Christopher L. Melby

Effect of exercise intensity and duration on postexercise energy expenditure

The purpose of this study was to examine 1) the effect of two exercise intensities of equal caloric output on the magnitude (kcal) and duration of excess postexercise oxygen consumption (EPOC) and 2) the effect of exercise of equal intensity but varying duration on EPOC. Ten trained male triathletes performed three cycle ergometer exercises: high intensity-short duration (HS), low intensity-short duration (LS), and low intensity-long duration (LL). Baseline VO2 was measured for 1 h prior to each exercise condition. Postexercise VO2 was measured continuously until baseline VO2 was achieved. The duration of EPOC was similar for HS (33 +/- 10 min) and LL (28 +/- 14 min), and both were significantly longer (P less than 0.05) than the EPOC following LS (20 +/- 5 min). However, total net caloric expenditure was significantly more (P less than 0.05) for HS (29 +/- 8 kcal) than for either LS (14 +/- 6 kcal) or LL (12 +/- 7 kcal). The exercise conditions used in this study did not produce a prolonged EPOC. However, the exercise intensity was shown to affect both the magnitude and duration of EPOC, whereas the exercise duration affected only the duration of EPOC. Moreover, the duration of EPOC and the subsequent caloric expenditure were not necessarily related. Based on the resulting magnitude of the postexercise energy expenditure, it is possible that EPOC may be of some value for weight control over the long term.

The Impact of Exercise and Diet Restriction on Daily Energy Expenditure

SummaryIn addition to the direct energy cost of physical activity, exercise may influence resting energy expenditure in 3 ways: (a) a prolonged increase in postexercise metabolic rate from an acute exercise challenge; (b) a chronic increase in resting metabolic rate associated with exercise training; and (c) a possible increase in energy expenditure during nonexercising time.It seems apparent that the greater the exercise perturbation, the greater the magnitude of the increase in postexercise metabolic rate. An exercise prescription for the general population that consists of exercise of low (<50% V̇O2max) or moderate intensity (50 to 75% V̇O2max) does not appear to produce a prolonged elevation of postexercise metabolic rate that would influence body-weight. Inconsistent results have been found with respect to the effects of exercise training and the trained state on resting metabolic rate. Whereas some investigators have found a higher resting metabolic rate in trained than untrained individuals and in individuals after an exercise training programme, other investigators have found no chronic exercise effect on resting metabolic rate. Differences in experimental design, genetic variation and alterations in energy balance may contribute to the discrepant findings among investigators. A relatively unexplored area concerns the influence of exercise training on energy expenditure during nonexercising time. It is presently unclear whether exercise training increases or decreases the energy expenditure associated with spontaneous or nonpurposeful physical activity which includes fidgeting, muscular activity, etc. The doubly labelled water technique represents a methodological advance in this area and permits the determination of total daily energy expenditure. Concomitant with the determination of the other components of daily energy expenditure (resting metabolic rate and thermic effect of a meal), it will now be possible to examine the adaptive changes in energy expenditure during nonexercising time.A plethora of studies have examined the combined effects of diet and exercise on body composition and resting metabolic rate. The hypothesis is that combining diet and exercise will accelerate fat loss, preserve fat-free weight and prevent or decelerate the decline in resting metabolic rate more effecively than with diet restriction alone. The optimal combination of diet and exercise, however, remains elusive. It appears that the combination of a large quantity of aerobic exercise with a very low calorie diet resulting in substantial loss of bodyweight may actually accelerate the decline in resting metabolic rate. These findings may cause us to re-examine the quantity of exercise and diet needed to achieve optimal fat loss and preservation of resting metabolic rate.

Body Mass Index and perceived weight status in young adults

Body Mass Index (BMI) was calculated from self-reported height and weight for 1,123 university students who returned a questionnaire mailed to a 10 percent random sample of the entire undergraduate population of a large midwestern university. Seventeen percent of the females and 20 percent of the males were determined to be in excess of normal BMI standards. However, significantly more women (40%) considered themselves overweight in comparison to men (24%). Also, significantly more women (53%) than men (20%) reported experiencing discomfort due to excessive weight. Inaccurate perceptions of body image are common among individuals with eating disorders. There is a higher incidence of eating disorders among college-age women than among their male peers. A distorted body image as reflected by perceived overweight may serve as a marker for individuals at risk for eating disorders.

