Sympathetic support of energy expenditure and sympathetic nervous system activity after gastric bypass surgery

Objective:

This study was designed to determine how gastric bypass affects the sympathetically‐mediated component of resting energy expenditure (REE) and muscle sympathetic nerve activity (MSNA).

Design and Methods:

We measured REE before and after beta‐blockade in seventeen female subjects approximately three years post‐gastric bypass surgery and in nineteen female obese individuals for comparison. We also measured MSNA in a subset of these subjects.

Results:

The gastric bypass subjects had no change in REE after systemic beta‐blockade, reflecting a lack of sympathetic support of REE, in contrast to obese subjects where REE was reduced by beta‐blockade by approximately 5% (P < 0.05). The gastric bypass subjects, while still overweight (BMI = 29.3 vs 38.0 kg·m^?2 for obese subjects, P < 0.05), also had significantly lower MSNA compared to obese subjects (10.9 ± 2.3 vs. 21.9 ± 4.1 bursts·min^?1, P < 0.05). The reasons for low MSNA and a lack of sympathetically mediated support of REE after gastric bypass are likely multifactorial and may be related to changes in insulin sensitivity, body composition, and leptin, among other factors.

Conclusions:

These findings may have important consequences for the maintenance of weight loss after gastric bypass. Longitudinal studies are needed to further explore the changes in sympathetic support of REE and if changes in MSNA or tissue responsiveness are related to the sympathetic support of REE.

     

Cardiac Parasympathetic Activity Is Increased by Weight Loss in Healthy Obese Women

Objective: We studied the effect of weight reduction on cardiac parasympathetic activity (PSA) in obese women. We also studied the relationship between the changes of PSA, resting energy expenditure (REE), and major cardiovascular risk factors. Research Methods and Procedures: Changes of cardiac vagal tone, an index of PSA, REE, and major cardiovascular risk factors, were measured in 52 healthy obese women after a 6‐month weight reduction. Ten of the women were remeasured at 12 and 24 months. Cardiac vagal tone was assessed by a vagal tone monitor and REE by indirect calorimeter. Results: Cardiac vagal tone increased significantly (p = 0.046), averaging a 9.5% weight loss in 6 months. The vagal tone increased further with weight loss during the following 6 months, and thereafter, it declined with weight regain. The increase of cardiac vagal tone correlated significantly with decreases of body weight, fat mass, waist circumference, serum insulin, and heart rate. REE adjusted for fat‐free mass and age did not change with weight loss and was not related to cardiac vagal tone at any time‐point. Discussion: Cardiac PSA activity increases with weight loss in obese women. This increase may not be maintained long‐term if body weight is regained. The rise of cardiac PSA is correlated with decreases of body fat mass, abdominal fat, serum insulin, and heart rate. Cardiac PSA is not related to REE.     

Influence of Sibutramine on Energy Expenditure in African American Women

Objective: African American women have a high prevalence of obesity, which partially may be explained by their lower rates of resting energy expenditure (REE). The aim of this study was to examine the influence of acute sibutramine administration on REE and post‐exercise energy expenditure in African American women. Research Methods and Procedures: A total of 15 premenopausal, African American women (age, 29 ± 5 years; body fat, 38 ± 7%) completed a randomized, double‐blind cross‐over design with a 30‐mg ingestion of sibutramine or a placebo. Each trial was completed a month apart in the follicular phase and included a 30‐minute measurement of REE 2.5 hours after sibutramine or placebo administration. This was followed by 40 minutes of cycling at ～70% of peak aerobic capacity and a subsequent 2‐hour measurement of post‐cycling energy expenditure. Results: There was no difference (p > 0.05) in REE (23.70 ± 2.81 vs. 23.69 ± 2.95 kcal/30 min), exercise oxygen consumption (1.22 ± 0.15 vs. 1.25 ± 0.15 liter/min), and post‐cycling energy expenditure (104.2 ± 12.7 vs. 104.9 ± 11.4 kcal/120 min) between the sibutramine and placebo trials, respectively. Cycling heart rate was significantly higher (p = 0.01) during the sibutramine (158 ± 14 beats/min) vs. placebo (150 ± 12 beats/min) trials. Discussion: These data demonstrate that acute sibutramine ingestion does not increase REE or post‐exercise energy expenditures but does increase exercising heart rate in overweight African American women. Sibutramine may, therefore, impact weight loss through energy intake and not energy expenditure mechanisms.     

