Adjustments in daily energy expenditure to caloric restriction and weight loss by adult obese and lean Zucker rats

The 24 h resting (postabsorptive) energy expenditure of adult female lean and obese Zucker rats was examined both at the body weights each genotype spontaneously maintained and at body weights that were reduced 6-10 percent by restricting food intake for 2 weeks to 70 or 55 percent of normal. At their normally-maintained body weight, lean rats expended energy at a daily rate appropriate to their body mass according to the Kleiber equation (predicted kcal/day = 70.0 x BW-0.75kg observed kcal/day = 70.66 x BW-0.75kg). However, expenditure rates declined significantly in the weight-reduced lean rats restricted to 70 or 55 percent of normal intake (to 64.1 and 61.3 kcal/kg0.75). The obese rats expended energy at a rate lower than predicted by the Kleiber equation prior to weight loss (49.5 x BW-0.75kg). But, rates of daily expenditure in the obese rats was further reduced by 70 or 55 percent restriction (to 43.7 and 42.4 x BW-0.75kg), a decline proportionately as large or larger than that displayed by restricted lean rats. With this reduced metabolic rate, the total daily caloric expenditure of obese rats restricted to 55 percent of normal intake approximated that of unrestricted lean rats weighing only half as much (27.8 vs 27.5 kcal/day; 569 vs 285 g). Evidently, Zucker obese rats display the same adaptive reductions in resting metabolism as do leans in response to energy deficit and weight loss. In both, these adjustments in expenditure act to stabilize body weight at the levels that typify each genotype.     

The role of energy expenditure in the differential weight loss in obese women on low-fat and low-carbohydrate diets

We have recently reported that obese women randomized to a low-carbohydrate diet lost more than twice as much weight as those following a low-fat diet over 6 months. The difference in weight loss was not explained by differences in energy intake because women on the two diets reported similar daily energy consumption. We hypothesized that chronic ingestion of a low-carbohydrate diet increases energy expenditure relative to a low-fat diet and that this accounts for the differential weight loss. To study this question, 50 healthy, moderately obese (body mass index, 33.2 +/- 0.28 kg/m(2)) women were randomized to 4 months of an ad libitum low-carbohydrate diet or an energy-restricted, low-fat diet. Resting energy expenditure (REE) was measured by indirect calorimetry at baseline, 2 months, and 4 months. Physical activity was estimated by pedometers. The thermic effect of food (TEF) in response to low-fat and low-carbohydrate breakfasts was assessed over 5 h in a subset of subjects. Forty women completed the trial. The low-carbohydrate group lost more weight (9.79 +/- 0.71 vs. 6.14 +/- 0.91 kg; P < 0.05) and more body fat (6.20 +/- 0.67 vs. 3.23 +/- 0.67 kg; P < 0.05) than the low-fat group. There were no differences in energy intake between the diet groups as reported on 3-d food records at the conclusion of the study (1422 +/- 73 vs. 1530 +/- 102 kcal; 5954 +/- 306 vs. 6406 +/- 427 kJ). Mean REE in the two groups was comparable at baseline, decreased with weight loss, and did not differ at 2 or 4 months. The low-fat meal caused a greater 5-h increase in TEF than did the low-carbohydrate meal (53 +/- 9 vs. 31 +/- 5 kcal; 222 +/- 38 vs. 130 +/- 21 kJ; P = 0.017). Estimates of physical activity were stable in the dieters during the study and did not differ between groups. These results confirm that short-term weight loss is greater in obese women on a low-carbohydrate diet than in those on a low-fat diet even when reported food intake is similar. The differential weight loss is not explained by differences in REE, TEF, or physical activity and likely reflects underreporting of food consumption by the low-fat dieters.     

