Thermic effects of food and exercise in lean and obese women

Measuring Physical Activity in the Elderly: Some Implications for Nutrition

Les méthodes possibles de mesurer l'activité physique comprennent une évaluation d'attitude, le complètement des questionnaires, l'utilisation des moniteurs personnels et la détermination de capacité physique. L'évaluation des sujets âgés présente quelques problèmes spécifiques. L'attitudé face à l'activité physique indique l'intention de l'individu de faire l'exercice, mais quelques barrières pratiques peuvent limiter l'expression de cette intention. Un questionnaire reste ouvert à une tendance d'exagérer l'activité physique, mais néanmoins, cela semble la façon la plus pratique d'évaluer une population importante. L'application des moniteurs personnels se limite aux échantillons assez limités, mais cette technologie peut apporter l'information conduisante à une amélioration progressive des questionnaires. Des épreuves de capacité physique sont influencées par les facteurs génétiques et peuvent favoriser un selectionnement de sujets actifs. Les mesures directes d'activité physique manquent de précision, mais peuvent identifier quelques sujets qui méritent une évaluation nutritive détaillée. Le développement des méthodes d'évaluation de l'activité physique peut enfin encourager une augmentation de l'activité habituelle de la part des sujets âgés.

The impact of food intake and exercise on energy expenditure

Food intake and physical exercise affect two components of energy expenditure, resting metabolic rate (RMR) and the thermic effect of feeding (TEF). Classic studies of overfeeding and underfeeding clearly showed that caloric deficit and surfeit conditions alter RMR. Recent work on short-term overfeeding of monozygotic twins provides new evidence that genetic factors influence individual sensitivity to changes in RMR and TEF when caloric excess is present. Exercise affects energy expenditure during nonactive times; acute bouts of vigorous exercise may result in increased RMR, and this effect appears most pronounced in the first 12 h after exercise. Acute exercise may potentiate the thermic effects of food when they are taken together, and high levels of exercise training may increase RMR. Thus, physical exercise appears to play an important role in the regulation of energy balance by way of its direct energy cost and its influence on RMR and TEF.

Impact of body fat mass and percent fat on metabolic rate and thermogenesis in men

To clarify further the independent relationships of body composition parameters to energy expenditure, resting metabolic rate (RMR) and postprandial thermogenesis were studied in four groups who were matched for absolute fat mass (study 1) and relative fatness (study 2). In study 1, five lean [group A, 15.4 +/- 0.6% (+/- SE) body fat] and five obese men (group B, 25.0 +/- 0.9% fat) were matched on body fat mass (13.0 +/- 0.9 vs. 14.4 +/- 0.8 kg, respectively). Fat-free mass (FFM) and total weight were greater for group A than B. RMR was measured for 3 h in the fasted state and after a 720-kcal mixed meal. RMR was greater for group A than B (1.38 +/- 0.08 vs. 1.14 +/- 0.04 kcal/min, P less than 0.05). The thermic effect of food, calculated as 3 h postprandial minus fasting RMR, was greater for group A than B (65 +/- 6 vs. 23 +/- 9 kcal/3 h; P less than 0.05). In study 2, two groups (n = 6 men/group) were matched for percent body fat (33 +/- 1% fat for both) but differed in lean, fat, and total weights: 50.8 +/- 3.1 kg FFM for the lighter (group C) vs. 68.0 +/- 2.8 kg FFM for the heavier (group D) group, P less than 0.05. RMR was lower for group C than D (1.17 +/- 0.06 vs. 1.33 +/- 0.04 kcal/min, P less than 0.05), but the thermic effect of food was not significantly different (31 +/- 3 vs. 20 +/- 6 kcal/3 h).(ABSTRACT TRUNCATED AT 250 WORDS)

Storage and expenditure of energy in obesity and their implications for management

We have seen in the past 20 years intensive investigation of the responses of the obese and the lean to caloric intake and to various environmental stresses. Although there is much discrepancy of results, the following are obvious: Obesity is not a clear-cut syndrome, and individuals differ significantly in their genetic subtypes and in the stages, type, and degree of their metabolic disturbances. A difference in the facultative component of the thermogenic effect of food can explain some of the variation. This in turn is closely related to insulin resistance, which bears a close relationship to subtypes of hypertension and hyperlipidemias. The greatest scope for clinical intervention lies in these fields. Both the obese and the lean subjects are adapted to retain dietary fat independently of the energy needs. The high ratio of fat to carbohydrate in the western diet and, increasingly in that of the east, is cause for concern.

