Positional Analysis of Body Composition Using Dual-Energy X-Ray Absorptiometry in National Collegiate Athletic Association Division I Football and Men's Lacrosse.

ABSTRACT: Zabriskie, HA, Dobrosielski, DA, Leppert, KM, Droege, AJ, Knuth, ND, and Lisman, PJ. Positional analysis of body composition using dual-energy X-ray absorptiometry in National Collegiate Athletic Association Division I football and men's lacrosse. J Strength Cond Res 36(6): 1699-1707, 2022-Despite the widespread use of dual-energy X-ray absorptiometry (DXA), few studies have examined differences in body composition between positions within sports and none have reported DXA-derived body composition reference values for men's lacrosse. The purpose of this study was to examine differences in measures of total and regional body composition and bone mineral density (BMD) using DXA across sport positions in a large cohort of National Collegiate Athletic Association Division I male lacrosse and football players. A total of 294 male athletes (football, n = 196; lacrosse, n = 98) underwent DXA. One-way analysis of variance or Kruskal-Wallis tests were used to examine whether body composition variables differed by sports position. In football, position was a significant determinant for every compositional variable in football athletes (all, p < 0.05; effect size range = 0.24-0.79). Offensive linemen had the highest total body fat percentage (30.1 ± 2.9%), followed by fullbacks (26.7 ± 3.3%) and defensive linemen (24.6 ± 5.7%); wide receivers had the lowest (14.5 ± 2.1%). For total body BMD, defensive linemen had the highest (1.70 ± 0.09 g·cm-3), followed by linebackers (1.67 ± 0.09 g·cm-3) and offensive linemen (1.65 ± 0.09 g·cm-3); kickers had the lowest (1.45 ± 0.11 g·cm-3) BMD. In lacrosse, no differences were found between positions for any total or regional body composition and BMD measure (all, p > 0.05). Our data confirm that total and regional measures of body composition and BMD vary across positions in football but not in men's lacrosse. Unlike football, similarities in body composition among lacrosse players may indicate that the uniformity of training demands or preferred player attributes in team selection outweigh the unique positional demands in gameplay.

Associations between vasodilatory capacity, physical activity and sleep among younger and older adults.

INTRODUCTION: Exercise promotes cardiovascular health through its direct impact on the vascular endothelium. Conversely, poor sleep quality is associated with endothelial dysfunction, which may explain the increased cardiovascular disease amongst poor sleepers. Yet, the influence of physical activity and poor sleep quality on vascular health is not clear. PURPOSE: This study examined the relationships between forearm vasodilatory capacity, self-reported sleep quality and free-living, actigraphy-derived energy expenditure in a group of young and older community dwelling adults. METHODS: Venous occlusion plethysmography determined baseline and peak forearm blood flow following reactive hyperemia. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI). Measures of body composition were assessed using dual energy X-ray absorptiometry. RESULTS: A total of 104 (61 young; 43 old) participants completed the study. In general, younger participants were more active, as determined by steps per day and average daily energy expenditure, but reported poorer sleep quality. In the combined sample, those who reported moderate sleep disturbances (PSQI total score; 11-15) had significantly lower vasodilatory capacity (16.8 ± 7.6 ml/100 ml/min) compared to those who reported no sleep disturbance (PSQI total score; 0-5) (22.3 ± 7.2 ml/100 ml/min) or mild sleep disturbance (PSQI total score; 6-10) (22.3 ± 8.1 ml/100 ml/min) (p < 0.01). After adjustment for physical activity, total body fat and age, moderately poor sleep remained an independent predictor of forearm vasodilatory capacity. CONCLUSIONS: These findings suggest that any positive vascular benefits accrued through increased physical activity might be offset by the negative consequences of chronically disturbed sleep.

Comparison of skeletal muscle oxidative function in young, middle-aged, and older males and females with similar physical activity levels.