Short term effects of energy restriction and dietary fat sub-type on weight loss and disease risk factors

Background and aimsDecreasing energy intake relative to energy expenditure is the indisputable tenet of weight loss. In addition to caloric restriction modification of the type of dietary fat may provide further benefits. The aim of the present study was to examine the effect of energy restriction alone and with dietary fat modification on weight loss and adiposity, as well as on risk factors for obesity related disease.Methods and resultsOne-hundred and fifty overweight men and women were randomized into a 3 month controlled trial with four low fat (30% energy) dietary arms: (1) isocaloric (LF); (2) isocaloric with 10% polyunsaturated fatty acids (LF-PUFA); (3) low calorie (LF-LC) (?2 MJ); (4) low calorie with 10% PUFA (LF-PUFA-LC). Primary outcomes were changes in body weight and body fat and secondary outcomes were changes in fasting levels of leptin, insulin, glucose, lipids and erythrocyte fatty acids. Changes in dietary intake were assessed using 3 day food records. One-hundred and twenty-two participants entered the study and 95 completed the study. All groups lost weight and body fat (P < 0.0001 time effect for both), but the LC groups lost more weight (P = 0.026 for diet effect). All groups reduced total cholesterol levels (P < 0.0001 time effect and P = 0.017 intervention effect), but the LC and PUFA groups were better at reducing triacylglycerol levels (P = 0.056 diet effect). HDL increased with LF-LC and LF-PUFA but not with LF-PUFA-LC (0.042 diet effect). The LF and LF-LC groups reported greater dietary fat reductions than the two PUFA groups (P = 0.043).ConclusionEnergy restriction has the most potent effect on weight loss and lipids, but fat modification is also beneficial when energy restriction is more modest.     

Effect of a high-protein, energy-restricted diet on weight loss and energy expenditure after weight stabilization in hyperinsulinemic subjects

OBJECTIVE: To determine the effect of replacing some dietary carbohydrate with protein, during energy restriction, on weight loss, total energy expenditure (TEE), resting energy expenditure (REE), respiratory quotient (RQ), and the thermic effect of feeding (TEF) in subjects with hyperinsulinemia. DESIGN: Parallel, clinical intervention study of 12 weeks energy restriction (6.5 MJ/day) and 4 weeks energy balance (8.2 MJ/day) in two groups of subjects randomly assigned to either a high-protein (HP) diet (27% of energy (%E) as protein, 45%E as carbohydrate) or a lower-protein (LP) diet (16%E as protein, 57%E as carbohydrate). SUBJECTS: A total of 36 obese nondiabetic volunteers with hyperinsulinemia (10 males/26 females, aged 34-65 y, BMI 28-43 kg/m(2), fasting insulin 12-45 mU/l). MEASUREMENTS: Body weight and composition, TEE, REE, and RQ were measured at baseline and at week 16. In addition, the TEF to an HP or LP meal was determined for 3 h, at baseline and at week 16. RESULTS: After 16 weeks, weight loss was similar in response to each diet; the overall decrease was 7.9+/-0.6 kg (P<0.001), of which 6.8+/-0.5 kg was fat (P<0.001). REE fell similarly with each diet; the overall decrease was 719+/-106 kJ/day (P<0.001). The TEF was 2% greater after the HP than after the LP meal at baseline (P<0.01) and 0.8% greater at week 16 (P=0.35). After 16 weeks, the TEF was not reduced in either dietary group. There was no change in TEE after 16 weeks. CONCLUSION: In subjects with hyperinsulinemia an energy-restrictive diet containing an increased protein-to-carbohydrate ratio does not enhance weight loss or significantly affect energy expenditure. Caloric restriction, rather than the macronutrient composition of the diet, is the most important determinant of weight loss.     

High circulating thyrotropin levels in obese women are reduced after body weight loss induced by caloric restriction

