Twenty-four-hour energy and nutrient balance in weight stable postobese patients after biliopancreatic diversion

Micronutrient Deficiencies After Bariatric Surgery: An Emphasis on Vitamins and Trace Minerals [Formula: see text]

Obesity has become a worldwide epidemic with a disproportionate increase in grade III obesity. Bariatric surgery offers an attractive option for sustained weight loss compared with traditional methods such as exercise and diet. Micronutrient deficiencies are common and clinically significant after bariatric surgery. These deficiencies are related to a combination of patient and surgical variables. A thorough understanding of specific micronutrient deficiencies is necessary for early recognition and optimal management. The purpose of this review is to describe indications, outcomes, and types of bariatric procedures, risk factors, and mechanisms for micronutrient deficiencies, as well as outline specific vitamin and trace element deficiencies after bariatric surgery.

Nutrient deficiencies after gastric bypass surgery

Bariatric surgery, and in particular, gastric bypass, is an increasingly utilized and successful approach for long-term treatment of obesity and amelioration of comorbidities. Nutrient deficiencies after surgery are common and have multiple causes. Preoperative factors include obesity, which appears to be associated with risk for several nutrient deficiencies, and preoperative weight loss. Postoperatively, reduced food intake, suboptimal dietary quality, altered digestion and absorption, and nonadherence with supplementation regimens contribute to risk of deficiency. The most common clinically relevant micronutrient deficiencies after gastric bypass include thiamine, vitamin B₁₂, vitamin D, iron, and copper. Reports of deficiencies of many other nutrients, some with severe clinical manifestations, are relatively sporadic. Diet and multivitamin use are unlikely to consistently prevent deficiency, thus supplementation with additional specific nutrients is often needed. Though optimal supplement regimens are not yet defined, most micronutrient deficiencies after gastric bypass currently can be prevented or treated by appropriate supplementation.

Remission of type 2 diabetes mellitus following bariatric surgery: review of mechanisms and presentation of the concept of 'reversibility'

PURPOSE OF REVIEW

Roux-en-Y gastric bypass (RYGB) leads to remission of type 2 diabetes mellitus (T2DM) in a majority of patients. This is prompting investigation of RYGB, and other bariatric operations as interventional therapies for T2DM.

RECENT FINDINGS

The impact of RYGB is due to an increase in the release of gastrointestinal hormones in response to a meal [glucagon-like peptide, peptide YY, oxyntomodulin]. This effect involves the parasympathetic nervous system. These same hormones are responsible for an early increase in β-cell secretion of insulin, leading to early remission of T2DM following RYGB. Progressive weight loss leads to a later improvement in peripheral insulin sensitivity, which is required for later remissions, and is responsible for re-emergence of T2DM in individuals who regain weight in long-term follow-up. As the success of bariatric surgery has prompted the emergence of the concept that T2DM is reversible, we offer a theory to predict reversibility of diabetes after bariatric surgery that is based on baseline beta cell function.

SUMMARY

This review will improve the understanding of the physiology of bariatric surgery and its impact on T2DM, stimulate investigations into new avenues to treat T2DM, and allow better selection of nonobese individuals for interventional therapy of T2DM.

Effects of maternal surgical weight loss in mothers on intergenerational transmission of obesity

BACKGROUND AND OBJECTIVES

By studying cardiometabolic risk factors in children born after maternal biliopancreatic diversion bariatric surgery (AMS) compared with those in children born before maternal surgery (BMS), we tested the hypothesis that significant maternal weight loss may modify obesity-related factors transmitted via the intrauterine environment.

DESIGN

Anthropometry and fasting blood levels were studied in 49 mothers who had lost 36 +/- 1.8% body weight sustained for 12 +/- 0.8 yr and their 111 children (54 BMS and 57 AMS) aged 2.5-26 yr.

