Different dietary strategies for weight loss in obesity: role of energy and macronutrient content

Obesity is a chronic disorder caused by an imbalance of the energy metabolism with high associated burdens. Therefore, huge efforts are being currently devoted in studying new types of hypoenergetic diets and their composition, in order to characterise more specific, long-lasting and safe slimming protocols. A number of investigations are trying to determine the specific influence of the macronutrient distribution in energy-restricted diets on the management of excessive body weight. In this context, very-low-energy diets supplying between 1670 and 3350 kJ (400 and 800 kcal)/d have been beneficial in short-term treatments causing a weight loss of 300-500 g/d. Such strategies place more emphasis on energy restriction than on the macronutrient composition of the diet prescription. Weight loss produced by either low-carbohydrate or low-fat moderately energy-restricted diets ranges from 0.5 to 1.0 kg/week, while diets with high or moderately high protein content have also been applied in weight-reducing programmes by inducing losses of 0.2-0.4 kg/week. Other factors that determine weight loss by dieting are sex, age, initial body weight, race, genetics, regional fat deposition, etc, which must be taken into account to explain the variability in the outcomes of different low-energy diets. Therefore, more research is needed about the impact of diets with different fuel substrates and foods on the characteristics of the weight-loss process.

Time-course changes in macronutrient metabolism induced by a nutritionally balanced low-calorie diet in obese women

The use of low-calorie diets is a common strategy for body-weight reduction purposes, but the time-course of the metabolic changes induced by moderately energy-restricted, otherwise balanced, diets is still poorly known. The aim of this nutritional intervention design was to study in obese women the effect of a balanced low-calorie diet on the metabolic rate, and metabolic fuel utilization changes during the weight loss process through the application of breath tests with stable isotope-labeled tracers. Seven obese (body mass index >30 kg/m(2)) women were assigned to a 10-week dietary hypoenergetic intervention regime supplying 55% of energy as carbohydrate, 30% as fat and 15% as protein. Metabolic rate and substrate utilization were evaluated for 6 h in separate occasions during the weight loss program by indirect calorimetry and after 13C-labeled glucose, triolein and leucine administration. Body weight loss after 10 weeks was 4.2+/-1.1 kg, while the percent body fat decrease was about 5%. Slimming was accompanied by a marked decrease in fasting leptin (about 25%). Postprandial carbohydrate utilization after the administration of a test meal with the same macronutrient distribution as the experimental low-energy diet was decreased (24.1%, P<0.05) as a consequence of the dietary restriction, which was associated with lower insulin plasma levels (P<0.05). Although protein and lipid oxidation were not significantly different after weight reduction (day 1 versus day 70), the metabolic utilization of these substrates tended to increase. Moreover, marginally significant indications obtained on days 15 and 45 suggest that the weight and body composition changes are attributable to a shift in endogenous and exogenous glucose utilization in favor of lipid burning. The breath tests determinations, which were performed on different occasions along the experimental trial, confirmed that the cumulative 13C output decreased for labeled tracers with time, being only statistically significant for the glucose utilization between days 15 and 45. In summary, the weight and fat mass losses were associated with a lower carbohydrate oxidation, which were probably compensated by an increase in lipid oxidation without major changes in protein mobilization.

Analytical validation of commercially available methods for acute phase proteins quantification in pigs

The aim of this study was to validate commercially available methods for porcine haptoglobin (Hp), C-reactive protein (CRP), serum amyloid A (SAA) and major acute phase protein (Pig-MAP) determinations. Intra and inter assay coefficients of variation (CVs) were lower than 20% in all cases with exception of inter assay CVs for CRP and Pig-MAP assays with samples of low acute phase proteins concentration, and for SAA assay at any acute phase proteins concentration. All methods showed good linearity and detection limits were low enough to detect APPs levels in healthy animals. Hp and SAA were very affected by haemolysis. Lipaemia influenced mainly on SAA determination. Over 15-fold increase was observed in CRP and SAA concentrations after artificially induced inflammation by a single subcutaneous dose of turpentine, whereas Hp and Pig-MAP increased less than 5-fold.

Randomized trial of weight-loss-diets for young adults varying in fish and fish oil content

OBJECTIVE

To investigate the effect of including seafood and fish oils, as part of an energy-restricted diet, on weight loss in young overweight adults.

