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Biology subjects

Hall, K. D.

Publications and source records attributed to Hall, K. D..

2 recordsLinked to original sources
bioRxiv2018

Objective versus Self-Reported Energy Intake Changes During Low-Carbohydrate and Low-Fat Diets

ObjectiveTo examine objective versus self-reported energy intake changes ({Delta}EI) during a 12-month diet intervention.\n\nMethodsWe calculated {Delta}EI in subjects who participated in a 1-year randomized low-carbohydrate versus low-fat diet trial using repeated body weight measurements as inputs to an objective mathematical model ({Delta}EIModel) and compared these values with self-reported energy intake changes assessed by repeated 24-hr recalls ({Delta}EI24hrRecall).\n\nResults{Delta}EI24hrRecall indicated a relatively persistent state of calorie restriction [&ge;]500 kcal/d throughout the year with no significant differences between diets. {Delta}EIModel demonstrated large early decreases in calorie intake >800 kcal/d followed by an exponential return to approximately 100 kcal/d below baseline at the end of the year. The low-carbohydrate diet resulted in {Delta}EIModel that was 162{+/-}53 kcal/d lower than the low-fat diet over the first 3 months (p=0.002), but no significant diet differences were found at later times. Weight loss at 12 months was significantly related to {Delta}EIModel at all time intervals for both diets (p<0.0001).\n\nConclusionsSelf-reported measurements of {Delta}EI were inaccurate. Model-based calculations of {Delta}EI found that instructions to follow the low-carbohydrate diet resulted in greater calorie restriction than the low-fat diet in the early phases of the intervention, but these diet differences were not sustained.\n\nWhat is already known about this subject?O_LIDiet assessments that rely on self-report, such as 24hr dietary recall, are known to underestimate actual energy intake as measured by doubly labeled water. However, it is possible that repeated self-reported measurements could accurately detect changes in energy intake over time if the absolute bias of self-reported of measurements is approximately constant for each subject.\nC_LI\n\nWhat this study addsO_LIWe compared energy intake changes measured using repeated 24hr dietary recall measurements collected over the course of the 1-year Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) trial versus energy intake changes calculated using repeated body weight measurements as inputs to a validated mathematical model.\nC_LIO_LIWhereas self-reported measurements indicated a relatively persistent state of calorie restriction, objective model-based measurements demonstrated a large early calorie restriction followed by an exponential rise in energy intake towards the pre-intervention baseline.\nC_LIO_LIModel-based calculations, but not self-reported measurements, found that low-carbohydrate diets led to significantly greater early decreases in energy intake compared to low-fat diets, but long-term energy intake changes were not significantly different.\nC_LI

physiology↗
bioRxiv2018

Potential Bias of Doubly Labeled Water for Measuring Energy Expenditure Differences Between Diets Varying in Carbohydrate

BackgroundVery low-carbohydrate diets have been reported to substantially increase human energy expenditure as measured by doubly labeled water (DLW) but not by respiratory chambers. Do the DLW data reflect true physiological differences that are undetected by respiratory chambers? Alternatively, are the apparent DLW energy expenditure a consequence of failure to fully account for respiratory quotient (RQ) differences between diets?\n\nObjectiveTo examine energy expenditure differences between diets varying drastically in carbohydrate and to quantitatively compare DLW data with respiratory chamber and body composition measurements within an energy balance framework.\n\nDesignDLW measurements were obtained during the final two weeks of month-long baseline (BD; 50% carbohydrate, 35% fat, 15% protein) and isocaloric ketogenic diets (KD; 5% carbohydrate, 80% fat, 15% protein) in 17 men with BMI 25-35 kg/m2. Subjects resided 2d/week in respiratory chambers to measure energy expenditure (EEchamber). DLW expenditure was calculated using chamber-determined respiratory quotients (RQ) either unadjusted (EEDLW) or adjusted (EEDLW{Delta}RQ) for net energy imbalance using diet-specific coefficients. Accelerometers measured physical activity. Body composition changes were measured by dual-energy X-ray absorptiometry which were combined with energy intake measurements to calculate energy expenditure by balance (EEbal).\n\nResultsAfter transitioning from BD to KD, neither EEchamber nor EEbal were significantly changed ({triangleup}EEchamber=24{+/-}30 kcal/d; p=0.43 and {triangleup}EEbal=-141{+/-}118 kcal/d; p=0.25). Similarly, physical activity (-5.1{+/-}4.8%; p=0.3) and exercise efficiency (-1.6{+/-}2.4%; p=0.52) were not significantly changed. However, EEDLW was 209{+/-}83 kcal/d higher during the KD (p=0.023) but was not significantly increased when adjusted for energy balance (EEDLW{Delta}RQ =139{+/-}89 kcal/d; p=0.14). After removing 2 outliers whose EEDLW were incompatible with other data, EEDLW and EEDLW{triangleup}RQ were marginally increased during the KD by 126{+/-}62 kcal/d (p=0.063) and 46{+/-}65 kcal/d (p=0.49), respectively.\n\nConclusionsDLW calculations failing to account for diet-specific energy imbalance effects on RQ erroneously suggest that very low carbohydrate diets substantially increase energy expenditure.

physiology↗