RESULTS

AMS children had lower birth weight (2.9 +/- 0.1 AMS vs. 3.3 +/- 0.1 kg BMS, P = 0.003) associated with a reduced prevalence of macrosomia (1.8 AMS vs. 14.8% BMS, P = 0.03) with no difference in underweight. At the time of follow-up, AMS children exhibited 3-fold lower prevalence of severe obesity (11 vs. 35%, P = 0.004), greater insulin sensitivity (homeostasis model assessment of insulin resistance index 3.4 +/- 0.3 vs. 4.8 +/- 0.5, P = 0.02), improved lipid profile (cholesterol/high-density lipoprotein cholesterol 2.96 +/- 0.11 vs 3.40 +/- 0.18, P = 0.03; high-density lipoprotein cholesterol 1.50 +/- 0.05 vs. 1.35 +/- 0.05 mmol/liter, P = 0.04), lower C-reactive protein (0.88 +/- 0.17 vs. 2.00 +/- 0.34 microg/ml, P = 0.004), and leptin (11.5 +/- 1.5 vs.19.7 +/- 2.5 ng/ml, P = 0.005) and increased ghrelin (1.28 +/- 0.06 vs.1.03 +/- 0.06 ng/ml, P = 0.005) than BMS offspring (AMS vs. BMS, respectively, for all).

CONCLUSIONS

This unique study of children aged 2.5-26 yr born before and after maternal antiobesity surgery demonstrated improvements in cardiometabolic markers sustained into adolescence, attributable to an improved intrauterine environment.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery medical guidelines for clinical practice for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice are systematically developed statements to assist health-care professionals in medical decision making for specific clinical conditions. Most of the content herein is based on literature reviews. In areas of uncertainty, professional judgment was applied. These guidelines are a working document that reflects the state of the field at the time of publication. Because rapid changes in this area are expected, periodic revisions are inevitable. We encourage medical professionals to use this information in conjunction with their best clinical judgment. The presented recommendations may not be appropriate in all situations. Any decision by practitioners to apply these guidelines must be made in light of local resources and individual patient circumstances. The American Society for Parenteral & Enteral Nutrition fully endorses sections of these guidelines that address the metabolic and nutritional management of the bariatric surgical patient.

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient

American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery Medical Guidelines for Clinical Practice are systematically developed statements to assist healthcare professionals in medical decision making for specific clinical conditions. Most of the content herein is based on literature reviews. In areas of uncertainty, professional judgment was applied. These guidelines are a working document that reflects the state of the field at the time of publication. Because rapid changes in this area are expected, periodic revisions are inevitable. We encourage medical professionals to use this information in conjunction with their best clinical judgment. The presented recommendations may not be appropriate in all situations. Any decision by practitioners to apply these guidelines must be made in light of local resources and individual patient circumstances. The American Society for Parenteral & Enteral Nutrition fully endorses sections of these guidelines that address the metabolic and nutritional management of the bariatric surgical patient.

Surgical treatment of obesity

Obesity is very prevalent. Most treatments fail owing to hard-wired survival mechanisms, linking stress and appetite, which have become grossly maladaptive in the industrial era. Antiobesity (bariatric) surgery is a seemingly drastic, efficacious therapy for this serious disease of energy surfeit. Technical progress during the last two decades has greatly improved its safety. The surgical principles of gastric restriction and/or gastrointestinal diversion have remained largely unchanged over 40 years, although mechanisms of action have been elucidated concomitant with advances in knowledge of the molecular biology of energy balance and appetite regulation. Results of bariatric surgery in large case-series followed for at least 10 years consistently demonstrate amelioration of components of the insulin-resistance metabolic syndrome and other comorbidities, significantly improving quality of life. Furthermore, bariatric surgery has convincingly been demonstrated to reduce mortality compared with nonoperative methods. This surgery requires substantial preoperative and postoperative evaluation, teaching, and monitoring to optimize outcomes. In the absence of effective societal changes to restore a healthy energy balance, bariatric surgery is an important tool for treating a very serious disease.

Biliopancreatic diversion reduces QT interval and dispersion in severely obese patients

OBJECTIVES

The objectives were to evaluate QT interval (QTc) and QT-interval dispersion (QTd) in severely obese individuals and to determine the effects of biliopancreatic diversion (BPD) and weight loss after BPD on ventricular repolarization parameters.

BACKGROUND

People with severe obesity (SO) have a 50% to 100% increased risk of death associated with a 1.6-fold increased risk of sudden death. BPD surgery induces rapid and considerable weight loss through severe lipid malabsorption, thus achieving long-term weight control.