DESIGN

Randomized controlled trial of energy-restricted diet varying in fish and fish oil content was followed for 8 weeks. Subjects were randomized to one of four groups: (1) control (sunflower oil capsules, no seafood); (2) lean fish (3 x 150 g portions of cod/week); (3) fatty fish (3 x 150 g portions of salmon/week); (4) fish oil (DHA/EPA capsules, no seafood). The macronutrient composition of the diets was similar between the groups and the capsule groups, were single-blinded.

SUBJECTS

A total of 324 men and women aged 20-40 years, BMI 27.5-32.5 kg/m(2) from Iceland, Spain and Ireland.

MEASUREMENTS

Anthropometric data were collected at baseline, midpoint and endpoint. Confounding factors were accounted for, with linear models, for repeated measures with two-way interactions. The most important interactions for weight loss were (diet x energy intake), (gender x diet) and (gender x initial-weight).

RESULTS

An average man in the study (95 kg at baseline receiving 1600 kcal/day) was estimated to lose 3.55 kg (95% CI, 3.14-3.97) (1); 4.35 kg (95% CI, 3.94-4.75) (2); 4.50 kg (95% CI, 4.13-4.87) (3) and 4.96 kg (95% CI, 4.53-5.40) on diet (4) in 4 weeks, from baseline to midpoint. The weight-loss from midpoint to endpoint was 0.45 (0.41-0.49) times the observed weight loss from baseline to midpoint. The diets did not differ in their effect on weight loss in women. Changes in measures of body composition were in line with changes in body weight.

CONCLUSION

In young, overweight men, the inclusion of either lean or fatty fish, or fish oil as part of an energy-restricted diet resulted in approximately 1 kg more weight loss after 4 weeks, than did a similar diet without seafood or supplement of marine origin. The addition of seafood to a nutritionally balanced energy-restricted diet may boost weight loss.

A time-resolved immunofluorometric assay for porcine C-reactive protein quantification in whole blood

A time-resolved immunofluorometric assay (TR-IFMA) for C-reactive protein (CRP) determination in whole blood of pigs was developed and validated. CRP was isolated from porcine acute-phase serum by affinity chromatography on agarose, coupled with phosphorylethanolamine and polyclonal antibodies to porcine CRP were purified from antiserum raised in sheep immunized with porcine CRP. Intra- and inter-assay coefficients of variation (CVs) were in the range 3.13-7.19% and 7.06-15.66%, respectively, showing good precision. The assay measured the CRP values in a proportional and linear manner (r=0.99); additionally, CRP concentrations measured in whole blood by the present TR-IFMA and in serum by an established immunoturbidimetric assay were highly correlated (R(2)=0.97). The limit of detection of the method was 0.0028 mg/L. Significantly lower CRP concentrations were observed after 7 days of sample storage at 4 degrees C. The injection of turpentine oil caused a significant increase in CRP concentrations and significantly higher CRP concentrations were observed in pigs with pathological processes compared to healthy animals.

Porcine Acute Phase Protein Concentrations in Different Diseases in Field Conditions

Five acute phase proteins (APPs) [C-reactive protein (CRP), serum amyloid A (SAA), haptoglobin (Hp), pig-MAP and albumin] were measured in pigs with naturally occurring infections by porcine reproductive and respiratory syndrome virus (PRRSV), Aujeszky's disease virus (ADV), porcine circovirus type 2 (PCV2) and Mycoplasma hyopneumoniae, and in animals with tail and ear bites, arthritis and other acute inflammatory processes. Healthy specific pathogen-free (SPF) pigs were used as controls. In PRRSV-infected pigs, all APPs with the exception of pig-MAP exhibited significant changes compared with controls. In animals affected with ADV only Hp presented changes of statistical significance, whereas pigs with PCV2 showed marked modifications in all APPs tested. Animals affected with Mycoplasmosis showed concentrations of all positive APPs significantly above levels obtained in SPF pigs, though albumin concentrations did not differ from controls. Finally, all APPs studied showed substantial changes in pigs with acute inflammation. The results indicated that an acute phase response was developed in the different diseases studied, this response being higher in animals with clinical signs and concurrent bacterial processes. Haptoglobin would be the APP that better reflects pathological states; however, to get more complete and valuable information it might be advisable to perform APPs profiles including another APP, such as CRP or SAA.

