Leonard S. Piers

The influence of the type of dietary fat on postprandial fat oxidation rates: monounsaturated (olive oil) vs saturated fat (cream)

Objective: To compare postprandial whole-body fat oxidation rates in humans, following high-fat (43% of total energy) mixed breakfast meals, of fixed energy and macronutrient composition, rich in either monounsaturated fat (MUFA) from extra virgin olive oil or saturated fat (SFA) from cream.Design: Paired comparison of resting metabolic rate (RMR), thermic effect of a meal and substrate oxidation rates following consumption of isocaloric breakfast meals, differing only in the type of fat, administered in random order 1–2 weeks apart.Subjects: Fourteen male volunteers, body mass index (BMI) in the range 20–32 kg/m2, aged 24–49 y and resident in Melbourne, Australia, were recruited by advertisement in the local media or by personal contact.Measurements: Body size and composition was determined by anthropometry and dual energy X-ray absorptiometry (DEXA). Indirect calorimetry was used to measure RMR, thermic effect of a meal, post-meal total energy expenditure and substrate oxidation rate. Blood pressure and pulse rates were measured with an automated oscillometric system. Fasting and 2 h postprandial glucose and insulin concentrations and the fasting lipid profile were also determined.Results: In the 5 h following the MUFA breakfast, there was a significantly greater postprandial fat oxidation rate (3.08±4.58 g/5 h, P=0.017), and lower postprandial carbohydrate oxidation rate (P=0.025), than after the SFA breakfast. Thermic effect of a meal was significantly higher (55 kJ/5 h, P=0.034) after the MUFA breakfast, in subjects with a high waist circumference (HWC≥99 cm) than those with a low waist circumference (LWC<99 cm). This difference was not detected following the SFA breakfast (P=0.910).Conclusion: If postprandial fat oxidation rates are higher after high MUFA, rather than SFA meals, then a simple change to the type of dietary fat consumed might have beneficial effects in curbing weight gain in men consuming a relatively high-fat diet. This may be particularly evident in men with a large waist circumference.

Indirect estimates of body composition are useful for groups but unreliable in individuals.

OBJECTIVE: To assess the usefulness of the body mass index (BMI) in identifying individuals classified as overweight or obese based on estimates of body fat percentage (BF%) obtained by the deuterium dilution (BF%DD) method. In addition, to assess the accuracy of bioelectrical impedance analysis (BIA) and skinfold thickness (SFT) measurements in the estimation of body composition of Australians at the individual and group level.DESIGN: Cross-sectional study.SUBJECTS: One hundred and seventeen healthy Australian volunteers of European descent, comprising of 51 males and 66 females, ranging in age from 19 to 77 y.MEASUREMENTS: BMI was calculated from body weight and height. Fat-free mass (FFM) was estimated from measures of total body water (TBW) using deuterium dilution (FFMDD), SFT using the equations of Durnin and Womersley (Br J Nutr 1974; 32: 77–97) (FFMSFT), and BIA using the equations of Lukaski et al (J Appl Physiol 1986; 60: 1327–1332) (FFMLU), Segal et al (Am J Clin Nutr 1988; 47: 7–14) (FFMSe) and Heitmann (Eur J Clin Nutr 1990; 44: 831–837) (FFMHe). Estimates of fat mass (FM) were calculated as the difference between body weight and FFM, while BF% was calculated by expressing FM as a percentage of body weight.RESULTS: BMI had poor sensitivity and positive predictive value in identifying individuals as being overweight/obese as classified by BF%DD. Furthermore, estimates of FFM (and hence FM) from BIA or SFT could not be used interchangeably with DD, without the risk of considerable error at the individual level. At the group level errors were relatively smaller, though statistically significant. While FFMSFT could be corrected by the addition of the bias (1.2 kg in males and 0.8 kg in females), no simple correction was possible with BIA estimates of FFM for any of the equations used. However, an accurate prediction of FFMDD was possible from the combination of FFMHe, biceps SFT and mid-arm circumference in both males and females. The bias of this prediction was small (<0.15 kg), statistically non-significant in both sexes, and unrelated to the mean FFM obtained by the two methods. The revision of Heitmanns estimate of FFM using anthropometric variables described in this study had the best sensitivity (79%), specificity (96%) and positive predictive value (92%) in identifying overweight/obese individuals in comparison to the other equations tested.CONCLUSION: BMI was a poor surrogate for body fatness in both males and females. The currently recommended equations for the prediction of body composition from SFT and BIA provided inaccurate estimates of FFM both at the individual and group level as compared to estimates from DD. However, Heitmanns equations, when combined with measures of the biceps SFT and mid-arm circumference, provided better estimates of FFM both at the individual and group level.