RESEARCH METHODS AND PROCEDURES

A total of 85 subjects with SO (age, 42 +/- 12 years; 66 females; mean body weight, 120 +/- 29 kg; BMI, 45 +/- 11 kg/m(2)) of 330 who had a bariatric surgical consultation between January 2001 and July 2002 were enrolled. Inclusion criteria were sinus rhythm, unremarkable 12 leads surface electrocardiogram, no atrioventricular blocks and/or bundle branch blocks, normal serum electrolyte profile, and no medical therapies exerting known effects on QTc. Exclusion criteria were previous diagnosis of coronary artery disease, known cardiovascular disease, atrial fibrillation or any other known cardiac arrhythmias, cancer, or renal dysfunction.

RESULTS

A total of 86% of patients had QTc >440 ms and/or QTd >60 ms. Subjects with SO showed a mean maximum QTc of 446 +/- 28 ms and a mean QTd of 52 +/- 20 ms. A close correlation was found between QTc and QTd (p < 0.0001; R(2) = 0.33). One month after BPD, mean QTc was 420 ms and remained stable at follow-up; QTd was 32 ms at 1 and 6 months and became 35 ms at 1 year.

CONCLUSIONS

Ventricular repolarization abnormalities are significantly increased in subjects with SO. Reduction of QT abnormalities after BPD is independent of weight loss and is caused by the 100% reduction of glucose plasma shortly after surgery. This effect may be related to surgical interruption of the entero-insular axis.

Why do obese patients not lose more weight when treated with low-calorie diets? A mechanistic perspective

Maximal weight loss observed in low-calorie diet (LCD) studies tends to be small, and the mechanisms leading to this low treatment efficacy have not been clarified. Less-than-expected weight loss with LCDs can arise from an increase in fractional energy absorption (FEA), adaptations in energy expenditure, or incomplete patient diet adherence. We systematically reviewed studies of FEA and total energy expenditure (TEE) in obese patients undergoing weight loss with LCDs and in patients with reduced obesity (RO), respectively. This information was used to support an energy balance model that was then applied to examine patient adherence to prescribed LCD treatment programs. In the limited available literature, FEA was unchanged from baseline in short-term (<12 wk) treatment studies with LCDs; no long-term (>or=26 wk) studies were found. Review of doubly labeled water and respiratory chamber studies identified 10 reports of TEE in RO patients (n = 150) with long-term weight loss. These patients, who were weight stable, had a TEE almost identical to measured or predicted values in never-obese subjects (weighted mean difference: 1.3%; range: -1.7-8.5%). Modeling of energy balance, as supported by reviewed FEA and TEE studies, suggests that obese subjects participating in LCD programs have a weight loss less than half of that predicted. The small maximal weight loss observed with LCD treatments thus is likely not due to gastrointestinal adaptations but may be attributed, by deduction, to difficulties with patient adherence or, to a lesser degree, to metabolic adaptations induced by negative energy balance that are not captured by the current models.

Surgery for morbid obesity

The prevalence of morbid obesity in the UK population is rising, bringing with it increased levels of cardiovascular disease, diabetes, arthritis and early mortality. The overall cost to the health service is high, and is set to increase over the coming decades as the overweight population ages. Dietary, lifestyle and pharmacological interventions offer at best reasonable, short-term weight reduction and often fail. Surgical intervention is a safe and effective means of delivering marked long-term weight reduction. This article compares and contrasts the options available for surgical treatment of morbid obesity based on a review of the current literature.

Large maternal weight loss from obesity surgery prevents transmission of obesity to children who were followed for 2 to 18 years

OBJECTIVE

Our aim was to compare the prevalence of obesity in 172 children who were aged 2 to 18 years and born to 113 obese mothers (BMI: 31 +/- 9 kg/m2) with substantial weight loss after biliopancreatic bypass surgery with 45 same-age siblings who were born before maternal surgery (mothers' BMI: 48 +/- 8 kg/m2) and with current population standards.

METHODS

In this case series, with >88% follow-up in a tertiary referral center, cross sectional office chart and telephone data on childhood and adolescent weights were transformed to z scores.