Weight control and calorie expenditure: thermogenic effects of pre-prandial and post-prandial exercise

The thermogenic effects of pre- and postprandial exercise was examined in seven lean active females. Energy expenditure was measured for 3 h via open circuit indirect calorimetry after four separate treatments: Exercise Only (25 min treadmill run at 60% VO2 max), Meal Only (910 kcal mixed meal), Exercise-Meal and Meal-Exercise. The thermogenic response to the Exercise-Meal treatment was similar to the Meal Only treatment. However, the Meal-Exercise treatment resulted in a greater energy expenditure than the Meal Only and Exercise-Meal treatments. The Exercise Only treatment showed the lowest thermogenic response. These data suggest that exercise following a meal would be more beneficial than exercise before a meal in increasing and maintaining an elevated energy expenditure.

Exercise and obesity

Exercise training in obese patients increases cardiorespiratory fitness, reduces cardiovascular disease risk factors, and increases caloric expenditure; however, significant exercise is required to induce changes in body composition in the absence of caloric restriction, particularly for people whose exercise capacity may initially be limited. Unless a large amount of lean tissue is lost by concomitant dietary restriction, it is unlikely that resting metabolism is altered by exercise, either long-term, or acutely after each workout. The thermic effect of food is negatively related to body fat content. Exercise prior to a meal improves the blunted thermic response to food in the obese but does not normalize it completely. It is noteworthy that physical activity is self-determined and is the only component of energy expenditure that is under volitional control. Exercise alone, without caloric restriction, is probably insufficient to yield significant fat loss except in individuals who are extremely motivated, whereas the combination of modest caloric restriction and physical training of different modes may be necessary to induce favorable changes in body composition.

Does aerobic conditioning cause a sustained increase in the metabolic rate?

We measured the metabolic rate by indirect calorimetry for 90 minutes following exercise in six healthy individuals. Ten and 30 minutes of cycling at 80% of maximal intensity produced comparable increases in the resting metabolic rate, (37% and 32%, respectively) immediately after exercise. However, by 30 minutes following exertion, the metabolic rate was not different from control values. The total additional caloric use during the 90 minutes of recovery was similar for the two exercise durations, and the mean increment in recovery energy expenditure was 11.4 +/- 7.1 kcals. The majority of caloric use with exercise is during the activity. Recovery energy expenditure following usual aerobic training results in only a minor contribution to total energy use.

Postprandial thermogenesis at rest and during exercise in elderly men ingesting two levels of protein

Seven elderly male subjects (69 +/- 3 yr, 67.8 +/- 9.2 kg, 24.5 +/- 3.6% body fat) lived for 12 consecutive weeks in a metabolic unit and maintained their weight with two different diets fed for 6 weeks each: Diet A, consisted of their habitual protein intake as determined on the outside by a dietary record (mean +/- SD, 1.12 +/- 0.22 g/kg d). Diet B was an isocaloric diet with reduced protein intake (70 mgN/kg d, i.e., 0.44 g protein/kg d) at the level of physiological protein requirement [7]. After 3 weeks on each diet, the thermogenic response to single meals A and B containing 38% of weight maintenance energy for each subject (731-994 kcal) was studied by indirect calorimetry under two situations: (1) at rest over a 4 hr period and (2) during graded exercise on a bicycle ergometer at four stepwise workloads (0,80, 200, and 300 kg/min). A postabsorptive control exercise was also performed in order to assess the net effect of the meal during exercise. Eating alone increased the energy expenditure by +0.18 +/- 0.07 kcal/min with meal A and +0.13 +/- 0.06 kcal/min with meal B. There was a positive correlation (r = 0.84, p less than 0.01) between the % energy derived from protein and the thermogenic response expressed as % of the energy content of test meal. Exercise failed to influence the thermogenic response to meals since the overall net increase in energy expenditure induced by the meals while exercising was not different from that obtained at rest: +0.22 +/- 0.17 kcal/min and +0.15 +/- 0.13 kcal/min with meal A and meal B, respectively. This study failed to show any interaction between exercise and postprandial thermogenesis in elderly individuals.