CONTEXT: Previous clinical studies concerning the impact of body weight loss on single plasma TSH concentration measurements or the TSH response to TRH in obese humans have shown variable results. OBJECTIVE: The objective of this study was to investigate the effect of weight loss induced by caloric restriction on diurnal TSH concentrations and secretion in obese humans. DESIGN: This was a clinical, prospective, crossover study. SETTING: The study was conducted at the Clinical Research Center of Leiden University Medical Center. PARTICIPANTS: Eleven obese premenopausal women (body mass index, 33.3 +/- 0.7 kg/m2) were studied. INTERVENTION: The study intervention was weight loss (50% reduction overweight by caloric restriction). MAIN OUTCOME MEASURE(S): Twenty-four-hour plasma TSH concentrations (10-min intervals) and the 24-h TSH secretion rate, calculated by a waveform-independent deconvolution technique (Pulse), were determined. RESULTS: The 24-h TSH secretion rate was significantly higher in obese women than in normal weight controls, and weight loss was accompanied by diminished TSH release (before weight loss, 43.4 +/- 6.4 mU/liter.24 h; after weight loss, 34.4 +/- 5.9 mU/liter.24 h; P = 0.02). Circulating free T3 levels decreased after weight loss from 4.3 +/- 0.19 to 3.8 +/- 0.14 pmol/liter (P = 0.04). Differences in 24-h TSH release correlated positively with the decline of circulating leptin (r2 = 0.62; P < 0.01). Conclusions: Elevated TSH secretion in obese women is significantly reduced by diet-induced weight loss. Among various physiological cues, leptin may be involved in this phenomenon. The decreases in TSH and free T3 may blunt energy expenditure in response to long-term calorie restriction, thereby frustrating weight loss attempts of obese individuals.     

Peptide YY is a regulator of energy homeostasis in obese children before and after weight loss

CONTEXT: The gut hormone peptide YY(3-36) (PYY) reduces food intake via hypothalamic Y2 receptors in the brain. There is not much known about PYY in obese children. OBJECTIVE: The objective of this study was to investigate the role of PYY in the metabolic changes in obese children and its change during weight loss. SETTING: The study was performed at a university medical center. PARTICIPANTS: We studied 73 obese children and 45 age-matched normal-weight children. INTERVENTIONS: We determined fasting serum total PYY and leptin by RIA in obese and normal-weight children. Fasting PYY was also measured in 28 obese children before and after completion of a 1-yr outpatient weight reduction program. MAIN OUTCOME MEASURES: PYY, insulin, and body mass index were the main outcome measures. RESULTS: Obese children demonstrated significantly lower PYY levels than lean children (median, 67 vs. 124 pg/ml; P < 0.001). Fasting PYY correlated negatively to the degree of overweight. PYY levels did not differ significantly between boys and girls, nor between prepubertal and pubertal children. The group of patients participating in the outpatient weight reduction program was divided into four quartiles according to their changes in body mass index SD score over a 1-yr period. PYY increased significantly in patients with the most effective weight loss, but decreased in the subgroup of children with weight gain. CONCLUSIONS: PYY is negatively correlated to the degree of overweight, with reduced values in obese compared with normal-weight children. Decreased PYY levels could predispose subjects to develop obesity. Our results indicate that low pretreatment PYY levels that increase during weight loss may be a predictor of maintained weight loss.     

Obese subjects carrying the 11482G>A polymorphism at the perilipin locus are resistant to weight loss after dietary energy restriction

CONTEXT: Dietary treatment of obesity could be improved if predictive information about the individual's genetic response to diet was available. Adipose tissue has been the focus of efforts to identify candidate genes. Perilipin is a major protein found in adipocytes, and perilipin knockout mice are lean and resistant to diet-induced obesity. OBJECTIVE: The objective of the study was to examine the association of several polymorphisms at the perilipin (PLIN) locus with obesity and weight reduction in response to a low-energy diet in obese patients. DESIGN: This study was a 1-yr randomized (depending on the PLIN genotype) trial with three follow-up evaluations. SETTING: The study was conducted at a university research center. SUBJECTS: One hundred fifty obese patients (body mass index, 42 +/- 8 kg/m2) at baseline and 48 patients who completed the dietary follow-up treatment for weight loss participated in the study. INTERVENTIONS: Subjects completed a 1-yr low-energy diet. MAIN OUTCOMES MEASUREMENTS: Body weight (BW) at baseline and 3, 6, and 12 months was measured. RESULTS: The minor A-allele at the PLIN 11482G>A polymorphism was associated with lower baseline BW. Moreover, we found a gene-diet interaction (P = 0.015) between this polymorphism and weight loss in patients that completed the 1-yr dietary treatment. Diet resulted in significant decreases in BW (from 114.3 +/- 3.9 kg at baseline to 105.5 +/- 3.5 kg at 1 yr; P lineal trend, 0.020) in GG patients (n = 33). Conversely, carriers of the minor A allele (n = 15) did not show significant changes in BW (from 105.0 +/- 4.6 kg at baseline to 104.3 +/- 4.4 kg at 1 yr; P lineal trend, 0.985). This gene-diet interaction remained statistically significant, even after adjustment for differences in BW at baseline and for other potential confounders. CONCLUSIONS: PLIN11482A carriers were resistant to weight loss, suggesting that this polymorphism may predict outcome of BW reduction strategies based on low-energy diets.     

