularly among overweight individuals. Supported by Cognis Co.

BODY MASS AND LIPID CHANGES BY HIBERNATING REPRODUCTIVE AND NONREPRODUCTIVE BLACK BEARS (URSUS AMERICANUS)

This study, conducted on female black bears from 3 study areas in the Rocky Mountains, showed that pregnant females in a state of diapause during early winter had about 89% larger fat depots than did nonreproductive females going into hibernation. Fat provided 92% of the total energy for lactation and gestation. Rates of fat loss (g/day) were 37% greater and protein loss about 2.4 times higher for reproductive females than for nonreproductive females. The cost of winter reproduction, including gestation and lactation, was 1,432 kJ/day to produce 2 young. Although reproduction required elevated protein breakdown, rates of overall protein loss were relatively small, perhaps due to a short period of implantation and an extraordinary ability to hydrolyze urea.

Body Mass and Lipid Changes by Hibernating Reproductive and Nonreproductive Black Bears

Black bears have delayed implantation with fetal development and lactation energy demands during a period of maternal hibernation and starvation. Pregnant females in a state of diapause had about 23% greater fat depots than non­reproductive females going into hibernation. Fat provided 92% of the total energy for lactation and gestation. Rates of fat loss were 27% and protein loss 58% higher for reproductive females compared to non-reproductive females. The cost of winter reproduction to include gestation and lactation was 1432 kj/day to produce two cubs. While reproduction required elevated protein breakdown, the overall loss was relatively small, perhaps due to a short gestation period and urea recycling.

Breath acetone analyzer: diagnostic tool to monitor dietary fat loss

Acetone, a metabolite of fat catabolism, is produced in excessive amounts in subjects on restricted-calorie weight-loss programs. Breath acetone measurements are useful as a motivational tool during dieting and for monitoring the effectiveness of weight-loss programs. We have developed a simple, easy-to-read method that quantifies the amount of acetone in a defined volume of exhaled breath after trapping the sample in a gas-analyzer column. The concentration of acetone, as measured by the length of a blue color zone in the analyzer column, correlates with results obtained by gas chromatography. Using the breath acetone analyzer to quantify breath acetone concentrations of dieting subjects, we established a correlation between breath acetone concentration and rate of fat loss (slope 52.2 nmol/L per gram per day, intercept 15.3 nmol/L, n = 78, r = 0.81). We also discussed the possibility of using breath acetone in diabetes management.

Novel solid-phase assay of ketone bodies in urine

This simple dip-and-read color-matching assay measures ketone bodies in urine. The result is matched with any of the seven colors provided in a color chart. The intensity and hue of the color formed depends on the concentration of acetoacetic acid and follows a gradation starting from light purple (0.2 mol/L acetoacetate) to dark purple and finally to dark violet (9 mol/L). The color developed is independent of pH in the range pH 4-9.5, and is stable for at least 1 h. 3-Hydroxybutyric acid produced no color at the concentrations tested (less than or equal to 100 mmol/L), and acetone was detectable only when greater than or equal to 15 mmol/L. The test was compared with the Ames Ketostix assay in subjects who were on restricted-calorie weight-loss programs. The two methods showed good agreement, except that 20% (21/103) of samples that were negative by Ketostix were read as positive by the new method, which may be more sensitive (detection limit = 0.2 mmol/L). Measurement of urine ketones was unreliable (in comparison with measurement of blood or breath acetone) for monitoring the rate of fat loss during a negative calorie balance.

Fat Levels in Female White-Tailed Deer during the Breeding Season and Pregnancy

Levels of stored body fat, based upon the kidney fat index, were measured for 238 pregnant white-tailed deer through the gestation period and 866 nonpregnant female deer through the breeding season. The deer were collected on the Savannah River Plant (SRP) near Aiken, South Carolina. The percentage of stored body fat of pregnant deer decreased significantly over the length of pregnancy. The rate of fat loss was significantly related to the number of in utero fetuses, conception date, and individual genic heterozygosity but not age, weight, or habitat (either swamp or upland). Greatest fat loss in pregnant deer was for females with two fetuses or females that conceived early in the breeding season. Among nonpregnant females, fat levels increased significantly from September through December. Nonlactating females gained fat during this period at a significantly greater rate than lactating ones. Fat levels of nonpregnant deer differed among age classes but rate of fat increase during the breeding season was not associated with age. Fat levels of nonpregnant deer from the swamp habitat of the SRP were related significantly to individual heterozygosity, with higher levels of stored body fat in heterozygous female deer throughout the breeding season. These results indicate an association between individual heterozygosity and levels of stored energy of white-tailed deer which, in turn, may be related to reproductive success.