The relevance of metabolic rate in behavioral medicine research

This article reviews research relating metabolism to areas of interest to behavioral medicine. Metabolic rate has been investigated as a possible mediator of a variety of problems related to energy balance. Metabolic rate has also been utilized to investigate excessive cardiac activity that may be associated with cardiovascular disease. Although resting metabolic rate does not appear to be different in obese compared with nonobese, diet-induced thermogenesis is diminished in obese subjects. Caloric restriction produces a decline in metabolic rate in both obese and nonobese and further reduces the diet-induced thermogenic effect in obese. Exercise may prevent the decline in metabolic rate following caloric restriction. Anorexic individuals have a lowered metabolic rate that appears to increase rapidly after refeeding. Although bulimic individuals who purge via self-induced vomiting do not have a lower metabolic rate than matched control subjects, the frequency of purging has been found to be inversely related to resting metabolic rate. Metabolic rate has also been investigated as a possible mediator of weight regulation in individuals who smoke cigarettes and has been shown to decrease with smoking cessation. Tissue overperfusion, or an increase in cardiovascular activity above metabolic need, has been shown to increase peripheral resistance and may lead to hypertension.

Thermic effects of food and exercise in lean and obese men of similar lean body mass

The thermic effect of food at rest, during 30 min of cycle exercise, and postexercise with two sequences of exercise and meal (before or after exercise) was compared in eight lean (mean +/- SE, 12.8 +/- 0.7% body fat) and eight obese men (29.7 +/- 0.6% fat) to determine whether exercise before or after a meal enhances thermogenesis. The groups were matched for age, height, and lean body mass (LBM) in order to study the relationship between thermogenesis and body fat independent of LBM. Metabolic rate was measured by indirect calorimetry on five mornings, in randomized order, after an overnight fast. Treatments on respective days were 1) 3-h rest, no meal; 2) 3-h rest after a 750-kcal mixed meal (14% protein, 31% fat, 55% carbohydrate); 3) during and 3 h after 30 min of cycling, no meal; 4) during and 3 h after 30 min of cycling, meal 30 min before exercise; and 5) 3 h after 30 min of cycling, meal immediately after exercise. The thermic effect of food, which is the fed minus fasted caloric expenditure, was significantly greater for the lean than the obese men under the resting (mean +/- SE 53 +/- 5 vs. 26 +/- 5 kcal over 3 h for the lean and obese groups, P less than 0.01), exercise (26 +/- 4 vs. 4 +/- 2 kcal over 30 min, P less than 0.01), and both postexercise conditions. However, for the lean men the thermic effect of food was significantly greater for the meal-before-exercise than the resting and the meal-after-exercise conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Determinants of 24-hour energy expenditure in man. Methods and results using a respiratory chamber

Daily human energy requirements calculated from separate components of energy expenditure are inaccurate and usually in poor agreement with measured energy intakes. Measurement of energy expenditure over periods of 24 h or longer is needed to determine more accurately rates of daily energy expenditure in humans. We provide a detailed description of a human respiratory chamber and methods used to determine rates of energy expenditure over 24-h periods in 177 subjects. The results show that: fat-free mass (FFM) as estimated by densitometry is the best available determinant of 24-h energy expenditures (24EE) and explains 81% of the variance observed between individuals (24EE [kcal/d] = 597 + 26.5 FFM); 24EE in an individual is very reproducible (coefficient of variation = 2.4%); and even when adjusted for differences in FFM, there is still considerable interperson variability of the daily energy expenditure. A large portion of the variability of 24EE among individuals, independent of differences in body size, was due to variability in the degree of spontaneous physical activity, i.e., "fidgeting," which accounted for 100-800 kcal/d in these subjects.