[Role of IL-6 and its -174G>C polymorphism in weight management and in the metabolic comorbidities associated with obesity]

Obesity and its comorbidities have been associated with a low grade proinflammatory state, in which the adipose tissue seems to be involved. In fact, this tissue produces different proinflammatory cytokines, such as IL-6 and others. High circulating concentrations of IL-6 have been related to high body mass index, to diabetes mellitus type 2, to lipid abnormalities and to high blood pressure. There are some studies, which reported a relationship between IL-6 and energy metabolism, so this cytokine and its -174G>C gene polymorphism could be factors involved in the development of obesity. Different studies have associated the G allele of the IL-6 gene with obesity, with insulin resistance and with different cardiovascular risk factors. However, other published reports have associated the C allele of this gene to these metabolic disturbances and pathologies. This paper reviews recently published evidences about IL-6 and its physiopathological involvement in obesity and comorbidities, with emphasis on the role of the -174G>C polymorphism in the aetiology of these disturbances, in which obesity is a major risk factor.

Concentrations of C-reactive protein in effusions in dogs

The concentration of C-reactive protein (CRP) was measured in effusions from 50 dogs to assess the potential for measuring this protein to differentiate body cavity fluids. The effusions were classified as either transudates, modified transudates or exudates according to their total protein concentration, total nucleated cell count, cytological findings and aetiology, and the concentration of CRP was determined by a time-resolved immunofluorometric assay. There were significant differences between the concentrations of CRP in the three types of effusion; the highest concentrations were observed in the exudates (4.47 to 54.59 microg/ml), the lowest were in the transudates (0.0094 to 7.87 microg/ml), and the modified transudates contained intermediate concentrations of CRP (0.045 to 10.78 microg/ml). A cut-off value of 4 microg/ml had a sensitivity of 100 per cent and a specificity of 94.4 per cent for differentiating transudates from exudates, and a cut-off value of 11 microg/ml had a sensitivity of 88.2 per cent and a specificity of 100 per cent for distinguishing modified transudates from exudates. However, a cut-off value of 1 microg/ml had a lower sensitivity (80 per cent) and an unacceptably low specificity (66.7 per cent) for differentiating transudates from modified transudates.

Inflammation and conjugated linoleic acid: mechanisms of action and implications for human health

Data from a number of studies and trials have shown that different conjugated linoleic acids (CLA's) may produce beneficial effects on cancer, atherosclerosis, hypertension, diabetes and changes in body composition. Despite the increasing knowledge about CLA's implications on health, the mechanism of action of these fatty acids is not completely understood. Moreover, human studies indicate that some of these beneficial effects are considerably less evident than anticipated from mice studies, while the efficacy and safety of dietary supplements containing CLA have been questioned in some intervention trials. Recently, it has been suggested that the anti-carcinogenic and anti-atherosclerosis effects of CLA's stem from its anti-inflammatory properties. Because inflammatory responses are associated with the pathophysiology of many diseases, including obesity and the metabolic syndrome, the investigation in this area is of growing interest in recent years.

Analytical and Clinical Validation of a Time-resolved Immunofluorometric Assay (TR-IFMA) for Canine C-reactive Protein in Serum

A time-resolved immunofluorometric assay (TR-IFMA) was developed for the determination of C-reactive protein (CRP) in canine serum. CRP was isolated from canine acute-phase serum by affinity chromatography on agarose coupled with phosphorylethanolamine. This isolated dog CRP was used as standard to calibrate the assay. Intra-assay and inter-assay coefficients of variation were in the ranges 5.3-7.1% and 4.8-13.3%, respectively. Accuracy, evaluated by adding 2 and 10 microg/ml of CRP to serum samples, provided recoveries of 99.9% and 106.8%. High correlation was found between CRP measurements by TR-IFMA and a by commercial enzyme-linked immunosorbent assay (R2 = 0.98). The limit of detection for the TR-IFMA method was 0.000067 microg/ml and the measurement of CRP in serial dilutions of acute-phase dog sera generated curves with the same slope as the one constructed with purified CRP. The TR-IFMA provides a precise, accurate and highly sensitive assay for CRP determination in dog samples. CRP levels in dogs with different diseases ranged between 10.2 and 210.7 microg/ml and were significantly higher than those observed in healthy dogs (< 7.1 microg/ml).

