Prior exercise potentiates the thermic effect of a carbohydrate load

Compensation for cold-induced thermogenesis during weight loss maintenance and regain

Prevalence of obesity is exacerbated by low rates of successful long-term weight loss maintenance (WLM). In part, relapse from WLM to obesity is due to a reduction in energy expenditure (EE) that persists throughout WLM and relapse. Thus, interventions that increase EE might facilitate WLM. In obese mice that were calorically restricted to reduce body weight by ~20%, we manipulated EE throughout WLM and early relapse using intermittent cold exposure (ICE; 4°C, 90 min/day, 5 days/wk, within the last 3 h of the light cycle). EE, energy intake, and spontaneous physical activity were measured during the obese, WLM, and relapse phases. During WLM and relapse, the ICE group expended more energy during the light cycle because of cold exposure but expended less energy in the dark cycle, which led to no overall difference in total daily EE. The compensation in EE appeared to be mediated by activity, whereby the ICE group was more active during the light cycle because of cold exposure but less active during the dark cycle, which led to no overall effect on total daily activity during WLM and relapse. In brown adipose tissue of relapsing mice, the ICE group had greater mRNA expression of Dio2 and protein expression of UCP1 but lower mRNA expression of Prdm16. In summary, these findings indicate that despite robust increases in EE during cold exposures, ICE is unable to alter total daily EE during WLM or early relapse, likely due to compensatory behaviors in activity.

Effects of short-lasting supramaximal-intensity exercise on diet-induced increase in oxygen uptake

This study was undertaken to quantify the additional increase in diet-induced oxygen uptake after exhaustive high-intensity intermittent exercise (HIIE), consisting of 6-7 bouts of 20-sec bicycle exercise (intensity: 170% V˙O2max) with a 10-sec rest between bouts. Using a metabolic chamber, the oxygen uptake of ten men was measured from 10:30 am to 07:00 am the next day on two separate days with or without HIIE, with lunch (12:00) and supper (18:00) (Diet experiment). On two other days, the oxygen uptake of six different subjects was measured from 10:30 to 16:00 with or without HIIE, but without meals (Fasting experiment). Ten minutes of exercise at 50% V˙O2maxpreceded the HIIE in both experiments; EPOC (excess postexercise oxygen consumption) after HIIE was found to wear off before 12:00 in both experiments. In the Diet experiment, oxygen uptake during HIIE and EPOC were 123.4 ± 12.0 and 115.3 ± 32.3 mL·kg-1, respectively. Meals elevated resting oxygen uptake on both days, but those on the HIIE day were significantly higher than on the control day. This enhanced diet-induced oxygen uptake (difference in resting oxygen uptake from 12:00-23:00 between HIIE and control day: ΔDIT) was 146.1 ± 90.9 mL·kg-1, comparable to the oxygen uptake during the HIIE and EPOC The ΔDIT was correlated with subjects' V˙O2max(52.1 ± 6.6 mL·kg-1·min-1) (r = 0.76, n = 10, P < 0.05). We concluded that HIIE enhances diet-induced oxygen uptake significantly, and that it is related to the cardiorespiratory fitness.

New approach for weight reduction by a combination of diet, light resistance exercise and the timing of ingesting a protein supplement

We have reported that ingesting a meal immediately after exercise increased skeletal muscle accretion and less adipose tissue accumulation in rats employed in a 10 week resistance exercise program. We hypothesized that a possible increase in the resting metabolic rate (RMR) as a result of the larger skeletal muscle mass might be responsible for the less adipose deposition. Therefore, the effect of the timing of a protein supplement after resistance exercise on body composition and the RMR was investigated in 17 slightly overweight men. The subjects participated in a 12-week weight reduction program consisting of mild energy restriction (17% energy intake reduction) and a light resistance exercise using a pair of dumbbells (3-5 kg). The subjects were assigned to two groups. Group S ingested a protein supplement (10 g protein, 7 g carbohydrate, 3.3 g fat and one-third of recommended daily allowance (RDA) of vitamins and minerals) immediately after exercise. Group C did not ingest the supplement. Daily intake of both energy and protein was equal between the two groups and the protein intake met the RDA. After 12 weeks, the bodyweight, skinfold thickness, girth of waist and hip and percentage bodyfat significantly decreased in the both groups, however, no significant differences were observed between the groups. The fat-free mass significantly decreased in C, whereas its decrease in S was not significant. The RMR and post-meal total energy output significantly increased in S, while these variables did not change in C. In addition, the urinary nitrogen excretion tended to increase in C but not in S. These results suggest that the RMR increase observed in S might be associated with an increase in body protein synthesis.