Optimal skeletal muscle oxidative function (microvascular reactivity and mitochondrial capacity) is an integral part of healthy aging and is related to physical function and quality of life. We aimed to extend upon the understanding of skeletal muscle oxidative function with healthy aging in males and females across the adult life span. Younger (N = 22; 11 males), middle-aged (N = 19; 10 males), and older (N = 21; 10 males) adults completed this study. Time spent in moderate and vigorous physical activity was self-reported and similar among groups. Near-infrared spectroscopy was used to investigate skeletal muscle microvascular reperfusion [oxyhemoglobin-myoglobin (O2Hb+Mb) half-time to peak hyperemia (T½)], mitochondrial capacity [muscle oxygen consumption (mV̇o2) recovery rate constant], and walking tissue oxygen saturation ([Formula: see text]) of the tibialis anterior (TA) muscle at seven incremental walking speeds. Mitochondrial capacity was not significantly different across groups (P = 0.07). Younger adults exhibited significantly slower T½ compared with older adults (P = 0.006) and middle-aged adults (P = 0.025). There were no observed sex differences for mitochondrial capacity (P = 0.442) or T½ (P = 0.402). Older adults exhibited significantly lower [Formula: see text] across all walking speeds compared with younger adults (P = 0.003). Mitochondrial capacity and microvascular reperfusion are maintained in middle and older age, with no sex differences in either outcome. However, in older adults whole body functional movement, such as walking, may place an additional demand on the TA as a compensatory response to lower functional reserve not evident in distinct measures of mitochondrial capacity and microvascular reperfusion.NEW & NOTEWORTHY Compared with younger adults, mitochondrial capacity and microvascular reperfusion of the tibialis anterior (TA) muscle are well maintained in similarly physically active middle-aged and older adults, with no sex differences observed in either outcome. However, greater tissue oxygen utilization in older adults during walking highlights how whole body functional movement may place an additional demand on the TA that reveals a potential compensatory response to lower functional reserve not evident in distinct measures of mitochondrial capacity and microvascular reperfusion.

Classification of Free-Living Body Posture with ECG Patch Accelerometers: Application to the Multicenter AIDS Cohort Study.

Purpose: As health studies increasingly monitor free-living heart performance via ECG patches with accelerometers, researchers will seek to investigate cardio-electrical responses to physical activity and sedentary behavior, increasing demand for fast, scalable methods to process accelerometer data. We extend a posture classification algorithm for accelerometers in ECG patches when researchers do not have ground-truth labels or other reference measurements (i.e., upright measurement). Methods: Men living with and without HIV in the Multicenter AIDS Cohort study wore the Zio XT® for up to two weeks (n = 1,250). Our novel extensions for posture classification include (1) estimation of an upright posture for each individual without a reference upright measurement; (2) correction of the upright estimate for device removal and re-positioning using novel spherical change-point detection; and (3) classification of upright and recumbent periods using a clustering and voting process rather than a simple inclination threshold used in other algorithms. As no posture labels exist in the free-living environment, we perform numerous sensitivity analyses and evaluate the algorithm against labelled data from the Towson Accelerometer Study, where participants wore accelerometers at the waist. Results: On average, 87.1% of participants were recumbent at 4am and 15.5% were recumbent at 1pm. Participants were recumbent 54 minutes longer on weekends compared to weekdays. Performance was good in comparison to labelled data in a separate, controlled setting (accuracy = 96.0%, sensitivity = 97.5%, specificity = 95.9%). Conclusions: Posture may be classified in the free-living environment from accelerometers in ECG patches even without measuring a standard upright position. Furthermore, algorithms that fail to account for individuals who rotate and re-attach the accelerometer may fail in the free-living environment.

Validation of accelerometer placement to capture energy expenditure using doubly labeled water.

This study compared accelerometer-measured physical activity by body placement to daily total energy expenditure (TEE) and activity energy expenditure (AEE) measured using doubly labeled water (DLW). Forty-nine adult participants wore accelerometers placed on the nondominant wrist, dominant wrist, and chest while also undergoing DLW assessments. In adjusted models, wrist-measured physical activity (p < 0.05), but not chest-measured physical activity (p > 0.05), was associated with TEE and AEE and explained a significant amount of variance that was not explained by age, sex, height, or body composition (R2 change = 0.04-0.08; all p < 0.05). Accelerometer placement location is an important consideration when using accelerometry to provide information about energy expenditure.

Association of Mitochondrial Function, Substrate Utilization, and Anaerobic Metabolism With Age-Related Perceived Fatigability.