Reversal of Small,Dense LDL Subclass Phenotype by Weight Loss Is Associated With Impaired Fat Oxidation

Adiposity is more prevalent among individuals with a predominance of small, dense low‐density lipoprotein (LDL) (pattern B) particles than among those with larger LDL (pattern A). We tested for differences in resting energy expenditure (REE) and respiratory quotient (RQ) in overweight men with pattern A (n = 36) or pattern B (n = 60). Men consumed a standardized isoenergetic diet for 3 weeks after which a ～9 kg weight loss was induced by caloric deficit for 9 weeks, followed by 4 weeks of weight stabilization. REE and RQ were measured by indirect calorimetry before and after weight loss. Results were analyzed separately in pattern B men who converted to pattern A (B→A; n = 35) and those who did not (B→B; n = 25). At baseline, B→B men had higher trunk fat, triacylglycerol (TG) and insulin concentrations, homeostasis model assessment of insulin resistance (HOMA_IR), and smaller LDL particles compared to B→A men and baseline pattern A men who remained pattern A (A→A; n = 35). REE normalized to fat‐free mass did not change after weight loss. RQ decreased in A→A men, increased in B→A men, and did not change significantly in B→B men after weight loss. Calculated fat oxidation rates paralleled the RQ results. Baseline plasma TG concentrations were positively correlated with RQ and inversely correlated with the magnitude of weight loss achieved for a given prescribed energy reduction in the entire study population. Pattern B men who converted to pattern A with weight loss may have an underlying impairment in fat oxidation that predisposes to both dyslipidemia and an impaired ability to achieve weight loss by energy restriction.     

Personality as a Predictor of Weight Loss Maintenance after Surgery for Morbid Obesity

Objective: Personality characteristics are assumed to underlie health behaviors and, thus, a variety of health outcomes. Our aim was to examine prospectively whether personality traits predict short‐ and long‐term weight loss after laparoscopic adjustable gastric banding. Research Methods and Procedures: Of patients undergoing laparoscopic adjustable gastric banding, 168 (143 women, 25 men, 18 to 58 years old, mean 37 years, preoperative BMI 45.9 ± 5.6 kg/m²) completed the Dutch Personality Questionnaire on average 1.5 years before the operation. The relationship between preoperative personality and short‐ and long‐term postoperative weight loss was determined using multilevel regression analysis. Results: The average weight loss of patients progressively increased to 10 BMI points until 18 months after surgery and stabilized thereafter. A lower baseline BMI, being a man, and a higher educational level were associated with a lower weight loss. None of the personality variables was associated with weight outcome at short‐term follow‐up. Six of seven personality variables did not predict long‐term weight outcome. Egoism was associated with less weight loss in the long‐term postoperative period. The effect sizes of the significant predictions were small. Discussion: None of the personality variables predicted short‐term weight outcome, and only one variable showed a small and unexpected association with long‐term weight outcome that needs confirmation. This suggests that personality assessment as intake psychological screening is of little use for the prediction of a poor or successful weight outcome after bariatric surgery.     