Reduction in Resting Energy Expenditure in Relation to Lean Tissue Loss in Obese Subjects during Prolonged Dieting

Resting energy expenditure (REE) was measured by indirect calorimetry during dieting (2.74-3.30 MJ/day) for up to 200 days in overweight patients undergoing continuous metabolic balance studies. The initial rapid reduction in REE in the first 2 weeks of dieting was related to the extent of the immediate nitrogen deficit that follows caloric restriction and was larger (p less than 0.01) in men dieting de novo than either women (NS) or 4 patients of comparable lean body mass who had dieted prior to admission (NS). Because of their smaller metabolic energy deficit on our diets, the reduction in REE in women was small and not significant. In men, the slower long-term reduction in REE (p less than 0.05) was related to a continuing loss of lean tissue with no changes in the REE/m2, REE/kg body weight and REE/mmol creatinine excreted with time. We have previously shown that total energy expenditure (estimated from the rate of fat loss as measured by the difference between body weight changes and weight changes in fluid and protein) does not change significantly during prolonged dieting. The fall in REE in parallel with lean body mass suggests that some increase in the energy expended in daily activities must have occurred.

The effects of energy intake during pregnancy in doe rabbits on pup birth weight, milk output and maternal body composition change in the ensuing lactation

SUMMARYA study was made in rabbits on the effects of energy intake during pregnanoy on pup birth weight and survival, and on doe body composition and milk output in the ensuing lactation. In addition the experiment examined the effects of varying crudeprotein intakes during lactation on the rate of fat loss of does and the resultant energetic efficiency of milk production.Forty-seven multiparous cross-bred does were used. They were offered one of two diets in pregnancy, either diet HE (14·8 MJ digestible energy (DE)/kg D.M.) to appetite or diet LE (12·9 MJ DE/kg D.M.) at maintenance levels. After parturition seven does on each treatment were slaughtered and their body composition analysed (control groups). In lactation the remaining does were evenly allocated to receive either diet LE (195 g crude protein (CP)/kg D.M.) or diet HP (240 g CP/kg D.M.) to appetite. Litter sizes were standardized to six pups and litter growth rates were used as an indirect estimate of milk production. Does were then killed, at random, on day 9 or day 18 of lactation to give an estimate of changes in body composition as lactation progressed.Does offered diet HE during pregnancy had higher carcass fat levels at parturition than their counterparts offered diet LE (496 cf. 370 g/kg carcass D.M. respectively). Litter size was unaffected by dietary treatment during pregnancy but litter weights at birth were significantly greater in HE does (442 cf. 398 g respectively). Pup mortality at birth, however, was also much higher in these animals (28 cf. 9% respectively). Voluntary food intake in early lactation (day 1—9) was depressed by feeding diet HE during pregnanoy. Milk composition was affected by pregnancy diet, with does offered diet HE producing milk containing significantly higher fat levels (HE 123 g fat/kg milk cf. LE 105 g fat/kg milk).Doe carcass composition changes revealed that fat was usually mobilized in early lactation and gained as lactation progressed independent of dietary treatment. The protein content of the fat-free dry matter appeared to be relatively unaffected by the dietary treatments imposed. The data were used to derive an estimate of the partial efficiency of dietary energy utilization (fc) for milk output and maternal tissue gain. The line of best fit was described by the equation ER = 0·65 (±0·17) MEI-1–25, where ER = milk energy output + carcass energy change and MEI = metabolizable energy intake in MJ.