Previous work has shown that poorer mitochondrial function is associated with age-related perceived fatigability. However, whether glucose oxidation and anaerobic metabolism are intermediate factors underlying this association remains unclear. We examined the total cross-sectional association between mitochondrial function and perceived fatigability in 554 adults aged 22-99 years. Mitochondrial function was assessed by skeletal muscle oxidative capacity (kPCr) using 31P magnetic resonance spectroscopy. Perceived fatigability was measured by rating of perceived exertion after a 5-minute (0.67 m/s) treadmill walk. The intermediate role of glucose oxidation (measured by the rate of change of respiratory exchange ratio [RER change rate] during the 5-minute treadmill walk) and anaerobic metabolism (measured by ventilatory threshold [VeT] during a maximal treadmill test) was evaluated by examining their cross-sectional associations with kPCr and perceived exertion. For each 0.01/s lower kPCr, perceived fatigability was 0.47 points higher (p = .002). A 0.01/s lower kPCr was also associated with 8.3 L/min lower VeT (p < .001). Lower VeT was associated with higher fatigability at lower levels of kPCr but not at higher kPCr levels (ß for interaction = 0.017, p = .002). kPCr and RER change rate were not significantly associated (p = .341), but a 0.01/min higher RER change rate was associated with 0.12-point higher fatigability (p = .001). Poorer mitochondrial function potentially contributes to higher perceived fatigability through higher glucose oxidation and higher anaerobic metabolism. Future studies to further explore the longitudinal mechanisms between these metabolic changes and fatigability are warranted.

Reducing dietary fat from a meal increases the bioavailability of exogenous carbohydrate without altering plasma glucose concentration.

The primary goal of this study was to determine the acute glycemic and endocrine responses to the reduction of fat content from a meal. On three separate occasions, nine overweight subjects (body mass index = 30 +/- 1 kg/m(2); 5 men, 4 women) consumed 1) a control meal ( approximately 800 kcal; 100 g of carbohydrate, 31 g of fat, and 30 g of protein), 2) a low-fat meal ( approximately 530 kcal; 100 g of carbohydrate, 1 g of fat, and 30 g of protein), or 3) a low-fat meal plus lipid infusion [same meal as low-fat meal, but the total energy provided was the same as control (800 kcal), with the "missing" fat ( approximately 30 g) provided via an intravenous lipid infusion]. All three meals contained [(13)C]glucose (3 mg/kg body wt) to assess the bioavailability of ingested glucose. During the 5-h period after each meal, we measured the recovery of [(13)C]glucose in plasma, plasma glucose, and insulin concentrations. We also measured plasma concentration of the gastrointestinal peptides: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and peptide YY(3-36) (PYY(3-36)). The recovery of the ingested [(13)C]glucose in the hour after ingestion was greater (P < 0.05) after the low-fat than after the control meal [area under the curve (AUC): 1,206 +/- 252 and 687 +/- 161 microM.h, respectively]. However, removing dietary fat from the meal did not affect the plasma concentration of glucose or insulin. Importantly, [(13)C]glucose recovery was not different during the low-fat and lipid infusion trials (AUC: 1,206 +/- 252 and 1,134 +/- 247 microM.h, respectively), indicating that the accelerated delivery of exogenous glucose found after removing fat from the meal is due exclusively to the reduction of fat in the gastrointestinal tract. In parallel with these findings, the reduction in fat calories from the meal reduced plasma concentration of GIP, GLP-1, and PYY(3-36). In summary, these data suggest that removing fat from the diet expedited exogenous glucose delivery into the systemic circulation and reduced the concentration of key gastrointestinal peptides, yet maintained plasma glucose concentration at control levels.

Increased Physical Activity Associated with Less Weight Regain Six Years After "The Biggest Loser" Competition.

OBJECTIVE: The aim of this study was to explore how physical activity (PA) and energy intake (EI) changes were related to weight loss and regain following "The Biggest Loser" competition. METHODS: At baseline, week 6 and week 30 of the competition, and 6 years after the competition, body composition was measured via dual-energy x-ray absorptiometry, resting energy expenditure was measured by using indirect calorimetry, and EI and PA were measured by using doubly labeled water. RESULTS: Six years after the competition, median weight loss in 14 of "The Biggest Loser" participants was 13%, with those maintaining a greater weight loss (mean ± SE) of 24.9% ± 3.8% having increased PA by 160% ± 23%, compared with a PA increase of 34% ± 25% (P = 0.0033) in the weight regainers who were 1.1% ± 4.0% heavier than the precompetition baseline. EI changes were similar between weight loss maintainers and regainers (-8.7% ± 5.6% vs. -7.4% ± 2.7%, respectively; P = 0.83). Weight regain was inversely associated with absolute changes in PA (r = -0.82; P = 0.0003) but not with changes in EI (r = -0.15; P = 0.61). EI and PA changes explained 93% of the individual weight loss variability at 6 years. CONCLUSIONS: Consistent with previous reports, large and persistent increases in PA may be required for long-term maintenance of lost weight.