Roux‐en‐Y Gastric Bypass Enhances Energy Expenditure and Extends Lifespan in Diet‐induced Obese Rats

Gastrointestinal weight‐loss surgery (GIWLS) is currently the most effective treatment for severe obesity, with Roux en‐Y gastric bypass (RYGB) among the best of the available surgical options. Despite its widespread clinical use, the mechanisms by which RYGB induces its profound weight loss remain largely unknown. This procedure effects weight loss by altering the physiology of weight regulation and eating behavior rather than by simple mechanical restriction and/or malabsorption as previously thought. To study how RYGB affects the physiology of energy balance, we developed a rat model of this procedure. In this report, we demonstrate that RYGB in diet‐induced obese (DIO) rats induces a 25% weight loss, prolongs mean survival by 45%, and normalizes glucose homeostasis and lipid metabolism. RYGB induced a 19% increase in total and a 31% increase in resting energy expenditure (REE). These effects, along with a 17% decrease in food intake and a 4% decrease in nutrient absorption account for the normalization of body weight after this procedure. These effects indicate that surgery acts by altering the physiology of weight regulation and help to explain the effectiveness of RYGB in comparison to restrictive dieting and other forms of dietary and pharmacological therapies for obesity. The clinical effectiveness of RYGB and its physiological effects on body weight regulation and energy expenditure (EE) suggest that this operation provides a unique opportunity to explore the mechanisms of energy homeostasis and to identify novel therapies for obesity and related metabolic diseases.     

Resting Energy Expenditure Changes With Weight Loss: Racial Differences

It is controversial whether weight loss reduces resting energy expenditure (REE) to a different magnitude in black and white women. This aim of this study was to determine whether changes in REE with weight loss were different between black and white postmenopausal women, and whether changes in body composition (including regional lean and fat mass) were associated with REE changes within each race. Black (n = 26) and white (n = 65) women (age = 58.2 ± 5.4 years, 25 < BMI < 40 kg/m²) completed a 20‐week weight‐loss intervention. Body weight, lean and fat mass (total body, limb, and trunk) via dual‐energy X‐ray absorptiometry, and REE via indirect calorimetry were measured before and after the intervention. We found that baseline REE positively correlated with body weight, lean and fat mass (total, limb, and trunk) in white women only (P < 0.05 for all). The intervention decreased absolute REE in both races similarly (1,279 ± 162 to 1,204 ± 169 kcal/day in blacks; 1,315 ± 200 to 1,209 ± 185 kcal/day in whites). REE remained decreased after adjusting for changes in total or limb lean mass in black (1,302–1,182 kcal/day, P = 0.043; 1,298–1,144 kcal/day, P = 0.006, respectively), but not in white, women. Changes in REE correlated with changes in body weight (partial r = 0.277) and fat mass (partial r = 0.295, 0.275, and 0.254 for total, limb, and trunk, respectively; P < 0.05) independent of baseline REE in white women. Therefore, with weight loss, REE decreased in proportion to the amount of fat and lean mass lost in white, but not black, women.     

Increased Postprandial Energy Expenditure May Explain Superior Long Term Weight Loss after Roux-en-Y Gastric Bypass Compared to Vertical Banded Gastroplasty

Background and Aims

Gastric bypass results in greater weight loss than Vertical banded gastroplasty (VBG), but the underlying mechanisms remain unclear. In addition to effects on energy intake the two bariatric techniques may differentially influence energy expenditure (EE). Gastric bypass in rats increases postprandial EE enough to result in elevated EE over 24 hours. This study aimed to investigate alterations in postprandial EE after gastric bypass and VBG in humans.

Methods

Fourteen women from a randomized clinical trial between gastric bypass (n = 7) and VBG (n = 7) were included. Nine years postoperatively and at weight stability patients were assessed for body composition and calorie intake. EE was measured using indirect calorimetry in a respiratory chamber over 24 hours and focused on the periods surrounding meals and sleep. Blood samples were analysed for postprandial gut hormone responses.

Results

Groups did not differ regarding body composition or food intake either preoperatively or at study visit. Gastric bypass patients had higher EE postprandially (p = 0.018) and over 24 hours (p = 0.048) compared to VBG patients. Postprandial peptide YY (PYY) and glucagon like peptide 1 (GLP-1) levels were higher after gastric bypass (both p<0.001).