Effects of dietary composition and exercise timing on substrate utilization and sympathoadrenal function in healthy young women

The effects of dietary composition (high-fat [FAT] or high-carbohydrate [CHO]) and exercise timing (preprandial exercise [Ex-] or postprandial exercise [-Ex]) on postprandial substrate utilization and sympathoadrenal function were studied in seven women aged 20 to 21 years. The experimental protocol included four different sessions (Ex-FAT, FAT-Ex, Ex-CHO, and CHO-Ex). The FAT and CHO diets provided 48% and 5% fat, respectively. On the experimental days, subjects ate a meal containing the same caloric energy at lunchtime, and they exercised for 30 minutes on a bicycle ergometer at an intensity of 60% maximal oxygen consumption (VO2max) before and after the meal, followed by rest for 3 hours. The resting respiratory quotient (RQ) was significantly lower (P < .05) with the FAT diet or postprandial exercise. The mean RQ during the experimental period was 0.78, 0.75, 0.81, and 0.77 in Ex-FAT, FAT-Ex, Ex-CHO, and CHO-Ex groups, respectively. The total area under the curve of serum norepinephrine (NE) as an index of NE secretion was significantly higher (P < .05) with the FAT diet or postprandial exercise (130.2, 175.8, 33.0, and 136.9 ng x mL(-1) x min, respectively). A negative correlation was observed between the RQ and the total area of NE (r = .49, P < .05). The serum thyroid hormone level was not influenced by dietary composition and exercise timing. These results suggest that postprandial exercise, especially after intake of a FAT diet, increases fat utilization via a slightly larger decrease in the RQ. This might be related to the sympathoadrenal system at rest and during exercise.

Influence of altered body weight on energy expenditure

Long-term metabolic studies indicate that over-feeding underfeeding to gain and lose body weight produce consistent increases and decreases in energy expenditure. These changes occur in both lean and obese subjects and cause deviations from the normal relationship between energy expenditure and metabolic body size. The low energy expenditure/metabolic body size in the reduced obese may contribute to the difficulty in maintaining the reduced body weight.

Optimizing exercise for fat loss

From the standpoint of promoting fat loss, the chief benefits of aerobic exercise are attributable to fat oxidation during exercise and a post-exercise reduction of respiratory quotient. The ability of exercise to selectively promote fat oxidation should be optimized if exercise is done post-absorptively (preferably during morning fasting metabolism), if caffeine and possibly hydroxycitrate/carnitine are administered prior to exercise, if the exercise regimen is of moderate intensity and prolonged duration, and if no calories are ingested for several hours following exercise. A simple mathematical model is presented which delineates the factors that determine daily fat balance during exercise training. This model clarifies the crucial importance of low-fat eating if exercise is to have an optimal impact on fat stores. As a complement to aerobics, resistance exercise can benefit dieters by helping to preserve lean mass and metabolic rate in the face of a persistently negative caloric balance.

Meal size and frequency: effect on potentiation of the thermal effect of food by prior exercise

Prior exercise potentiates the thermic effect of a carbohydrate meal. The purpose of this study was to determine if meal size or feeding pattern influences this response. Two groups of healthy, normal-weight young women exercised for 45 min on a cycle ergometer at 70% of maximal aerobic capacity. Once aerobic capacity returned to pre-exercise baseline, the thermic effect of food (TEF) was determined by indirect calorimetry over a 2-h period. One group of subjects ingested a 2510-kJ meal and the other a 5020-kJ meal. As a control, subjects ingested the test meal without prior exercise. In addition, subjects ingesting the 5020-kJ meal were studied for an additional 2 h. In a separate trial, these subjects ingested a 5020-kJ meal in two equal portions after a bout of exercise, the second portion 120 min after the first. TEF was less for the 2510-kJ meal compared with the 5020-kJ meal for both the control [mean (SE), 76 (17) vs 158 (19) kJ.2h-1, P < 0.01), and prior exercise [124 (23) vs 197 (24) kJ.2h-1, P < 0.01) trials. However, the same increment in TEF resulted from the prior bout of exercise [48 (9) vs 40 (8) kJ.2h-1 for 2510-and 5020-kJ meals, respectively). TEF was 31% lower when the 5020-kJ meal was given in two portions compared with one [281 (30) vs 369 (41) kJ.4h-1, P < 0.05]. No difference in TEF was found between the first and second 2510-kJ portion.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise prescription for individuals with metabolic disorders. Practical considerations