Persistent metabolic adaptation 6 years after "The Biggest Loser" competition.

OBJECTIVE: To measure long-term changes in resting metabolic rate (RMR) and body composition in participants of "The Biggest Loser" competition. METHODS: Body composition was measured by dual energy X-ray absorptiometry, and RMR was determined by indirect calorimetry at baseline, at the end of the 30-week competition and 6 years later. Metabolic adaptation was defined as the residual RMR after adjusting for changes in body composition and age. RESULTS: Of the 16 "Biggest Loser" competitors originally investigated, 14 participated in this follow-up study. Weight loss at the end of the competition was (mean ± SD) 58.3 ± 24.9 kg (P < 0.0001), and RMR decreased by 610 ± 483 kcal/day (P = 0.0004). After 6 years, 41.0 ± 31.3 kg of the lost weight was regained (P = 0.0002), while RMR was 704 ± 427 kcal/day below baseline (P < 0.0001) and metabolic adaptation was -499 ± 207 kcal/day (P < 0.0001). Weight regain was not significantly correlated with metabolic adaptation at the competition's end (r = -0.1, P = 0.75), but those subjects maintaining greater weight loss at 6 years also experienced greater concurrent metabolic slowing (r = 0.59, P = 0.025). CONCLUSIONS: Metabolic adaptation persists over time and is likely a proportional, but incomplete, response to contemporaneous efforts to reduce body weight.

Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity.

Dietary carbohydrate restriction has been purported to cause endocrine adaptations that promote body fat loss more than dietary fat restriction. We selectively restricted dietary carbohydrate versus fat for 6 days following a 5-day baseline diet in 19 adults with obesity confined to a metabolic ward where they exercised daily. Subjects received both isocaloric diets in random order during each of two inpatient stays. Body fat loss was calculated as the difference between daily fat intake and net fat oxidation measured while residing in a metabolic chamber. Whereas carbohydrate restriction led to sustained increases in fat oxidation and loss of 53 ± 6 g/day of body fat, fat oxidation was unchanged by fat restriction, leading to 89 ± 6 g/day of fat loss, and was significantly greater than carbohydrate restriction (p = 0.002). Mathematical model simulations agreed with these data, but predicted that the body acts to minimize body fat differences with prolonged isocaloric diets varying in carbohydrate and fat.

"IDEAL" aging is associated with lower resting metabolic rate: the Baltimore Longitudinal Study of Aging.

OBJECTIVES: To assess the associations among age, health status, and resting metabolic rate (RMR) in a large population of older adults. DESIGN: Cross-sectional analysis. SETTING: Community-dwelling volunteers from the Baltimore Longitudinal Study of Aging (BLSA). PARTICIPANTS: Persons aged 40 to 96 (mean 68.2 ± 11.0) who underwent a comprehensive physical examination, cognitive assessment, RMR testing, body composition assessment, and physical function testing during a 3-day clinic visit (N = 420). MEASUREMENTS: Participants were assigned to Insight into the Determination of Exceptional Aging and Longevity (IDEAL) or non-IDEAL categories based on health status. IDEAL participants were defined according to the absence of physical and cognitive impairments, chronic conditions and comorbidities, and blood profile abnormalities. A three-stage linear regression model was used to assess the relationship between RMR and age, using IDEAL classification as a predictor and adjusting for sex and body composition. RESULTS: Resting metabolic rate averaged 1,512.4 ± 442.9 kcal/d and was lower with older age (ß = -8.55, P < .001). After adjusting for age, sex, and body composition, RMR was 109.6 kcal/d lower in IDEAL than non-IDEAL participants (P < .005). CONCLUSION: Individuals who are fully functional and free of major medical conditions have lower RMR than those with disease and functional impairments. These findings suggest that health status plays a role in energy use and regulation independent of age and body composition and that elevated RMR may be a global biomarker of poor health in older persons.

