Lipid oxidation according to intensity and exercise duration in overweight men and women

No Influence of Overweight/Obesity on Exercise Lipid Oxidation: A Systematic Review

Compared to lean counterparts, overweight/obese individuals rely less on lipid during fasting. This deficiency has been implicated in the association between overweight/obesity and blunted insulin signaling via elevated intramuscular triglycerides. However, the capacity for overweight/obese individuals to use lipid during exercise is unclear. This review was conducted to formulate a consensus regarding the influence of overweight/obesity on exercise lipid use. PubMed, ProQuest, ISI Web of Science, and Cochrane Library databases were searched. Articles were included if they presented original research on the influence of overweight/obesity on exercise fuel use in generally healthy sedentary adults. Articles were excluded if they assessed older adults, individuals with chronic disease, and/or exercise limitations or physically-active individuals. The search identified 1205 articles with 729 considered for inclusion after duplicate removal. Once titles, abstracts, and/or manuscripts were assessed, 24 articles were included. The preponderance of evidence from these articles indicates that overweight/obese individuals rely on lipid to a similar extent during exercise. However, conflicting findings were found in eight articles due to the outcome measure cited, participant characteristics other than overweight/obesity and characteristics of the exercise bout(s). We also identified factors other than body fatness which can influence exercise lipid oxidation that should be controlled in future research.

Low capacity to oxidize fat and body weight

For a given positive energy balance, a low capacity to oxidize fat could contribute to weight gain (low fat oxidation hypothesis). This hypothesis is based on the arguments that for a given stable diet and food quotient (FQ), the respiratory quotient (RQ) is higher in obesity prone (OP) than in obesity resistant individuals (OR) and that a high RQ predicts higher future weight gain. A review of 42 studies shows that there is no convincing experimental support to these arguments and thus for the low fat oxidation hypothesis. A power analysis also shows that this hypothesis might be impossible to experimentally confirm because very large numbers of subjects would be needed to reject the null hypotheses that the 24-h RQ is not different in OP and OR or that future weight gain is not different in individuals with a low and high 24-h RQ at baseline. A re-examination of the significance of the 24-hour and fasting RQ also shows that the assumption underlying the low fat oxidation hypothesis that a high RQ reflects a low capacity to oxidize fat is not valid: For a stable diet, the 24-h RQ entirely depends on FQ and energy balance, and the fasting RQ mainly depends on the FQ and energy balance and on the size of glycogen stores.

Efecto de un programa de entrenamiento físico sobre condición física saludable en hipertensos

Resumo Objetivo: Determinar el efecto de un programa de entrenamiento físico sobre la condición física saludable en sujetos con hipertensión arterial controlada. Método: Se desarrolló un ensayo clínico en 78 personas diagnosticadas con hipertensión arterial controlada que voluntariamente aceptaron participar en la investigación y que reunieron los criterios de inclusión, de entre ellos fue seleccionado el grupo de estudio: 39 sujetos con hipertensión arterial controlada a quienes se les aplicó el programa de entrenamiento físico; y el grupo control: 39 sujetos con hipertensión arterial controlada a quienes se les aplicó un programa educativo combinado con el ejercicio no dirigido que practicaban habitualmente (tejo, rana, ajedrez). Al inicio del estudio se diligenció una encuesta para la caracterización sociodemográfica y clínica de los participantes, esta última diligenciada al final del estudio. Se utilizó el estadístico t Student para muestras independientes; también se hizo t de student pareada antes-después o en su defecto la prueba no paramétrica U de Mann-Whitney. Resultados: El 84,6 por ciento fueron mujeres; 64,1 por ciento cuentan con nivel escolar de primaria. Las diferencias de medias mostraron significancia estadística p<0,05 en colesterol HDL (lipoproteina de alta densidad), LDL (lipoproteina de baja densidad), triglicéridos, fuerza de miembros inferiores y fuerza abdominal. Conclusion: Los resultados reportados permiten concluir que las variables medidas HDL, LDL y triglicéridos muestran diferencias estadísticamente significativas entre los grupos experimentales y de control en los dos momentos del estudio, pero no entre los tiempos. Lo mismo ocurre en las variables de fuerza de las extremidades inferiores y abdominales, lo que sugiere un efecto positivo del programa implementado.

Endurance exercise training up-regulates lipolytic proteins and reduces triglyceride content in skeletal muscle of obese subjects

CONTEXT

Skeletal muscle lipase and intramyocellular triglyceride (IMTG) play a role in obesity-related metabolic disorders.

OBJECTIVES

The aim of the present study was to investigate the impact of 8 weeks of endurance exercise training on IMTG content and lipolytic proteins in obese male subjects.

DESIGN AND VOLUNTEERS

Ten obese subjects completed an 8-week supervised endurance exercise training intervention in which vastus lateralis muscle biopsy samples were collected before and after training.

MAIN OUTCOME MEASURES

Clinical characteristics and ex vivo substrate oxidation rates were measured pre- and posttraining. