Jamie A. Cooper

Assessing validity and reliability of resting metabolic rate in six gas analysis systems.

The Deltatrac Metabolic Monitor (DTC) (VIASYS Healthcare Inc, SensorMedics, Yorba Linda, CA), one of the most popular indirect calorimetry systems for measuring resting metabolic rate (RMR) in human subjects, is no longer being manufactured. This study compared five different gas analysis systems to the DTC. RMR was measured by the DTC and at least one other instrument at three study sites for a total of 38 participants. The five indirect calorimetry systems included the MedGraphics CPX Ultima (Medical Graphics Corp, St Paul, MN), the MedGem (Microlife USA, Golden, CO), Vmax Encore 29 System (VIASYS Healthcare Inc, Yorba Linda, CA), the TrueOne 2400 (Parvo Medics, Sandy, UT), and the Korr ReeVue (Korr Medical Technologies, Salt Lake City, UT). Validity was assessed using paired t tests to compare means; reliability was assessed by using both paired t tests and root mean square calculations with F tests for significance. Within-subject comparisons for validity of RMR revealed a significant difference between the DTC and the Ultima system. Bland-Altman plot analysis showed significant bias with increasing RMR values for the Korr and MedGem systems. Respiratory exchange ratio (RER) analysis showed a significant difference between the DTC and the Ultima system and a trend for a difference with the Vmax system (P=0.09). Reliability assessment for RMR revealed that all instruments had a significantly larger coefficient of variation (CV) (ranging from 4.8% to 10.9%) for RMR compared to the 3.0% CV for the DTC. Reliability assessment for RER data showed none of the instrument CVs was significantly larger than the DTC CV. The results were quite disappointing because none of the instruments equaled the within-person reliability of the DTC. The TrueOne and Vmax systems were the most valid instruments in comparison with the DTC for both RMR and RER assessment. Further testing is needed to identify an instrument with the reliability and validity of the DTC.

Impact of exercise and dietary fatty acid composition from a high-fat diet on markers of hunger and satiety.

To compare the effects of both dietary fatty acid composition and exercise vs. sedentary conditions on circulating levels of hunger and satiety hormones. Eight healthy males were randomized in a 2 × 2 crossover design. The four treatments were 3 days of HF diets (50% of energy) containing high saturated fat (22% of energy) with exercise (SE) or sedentary (SS) conditions, and high monounsaturated fat (30% of energy) with exercise (UE) or sedentary (US) conditions. Cycling exercise was completed at 45% of VO(2)max for 2h daily. On the third HF day, 20 blood samples were drawn over a 24h period for each hormone (leptin, insulin, ghrelin, and peptide YY (PYY)). A visual analog scale (VAS) was completed hourly between 0800 and 2200. Average 24h leptin and insulin levels were lower while 24h PYY was higher during exercise vs. sedentary conditions. FA composition did not differentially affect 24h hormone values. VAS scores for hunger and fullness did not differ between any treatment but did correlate with ghrelin, leptin, and insulin. High saturated or unsaturated fat diets did not differ with respect to markers of hunger or satiety. Exercise decreased 24h leptin and insulin while increasing PYY regardless of FA composition.

Factors affecting circulating levels of peptide YY in humans: a comprehensive review

As obesity continues to be a global epidemic, research into the mechanisms of hunger and satiety and how those signals act to regulate energy homeostasis persists. Peptide YY (PYY) is an acute satiety signal released upon nutrient ingestion and has been shown to decrease food intake when administered exogenously. More recently, investigators have studied how different factors influence PYY release and circulating levels in humans. Some of these factors include exercise, macronutrient composition of the diet, body-weight status, adiposity levels, sex, race and ageing. The present article provides a succinct and comprehensive review of the recent literature published on the different factors that influence PYY release and circulating levels in humans. Where human data are insufficient, evidence in animal or cell models is summarised. Additionally, the present review explores the recent findings on PYY responses to different dietary fatty acids and how this new line of research will make an impact on future studies on PYY. Human demographics, such as sex and age, do not appear to influence PYY levels. Conversely, adiposity or BMI, race and acute exercise all influence circulating PYY levels. Both dietary fat and protein strongly stimulate PYY release. Furthermore, MUFA appear to result in a smaller PYY response compared with SFA and PUFA. PYY levels appear to be affected by acute exercise, macronutrient composition, adiposity, race and the composition of fatty acids from dietary fat.