Substitution of saturated with monounsaturated fat in a 4-week diet affects body weight and composition of overweight and obese men.

A randomised crossover study of eight overweight or obese men (aged 24-49 years, BMI 25.5-31.3 kg/m(2)), who followed two diets for 4 weeks each, was performed to determine whether substitution of saturated fat with monounsaturated fat affects body weight and composition. Subjects were provided with all food and beverages as modules (selected ad libitum) of constant macronutrient composition, but differing energy content. The % total energy from saturated fat, monounsaturated fat and polyunsaturated fat was 24, 13 and 3 % respectively on the saturated fatty acid (SFA)-rich diet and 11, 22 and 7 % respectively on the monounsaturated fatty acid (MUFA)-rich diet. MUFA accounted for about 80 % of the unsaturated fats consumed on both diets. Body composition, blood pressure, energy expenditure (resting and postprandial metabolic rates, substrate oxidation rate, physical activity), serum lipids, the fatty acid profile of serum cholesteryl esters and plasma glucose and insulin concentrations were measured before and after each diet period. Significant (P< or =0.05) differences in total cholesterol and the fatty acid composition of serum cholesteryl esters provided evidence of dietary adherence. The men had a lower weight (-2.1 (SE 0.4) kg, P=0.0015) and fat mass (-2.6 (SE 0.6) kg, P=0.0034) at the end of the MUFA-rich diet as compared with values at the end of the SFA-rich diet. No significant differences were detected in energy or fat intake, energy expenditure, substrate oxidation rates or self-reported physical activity. Substituting dietary saturated with unsaturated fat, predominantly MUFA, can induce a small but significant loss of body weight and fat mass without a significant change in total energy or fat intake.

Mechanistic roles for calcium and vitamin D in the regulation of body weight

Low intakes of calcium and inadequate vitamin D status often cluster with higher prevalence rates of obesity. Consequently, there has been much interest in the mechanisms by which calcium and vitamin D could regulate body weight and adiposity. This review has focused on randomized controlled trials (RCTs) that have manipulated these nutrients and studied pathways of energy balance. Overall, there is consistent evidence that calcium and vitamin D increase whole body fat oxidation after single and multiple meals, and that calcium promotes a modest energy loss through increased faecal fat excretion. The evidence is equivocal for a greater diet‐induced thermogenesis, increased lipolysis, suppression of key lipogenic enzymes, decreased hunger ratings or reduced energy/macronutrient intake. Emerging evidence suggests a potential improvement in insulin sensitivity following vitamin D that would impinge on food intake and substrate oxidation. However, the very few RCTs on supplemental vitamin D and energy balance have not explored postprandial avenues of the hormones actions. Future efforts in this area need to define the threshold intake of these nutrients that would maximize metabolic and gastrointestinal outcomes. Such studies would provide a platform for endorsing the non‐skeletal role of calcium and vitamin D in human pathophysiology.

Relation of adiposity and body fat distribution to body mass index in Australians of Aboriginal and European ancestry.

Objective: To compare the relations of adiposity and body fat distribution to body mass index (BMI) in Australians of Aboriginal and European ancestry.Design: Cross-sectional volunteer samples.Setting: Australian Aboriginal communities in remote central and northern Australia, urban European Australians resident in Melbourne, Australia.Subjects: Healthy Aboriginal (130 women, 120 men) and European Australians (100 women, 47 men) with a BMI<30 kg/m2, aged 18–35 y; all women were nonpregnant.Interventions: Anthropometric variables and resistance—using a four-terminal impedance plethysmograph—were measured.Results: Aboriginal women and men were significantly shorter and weighed less than European Australians (P<0.05). Aboriginal women had a significantly larger waist circumference and waist-to-hip ratio (WHR, P<0.0005) compared to European Australian women. The sum of four skinfold thicknesses (SFT) (S4) and trunk SFT was higher in Aboriginals as compared to European Australian women (P<0.0005); however, limb SFT tended to be lower (P=0.06). On the other hand, BMI was significantly lower in Aboriginals compared to European Australian men (P=0.011), as was hip circumference (P=0.001); however, WHR was significantly (P=0.007) higher. On regression analysis, Aboriginal women and men were significantly heavier than European Australians for the same height2/resistance (surrogate for fat-free mass) and S4 (surrogate for subcutaneous fat); and that Aboriginal men had a significantly higher BMI (by 1.2 kg/m2; P<0.0005) for any given S4 and height2/resistance values, compared to European Australian men.Conclusion: Aboriginal and European Australians have a significantly different body fat distribution and fat mass for a given body weight or BMI. Use of the World Health Organization recommended BMI ranges to determine weight status may be inappropriate in Australian Aboriginal people.Sponsorship: This study was supported, in part, by the National Health and Medical Research Council (NHMRC) of Australia grants (Nos. 934502, 954605). LSP was supported by an NHMRC grant (No. 981019). KGR was supported by an NH&MRC Postdoctoral Research Fellowship (No. 974302) and is currently a VicHealth Public Health Research Fellow.