The comparative and cumulative effects of a dietary restriction and exercise on weight loss

OBJECTIVE: To assess the independence of changes made in diet and physical activity for weight loss; and, to examine the comparative and cumulative effects of these behavioral changes on weight loss outcomes. DESIGN: The observational study is based on longitudinal data collected from 674 women and 288 men enrolled in a 2-year weight loss program introduced into a managed care setting. MEASUREMENTS: The outcome variable was body mass index (BMI) change from baseline to 2-year follow-up. Primary independent variables were changes in physical activity and dietary fat intake, assessed as continuous measures using the Paffenbarger Physical Activity Questionnaire and Block Fat Screener Questionnaire, respectively. Two-way ANCOVA was used to assess the relative effect on BMI of behavioral changes. RESULTS: Study results showed no preference for diet or physical activity change as a weight loss strategy. For both genders, the relationship between the two behaviors was synergistic rather than compensatory. Examination of the comparative benefits of behavioral changes indicated that, for women and men, restricting fat intake was more effective than increasing exercise for weight loss. While fat restrictions alone contributed to weight loss in both genders, exercise alone provided weight loss benefits to men, only. The cumulative effect of weight loss behaviors varied by gender. In women, an interaction was observed. The response of weight to fat restriction was greater among those who increased their exercise moderately or substantially. In men, there was no interaction; exercise increases helped to offset weight gain or provided small weight loss benefits at all levels of dietary fat change. CONCLUSION: Dietary changes appeared to be more effective than increased physical activity for weight loss. For women, the cumulative effect of concomitant changes in diet and exercise on weight loss was more than additive.     

Effect of weight loss on inflammatory and endothelial markers and FMD using two low-fat diets

OBJECTIVE: Cardiovascular disease is strongly associated with obesity and there is evidence that weight loss has positive effects on cardiovascular disease risk. The aims of this study were to compare meal replacements (MR) with a conventional low-fat diet as weight loss strategies and to examine the effect of weight loss on flow-mediated dilatation (FMD) and other markers of endothelial function in overweight Australians with raised triglycerides (TG) (> 2 mmol/l). RESEARCH METHODS: Subjects matched for age, gender, fasting plasma TG and body mass index were randomized to two low- fat high- carbohydrate weight loss strategies (both < 6000 kJ), one using MR and the other a structured eating plan, control (C). Subjects followed both diets for 3 months. In total, 55 subjects completed the study. FMD, pulse wave velocity and blood pressure (BP) were measured at baseline and at 3 months, as were fasting blood samples for lipids, glucose, insulin, C reactive protein (CRP) and endothelium-derived factors. RESULTS: Mean weight loss was 6.3 +/- 3.7 kg (6.0 +/- 4.2 vs 6.63 +/- 3.35 kg, MR vs C) with no difference between diet groups. TG, insulin, CRP, plasminogen activator inhibitor 1 (PAI-1) and soluble intracellular adhesion molecule-1 (sICAM1) fell after weight loss, but FMD did not change. Systolic BP fell by 8 mmHg and pulse wave velocity improved. DISCUSSION: In subjects with elevated TG, weight loss resulted in significant improvements in cardiovascular risk markers, particularly endothelium-derived factors (PAI-1 and sICAM1). However, FMD did not improve with weight loss.     