RESULTS

After maternal surgery, the prevalence of obesity in the offspring decreased by 52% and severe obesity by 45.1%, with no increase in the prevalence of underweight. The z score reduction in obesity was gender specific, with boys reducing from 1.4 +/- 1.3 before to 0.57 +/- 1.7 after maternal surgery, corrected for birth order. The difference was not significant in girls (0.8 +/- 1.3 vs 0.8 +/- 1.2). Among children of both genders who were aged 6 to 18 years of age and born after maternal surgery, the prevalence of overweight was reduced to population levels.

CONCLUSIONS

Contrary to outcomes after intrauterine under- and overnutrition, the prevalence of overweight and obesity in children of mothers with large voluntary postsurgical weight loss was similar to that in the general population, with no increase in underweight. The results demonstrate the importance of potentially modifiable epigenetic factors in the cause of obesity.

Surgical options for obesity

Several bariatric procedures are available that have excellent long-term weight loss results and are backed by several large clinical trials. Purely restrictive procedures like VBG have fallen out of favor because of inadequate long-term weight loss. Gastric bypass and the BPD are well-studied and show significant resolution of obesity-related comorbidities. Long-term nutritional consequences are seen more commonly after malabsorptive procedures like the BPD than after hybrid malabsorptive-restrictive procedures like the gastric bypass. Because compliance and long-term nutritional follow-up are mandatory after any bariatric procedure, purely malabsorptive procedures should be reserved for super obese patients who are at risk for inadequate long-term weight loss. Furthermore, minimally invasive techniques have evolved and essentially have eliminated the high incidence of postoperative wound complications and incisional hernias frequently seen after open gastric bypass. Until the development ofa similarly successful procedure, gastric bypass will continue to be the gold standard bariatric procedure with its concurrent sustained weight loss benefits and resolution of comorbidities.

Differential effect of weight loss on insulin resistance in surgically treated obese patients

PURPOSE

To compare the effects of equivalent weight loss induced by two bariatric surgical techniques on insulin action in severely obese patients.

METHODS

Eighteen nondiabetic patients with severe obesity (mean [+/- SD] body mass index: 53.5 +/- 9.0 kg/m(2)) and 20 sex- and age-matched lean subjects (body mass index: 23.8 +/- 3.0 kg/m(2)) underwent metabolic studies, including measurement of insulin sensitivity by the insulin clamp technique. Patients then underwent either vertical banded gastroplasty with Roux-en-Y gastric bypass, or biliopancreatic diversion, and were restudied at 5 to 6 months and again at 16 to 24 months postsurgery.

RESULTS

At baseline, patients were hyperinsulinemic (194 +/- 47 pmol/L vs. 55 +/- 25 pmol/L, P < 0.0001), hypertriglyceridemic (1.56 +/- 0.30 mmol/L vs. 0.78 +/- 0.32 mmol/L, P < 0.0001), and profoundly insulin resistant (insulin-mediated glucose disposal: 20.8 +/- 4.4 micromol/min/kg fat-free mass vs. 52.0 +/- 10.1 micromol/min/kg, P < 0.0001) as compared with controls. Weight loss by the two procedures was equivalent in both amount (averaging -53 kg) and time course. In the gastric bypass group, insulin sensitivity improved (23.8 +/- 6.0 micromol/min/kg at 5 months and 33.7 +/- 11.3 micromol/min/kg at 16 months, P < 0.01 vs. baseline and controls). In contrast, in the biliopancreatic diversion group, insulin sensitivity was normalized already at 6 months (52.5 +/- 12.4 micromol/min/kg, P = 0.72 vs. controls) and increased further at 24 months (68.7 +/- 9.5 micromol/min/kg, P < 0.01 vs. controls) despite a persistent obese phenotype (body mass index: 33.2 +/- 8.0 kg/m(2)).

CONCLUSION

In surgically treated obese patients, insulin sensitivity improves in proportion to weight loss with use of predominantly restrictive procedures (gastric bypass), but is reversed completely by predominantly malabsorptive approaches (biliopancreatic diversion) long before normalization of body weight. Selective nutrient absorption and gut hormones may interact with one another in the genesis of the metabolic abnormalities of obesity.