Maximal Sustained Levels of Energy Expenditure in Humans during Exercise

UNLABELLED Migrating birds have been able to sustain an energy expenditure (EE) that is five times their basal metabolic rate. Although humans can readily reach these levels, it is not yet clear what levels can be sustained for several days. PURPOSE The studys purposes were 1) to determine the upper limits of human EE and whether or not those levels can be sustained without inducing catabolism of body tissues and 2) to determine whether initial body weight is related to the levels that can be sustained. METHODS We compiled data on documented EE as measured by doubly labeled water during high levels of physical activity (minimum of five consecutive days). We calculated the physical activity level (PAL) of each individual studied (PAL = total EE / basal metabolic rate) from the published data. Correlations were run to examine the relationship between initial body weight and body weight lost with both total EE and PAL. RESULTS The uppermost limit of EE was a peak PAL of 6.94 that was sustained for 10 consecutive days of a 95-d race. Only two studies reported PALs above 5.0; however, significant decreases in body mass were found in each study (0.45-1.39 kg·wk(-1) of weight loss). To test whether initial weight affects the ability to sustain high PALs, we found a significant positive correlation between TEE and initial body weight (r = 0.46, P < 0.05) but no correlation between PAL and body weight (r = 0.27, not statistically significant). CONCLUSIONS Some elite humans are able to sustain PALs above 5.0 for a minimum of 10 d. Although significant decreases in body weight occur at this level, catabolism of body tissue may be preventable in situations with proper energy intake. Further, initial body weight does not seem to affect the sustainability of PALs.

Effects of dietary fatty acid composition from a high fat meal on satiety

UNLABELLED The composition of fats within a high-fat (HF) meal may differentially affect hunger and satiety. PURPOSE Compare HF meals rich in either monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), or saturated fatty acids (SFAs) on the satiety hormone, peptide YY (PYY), and subjective feelings of hunger and fullness. METHODS Fifteen normal weight women (18-45 year) were randomized in a crossover design to complete three study visits. The three treatments (three visits) were HF meals (70% of energy from fat) rich in MUFAs (42% of total energy), PUFAs (42% of total energy), or SFAs (45% of total energy). At each visit, subjects consumed a HF meal and eight blood draws were collected over a 5 h period. A visual analog scale (VAS) was completed at the same time as each blood draw for subjective feelings of hunger and fullness. RESULTS The postprandial PYY response (area under the curve) was significantly lower (p<0.05) for the MUFA-rich meal (MUFA: 534.5±27.2 pg/mL/5 h) vs. the SFA-rich or PUFA-rich meals (SFA: 607.3±51.6 pg/mL/5h, PUFA: 633.1±35.8 pg/mL/5 h). The SFA-rich meal elicited greater subjective feelings of fullness compared to MUFA- and PUFA-rich meals (288.1±9.6 vs. 236.8±7.9 and 220.9±7.4 mm/5 h; p=0.04, for 5h AUC for SFA, MUFA, and PUFA, respectively). The only significant correlations between PYY levels and VAS measures were found with the SFA-rich meal. CONCLUSION Our data shows that liquid meals rich in MUFAs may elicit a weaker satiety response based on PYY levels compared to liquid meals rich in PUFAs or SFAs in normal weight women.

Validation Study of the Body Adiposity Index as a Predictor of Percent Body Fat in Older Individuals: Findings From the BLSA