Metabolic adaptation following massive weight loss is related to the degree of energy imbalance and changes in circulating leptin.

OBJECTIVE: To measure changes in resting metabolic rate (RMR) and body composition in obese subjects following massive weight loss achieved via bariatric surgery or calorie restriction plus vigorous exercise. METHODS: Body composition and RMR were measured in 13 pairs of obese subjects retrospectively matched for sex, body mass index, weight, and age who underwent either Roux-en-Y gastric bypass surgery (RYGB) or participated in "The Biggest Loser" weight loss competition (BLC). RESULTS: Both groups had similar final weight loss (RYGB: 40.2 ± 12.7 kg, BLC: 48.8 ± 14.9 kg; P = 0.14); however, RYGB lost a larger proportion of their weight as fat-free mass (FFM) (RYGB: 30 ± 12%, BLC: 16 ± 8% [P < 0.01]). In both groups, RMR decreased significantly more than expected based on measured body composition changes. The magnitude of this metabolic adaptation was correlated with the degree of energy imbalance (r = 0.55, P = 0.004) and the decrease in circulating leptin (r = 0.47, P = 0.02). CONCLUSIONS: Calorie restriction along with vigorous exercise in BLC participants resulted in preservation of FFM and greater metabolic adaption compared to RYGB subjects despite comparable weight loss. Metabolic adaptation was related to the degree of energy imbalance and the changes in circulating leptin.

Metabolic slowing with massive weight loss despite preservation of fat-free mass.

CONTEXT: An important goal during weight loss is to maximize fat loss while preserving metabolically active fat-free mass (FFM). Massive weight loss typically results in substantial loss of FFM potentially slowing metabolic rate. OBJECTIVE: Our objective was to determine whether a weight loss program consisting of diet restriction and vigorous exercise helped to preserve FFM and maintain resting metabolic rate (RMR). PARTICIPANTS AND INTERVENTION: We measured body composition by dual-energy x-ray absorptiometry, RMR by indirect calorimetry, and total energy expenditure by doubly labeled water at baseline (n = 16), wk 6 (n = 11), and wk 30 (n = 16). RESULTS: At baseline, participants were severely obese (× ± SD; body mass index 49.4 ± 9.4 kg/m(2)) with 49 ± 5% body fat. At wk 30, more than one third of initial body weight was lost (-38 ± 9%) and consisted of 17 ± 8% from FFM and 83 ± 8% from fat. RMR declined out of proportion to the decrease in body mass, demonstrating a substantial metabolic adaptation (-244 ± 231 and -504 ± 171 kcal/d at wk 6 and 30, respectively, P < 0.01). Energy expenditure attributed to physical activity increased by 10.2 ± 5.1 kcal/kg.d at wk 6 and 6.0 ± 4.1 kcal/kg.d at wk 30 (P < 0.001 vs. zero). CONCLUSIONS: Despite relative preservation of FFM, exercise did not prevent dramatic slowing of resting metabolism out of proportion to weight loss. This metabolic adaptation may persist during weight maintenance and predispose to weight regain unless high levels of physical activity or caloric restriction are maintained.

Energy deficit after exercise augments lipid mobilization but does not contribute to the exercise-induced increase in insulin sensitivity.