Intramyocitic lipid accumulation and SREBP-1c expression are related to insulin resistance and cardiovascular risk in morbid obesity

The aim of this study was to investigate the sterol regulatory element-binding protein 1c (SREBP1c) mRNA muscle expression in morbid obese subjects before and after massive lipid malabsorption due to bariatric surgery (bilio-pancreatic diversion, BPD). We studied 11 obese subjects (BMI 49+/-2 kg/m2) before and 24 months after BPD. Skeletal muscle SREBP1c mRNA expression was determined using RT-competitive PCR. Intramyocytic triglycerides were quantified by HPLC. Insulin sensitivity (M/I) was assessed by euglycemic-hyperinsulinemic clamp. Energy expenditure and respiratory quotient (RQ) were measured over 24 h in a calorimetric chamber. Total cardiovascular risk dropped from 2 before to -2.5 after BPD (P<0.0001). The M/I value was normalized after surgery (0.036+/-0.0148 to 0.095+/-0.0147 micromol kgFFM(-1) min(-1) pmoles(-1) P<0.001). SREBP-1c mRNA levels were decreased (from 4.12+/-2.43 to 2.69+/-1.83% of cyclophilin mRNA, P=0.02) after BPD. In a multiple regression analysis, M/I values (P<0.0001) as well as the intramyocytic triglyceride levels (P=0.039) were the most powerful independent variables for predicting cardiovascular risk. Our results show that the reduction of cardiovascular risk after bariatric massive weight loss is strongly related to the reversion of insulin resistance and to the lowering of intramyocytic triglyceride depots. These two parameters are associated with a significant reduction in SREBP-1c mRNA expression in skeletal muscle, suggesting that this transcription factor might be involved in the accumulation of triglycerides in muscle cells of morbidly obese subjects.

Decreased uncoupling protein expression and intramyocytic triglyceride depletion in formerly obese subjects

OBJECTIVE

To examine the muscular uncoupling protein expression 2 (UCP2) and UCP3 gene expression in morbid obese subjects before and after bariatric surgery [bilio-pancreatic diversion (BPD)].

RESEARCH METHODS AND PROCEDURES

Eleven obese subjects (BMI = 49 +/- 2 kg/m(2)) were studied before BPD and 24 months after BPD. Skeletal muscle UCP2 and UCP3 mRNA was measured using reverse transcriptase-competitive polymerase chain reaction and UCP3 protein by Western blotting. Intramyocytic triglycerides were quantified by high-performance liquid chromatography. Twenty-four-hour energy expenditure and respiratory quotient (RQ) were measured in a respiratory chamber.

RESULTS

After BPD, the average weight loss was approximately 38%. Nonprotein RQ was increased in the postobese subjects (0.73 +/- 0.00 vs. 0.83 +/- 0.02, p < 0.001). The intramyocytic triglyceride level dropped (3.66 +/- 0.16 to 1.60 +/- 0.29 mg/100 mg of fresh tissue, p < 0.0001) after BPD. Expression of UCP2 and UCP3 mRNA was significantly reduced (from 35.9 +/- 6.1% to 18.6 +/- 4.5% of cyclophilin, p = 0.02; from 60.2 +/- 14.0% to 33.4 +/- 8.5%, p = 0.03; respectively). UCP3 protein content was also significantly reduced (272.19 +/- 84.13 vs. 175.78 +/- 60.31, AU, p = 0.04). A multiple regression analysis (R(2) = 0.90) showed that IMTG levels (p = 0.007) represented the most powerful independent variable for predicting UCP3 variation.

DISCUSSION

The strong correlation of UCP expression and decrease in IMTG levels suggests that triglyceride content plays an even more important role in the regulation of UCP gene expression than the circulating levels of free fatty acids or the achieved degree of weight loss.

Computing DIT from energy expenditure measures in a respiratory chamber: a direct modeling method

The possibility of computing Diet Induced Thermogenesis (DIT) is an important feature of metabolic investigations. However, methodological problems have affected the determination of DIT in the indirect calorimetric chamber. DIT has been commonly estimated by regressing energy expenditure on a measure of physical activity. Although used for many years as the only feasible approach to calculate DIT in a respiratory chamber, this traditional method has been criticized because of an apparent underestimation of the DIT, but no alternative method has been suggested so far. The present work proposes to estimate DIT directly by means of a mathematical model. This approach also allows to simultaneously estimate other parameters, namely resting energy expenditure (REE), physical activity (PA) and physical exercise (PE).