Changes in renal function during weight loss induced by high vs low-protein low-fat diets in overweight subjects

BACKGROUND: Due to the high satiating effect of protein, a high-protein diet may be desirable in the treatment of obesity. However the long-term effect of different levels of protein intake on renal function is unclear. OBJECTIVE: To assess the renal effects of high vs low protein contents in fat-reduced diets. DESIGN: Randomized 6 months dietary intervention study comparing two controlled ad libitum diets with 30 energy (E%) fat content: high-protein (HP; 25 E%) or low-protein, (LP, 12 E% protein). All food was provided by self-selection in a shop at the department, and high compliance to the diet composition was confirmed by measurements of urinary nitrogen excretion. SUBJECTS: 65 healthy, overweight and obese (25相似文献   

A low-fat diet has a higher potential than energy restriction to improve high-fat diet-induced insulin resistance in mice

Previous studies have shown that energy restriction (ER) or low-fat (LF) diets have beneficial effects on high-fat (HF) diet-induced obesity and non-insulin-dependent diabetes. However, comparison between ER and low-fat diet regarding the effect on insulin resistance and lipid metabolism has not been reported. After inducing insulin resistance by HF feeding for 20 weeks, male C57BL/6J mice were divided into 3 groups. For a period of 12 weeks, group 1 received energy restriction (70% of ad libitum, HF diet), group 2 LF diet, and group 3 maintained on HF diet. Body weight and energy intake were reduced equally in ER and LF feeding. Plasma insulin levels were decreased on LF feeding, but were unchanged on ER, when compared with HF feeding. Glucose tolerance and insulin sensitivity tests revealed that insulin sensitivity was improved more efficiently by LF feeding than on ER. Plasma triglyceride (TG) levels were lower on LF feeding compared with ER and HF feeding. Measurement of hepatic very low-density lipoprotein (VLDL)-TG production revealed a lower production after LF diet feeding or ER compared with HF diet feeding. In summary, our data show that LF diet has a higher potential than ER to improve HF diet-induced insulin resistance, and that there is an association between improvement of insulin resistance and decrease of TG levels.     

HMB attenuates muscle loss during sustained energy deficit induced by calorie restriction and endurance exercise

ObjectiveTo investigate the efficacy and underlying mechanisms of β-hydroxy-β-methylbutyrate (HMB) on body composition, muscle mass and physical performance under catabolic versus normal training conditions.Materials/MethodsMice were divided into four groups (n = 10/group): 1) ALT = ad libitum + trained (1 h/d for 3 d/wk); 2) ALTH = ALT + HMB (0.5 g/kg BW/d); 3) C = calorie restricted (? 30%) + trained (6 h/d, 6 d/wk); and 4) CH = C + HMB. Repeated in vivo assessments included body composition, grip strength and sensorimotor coordination before and after the experimental protocol, while in vitro analyses included muscle wet weights, expression of selected genes and proteins regulating muscle mass, and myofiber cross-sectional area. ANOVAs were used with significance set at p < 0.05.ResultsALTH had greater lean mass than ALT and sensorimotor function increased in ALTH, but decreased in ALT under normal training conditions. Grip strength decreased only in C, but was maintained in CH. Gastrocnemius mass and myofiber CSA were greater in CH than C following catabolic conditions. Gastrocnemius atrogin-1 mRNA expression was elevated in C but not in CH compared to all other groups whereas atrogin-1 protein levels showed no significant changes.ConclusionHMB improves body composition and sensorimotor function during normal training and attenuates muscle mass and strength loss during catabolic conditions.     

The energy density of weight loss in semistarvation

The energy density of weight loss in semistarvation has been calculated using the two-reservoir energy model and has been found to be 4436 +/- 869 kcal/kg (18.57 +/- 3.60 MJ/kg). For the first 12 weeks of the semistarvation period, the coefficient of variation was 0.19 indicating that the energy density was reasonably constant. The value reported here is considerably less than the commonly accepted value. Calculation of the energy density of the change in the lean body mass shows a general decline in value which we attribute to a decrease in the rate of protein catabolism. The initial protein loss rate was 0.48 +/- 0.12 kg/wk while the average protein loss rate for the second 6 weeks of semistarvation was found to be 0.12 +/- 0.03 kg/week. It is also shown that the response time of the lean body mass decrease was 64 +/- 2 days while that of the fat store decrease was 135 +/- 4 days.     