The content of meals consumed after exercise can impact metabolic responses for hours and even days after the exercise session. The purpose of this study was to compare the effect of low dietary carbohydrate (CHO) vs. low energy intake in meals after exercise on insulin sensitivity and lipid metabolism the next day. Nine healthy men participated in four randomized trials. During the control trial (CON) subjects remained sedentary. During the other three trials, subjects exercised [65% peak oxygen consumption (Vo(2 peak)); cycle ergometer and treadmill exercise] until they expended approximately 800 kcal. Dietary intake during CON and one exercise trial (BAL) was designed to provide sufficient energy and carbohydrate to maintain nutrient balance. In contrast, the diets after the other two exercise trials were low in either CHO (LOW-CHO) or energy (LOW-EN). The morning after exercise we obtained a muscle biopsy, assessed insulin sensitivity (S(i); intravenous glucose tolerance test) and measured lipid kinetics (isotope tracers). Although subjects were in energy balance during both LOW-CHO and CON, the lower muscle glycogen concentration during LOW-CHO vs. CON (402 +/- 29 vs. 540 +/- 33 mmol/kg dry wt, P < 0.01) coincided with a significant increase in S(i) [5.2 +/- 0.7 vs. 3.8 +/- 0.7 (mU/l)(-1) x min(-1); P < 0.05]. Conversely, despite ingesting several hundred fewer kilocalories after exercise during LOW-EN compared with BAL, this energy deficit did not affect S(i) the next day [4.9 +/- 0.9, and 5.0 +/- 0.8 (mU/l)(-1) x min(-1)]. Maintaining an energy deficit after exercise had the most potent effect on lipid metabolism, as measured by a higher plasma triacylglycerol concentration, and increased plasma fatty acid mobilization and oxidation compared with when in nutrient balance. Carbohydrate deficit after exercise, but not energy deficit, contributed to the insulin-sensitizing effects of acute aerobic exercise, whereas maintaining an energy deficit after exercise augmented lipid mobilization.

Adding carbohydrate to a high-fat meal blunts postprandial lipemia in women and reduces meal-derived fatty acids in systemic circulation.

The lipemic response to a meal is an important independent risk factor for the development of cardiovascular disease. The purpose of this study was to determine the effect of adding carbohydrate (CHO) to a fat meal on the bioavailability of ingested fat in different blood lipid fractions in men and women. On two separate occasions, 18 healthy adults (9 women, 9 men) ate either a high-fat meal (0.7 grams fat per kilogram) (FAT), or the same meal with added CHO (1 gram CHO per kilogram) (FAT+CHO) in the morning after a 12 h fast. Both meals were supplemented with [13C]-palmitate (25 mg.kg(-1)). Plasma concentrations of triglyceride (TG), fatty acids, insulin, and glucose were measured in blood samples taken hourly from 0 to 8 h after the meal. In addition, we measured TG concentrations in chylomicron (CHYLO-TG) and in very-low-density lipoprotein (VLDL-TG) fractions. The addition of CHO to the fat meal increased plasma glucose and insulin concentrations identically in men and women. In contrast, adding CHO to the fat meal reduced the plasma TG concentration in the 5 h after the meal in women (average 5 h [TG]: 1.27 +/- 0.11 and 1.01 +/- 0.09 mmol.L(-1); p <0.05), but not in men (1.25 +/- 0.23 and 1.24 +/- 0.20 mmol.L(-1)). Despite differences in the lipemic response to the meals between men and women, we found that adding carbohydrate to a fat meal decreased the bioavailability of meal-derived [13C]-palmitate in the systemic fatty acid pool, and decreased the incorporation of [13C]-palmitate into VLDL-TG in both men and women. In summary, adding CHO to a fat meal markedly blunted the plasma TG response in women, but not in men, which may augment the atherogenic potential after each meal in men.

The elevation of ingested lipids within plasma chylomicrons is prolonged in men compared with women.

The lipemic response to a high-fat meal is greater in men than in women. However, sex-related differences in the metabolic fate of ingested fat are not well understood. The purpose of this study was to measure the recovery of ingested fat in plasma fractions of chylomicrons (CHYLO), VLDL, and plasma fatty acids, as well as in expired breath (i.e., oxidation) in men and women. Nonobese subjects (n = 10; 5 men, 5 women) consumed 0.7 g fat/kg body weight containing 7 mg/kg of [1,1,1-13C]-trioleate the morning after an overnight fast. Plasma total triglyceride (TG) concentration and 13C recovery in the CHYLO, VLDL, and plasma fatty acid fractions, as well as expired breath samples, were measured over the 11-h period after the meal. Plasma total TG excursion was greater (P < 0.05) in men than in women during the 11-h period after the meal. Similarly, the recovery of the ingested tracer-labeled fat in the CHYLO fraction was greater in men than in women (main effect for sex; P < 0.05). Recovery of ingested tracer-labeled fat in VLDL, the plasma fatty acid fraction, and expired breath did not differ in men and women. Therefore, the elevated postprandial lipemia found in men compared with women was due to a prolonged availability of the lipid in chylomicrons, but was not related to differences in oxidation rates or incorporation of the ingested lipid into VLDL by the liver.