METHOD FOR ESTIMATING RATE OF FAT LOSS DURING TREATMENT OF OBESITY BY CALORIE RESTRICTION

Rates of weight and fat loss in sixteen female and nine male obese patients during calorie restriction (655-789 kcal/day) for up to 120 days were studied by a method for estimating daily changes in body composition. Fat mass is calculated by subtracting daily fluid (calculated from sodium and potassium balances) and protein mass changes from daily weight changes. After the natriuresis of the first 4 days, there was a slower rate of weight loss between days 5 and 28 due largely to a decreasing contribution from fluid and protein losses. No significant change in the rate of weight loss could be shown after the first 28 days. The rate of fat loss did not change significantly from day 5 onwards suggesting no significant change in total energy expenditure during the study period. After 68 days, 93·4% of the weight loss was fat.

Variability in body protein loss during protracted, severe caloric restriction: role of triiodothyronine and other possible determinants

Six morbidly obese subjects were maintained in a metabolic ward for 64 days on liquid diets providing 600 to 800 kcal/day. Three received protein at a level of 1.5 g/kg desirable weight per day. The other three were given an identical diet in which half the protein was replaced by carbohydrate. Because there were no significant differences in either mean protein or mean fat losses between the two groups, the data on all six subjects were combined. Over the 64 days, the mean weight loss (±SEM) of the subjects per 1000 kcal deficit was 174.3 ± 25.5 g. The composition of this weight loss was 36.0% water, 58.9% fat, and 5.1% protein. Although the rate of fat loss was relatively constant throughout the study, wide interindividual variations in cumulative protein (nitrogen) deficit were observed. Total nitrogen losses per subject ranged from 90.5 to 278.7 g. Cumulative nitrogen loss during the first 16 days tended to correlate negatively with initial mean fat cell size and positively with initial lean body mass. Most notable was the strong negative correlation between the size of the decrease in serum triiodothyronine over the 64-day study and the magnitude of the concurrent cumulative N deficit. During severe caloric restriction, one's ability to decrease circulating serum triiodothyronine levels may be critical to achievement of an adaptational decrease in body protein loss.

A note on the effects of body fatness and level of food intake on the rate of fat loss in lactating ewes

ABSTRACTData from three comparative slaughter experiments involving a total of 73 ewes were used to study the influence of body fat content at the start of lactation (X1 kg) and of metabolizable energy intake (X2, MJ/day), on the rate of loss of body fat by lactating ewes over the first 6 weeks of lactation (Y, g/day). The relationship was described by the equation:Thus the rate of fat loss was greater for ewes with higher initial fat contents, but the differential became less as metabolizable energy intake increased. Since increases in body fatness depress food intake it was not possible to prevent loss of body fat during early lactation in fat ewes given high concentrate diets ad libitum. The likely response in milk yield to increase in body fatness at parturition is therefore strongly dependent on the relative levels of body fatness and metabolizable energy intake. The value of any improvement in condition of the ewe at parturition may be considerable when metabolizable energy intake during lactation is low but much less when it is expected to be high.

Studies on reproduction in prolific ewes. 4. Sequential changes in the maternal body during pregnancy

SUMMARYSeventy-eight Finnish Landrace × Dorset Horn ewes in lamb to Suffolk rams were slaughtered serially between 50 and 145 days of gestation. The mean litter size was 2·7. The daily feeding regime aimed to provide each ewe with 15 MJ of metabolizable energy (ME) in the first month of gestation and 9·4 MJ in the second and third. Thereafter the ewes were provided with a basal intake of either 9·6 MJ (low plane, LP) or 13·4 MJ (high plane, HP) plus 1·3 MJ for each foetus.For ewes with 2, 3 and 4 foetuses the mean percentage changes in maternal body weight over pregnancy were respectively — 5, — 10 and — 14 (LP) or + 3, — 2 and — 6 (HP). Changes in weights of blood, liver and the empty gastro-intestinal tract through gestation varied with the plane of nutrition but not with number of foetuses. In contrast, udder weight at parturition was dependent on number of foetuses but not on plane of nutrition.Increased hydration of the maternal tissues in late pregnancy tended to mask concurrent losses of body fat. For example, over the last 2 months, HP ewes carrying quadruplets lost on average 1·0 kg in body weight but 5·5 kg of (chemically determined) fat. The latter was lost at a rate which increased up to an average of 170 g/day over the last 2 weeks of pregnancy. Net changes in body protein were estimated to be relatively small, but there was some redistribution, including loss from muscle and gain by the udder. There was no evidence of any demineralization of the maternal skeleton.The practical significance of the changes in body composition is discussed, in particular that of the increasing rates of loss of body fat with increasing litter size. It is suggested that the dangers implicit in these rates of fat loss must be taken into consideration when deciding on dietary regimes and the timing of breeding cycles for highly prolific ewes, or indeed when embarking on a programme of increased prolificacy.