Conclusions

Gastric bypass patients have greater meal induced EE and total 24 hours EE compared to VBG patients when assessed 9 years postoperatively. Postprandial satiety gut hormone responses were exaggerated after gastric bypass compared to VBG. Long-term weight loss maintenance may require significant changes in several physiological mechanisms which will be important to understand if non-surgical approaches are to mimic the effects of bariatric surgery.     

Resistance training conserves fat-free mass and resting energy expenditure following weight loss

Objective: To determine what effect diet‐induced ～12 kg weight loss in combination with exercise training has on body composition and resting energy expenditure (REE) in premenopausal African‐American (AA) and European‐American (EA) women. Methods and Procedures: This study was a longitudinal, randomized weight loss clinical intervention, with either aerobic (AT), resistance (RT), or no exercise training (NT). Forty‐eight AA and forty‐six EA premenopausal overweight (BMI between 27 and 30) women underwent weight loss to a BMI <25. Body composition (densitometry), REE (indirect calorimetry), maximal oxygen uptake (VO₂max), and muscular strength (isometric elbow flexion) were evaluated when subjects were in energy balance. Results: AA women lost less fat‐free mass (FFM, P ≤ 0.05) (47.0 ± 4.6 to 46.9 ± 5.0 kg) than EA women (46.4 ± 4.9 to 45.2 ± 4.6 kg). Regardless of race, RT maintained FFM (P ≤ 0.05) following weight loss (46.9 ± 5.2 to 47.2 ± 5.0 kg) whereas AT (45.4 ± 4.2 to 44.4 ± 4.1 kg) and NT (47.9 ± 4.7 to 46.4 ± 5.1 kg) decreased FFM (P ≤ 0.05). Both AT and NT decreased in REE with weight loss but RT did not. Significant time by group interactions (all P ≤ 0.05) for strength indicated that RT maintained strength and AT did not. Discussion: AA women lost less FFM than EA women during equivalent weight losses. However, following weight loss in both AA and EA, RT conserved FFM, REE, and strength fitness when compared to women who AT or did not train.     

Efficacy of α‐Lactalbumin and Milk Protein on Weight Loss and Body Composition During Energy Restriction

Our objective was to examine whether elevated α‐lactalbumin (αlac) protein intake compared to elevated supra sustained milk protein (SSP) and sustained milk protein (SP) intake results into a difference in body weight and body composition over a 6‐month energy‐restriction intervention. Body weight, body composition, resting energy expenditure (REE), satiety and blood‐ and urine‐parameters of 87 subjects (BMI 31 ± 5 kg/m² and fat percentage 40 ± 8%) were assessed before and after daily energy intakes of 100, 33, and 67% for 1, 1, and 2 months respectively (periods 1, 2, and 3), with protein intake from meal replacements and 2 months of 67% with ad libitum protein intake additional to the meal replacements (period 4). The diets resulted in 0.8 ± 0.3 g/kg body mass (BM) for SP and significant higher protein intake (24‐h nitrogen) of 1.2 ± 0.3 and 1.0 ± 0.3 g/kgBM for SSP and αlac (P < 0.05). Body weight and fat percentage was decreased in all groups after 6 months (SP ?7 ± 5 kg and ?5 ± 3%; SSP ?6 ± 3 kg and ?5 ± 3%; αlac ?6 ± 4 kg and ?4 ± 4%, P < 0.001; there was no significant group by time difference). Furthermore, sparing of fat‐free mass (FFM) and preservation of REE in function of FFM during weight loss was not significantly different between the αlac‐group and the SSP‐ and SP‐groups. In conclusion, the efficacy of αlac in reduction of body weight and fat mass (FM), and preservation of FFM does not differ from the efficacy of similar daily intakes of milk protein during 6 months of energy restriction.     

Normal vs. high‐protein weight loss diets in men: Effects on body composition and indices of metabolic syndrome

Objective:

This study assessed the effectiveness of a prescribed weight‐loss diet with 0.8 versus 1.4 g protein·kg^?1 day^?1 on changes in weight, body composition, indices of metabolic syndrome, and resting energy expenditure (REE) in overweight and obese men.