Regular exercise has been recognised as an important component in the management of patients with diabetes mellitus. In addition to acutely lowering blood glucose, exercise training improves glucose tolerance and peripheral insulin sensitivity, contributes to weight loss and reduces several risk factors for cardiovascular disease. When proper precautions are taken to prevent hypoglycaemia, individuals with diabetes can enjoy the same benefits from exercise as nondiabetic healthy individuals. As a guideline, moderate intensity, aerobic endurance activities should be performed for 20 to 40 minutes at least 3 times a week. Blood glucose should be monitored, and insulin dose and carbohydrate intake adjusted based on the blood glucose response to the type and duration of exercise. This review will summarise current understanding of the therapeutic role of exercise in the treatment of diabetes and will present guidelines for prescribing exercise in diabetic patients.

Insulin resistance in Mexican Americans--a precursor to obesity and diabetes?

Mexican Americans appear to have a strong genetic predisposition to insulin resistance, android obesity, and type II diabetes, apparently as a function of Native American genetic heritage. Theoretical considerations suggest that insulin resistance may be a primary factor that plays a causative role in the induction of both obesity and diabetes. Measures which promote optimal insulin sensitivity--chromium picolinate, brewer's yeast, soluble fiber supplements, metformin, very-low-fat diet, exercise training--may have value for preventing, treating, or retarding the onset of obesity and diabetes, and merit clinical evaluation in this regard. Correction of insulin resistance may also lessen cardiovascular risk, in part by reducing LDL cholesterol and improving risk factors associated with Syndrome X. These comments are likely to be valid for other Native American groups at high risk for diabetes.

Independent effects of obesity and insulin resistance on postprandial thermogenesis in men

The putative blunted thermogenesis in obesity may be related to insulin resistance, but insulin sensitivity and obesity are potentially confounding factors. To determine the independent effects of obesity and insulin resistance on the thermic effect of food, at rest and after exercise, lean and obese men were matched at two levels of insulin sensitivity determined by insulin-stimulated glucose disposal (milligrams per kilogram fat-free mass [FFM] per minute) during the euglycemic, hyperinsulinemic (40 mU/m2.min) clamp: 5.4 mg/kg FFM for the lean and obese groups with low insulin sensitivity, and 8.1 mg/kg FFM for the groups with high insulin sensitivity. The two lean groups were matched for percent fat (approximately 15 +/- 1% fat), as were the two obese groups (approximately 33 +/- 2% fat). Energy expenditure was measured for 3 h in the fasting state and for 3 h after a 720-kcal mixed meal, each at rest and immediately after 1 h of cycling at 100 W. The thermic effect of food (TEF) was calculated as the postprandial minus fasting energy expenditure (kcal/3 h) during rest and after exercise. During rest, TEF was blunted by both obesity (24 +/- 5 and 34 +/- 6 kcal/3 h for obese groups with low and high insulin sensitivity vs. 56 +/- 6 and 74 +/- 6 kcal/3 h for the lean groups with low and high insulin sensitivity; P less than 0.01 lean vs. obese) and insulin resistance (insulin-resistant less than insulin-sensitive, at both levels of obesity; P less than 0.01). After exercise, TEF was also impaired in the obese (47 +/- 6 and 44 +/- 5 kcal/3 h for the insulin-resistant and -sensitive groups) and in the lean insulin-resistant (55 +/- 5 kcal/3 h), compared with the lean insulin-sensitive men (71 +/- 3 kcal/3 h), P less than 0.01. Compared with rest, TEF after exercise was improved, but not normalized, in both obese groups (P less than 0.05), but unchanged in the lean groups. These results suggest that both insulin resistance and obesity are independently associated with impaired TEF at rest, but the responsiveness of thermogenesis to exercise before a meal is related to the obese state and not independently to insulin resistance per se.