Retention rates and weight loss in a commercial weight loss program

OBJECTIVE: To evaluate and describe retention rates and weight loss in clients participating in a commercial weight loss program. SUBJECTS: A total of 60 164 men and women ages 18-79 years who enrolled in the Jenny Craig Platinum program between May 2001 and May 2002. METHODS: Retention rates, mean weight loss and percent weight loss were calculated on a weekly basis for the 52-week period following initial enrollment in the weight loss program. Clients were categorized based on final week of participation in the program (weeks 1-4, weeks 5-13, weeks 14-26, weeks 27-39 and weeks 40-52) and weight loss was calculated at final week. A subgroup of clients was identified based on attendance through 13, 26 and 52 weeks. Mean and percent weight loss was calculated for these subgroups of clients. RESULTS: Of the 60 164 men and women who enrolled in the weight loss program, 73% were retained in the program after 4 weeks, 42% at 13 weeks, 22% at 26 weeks and 6.6% at 52 weeks. Clients who dropped out of the program during the first 4 weeks lost 1.1+/-1.6% (mean+/-s.d.) of their initial body weight, whereas clients who dropped out between 40 and 52 weeks lost 12.0+/-7.2%. Clients in the 13-week, 26-week and 52-week cohorts lost 8.3+/-3.3, 12.6+/-5.1 and 15.6+/-7.5% of their initial body weight, respectively. CONCLUSION: Weight loss was greater among clients who were retained in the program longer. The findings from this study suggest that a commercial weight loss program can be an effective weight loss tool for individuals who remain active in the program.     

Effects of low-carbohydrate vs low-fat diets on weight loss and cardiovascular risk factors: a meta-analysis of randomized controlled trials

BACKGROUND: Low-carbohydrate diets have become increasingly popular for weight loss. However, evidence from individual trials about benefits and risks of these diets to achieve weight loss and modify cardiovascular risk factors is preliminary. METHODS: We used the Cochrane Collaboration search strategy to identify trials comparing the effects of low-carbohydrate diets without restriction of energy intake vs low-fat diets in individuals with a body mass index (calculated as weight in kilograms divided by the square of height in meters) of at least 25. Included trials had to report changes in body weight in intention-to-treat analysis and to have a follow-up of at least 6 months. Two reviewers independently assessed trial eligibility and quality of randomized controlled trials. RESULTS: Five trials including a total of 447 individuals fulfilled our inclusion criteria. After 6 months, individuals assigned to low-carbohydrate diets had lost more weight than individuals randomized to low-fat diets (weighted mean difference, -3.3 kg; 95% confidence interval [CI], -5.3 to -1.4 kg). This difference was no longer obvious after 12 months (weighted mean difference, -1.0 kg; 95% CI, -3.5 to 1.5 kg). There were no differences in blood pressure. Triglyceride and high-density lipoprotein cholesterol values changed more favorably in individuals assigned to low-carbohydrate diets (after 6 months, for triglycerides, weighted mean difference, -22.1 mg/dL [-0.25 mmol/L]; 95% CI, -38.1 to -5.3 mg/dL [-0.43 to -0.06 mmol/L]; and for high-density lipoprotein cholesterol, weighted mean difference, 4.6 mg/dL [0.12 mmol/L]; 95% CI, 1.5-8.1 mg/dL [0.04-0.21 mmol/L]), but total cholesterol and low-density lipoprotein cholesterol values changed more favorably in individuals assigned to low-fat diets (weighted mean difference in low-density lipoprotein cholesterol after 6 months, 5.4 mg/dL [0.14 mmol/L]; 95% CI, 1.2-10.1 mg/dL [0.03-0.26 mmol/L]). CONCLUSIONS: Low-carbohydrate, non-energy-restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for up to 1 year. However, potential favorable changes in triglyceride and high-density lipoprotein cholesterol values should be weighed against potential unfavorable changes in low-density lipoprotein cholesterol values when low-carbohydrate diets to induce weight loss are considered.