Postprandial insulin response and mitochondrial oxidation in obese men nutritionally treated to lose weight

Obesity, hyperglycemia, and insulin resistance have been associated to an oxidative mitochondrial dysfunction. The aim of this research was to evaluate the relation between carbohydrate metabolism and mitochondrial oxidation, as affected by the weight status and the weight loss induced by a calorie-restricted diet. Lean control men (BMI<25 kg/m2, n = 6) and obese men (BMI>30 kg/m2, n = 14), who were characterized as insulin resistant (n = 6) or insulin sensitive (n = 8) based on HOMA index values, participated in the trial. Plasma insulin levels and mitochondrial oxidation estimated by the 2-keto(1-13C)isocaproate breath test, were measured after ingestion of a test meal during 3 h. Obese subjects repeated the breath test protocol after a 10-week caloric restriction diet to lose weight. Postprandial insulin secretion tended to be marginally higher (P = 0.059) in both obese groups than in controls, while the rate of postprandial mitochondrial oxidation was markedly decreased (P = 0.019) in the obese subjects as compared with lean individuals. The nutritionally induced weight loss produced a rise in the postprandial oxidative process in volunteers initially considered as insulin resistant (P = 0.036), while no statistical differences in the insulin-sensitive obese (P = 0.241) were found. Interestingly, the percentage of oxidized tracer was inversely related to postprandial insulin secretion (r = -0.56; P = 0.001). In conclusion, these results support the hypothetized relation between carbohydrate metabolism and mitochondrial oxidation at a postprandial state in obese subjects, raising interest about mitochondria stimulation as a target in the therapy of obesity.

Daily ingestion of fermented milk containing Lactobacillus casei DN114001 improves innate defense capacity in healthy middle-aged people

Different lactic acid bacteria have often been administered as a dietary means to enhance immune system activity. Based on this statement, the aim of the current work was to test the effects of a Lactobacillus casei DN114001 fermented milk consumption on the immune response capacity in middle-age volunteers. Forty-five healthy volunteers, 24 women and 21 men (aged: 51-58 years), were randomized into two groups to receive three cups per day of a L. casei DN114001 (10(8)-10(10) ufc/g) fermented milk (n = 23), or placebo (n = 22), during an 8-week period. Measurements were performed before (day 0), and after the nutritional intervention (day 56). After the trial, no changes in immune cell proportions were detected, but the probiotic-treated group increased oxidative burst capacity of monocytes (probiotic group: p = 0.029; placebo group: p = 0.625), as well as NK cells tumoricidal activity (probiotic group: p = 0.023; placebo group: p = 0.125). Results showed that daily intake of fermented milk containing Lactobacillus casei DN114001 could have a positive effect in modulating the innate immune defense in healthy-middle-age people.

Cortisol and free thyroxine determination by time-resolved fluorometry in canine serum

Validation for canine serum of 2 commercially available time-resolved fluoroimmunoassays (TR-FIAs) designed for analysis of cortisol and free thyroxine (fT4) in human serum was carried out. Included was the study of interference by hemolysis, lipemia, and bilirubinemia. With the dissociation enhancement lanthanide fluoroimmunoassay kits, the intra-assay coefficient of variation (CV) ranged from 6.4% to 8.7% for cortisol and from 5.3% to 9.8% for fT4; the interassay CVs ranged from 5.8% to 10.8% and from 3.9% to 14.1%, respectively. Accuracy was evaluated by comparing cortisol and fT4 results obtained with TR-FIA and those obtained with a validated enzyme-linked immunosorbent assay (ELISA) and an equilibrium dialysis (ED) assay, respectively. The regression equations obtained were y = 0.57x + 1.18 (r2 = 0.90) for cortisol and y = 0.87x + 0.82 (r2 = 0.93) for fT4. The limits of detection for cortisol and fT4 were 4.84 nmol/L and 2.68 pmol/L, respectively. The results of adrenocorticotropin-stimulation and dexamethasone-suppression tests were similar to those published previously; likewise, serial dilution of a canine serum sample with a high cortisol content demonstrated that the TR-FIA was immunologically specific. Serial dilution of a serum sample with a high fT4 concentration showed a methodologic bias, a dependence on serum binding capacity, which indicates that the results obtained with this method should be interpreted with caution. Finally, hemolysis and lipemia significantly interfered with cortisol and fT4 measurements, whereas bilirubinemia did not affect the results.