Design and Methods:

Men were randomized to groups that consumed diets containing 750 kcal day^?1 less than daily energy needs for weight maintenance with either normal protein (NP, n = 21) or higher protein (HP, n = 22) content for 12 weeks. The macronutrient distributions of the NP and HP diets were 25:60:15, and 25:50:25 percent energy from fat, carbohydrate, and protein, respectively. Assessments were made pre and post intervention. The subjects were retrospectively subgrouped into overweight and obese groups.

Results and Conclusion:

Both diet groups lost comparable body weight and fat. The HP group lost less lean body mass than the NP group (?1.9 ± 0.3 vs. ?3.0 ± 0.4 kg). The effects of protein and BMI status on lean body mass loss were additive. The reductions in total cholesterol, HDL‐C, triacylglycerol, glucose, and insulin, along with LDL‐C, total cholesterol‐to‐HDL‐C ratio, and HOMA‐IR, were not statistically different between NP and HP. Likewise, macronutrient distributions of the diet did not affect the reductions in REE, and blood pressure. In conclusion, energy restriction effectively improves multiple clinical indicators of cardiovascular health and glucose control, and consumption of a higher‐protein diet and accomplishing weight loss when overweight versus obese help men preserve lean body mass over a short period of time.

     

Effect of calorie restriction on resting metabolic rate and spontaneous physical activity

Objective: It is unclear if resting metabolic rate (RMR) and spontaneous physical activity (SPA) decrease in weight‐reduced non‐obese participants. Additionally, it is unknown if changes in SPA, measured in a respiratory chamber, reflect changes in free‐living physical activity level (PAL). Research Methods and Procedures: Participants (N = 48) were randomized into 4 groups for 6 months: calorie restriction (CR, 25% restriction), CR plus structured exercise (CR+EX, 12.5% restriction plus 12.5% increased energy expenditure via exercise), low‐calorie diet (LCD, 890 kcal/d supplement diet until 15% weight loss, then weight maintenance), and control (weight maintenance). Measurements were collected at baseline, Month 3, and Month 6. Body composition and RMR were measured by DXA and indirect calorimetry, respectively. Two measures of SPA were collected in a respiratory chamber (percent of time active and kcal/d). Free‐living PAL (PAL = total daily energy expenditure by doubly labeled water/RMR) was also measured. Regression equations at baseline were used to adjust RMR for fat‐free mass and SPA (kcal/d) for body weight. Results: Adjusted RMR decreased at Month 3 in the CR group and at Month 6 in the CR+EX and LCD groups. Neither measure of SPA decreased significantly in any group. PAL decreased at Month 3 in the CR and LCD groups, but not in the CR+EX group, who engaged in structured exercise. Changes in SPA in the chamber and free‐living PAL were not related. Discussion: Body weight is defended in non‐obese participants during modest caloric restriction, evidenced by metabolic adaptation of RMR and reduced energy expenditure through physical activity.     

Increased exercise capacity after surgically induced weight loss in morbid obesity

Objective: To investigate the effects of surgically induced weight loss on exercise capacity in patients with morbid obesity (MO). Research Methods and Procedures: A prospective 1‐year follow‐up study was carried out, with patients being their own controls. A symptom‐limited cardiopulmonary exercise stress test was performed in 31 MO patients (BMI > 40 kg/m²) before and 1 year after undergoing bariatric surgery. Results: At 1 year after surgery, weight was reduced from 146 ± 33 to 95 ± 19 kg (p < 0.001), and BMI went from 51 ± 4 to 33 ± 6 kg/m² (p < 0.001). After weight loss, obese patients performed each workload with lower oxygen consumption, heart rate, systolic arterial pressure, and ventilatory volume (p < 0.001). This reduced energy expenditure allowed them to increase the duration of their effort test from 13.8 ± 3.8 to 21 ± 4.2 minutes (p < 0.001). Upon finishing the exercise, MO patients before surgery were able to reach only 83% of their age‐predicted maximal heart rate, and their respiratory exchange ratio was 0.87 ± 0.06. After weight loss, those values were 90% and 1 ± 0.08, respectively (p < 0.01). When we compared the peak O₂ pulse corrected by fat free mass before and after surgery, no significant differences between the groups were found. Discussion: After surgically induced weight loss, MO patients markedly improved their exercise capacity. This is due to the fact that they were able to perform the external work with lower energy expenditure and also to increase cardiovascular stress, optimizing the use of cardiac reserve. There were no differences in cardiac function before and after surgery.     