Lowering of circulating free-fatty acids levels and reduced expression of leptin in white adipose tissue in postobesity status

BACKGROUND

Our aim was to investigate the regulation of the gene expression of leptin in subcutaneous adipose tissue biopsies in morbid obesity before and after biliopancreatic diversion (BPD).

METHODS

Longitudinal study in morbidly obese subjects investigated twice: before and 6 months after BPD. Fourteen morbidly obese women, 37+/-13 years old and with a body mass index of 51.6+/-8.2 kg/m2, were studied before and 6 months after BPD (40.6+/-8.0 kg/m2). Using reverse transcriptase polymerase chain reaction analysis, the mRNA expression of leptin was investigated in adipose tissue. Plasma leptin was measured by radioimmunoassay; plasma insulin was measured by microparticle enzyme immunoassay. Free fatty acids (FFA) were measured using a colorimetric kit.

RESULTS

A significant decrease in leptin mRNA level was observed in comparison with pretreatment in BPD patients (59+/-34 vs 143+/-85 arbitrary units, P<0.01). A strict relationship between adipose tissue leptin mRNA and plasma leptin either before (R2=0.80, P<0.0001) or after BPD (R2=0.86, P<0.0001) and between plasma FFA concentration and insulin either before (R2=0.65, P<0.001) or after BPD (R2=0.92, P<0.0001) was observed. Finally, a significant correlation was found between changes in FFA and insulin (R2=0.64, P<0.001), insulin and leptin (R2=0.88, P<0.0001), and insulin and leptin mRNA (R2=0.83, P<0.0001).

CONCLUSION

These data demonstrate a high correlation between leptin mRNA expression in adipose tissue and plasma leptin in postobese subjects after BPD. The significant relationship between both leptin mRNA and plasma leptin with insulin suggests that circulating insulin might regulate leptin expression. It might be hypothesized that plasma FFA concentration can act on the insulin secretion and subsequently on the leptin secretory pathway.

Insulin resistance in morbid obesity: reversal with intramyocellular fat depletion

Obesity is a frequent cause of insulin resistance and poses a major risk for diabetes. Abnormal fat deposition within skeletal muscle has been identified as a mechanism of obesity-associated insulin resistance. We tested the hypothesis that dietary lipid deprivation may selectively deplete intramyocellular lipids, thereby reversing insulin resistance. Whole-body insulin sensitivity (by the insulin clamp technique), intramyocellular lipids (by quantitative histochemistry on quadriceps muscle biopsies), muscle insulin action (as the expression of Glut4 glucose transporters), and postprandial lipemia were measured in 20 morbidly obese patients (BMI = 49 +/- 8 [mean +/- SD] kg x m(-2)) and 7 nonobese control subjects. Patients were restudied 6 months later after biliopancreatic diversion (BPD; n = 8), an operation that induces predominant lipid malabsorption, or hypocaloric diet (n = 9). At 6 months, BPD had caused the loss of 33 +/- 10 kg through lipid malabsorption (documented by a flat postprandial triglyceride profile). Despite an attained BMI still in the obese range (39 +/- 8 kg x m(-2)), insulin resistance (23 +/- 3 micromol/min per kg of fat-free mass; P < 0.001 vs. 53 +/- 13 of control subjects) was fully reversed (52 +/- 11 micromol/min per kg of fat-free mass; NS versus control subjects). In parallel with this change, intramyocellular-but not perivascular or interfibrillar-lipid accumulation decreased (1.63 +/- 1.06 to 0.22 +/- 0.44 score units; P < 0.01; NS vs. 0.07 +/- 0.19 of control subjects), Glut4 expression was restored, and circulating leptin concentrations were normalized. In the diet group, a weight loss of 14 +/- 12 kg was accompanied by very modest changes in insulin sensitivity and intramyocellular lipid contents. We conclude that lipid deprivation selectively depletes intramyocellular lipid stores and induces a normal metabolic state (in terms of insulin-mediated whole-body glucose disposal, intracellular insulin signaling, and circulating leptin levels) despite a persistent excess of total body fat mass.