Prior exercise potentiates the thermic effect of a carbohydrate load

It is unclear whether dietary-induced thermogenesis (DIT) is increased after exercise. To test this possibility, six healthy volunteers, male and female, exercised for 45 minutes at 70% of maximal aerobic capacity (VO2 max) in the morning after an overnight fast. Two hours after the end of the exercise, by which time VO2 had returned to near baseline levels, subjects ingested a 100-g glucose load. Blood samples and respiratory gas exchange data were collected over the next three hours. On a separate day on which the subjects did not exercise, the test procedure was repeated. Glucose tolerance and the insulin response to the glucose load were not significantly different between the two trials; however, VO2 increased by 15.5% over baseline on the exercise day, compared with only 8.9% when exercise was not performed. The net increase in energy expenditure for the three-hour period following glucose ingestion was 15 kcal/180 min greater on the exercise than on the control day, with increases upwards of 20 kcal/180 min in several individuals. No correlation was found between the magnitude of exercise-enhanced DIT and VO2 max, suggesting that this effect is independent of the state of training. The results indicate that the thermic effect of exogenous carbohydrate can be potentiated by prior exercise.

Commentary

The authors think the approach to weight reduction that makes sense in industrialized countries also will work in Third-World countries as they begin to face some of the problems that result from the introduction of labor-saving technology and diets rich in fats and sugars.

The effect of dextrose and amino acids on respiratory function and energy expenditure in morbidly obese patients following gastric bypass surgery

Hypocaloric dextrose administration results in a diminished minute ventilation, metabolic rate, and ventilatory responsivity to hypercapnea and hypoxia which is rapidly reversed by provision of amino acids in individuals of normal weight. This study compared the effects of peripheral intravenous dextrose and amino acid infusion on respiratory parameters and energy expenditure in 25 morbidly obese patients undergoing gastric bypass surgery. On the first postoperative day, respiratory rate increased (P less than 0.01) and tidal volume decreased (P less than 0.001) maintaining minute ventilation at slightly less than preoperative levels but on subsequent days minute ventilation exceeded baseline values (P less than 0.005) primarily by a sustained increased respiratory rate. Oxygen consumption (P less than 0.005), carbon dioxide production (P less than 0.05), and resting energy expenditure (P less than 0.01) all declined 25% from baseline values on the first postoperative day and subsequently reverted to preoperative values. The type of intravenous fluid had no effect on any of these parameters. A significant difference in respiratory quotient (P less than 0.05) was noted between the two intravenous fluid regimens attributable to the oxidation of the dextrose calories. The failure to detect a difference in metabolic rate or to stimulate respiration despite elevation of serum branched chain amino acids (P less than 0.0001) and ketone bodies (P less than 0.0001) with protein infusion does not suggest a role for nutrient manipulation of respiration in the postoperative care of the morbidly obese patient.

Thermic effect of food at rest, during exercise, and after exercise in lean and obese men of similar body weight

The thermic effect of food at rest, during 30 min of cycle ergometer exercise, and after exercise was studied in eight lean (mean +/- SEM, 10 +/- 1% body fat, hydrostatically-determined) and eight obese men (30 +/- 2% body fat). The lean and obese mean were matched with respect to age, height, weight, and body mass index (BMI) to determine the relationship between thermogenesis and body composition, independent of body weight. All men were overweight, defined as a BMI between 26-34, but the obese had three times more body fat and significantly less lean body mass than the lean men. Metabolic rate was measured by indirect calorimetry under four conditions on separate mornings, in randomized order, after an overnight fast: 3 h of rest in the postabsorptive state; 3 h of rest after a 750-kcal mixed meal (14% protein, 31.5% fat, and 54.5% carbohydrate); during 30 min of cycling and for 3 h post exercise in the postabsorptive state; and during 30 min of cycling performed 30 min after the test meal and for 3 h post exercise. The thermic effect of food, which is the difference between postabsorptive and postprandial energy expenditure, was significantly higher for the lean than the obese men under the rest, post exercise, and exercise conditions: the increments in metabolic rate for the lean and obese men, respectively, were 48 +/- 7 vs. 28 +/- 4 kcal over 3 h rest (P less than 0.05); 44 +/- 7 vs. 16 +/- 5 kcal over 3 h post exercise (P less than 0.05); and 19 +/- 3 vs. 6 +/- 3 kcal over 30 min of exercise (P less than 0.05). The thermic effect of food was significantly negatively related to body fat content under the rest (r = -0.55), post exercise (r = -0.66), and exercise (r = -0.58) conditions. The results of this study indicate that for men of similar total body weight and BMI, body composition is a significant determinant of postprandial thermogenesis; the responses of obese are significantly blunted compared with those of lean men.