Effects of Energy Expenditure and Ucp1 on Photoperiod‐Induced Weight Gain in Collared Lemmings

Objective: To determine the role of total energy expenditure (TEE) and its components in the ability of collared lemmings to increase weight in response to a decrease in photoperiod. Research Methods and Procedures: Energy expenditure was measured by 24‐hour indirect calorimetry concurrent with food‐intake studies. TEE and resting and nonresting energy expenditure (REE and NREE, respectively) were adjusted for body weight by analysis of covariance (ANCOVA). Uncoupling protein 1 (Ucp1) mRNA levels from interscapular brown adipose tissue were determined by Northern blot. Results: TEE and REE of lemmings exposed to a short photoperiod for 10 days were significantly lower than that of lemmings exposed to a long photoperiod (p < 0.05), whereas NREE was not significantly different (p = 0.44). Ucp1 mRNA levels in interscapular brown adipose tissue were 50% lower in short‐ vs. long‐photoperiod lemmings (p < 0.01). Ucp1 mRNA levels were positively related to REE (r² = 0.79, p < 0.01). After adjustment of REE for differences in Ucp1 mRNA levels, there was no longer a significant difference attributable to photoperiod treatment (p = 0.54). Discussion: The results of this study indicate that the increase in body mass that occurs when collared lemmings are exposed to a short photoperiod may be primarily fueled by a decrease in REE and is correlated with a decrease in Ucp1 mRNA levels.     

Quality of Life after Lap‐Band Placement: Influence of Time,Weight Loss,and Comorbidities

Objective: To assess the quality of life (QOL) in severely obese subjects before and after Lap‐Band gastric restrictive surgery and identify factors that may influence change. Research Methods and Procedures: All patients, over a 3‐year period, attending for preoperative assessment (n = 459) or annual review after surgery (n = 641) have completed the Short Form‐36 (SF‐36) health survey. Eight domain and physical component summary (PCS) and mental component summary (MCS) scores were calculated. Scores were analyzed in groups based on time after surgery and compared with community normal (CN) values. Paired preoperative and 1‐year scores (n = 218) data were used to find predictors of QOL change. Results: All preoperative mean scores (n = 459) were lower than CN values, with greater impairment in the PCS (36.8 ± 9.5 vs. CN: 51.3 ± 8.3, p < 0.001) than in the MCS (45.7 ± 8.2 vs. CN: 48.8 ± 9.5, p < 0.001) scores. After 1 year, scores were closer to CN scores (PCS: 52.4 ± 8.2 and MCS: 48.4 ± 7.7), and these remained closer for 4 years. Preoperative obesity comorbidity, especially physical disability, was the best predictor of poor preoperative SF‐36 scores and of improvement in scores at 1 year. The percentage of excess weight loss at 1 year (46 ± 16%) was of little predictive value of improved QOL. Discussion: Severely obese subjects have poor health‐related QOL as measured by the SF‐36 health survey. Lap‐Band surgery for this group has provided a dramatic and sustained improvement in all measures of the SF‐36. Improvement is greater in those with greater preoperative disability, and the extent of weight loss is not a good predictor of improved QOL.     