The energetic costs of rough-and-tumble play in the juvenile rat

The metabolic costs of rough-and-tumble play behavior were studied in juvenile rats. Using indirect calorimetry, it was determined that energy expenditure during play is increased by 66-104% over the resting metabolic rate, indicating that play accounts for between 2% and 3% of the total daily energy budget of the rat. In a subsequent experiment, food intake and body weight were monitored for 3 weeks in rats allowed to play for 1 hr/day and in rats not allowed to play. While the body weights of the two groups did not differ significantly from each other, those rats allowed to play ate 7% more over the 3-week period than did those rats not given an opportunity to play. These data are consistent with previous reports describing the energetic costs of mammalian play, with play accounting for less than 10% of the daily energy budget in three species tested so far. These data are also consistent with viewing play as a type of exercise and may lead to a better understanding of putative benefits of this behavior.

Effects of exercise on energy balance in meal-fed mice

The effects of exercise on energy balance have been investigated in mice accustomed to eating their daily food ration in three meals. A meal period lasts 1 hour, and during that period mice were allowed to eat unrestrictedly a pelleted stock diet. Two series of experiments were conducted. In one series of experiments indirect calorimetric measurements were carried out in untrained mice that were assigned to 3 experimental groups; a first group of mice was allowed to rest; a second group of mice was exercised immediately before one of the 3 meals; a third group of mice was exercised immediately after one of the 3 meals. The exercise bout consisted of 1 hour of forced exercise on a rodent treadmill at a speed of 20 meters per minute. O2 consumption (VO2) and CO2 production were monitored throughout a full day except at the time the exercising animals were on the treadmill. In a second series of experiments long-term energy balance measurements were carried out. Mice were then assigned to experimental conditions similar to those previously described for 31 days during which period food intake and body weight were continuously monitored. At the end of 31 days of experiment, mice were killed, and their carcasses were individually analysed for their contents of energy, fat and protein. Carcass and food gross energy contents were assessed by bomb calorimetry. At the end of the long-term energy balance trial, the percentage of fat, the energy gain, the energy density and the weight of the dry carcass were significantly lower in exercised groups of mice than in the resting group of animals.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of short-term carbohydrate overfeeding and prior exercise on resting metabolic rate and diet-induced thermogenesis

In 10 young, normal-weight subjects, the effects were investigated of carbohydrate overfeeding and prior glycogen-depleting exercise on resting metabolic rate (RMR) and diet-induced thermogenesis (DIT). Subjects were kept on controlled diets in a crossover design for two periods of 8 days, with a 1-week interval in between. During the last 4 days of each period, additional carbohydrates were added to the subjects' diet. The carbohydrate overfeeding started at 15% in excess of the energy requirements on day 1 and increased to 60% on day 4. At the beginning and the end of the carbohydrate overfeeding periods, RMR and DIT were measured, respectively, for 1 and 3.5 hours using a ventilated hood system. In one of the 8-day periods, on evenings before the energy exchange measurements, subjects performed a maximum work capacity test on a cycle ergometer, and then cycled for a total of approximately 80 minutes at fixed percentages of their maximum work capacity. Carbohydrate overfeeding did not affect RMR, but increased DIT significantly, on average by 39%. Glycogen-depleting exercise the day before increased RMR significantly by, on average, 9% and increased DIT (P = .08), on average, by 23%. The impact of exercise on RMR was less when carbohydrate overfeeding was administered, but there was no significant interaction effect of carbohydrate overfeeding and exercise on RMR or DIT. It is concluded that both prior glycogen-depleting exercise and an antecedent diet high in carbohydrates may influence RMR or DIT.