The acute effects of olive oil v. cream on postprandial thermogenesis and substrate oxidation in postmenopausal women

The influence of the source of dietary fat on postprandial thermogenesis and substrate oxidation rates, was examined in twelve postmenopausal women aged 57-73 years, with BMI 21.9-38.3 kg/m(2). A single blind, randomised, paired comparison of two high-fat, isoenergetic, mixed test meals was conducted. The major source of fat was either cream (CREAM) or extra virgin olive oil (EVOO). RMR, diet-induced thermogenesis (DIT) and substrate oxidation rates over 5 h were measured by indirect calorimetry. There were no differences in body weight, RMR, fasting carbohydrate or fat oxidation rates between the two occasions. DIT (EVOO 97 (SD 46) v. CREAM 76 (SD 69) kJ/5 h and EVOO 5.2 (SD 2.5) v. CREAM 4.1 (SD 3.7)% energy) did not differ between the two test meals. The postprandial increase in carbohydrate oxidation rates, relative to their respective fasting values (DeltaCOX), was significantly lower following the EVOO meal (EVOO 10.6 (SD 8.3) v. CREAM 17.5 (SD 10) g/5 h; paired t test, P=0.023), while postprandial fat oxidation rates (DeltaFOX) were significantly higher (EVOO 0.0 (SD 4.4) v. CREAM -3.6 (sd 4.0) g/5 h; P=0.028). In the eight obese subjects, however, DIT was significantly higher following the EVOO meal (EVOO 5.1 (SD 2.0) v. CREAM 2.5 (sd 2.9) %; P=0.01). This was accompanied by a significantly lower DeltaCOX (EVOO 10.9 (SD 9.9) v. CREAM 17.3 (SD 10.5) g/5 h; P=0.03) and significantly higher DeltaFOX (EVOO 0.11 (SD 4.4) v. CREAM -4.1 (SD 4.5) g/5 h, P=0.034). The present study showed that olive oil significantly promoted postprandial fat oxidation and stimulated DIT in abdominally obese postmenopausal women.

Central obesity is associated with reduced peripheral wave reflection in Indigenous Australians irrespective of diabetes status

Objective To determine the influence of central obesity and type 2 diabetes on peripheral wave reflection in Indigenous Australians. Design and methods A cross-sectional study of remote Indigenous Australians with (n = 43) and without (n = 54) type 2 diabetes of similar age (47 years) and sex; using anthropometric and bioelectrical impedance measures of obesity and applanation tonometry to determine the aortic augmentation index (AI) as an index of peripheral wave relfection. Results Indices of obesity were significantly higher in the diabetic than non-diabetic participants [body mass index (BMI): 27.3 versus 24.6 kg/m2, P = 0.018; waist circumference: women 101 versus 94 cm, P = 0.008, men 102 versus 91 cm, P = 0.039]. AI was negatively related to obesity: BMI (r = −0.35, P = 0.0003), weight (r = −0.44, P < 0.0005), waist circumference (r = −0.34, P = 0.0003) and fat mass (r = −0.35, P < 0.0005). There was no significant difference in AI between the groups with and without diabetes. On multiple regression analysis, 66% of the variance in AI was explained with the following significant predictors: age, heart rate, male gender, fat mass and mean arterial pressure. Similar results were obtained when weight, waist circumference or BMI were substituted for fat mass. Conclusion When compared with Indigenous Australians without diabetes, those with type 2 diabetes do not have greater aortic pressure augmentation from peripheral wave reflection. However, obesity, irrespective of the index used, was related to lower peripheral wave reflection in both those with and without type 2 diabetes.