Gastric Bypass in a Low‐Income,Inner‐City Population: Eating Disturbances and Weight Loss

Objective: To examine the prevalence of eating disturbances and psychiatric disorders among extremely obese patients before and after gastric bypass surgery and to examine the relationship between these disturbances and weight outcomes. Research Methods and Procedures: Sixty‐five women patients (ages 19 to 67) with a mean BMI of 54.1 were assessed by semistructured psychiatric interview before surgery and by telephone interview after surgery (mean follow‐up: 16.4 months) to determine psychiatric status, eating disturbances, and weight and health‐related variables. Results: Patients lost a mean of 71% of their excess BMI, with significantly poorer weight loss outcomes among African Americans. Psychiatric disorders remained prevalent before (37%) and after (41%) surgery. In contrast, binge eating disorder dropped from 48% to 0%. Psychiatric diagnosis did not affect weight outcomes. Instead, more frequent preoperative binge eating, along with greater initial BMI, follow‐up length, and postoperative exercise, predicted greater BMI loss. Postsurgical health behaviors (exercise and smoking) and nocturnal eating episodes were also linked to weight loss. Exercise frequency increased and smoking frequency tended to decrease after surgery. Discussion: These findings indicated that eating and psychiatric disturbances did not inhibit weight loss after gastric bypass and should not contraindicate surgery. Prior binge eating, eliminated after surgery, predicted BMI loss and, thus, may have previously been a maintaining factor in the obesity of these patients. The association between health behaviors and outcome suggests possible targets for intervention to improve surgical results. Poorer outcomes among African Americans indicate that these patients should be closely monitored and supported after surgery.     

Low Resting and Sleeping Energy Expenditure and Fat Use Do Not Contribute to Obesity in Women

Objective: Determine whether sleeping and resting energy expenditure and sleeping, resting, and 24‐hour fuel use distinguish obesity‐prone from obesity‐resistant women and whether these metabolic factors explain long‐term weight gain. Research Methods and Procedures: Forty‐nine previously overweight but currently normal‐weight women were compared with 49 never‐overweight controls. To date, 87% of the 98 women have been re‐evaluated after 1 year of follow‐up, without intervention, and 38% after 2 years. Subjects were studied at a General Clinical Research Center after 4 weeks of tightly controlled conditions of energy balance and macronutrient intake. Forty‐nine obesity‐prone weight‐reduced women were group‐matched with 49 never‐overweight obesity‐resistant controls. All were premenopausal, sedentary, and normoglycemic. Energy expenditure and fuel use were assessed using chamber calorimetry. Body composition was assessed using DXA. Results: At baseline, percent body fat was not different between the obesity‐prone and control women (33 ± 4% vs. 32 ± 5%, respectively; p = 0.22). Analysis of covariance results show that after adjusting for lean and fat mass, sleeping and resting energy expenditure of obesity‐prone women was within 2% of controls. Neither sleeping nor resting energy expenditure nor sleeping, resting, or 24‐hour fuel use was significantly different between the groups (p > 0.25). None of the metabolic variables contributed significantly to patterns of weight gain at 1 or 2 years of follow‐up. Discussion: The results suggest that when resting and sleeping energy expenditure and fuel use are assessed under tightly controlled conditions, these metabolic factors do not distinguish obesity‐prone from obesity‐resistant women or explain long‐term weight changes.     

Lipid Profile in the Severely Obese: Changes with Weight Loss after Lap‐Band Surgery

Objective: To characterize dyslipidemia before and after weight loss in the severely obese. Research Methods and Procedures: Five hundred fifteen subjects who had Lap‐Band surgery were followed with yearly conventional lipid profiles for up to 4 years. Preoperative data were collected from the most recent 381 subjects, and predictors of dyslipidemia were sought. One hundred seventy‐one subjects completed a 1‐year review, providing data to assess predictors of change in lipids. Results: Favorable changes in fasting triglycerides (TG), high‐density lipoprotein‐cholesterol (HDL‐C), and total cholesterol (TC):HDL‐C ratio occurred within 1 year. All improvements were maintained up to 4 years. Male gender, central obesity, elevated fasting glucose, and insulin resistance were associated with less favorable lipid levels. Fasting plasma glucose best predicted TG (r = 0.46, p < 0.001), whereas insulin sensitivity using the homeostatic model assessment (HOMA %S) correlated best with the HDL‐C (r =0.34, p < 0.001). Higher preoperative fasting glucose best predicted the decrease in TG; improved HOMA %S with weight loss correlated best with HDL‐C. The extent of weight loss had limited influence on lipid changes. However, low preoperative HOMA %S was associated with lower weight loss. Greater weight loss was associated with more favorable lipid measures after controlling for preoperative HOMA %S. Discussion: Dyslipidemia of obesity is related to weight distribution, insulin sensitivity, and impaired glucose tolerance. Improvement with weight loss is related to the decrease in fasting glucose, improvement in insulin sensitivity, and the extent of weight lost. Improvement in dyslipidemia is sustained with long‐term weight loss.     