Failure of prior low-intensity exercise to potentiate the thermic effect of glucose

We have previously shown that following recovery from 45 min exercise at 67% maximum oxygen consumption (VO2max) the thermic effect of a glucose load is increased by 65% over that observed on a non-exercise day (Young et al. 1986). The purpose of this study was to determine if potentiation of the thermic effect of glucose by prior exercise is dependent on exercise intensity. The thermic response to a 1674 kJ glucose load was measured in five subjects in the absence of exercise (control) and following recovery from 45 min cycling exercise at each of three intensities: low (34% VO2max), moderate (54% VO2max), and high (75% VO2max). The average percentage increase in oxygen consumption over baseline due to glucose ingestion was similar for the control (9.9%, SE 2.0%), and the low- (10.2%, SE 0.9%) and moderate- (12.6%, SE 1.2%) intensity exercise conditions, while a significant increase in average VO2 was observed after the high-intensity condition (18.0%, SE 2.3%, P less than 0.05). The total energy expenditure (kJ) over baseline for 3 h was also similar for the control (84.5, SE 11.7), and the low-(100.0, SE 9.2) and moderate- (118.8, SE 5.0) intensity exercise conditions. The thermic response following high-intensity exercise (146.4 kJ, SE 13.4) was significantly greater than that observed in the control (P less than 0.01) or low-intensity (P less than 0.05) exercise conditions. These findings demonstrate that unlike prior high-intensity exercise (75% VO2max), low- or moderate-intensity exercise (i.e., 34% or 54% VO2max) fails to potentiate the thermic effect of a glucose load.(ABSTRACT TRUNCATED AT 250 WORDS)

Diet-induced thermogenesis in well-trained subjects

The purpose of this study was to examine the possible relationship between the thermogenic response to a mixed meal and the aerobic capacity in healthy subjects. Fourteen male subjects participated, and their maximal oxygen uptake was determined on a bicycle exercise ergometer. Two groups, each comprising seven individuals, were compared: a well-trained group, with an oxygen uptake of 58 +/- 2 ml min-1 kg-1 and a sedentary group, with an oxygen uptake of 39 +/- 2 ml min-1 kg-1. Respiratory gas exchange was measured continuously for 1 h in the basal state and then for 3 h postprandially. The subjects ingested a test meal in liquid form, consisting of 17% kJ protein, 28% kJ lipids and 55% kJ carbohydrates, and corresponding to 60% of the individually computed 24-h basal energy expenditure. Basal oxygen uptake and energy expenditure were similar in the two groups. After the meal, pulmonary oxygen uptake and energy expenditure rose rapidly and reached a plateau after 1 h. The responses were no different in the two groups: the average rise in pulmonary oxygen uptake above basal during the whole study period was 24.0 +/- 2.1% in well-trained and 26.7 +/- 1.5% in sedentary subjects (NS); the corresponding values for energy expenditure were 25.0 +/- 2.1% and 29.0 +/- 1.6% (NS). Also, when expressed in absolute terms the increments above basal were not significantly different. There was no discernible relationship between the individual thermogenic response and maximal oxygen uptake. In conclusion, the present findings do not indicate that diet-induced thermogenesis is proportional to aerobic capacity in healthy young men.

Weight loss leads to a marked decrease in nonresting energy expenditure in ambulatory human subjects

The extent to which the resting and nonresting components of 24-hour energy expenditure decrease after weight reduction has not been prospectively assessed in ambulatory, weight-stable, reduced-obese humans. Accordingly, 24-hour energy expenditure was estimated as the weight-stabilizing (+/- 50 g/d) daily caloric intake of a defined liquid diet in a cross-sectional study of ten reduced-obese subjects after a 23.2% +/- 9.4% weight loss and 18 obese subjects at baseline weight. A regression analysis demonstrated an 18% decrease in the mean daily energy requirement of the reduced-obese subjects compared with that of subjects of the same relative body weight who had never dieted. Strong linear relationships were noted between estimated 24-hour energy expenditure and fat-free mass (FFM), and between resting metabolic rate (RMR) and FFM in the subjects at baseline weight. In six reduced-obese men, the 24-hour energy expenditure was only 75.7% +/- 5.6% of the value predicted by regression analysis for the decreased FFM. In these six subjects the RMR was 97.4% +/- 7.5% of that predicted for the decreased FFM, suggesting that essentially all the energy savings relative to FFM in the reduced-obese state occurred in nonresting energy expenditure. In a subsequent group of seven subjects studied longitudinally before and after a 21.5% +/- 2.3% weight loss, the decrease in nonresting energy expenditure accounted for 582 +/- 276 kcal/d or 71% of the decrease in estimated 24-hour energy expenditure. These data suggest a decrease in the nonresting energy expenditure of ambulatory reduced-obese individuals, which is greater than previously appreciated.(ABSTRACT TRUNCATED AT 250 WORDS)