The validity of predicting the basal metabolic rate of young Australian men and women

Objectives: To assess the accuracy of the Schofield, Schofield & James (1985) equations and those of Hayter & Henry (1994) for the prediction of the basal metabolic rate (BMR), of young Australians. Design: BMR was measured by indirect calorimetry, while fat free mass (FFM) and fat mass (FM) were measured by bioelectric impendence analysis (BIA) in 128 volunteers (39 men and 89 women), aged between 18 and 30 y. Setting: Deakin Institute of Human Nutrition, Deakin University, Melbourne, Australia. Results: The measured BMR of Australian men and women were significantly lower (P≤0.001) than the predicted BMR using the Schofield et al (1985) equation, with a mean (s.d.) bias (bias=measured−predicted BMR) of −406 (513) kJ/d in men and −124 (348) kJ/d in women. The measured BMR of Australian men and women were similar to the predicted BMR using the equations of Hayter & Henry (1994) and bias was unrelated to body weight. BMR adjusted for FFM and FM was significantly higher by three percent in women on oral contraceptive agents (OCA) as compared to those not on OCA. Conclusions: The Schofield et al (1985) equations are not valid for the prediction of BMR of young Australian men and women. The equations of Hayter & Henry (1994) for North Europeans and Americans, provide an accurate estimate of the BMR of Australian men and women at the group level. However, in young women not using OCA a correction factor of 0.97 applied to the predicted BMR provides a better estimate. Sponsorship: Deakin University, Australia.

Anthropometric indices and their relationship with diabetes, hypertension and dyslipidemia in Australian Aboriginal people and Torres Strait Islanders

Background Australian indigenous people have a body shape and cardiovascular risk profiles different from that of other ethnic populations. This present study aims to examine the association of anthropometric indices with diabetes, hypertension and dyslipidemia, and to determine what indices can best predict these individual risk factors for the risk of cardiovascular disease (CVD). Design A cross-sectional study of Australian Aboriginal people and Torres Strait Islanders. Methods A total of 747 Australian Aboriginal people and 439 Torres Strait Islanders aged 25 years and over were examined between 1993 and 1997. Body weight, height, waist and hip circumferences, blood pressure, plasma glucose, triglycerides, total and high-density lipoprotein cholesterol were measured. Results The best predictor of hypertension among five anthropometric indices was waist:height ratio for Australian Aboriginal people and waist circumference for Torres Strait Islanders. Waist:hip ratio (WHR) was the best predictor for both diabetes and dyslipidemia in both populations. In multivariate regression analyses, WHR and body mass index were independently associated with the 10-year predicted absolute probability of coronary heart disease (CHD) for Torres Strait Islanders. However, overall WHR appeared to be the best predictor of the estimated CHD risk for both populations. Conclusions This study shows that WHR was the best predictor for diabetes, dyslipidemia and absolute CHD risk in Australian Aboriginal people and Torres Strait Islanders. Incorporating WHR into routine health examinations in Australian indigenous people will enhance the evaluation of CVD risk.

Study Protocol--accurate assessment of kidney function in Indigenous Australians: aims and methods of the eGFR study.

BackgroundThere is an overwhelming burden of cardiovascular disease, type 2 diabetes and chronic kidney disease among Indigenous Australians. In this high risk population, it is vital that we are able to measure accurately kidney function. Glomerular filtration rate is the best overall marker of kidney function. However, differences in body build and body composition between Indigenous and non-Indigenous Australians suggest that creatinine-based estimates of glomerular filtration rate derived for European populations may not be appropriate for Indigenous Australians. The burden of kidney disease is borne disproportionately by Indigenous Australians in central and northern Australia, and there is significant heterogeneity in body build and composition within and amongst these groups. This heterogeneity might differentially affect the accuracy of estimation of glomerular filtration rate between different Indigenous groups. By assessing kidney function in Indigenous Australians from Northern Queensland, Northern Territory and Western Australia, we aim to determine a validated and practical measure of glomerular filtration rate suitable for use in all Indigenous Australians.Methods/DesignA cross-sectional study of Indigenous Australian adults (target n = 600, 50% male) across 4 sites: Top End, Northern Territory; Central Australia; Far North Queensland and Western Australia. The reference measure of glomerular filtration rate was the plasma disappearance rate of iohexol over 4 hours. We will compare the accuracy of the following glomerular filtration rate measures with the reference measure: Modification of Diet in Renal Disease 4-variable formula, Chronic Kidney Disease Epidemiology Collaboration equation, Cockcroft-Gault formula and cystatin C- derived estimates. Detailed assessment of body build and composition was performed using anthropometric measurements, skinfold thicknesses, bioelectrical impedance and a sub-study used dual-energy X-ray absorptiometry. A questionnaire was performed for socio-economic status and medical history.DiscussionWe have successfully managed several operational challenges within this multi-centre complex clinical research project performed across remote North, Western and Central Australia. It seems unlikely that a single correction factor (similar to that for African-Americans) to the equation for estimated glomerular filtration rate will prove appropriate or practical for Indigenous Australians. However, it may be that a modification of the equation in Indigenous Australians would be to include a measure of fat-free mass.