Body Composition and Energy Metabolism Following Roux‐en‐Y Gastric Bypass Surgery

Roux‐en‐Y gastric bypass (RYGB) surgery has become an accepted treatment for excessive obesity. We conducted a longitudinal study to assess regional body composition, muscle proteolysis, and energy expenditure before RYGB, and 6 and 12 months after RYGB. Whole‐body and regional fat mass (FM) and lean mass (LM) were assessed via dual energy X‐ray absorptiometry (DXA), and myofibrillar protein degradation was estimated by urinary 3‐methylhistidine (3‐MeH) in 29 subjects. Energy expenditure and substrate oxidation were also determined using a whole‐room, indirect calorimeter in 12 of these subjects. LM loss constituted 27.8 ± 10.2% of total weight loss achieved 12 months postoperatively, with the majority of LM loss (18 ± 6% of initial LM) occurring in the first 6 months following RYGB. During this period, the trunk region contributed 66% of whole‐body LM loss. LM loss occurred in the first 6 months after RYGB despite decreased muscle protein breakdown, as indicated by a decrease in 3‐MeH concentrations and muscle fractional breakdown rates. Sleep energy expenditure (SEE) decreased from 2,092 ± 342 kcal/d at baseline to 1,495 ± 190 kcal/day at 6 months after RYGB (P < 0.0001). Changes in both LM and FM had an effect on the reduction in SEE (P < 0.001 and P = 0.005, respectively). These studies suggest that loss of LM after RYGB is significant and strategies to maintain LM after surgery should be explored.     

Restrained Eating Behavior and the Metabolic Response to Dietary Energy Restriction in Women

Objective: To determine whether prior eating behavior characterized by dietary restraint alters responses in energy expenditure and substrate oxidation associated with a short‐term, energy‐restricted diet. Research Methods and Procedures: A repeated‐measures, 3‐day diet‐intervention study of adequate (125 kJ/kg of body weight) or restricted (62.5 kJ/kg) energy intake was conducted with 30 women, 20 to 46 years, BMI 25 to 45 kg/m², whose prior eating behavior was “restrained” or “unrestrained.” The Eating Inventory (cognitive restraint subscale) was used to measure restrained eating behavior. Energy expenditure and substrate oxidation were measured after a 12‐hour fast and during the first and fourth hours after a standard meal. Plasma glucose, nonesterified fatty acids, and insulin were measured at corresponding times. Body composition was determined by total body electrical conductivity. Results: Resting energy expenditure was not affected by 3 days of energy restriction. Short‐term energy restriction resulted in lower respiratory‐exchange ratios, higher rates of fat oxidation, and lower rates of carbohydrate oxidation. Subjects classified as restrained eaters had higher postprandial respiratory‐exchange ratios and carbohydrate‐oxidation rates compared with unrestrained eaters. Fasting insulin concentrations were lower in restrained eaters. These effects associated with prior eating behavior were independent of the diet intervention. Discussion: Metabolic outcomes associated with a 3‐day energy‐restricted diet (i.e., increased fat oxidation and decreased carbohydrate oxidation) were not affected by prior restrained eating behavior. However, restrained eating behavior was associated with increased carbohydrate oxidation after a mixed meal. This effect of restrained eating behavior may be attributable to increased insulin sensitivity.