The effect of high fat and high carbohydrate diets on rates of weight loss in mice

The rate of weight loss in mice produced by restricting calorie intake below normal requirements is influenced by the type of food predominating in the diet; fat producing a rapid loss and carbohydrate a slower one. The amount of weight loss in both instances can be accounted for almost entirely by the extent of the negative carbon balances. The varying rates of weight loss are due to differences in the rate of fat loss and not to changes in total body water. This is confirmed by carcass analysis. In mice on a normal diet and in carbon equilibrium, about half the carbon is excreted as CO2 and half in the form of organic molecules with an energy value of their own. With restricted calorie high carbohydrate diets the proportion excreted as CO2 rises to over 80 per cent of the total while the proportion excreted in the form of complex molecules falls. With restricted calorie high fat diets the proportion excreted as CO2 remains normal. The half excreted as complex organic moleceules is significantly altered as to its distribution between feces and urine. With restricted calorie feeding the proportion of food and/or tissue totally degraded to CO2 influences the amount of energy available to the organism. The demands on its own fat stores are consequently greater when fat is the major constituent of such a diet. It is suggested that this view provides a partial explanation of the different rates of weight loss with alteration in dietary composition. The rate of weight loss in mice produced by restricting calorie intake below normal requirements is influenced by the type of food predominating in the diet; fat producing a rapid loss and carbohydrate a slower one. The amount of weight loss in both instances can be accounted for almost entirely by the extent of the negative carbon balances. The varying rates of weight loss are due to differences in the rate of fat loss and not to changes in total body water. This is confirmed by carcass analysis. In mice on a normal diet and in carbon equilibrium, about half the carbon is excreted as CO2 and half in the form of organic molecules with an energy value of their own. With restricted calorie high carbohydrate diets the proportion excreted as CO2 rises to over 80 per cent of the total while the proportion excreted in the form of complex molecules falls. With restricted calorie high fat diets the proportion excreted as CO2 remains normal. The half excreted as complex organic moleceules is significantly altered as to its distribution between feces and urine. With restricted calorie feeding the proportion of food and/or tissue totally degraded to CO2 influences the amount of energy available to the organism. The demands on its own fat stores are consequently greater when fat is the major constituent of such a diet. It is suggested that this view provides a partial explanation of the different rates of weight loss with alteration in dietary composition.

Chemical and Histological Studies of Wild and Hatchery Salmon in Fresh Water

Abstract In a study of coho salmon (Oncorhynchus kisutch), the gross chemical and histological changes occurring over a 14-month period spent in fresh water were determined. The determinations were made at 3-month intervals on: 1) hatchery-reared fish, 2) fish hatchery-reared for 3, 6, 9, and 12 months and then planted in a controlled stream for the remainder of the period; and 3) an indigenous group of wild fish in this stream. Wild fish showed high incidence of tissue damage from spinose hairs of the moth larva, Halisidota argentata. Hatchery fish were similarly affected with the severity and incidence of lesions varying directly with the time of exposure of the larvae in the wild environment. Both groups of fish were heavily parasitized by sporozoan organisms in the kidney and spinal cord. Kidney disease appeared in both wild and planted hatchery fish. The gross chemical composition of hatchery fish transformed rapidly after planting to that of the wild fish. Although the initial rate of fat loss is es...