Cardiovascular Disease Risk Factors are Lower in African-American Vegans Compared to Lacto-Ovo-vegetarians

OBJECTIVEnThis study was undertaken to determine if African-American strict vegetarians (vegans) exhibit lower blood pressure (BP) and a more favorable serum lipid profile than their lacto-ovo vegetarian (LOV) counterparts, and if plasma ascorbic acid (AA) concentrations could explain any group differences in these cardiovascular disease (CVD) risk factors.nnnMETHODSnHabitual dietary intake, anthropometric characteristics, blood pressure, and blood lipids and ascorbic acid concentrations were determined in African-American study participants (male vegans, n = 14, age = 45.6 years; male LOV, n = 49, age = 49.8; female vegans, n = 31, age = 51.1, female LOV, n = 94, age = 52.1) recruited from Seventh-Day Adventist Churches in several cities in the northeastern United States.nnnRESULTSnBody mass index (BMI) was significantly lower in the vegans (24.7 +/- 1.9 kg/m2) compared to LOV (26.4 +/- 0.45 kg/m2). There were no diet or gender differences in BP. Serum total cholesterol (3.75 +/- 0.12 vs. 4.51 +/- 0.10 mmol/L), LDL-cholesterol (2.06 +/- 0.13 vs. 2.65 +/- 0.09 mmol/l), and triglycerides (0.94 +/- 0.07 vs. 1.17 +/- 0.04 mmol/L) were significantly (p < 0.05) lower in vegans compared to LOV, but there were no dietary group differences in HDL-C. The ratio of total to HDL-cholesterol was significantly lower in vegans than in LOV (3.0 +/- 0.13 vs. 3.7 +/- 0.13). There were no dietary group differences in plasma AA concentrations. However, in the entire sample, plasma AA was inversely associated with BP (SBP: r = -0.46, p < 0.001, DBP: r = -0.32, p < 0.001), but unrelated to the serum lipid concentrations.nnnCONCLUSIONnAfrican-American vegans exhibit a more favorable serum lipid profile than lacto-ovo-vegatarians and plasma AA is inversely related to BP in African-American vegetarians but does not explain any of the differences in CVD risk factors between vegans and lacto-ovo vegetarians.

Risk Factors for Cardiovascular Disease and Diabetes in Two Groups of Hispanic Americans with Differing Dietary Habits

OBJECTIVEnThe purpose of this study was to determine if Hispanic Seventh-Day Adventists (SDAs), who typically eat a diet lower in fat, saturated fat and protein, and higher in complex carbohydrates and dietary fiber than the usual omnivorous diet, exhibit lower risk factors for cardiovascular disease (CVD) and Type 2 diabetes compared to Hispanic Catholic omnivores.nnnMETHODSnAnthropometric characteristics, dietary intake, blood pressure, serum lipids, glucose and insulin, as well as plasma ascorbic acid and vitamin E concentrations, were measured in two groups of Hispanic study participants residing in Denver, Colorado: 74 SDA study participants (x age: 42+/-1.5 y) and 45 Catholic participants (x age: 44+/-2.2 y).nnnRESULTSnThe SDAs reported lower dietary intakes of total fat, saturated fat and cholesterol and higher relative intakes of carbohydrate and dietary fiber compared to their Catholic counterparts. The SDAs exhibited significantly lower body mass index (BMI = 27.2+/-0.6) and waist-to-hip ratios (WHR = 0.84+/-0.01) compared to the Catholics (BMI = 31.4+/-1.1; WHR = 0.88+/-0.01). The SDAs, compared to the Catholics, had lower fasting insulin (11.4+/-0.6 vs. 18.9+/-3.1 microu/ml) and glucose concentrations (88.6+/-1.1 vs. 104.1+/-5.4 mg/dl). The SDA Hispanics, compared to the Catholic Hispanics, exhibited significantly lower values for systolic blood pressure (SBP = 1102 vs. 118+/-3 mm Hg), serum total cholesterol (STC = 198+/-5 vs. 214+/-6 mg/dl) and serum triglycerides (TG = 152+/-12 vs. 232+/-27) and higher serum concentrations of high-density lipoprotein cholesterol (HDL-C = 44.7+/-1.3 vs. 39.1+/-1.4 mg/dl) and ascorbic acid (1.14+/-0.08 vs. 0.87+/-0.07 mg/dl). Low-density lipoprotein cholesterol (LDL-C) and vitamin E concentrations were not significantly different between groups, but the SDAs exhibited lower ratios of STC/HDL-C and LDL-C/HDL-C.nnnCONCLUSIONnHispanic American SDAs, who eat a plant-based diet, exhibit a more favorable blood lipid profile, lower blood pressure and lower risk for Type 2 diabetes compared to Hispanic American Catholics, who do not eat a plant-based diet.