A new body adiposity index (BAI = (hip circumference)/((height)(1.5)) - 18) has been developed and validated in adult populations. We aimed to assess the validity of BAI in an older population. We compared the concordance correlation coefficient between BAI, body mass index (BMI), and percent body fat (fat%; by dual-energy X-ray absorptiometry) in an older population (n = 954) participating in the Baltimore Longitudinal Study of Aging. BAI was more strongly correlated with fat% than BMI (r of .7 vs .6 for BAI vs BMI and fat%, respectively, p < .01) and exhibited a smaller mean difference from fat% (-5.2 vs -7.6 for BAI vs BMI and fat%, respectively, p < .01) indicating better agreement. In men, however, BMI was in better agreement with fat% (r of .6 vs .7 for BAI vs BMI and fat%, respectively, p < .01) with a smaller mean difference from fat% (-3.0 vs -2.2 for BAI vs BMI and fat%, respectively, p < .01). Finally, BAI did not accurately predict fat% in people with a fat% below 15%. BAI provides valid estimation of body adiposity in an older adult population; however, BMI may be a better index for older men. Finally, BAI is not accurate in people with extremely low or high body fat percentages.

Zumba® dance improves health in overweight/obese or type 2 diabetic women.

OBJECTIVE To evaluate the feasibility and health improvements from a Zumba® intervention in overweight/obese women. METHODS Twenty-eight (14 type 2 diabetic and 14 non-diabetic) over-weight/obese women (BMI: 37.3±1.5 kg/m(2)) 50.8±1.8 y of age, completed a 16-week intervention attending Zumba® dance classes 3 days/week, 60 minutes/class. We measured aerobic fitness, body weight, body fat %, and motivation to exercise before and after the study. RESULTS Intrinsic motivation to exercise (p < .05) and aerobic fitness (1.01 ± 0.40 mL/kg/min, p < .05) improved, and the participants lost body weight (-1.05 ± 0.55kg, p < .05) and body fat% (-1.2 ± 0.6%, p < .01). CONCLUSION The Zumba® intervention improved health and physical fitness in women.

Acute effect of dietary fatty acid composition on postprandial metabolism in women.

What is the central question of this study? We wanted to determine the effect of three high‐fat meals enriched with different fatty acids [monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs) or saturated fatty acids (SFAs)] on diet‐induced thermogenesis and substrate oxidation in premenopausal women of normal weight. What is the main finding and its importance? We found that a PUFA‐rich high‐fat meal led to a greater diet‐induced thermogenesis in normal‐weight premenopausal women compared with SFA‐ or MUFA‐rich high‐fat meals. The greater diet‐induced thermogenesis for PUFA‐rich meals could contribute to differences in long‐term overall energy balance, and thus, weight maintenance. Substrate utilization was not different between treatments.

Metabolic responses to dietary fatty acids in obese women.

BACKGROUND The composition of fatty acids in a diet may differentially affect metabolism, thus playing a role in the development of obesity. Our purpose was to study the effects of three high-fat (HF) meals with different dietary fatty acid compositions on the thermic effect of meal (TEM) and substrate oxidation in obese premenopausal women. METHODS 16 healthy obese women, aged 18-39 years, participated in a single-blinded randomized cross-over study, in which they consumed isocaloric HF meals (70% of energy from fat) rich in either saturated fat (SFA), monounsaturated fat (MUFA) or polyunsaturated fat (PUFA). Indirect calorimetry was used to measure respiratory gases for a 5-hour postprandial period. Data collected was used to determine respiratory exchange ratio (RER) for assessing substrate oxidation, and energy expenditure for the determination of TEM. RESULTS There was a significant time effect on both substrate oxidation and TEM (p<0.05). With and without using RMR as a covariate, there were no significant differences in TEM between test meals (TEM of 10.8±0.8 vs 11.0±1.0 kcal ∗ 5 h for high-MUFA vs. high-SFA meals, respectively, p=0.06). No treatment difference was found for postprandial substrate utilization (4.9±0.4, 4.9±0.3 and 4.6±0.4 g of fat oxidation following SFA, MUFA, and PUFA-rich HF meals, respectively; 13.2±0.9, 13.3±0.5 and 13.9±0.6 g of carbohydrate oxidation following SFA, MUFA, and PUFA-rich HF meals, respectively). CONCLUSIONS In premenopausal obese women, HF meals rich in either MUFAs, PUFAs, or SFAs did not differentially affect TEM or postprandial substrate oxidation.

Lipocalin‐2 increases fat oxidation in vitro and is correlated with energy expenditure in normal weight but not obese women

The role of lipocalin‐2 (Lcn2) was determined in regulating metabolism in cell, animal, and human models.