The thermic effect of carbohydrate versus fat feeding in man

Metabolic rate increases and heat is produced after eating a meal. This response has been termed the thermic effect of feeding. While some studies have found this response to be defective in obese subjects others have not. It is also unclear how dietary composition affects the thermic response to a meal. In this study, we evaluated the thermic response to both a high carbohydrate meal and a high fat meal in normal and obese subjects. Using the ventilated hood technique, metabolic rate was measured in seated subjects before and for 6 hours following a meal. Blood samples for insulin, glucose, and catecholamines were withdrawn each half hour to evaluate their possible role in regulating the thermic response. The overall response to the high carbohydrate meal was greater than to high fat (0.26 +/- .07 v 0.18 +/- 0.11 kcal/min; P less than .01). The thermic response to the high fat meal, however, was similar in the normal and obese groups. Although the 6-hour response to the high carbohydrate diet was not statistically different between the subject groups, there was a trend toward a diminished response in the obese relative to the normal group during the first 3 hours following the meal (0.30 +/- .06 v .22 +/- .09; P = .06). In our seated subjects, the thermic response to a meal accounted for 8%-13% of the total calories ingested, with the highest value found in the normal weight subjects after a high carbohydrate meal. No significant thermic response was noted when subjects were fed a noncaloric meal.(ABSTRACT TRUNCATED AT 250 WORDS)

Blunted norepinephrine responsiveness to changing energy states in obese subjects

We have previously reported in lean subjects a significant relationship between plasma norepinephrine metabolism and energy state. The present study has examined in six obese men the response in plasma norepinephrine flux to ten day periods of overeating (+ 1000 kcal/m2 above isocaloric requirements) or undereating (400 kcal/d). Despite significant gains or losses in body weight, norepinephrine flux, measured during constant infusions of 3H-l-norepinephrine, failed to change significantly. Measurements of glucose utilization during constant infusions of insulin, showed significant changes with changing energy state, falling with overeating and rising with undereating. Insulin sensitivity was not correlated with plasma norepinephrine metabolism.

Insulin increases thermogenesis in rat skeletal muscle following exercise

Insulin increased O2 consumption in isolated perfused rat muscle for upward of 2 h after a treadmill run. Insulin did not increase O2 consumption in nonexercised rats, nor did prior exercise increase O2 consumption in the absence of added insulin. The stimulation of glycogen synthesis by insulin was also enhanced in muscle of previously exercised rats. The additional energy required for this was not sufficient to account for the increase in O2 consumption, however. The results indicate that insulin increases thermogenesis in skeletal muscle after exercise. They also raise the possibility that in intact organisms the thermogenic effect of foods that increase insulin secretion could be increased by prior exercise.

Nutrition and exercise

The nutritional aspects of exercise are topics of popular interest, misconception, and active research. In this article, the authors review basic concepts of muscle metabolism; information concerning the role of exercise in weight loss; dietary supplements for athletes, including nutrition for competition; and eating disorders among those performing vigorous exercise.

Insulin is the mediator of feeding-related thermogenesis: insulin resistance and/or deficiency results in a thermogenic defect which contributes to the pathogenesis of obesity

Obesity is characterized by insulin resistance which predisposes to the development of impaired glucose tolerance. It is postulated that in addition to its role in carbohydrate metabolism, insulin is the mediator of feeding-related increases in thermogenesis (the thermic effect of food and dietary-induced thermogenesis). The development of insulin resistance and/or deficiency is postulated to result in a decrease in feeding-related, insulin-mediated thermogenesis. As a consequence of this thermogenic defect there is an increase in efficiency of weight gain which accelerates the development and facilitates the maintenance of the obese state. Abnormalities in the insulin axis are thus not only involved in the pathogenesis of the carbohydrate intolerance of obesity but are also proposed as having a central role in a dysregulation of energy balance which contributes to the pathogenesis of obesity.