Effect of resistance exercise, with or without carbohydrate supplementation, on plasma ghrelin concentrations and postexercise hunger and food intake

The effects of resistance exercise with and without carbohydrate (CHO) supplementation on hunger, postexercise food intake, and plasma ghrelin, an orexigenic gastric peptide, are poorly characterized. We examined the individual and combined effects of a resistance exercise bout and CHO consumption on plasma ghrelin and postexercise food intake. Twenty-one apparently healthy young male participants ([mean +/- SD] age = 20 +/- 1.8 years, body mass index = 24.8 +/- 3.3 kg/m(2)) completed in random order 3 treatment conditions: (1) ExCHO-80-minute resistance exercise bout while consuming CHO ( approximately 77 g CHO, 306 kcal); (2) ExPLA-identical exercise with a non=caloric placebo; and (3) NoExCHO-no-exercise trial of quiet sitting and CHO consumption. Blood samples were obtained before, during, and immediately postexercise, and 110 minutes after exercise. At 2 hours postexercise, they were provided a buffet of food from which they ate ad libitum. There was a significant time x treatment interaction for plasma ghrelin caused by a decline from pre- to postexercise in the 2 exercise conditions compared with an increase over time in the NoExCHO condition. At 110 minutes postexercise, ghrelin was 21% and 13% lower in ExCHO and ExPLA compared with NoExCHO (both Ps < .05). However, despite the lower ghrelin concentrations for the 2 exercise conditions, the subjective ratings of hunger were not lower for these conditions compared with the NoExCHO. There were no differences in absolute ad libitum energy intake from the buffet among the 3 conditions, but relative energy intake from the buffet accounting for the estimated cost of exercise was lowest among the 2 exercise conditions. We conclude that (1) weight lifting lowers plasma ghrelin concentrations during exercise and attenuates its rise during the postexercise period in young men and (2) the lower plasma ghrelin concentration is not associated with lower subjective feelings of hunger measured 100 minutes postexercise, but is associated with a lower relative food intake.

Total daily energy expenditure is increased following a single bout of sprint interval training

Regular endurance exercise is an effective strategy for healthy weight maintenance, mediated via increased total daily energy expenditure (TDEE), and possibly an increase in resting metabolic rate (RMR: the single largest component of TDEE). Sprint interval training (SIT) is a low‐volume alternative to endurance exercise; however, the utility of SIT for healthy weight maintenance is less clear. In this regard, it is feasible that SIT may evoke a thermogenic response above and beyond the estimates required for prevention of weight gain (i.e., >200–600 kJ). The purpose of these studies was to investigate the hypotheses that a single bout of SIT would increase RMR and/or TDEE. Study 1: RMR (ventilated hood) was determined on four separate occasions in 15 healthy men. Measurements were performed over two pairs of consecutive mornings; each pair was separated by 7 days. Immediately following either the first or third RMR measurement (randomly assigned) subjects completed a single bout of SIT (cycle ergometer exercise). RMR was unaffected by a single bout of SIT (7195 ± 285 kJ/day vs. 7147 ± 222, 7149 ± 246 and 6987 ± 245 kJ/day (mean ± SE); P = 0.12). Study 2: TDEE (whole‐room calorimeter) was measured in 12 healthy men, on two consecutive days, one of which began with a single bout of SIT (random order). Sprint exercise increased TDEE in every research participant (9169 ± 243 vs. 10,111 ± 260 kJ/day; P < 0.0001); the magnitude of increase was 946 ± 62 kJ/day (~10%). These data provide support for SIT as a strategy for increasing TDEE, and may have implications for healthy body weight maintenance.