Daily energy and substrate metabolism in patients with cirrhosis

Twenty-four-hour energy expenditure (EE) and substrate oxidation (respiratory chamber), and whole-body glucose uptake and oxidation rates (euglycemic hyperinsulinemic clamp [EHC] and indirect calorimetry) were measured in 10 male patients with posthepatitis, Child B cirrhosis, and 8 healthy male controls matched for age, body size, and body composition. Twenty-four-hour EE was higher in cirrhotic patients than in controls (8,567 +/- 764 vs. 6,825 +/- 507 kJ/d; P < .001). Resting energy expenditure (REE) was also higher in cirrhotic patients than in controls (7,881 +/- 1,125 vs. 5,868 +/- 489 kJ/d; P < .01). Twenty-four-hour respiratory quotient (RQ) (trend) and fasting RQ (0.76 +/- 0.05 vs. 0.82 +/- 0.04; P < .05) were lower in cirrhotic patients than in controls, reflecting higher lipid oxidation rates in the former group. Whole-body glucose uptake was markedly reduced in cirrhotic patients when compared with controls (22.4 +/- 3.2 vs. 44.5 +/- 7.6 mmol/kg/min; P < .001). Carbohydrate oxidation rates, computed during the last 40 minutes of the clamp, were 8.5 +/- 1.1 mmol/kg/min in cirrhotic patients and 22.6 +/- 6.1 mmol/kg/min in controls (P < .001). Nonoxidative glucose disposal was 13.9 +/- 2.5 mmol/kg/min in cirrhotic patients and 22.0 +/- 5.5 mmol/kg/min in normal controls (P < .01). In conclusion, our data indicate that patients with Child B cirrhosis who still maintain a nutritional status (i.e., body composition) comparable with healthy controls are characterized by a cluster of metabolic defects that include hypermetabolism, increased lipid utilization, and insulin resistance. This suggests that the above metabolic syndrome precedes and probably leads to malnutrition in the natural history of the liver disease. In fact, in spite of the absence of a significant difference in caloric intake between cirrhotic patients and normal controls, the elevated 24-hour EE might allow for a relevant weight loss in cirrhotic patients, because, with time, the differences may be cumulative. However, whether this hypermetabolism can lead to a real weight loss remains to be evaluated in a longitudinal study.

Dietary fat and human obesity

When energy is in excess, the human body processes nutrients according to an oxidative hierarchy. Excessive carbohydrate and protein intakes are disposed of by increased oxidation. In contrast, excess fat intake does not promote its own oxidation in the short- and mid-term. This leads, in the long-term, to an increase in fat stores. Although increased adiposity represents the common response to increased fat intake, there are interindividual differences in lipid oxidation (probably genetically determined) that may protect from or predispose to obesity.

Effect of fat intake on energy balance

Most epidemiological studies indicate that obesity is more prevalent in populations consuming high fat diets. Furthermore, changes from a traditional to a westernized life style, characterized by a high-fat diet and decreased physical activity, result in dramatic increases in the prevalence and incidence of obesity in Native Americans, Pacific Islanders, and African populations. A possible explanation for the epidemic of obesity in response to high-fat intake can be found in the "oxidative hierarchy" that regulates macronutrient balance in the human body. Although carbohydrate and protein balances seem promptly regulated, fat balance is not. Short and midterm studies show that, unlike carbohydrate and protein intake, fat intake does not promote fat oxidation. Thus, "excess" fat intake results in fat deposition. As fat mass increases, so does fat oxidation, and a new equilibrium is reached when fat oxidation matches fat intake. However, there are large interindividual differences in this compensatory response to increased fat intake. Substrate oxidation is a familial trait, and individuals with a low fat-to-carbohydrate oxidation ratio are more prone to develop obesity than those with a high fat-to-carbohydrate oxidation ratio. Genetics may influence nutrient partitioning by influencing the activity of key enzymes of intermediate metabolism, such as lipoprotein lipase, beta-hydroxyl acyl CoA dehydrogenase, and acetyl CoA carboxylase.