Linking dietary patterns with gut microbial composition and function

ABSTRACT Emerging insights have implicated the gut microbiota as an important factor in the maintenance of human health. Although nutrition research has focused on how direct interactions between dietary components and host systems influence human health, it is becoming increasingly important to consider nutrient effects on the gut microbiome for a more complete picture. Understanding nutrient-host-microbiome interactions promises to reveal novel mechanisms of disease etiology and progression, offers new disease prevention strategies and therapeutic possibilities, and may mandate alternative criteria to evaluate the safety of food ingredients. Here we review the current literature on diet effects on the microbiome and the generation of microbial metabolites of dietary constituents that may influence human health. We conclude with a discussion of the relevance of these studies to nutrition and public health and summarize further research needs required to realize the potential of exploiting diet-microbiota interactions for improved health.

Effect of Inpatient versus Outpatient Measurement Protocol on Resting Metabolic Rate and Respiratory Exchange Ratio

Resting metabolic rate (RMR) and respiratory exchange ratio (RER) were measured, using indirect calorimetry, in 9 healthy, male subjects (28.6 +/- 3.3 years) under three conditions: (1) an inpatient, meal-controlled protocol (IPM) in which subjects were fed an evening meal and slept overnight in the laboratory prior to the morning test; (2) an outpatient, meal-controlled protocol (OPM) in which subjects were fed the same meal but slept at home prior to being transported to the laboratory for testing, and (3) and outpatient protocol (OP) in which meal was not controlled, but subjects were instructed to fast for 12 h prior to testing. There were no statistically significant differences in RMR between protocols (IPM = 7,928 +/- 360, OPM = 8,015 +/- 331 and OP = 7,987 +/- 315 kJ/day) or in fasting RER (IPM = 0.82 +/- 0.01, OPM = 0.82 +/- 0.02 and OP = 0.81 +/- 0.02). These data indicate that in young, healthy males RMR and RER are similar when measured under inpatient or outpatient conditions.

Blood Pressure and Anthropometric Differences in Regularly Exercising and Nonexercising Black Adults

Few studies have examined the relationship between exercise and BP in Black adults, a population with substantial risk for hypertension. This pilot study was undertaken to examine BP, anthropometric characteristics, dietary intake, and resting pulse rate by level of exercise participation in a group of Black Seventh Day Adventists. Subjects were classified as regular exercisers (n = 54, age = 54.6 yrs) if they reported at least two exercise sessions per week (x = 4.0 times per week) lasting a minimum of 20 minutes each, in which they engaged in vigorous exercise. Nonexercisers (n = 60, age = 56.2 yrs) were those who reported participation in such exercise no more than once per week (x = 0.1 times per week). There were no group differences in dietary intake of any macro or micronutrients, but exercisers exhibited significantly lower body mass index, waist circumference, triceps skinfold thickness, and resting pulse rate. Forty-two percent of the nonexercisers were confirmed hypertensives compared to only 20 percent of the exercisers. Age and gender-adjusted BP was significantly lower in the exercisers (BP = 123.8/73.4 mm Hg) compared to the nonexercisers (BP = 133.5/77.1 mm Hg). After adjustment for anthropometric differences, the systolic BP of the exercisers remained approximately 8 mm Hg lower than their nonexercising counterparts. These data suggest that participation in vigorous exercise is favorably related to blood pressure and may attenuate the risk of hypertension in Black Seventh Day Adventists.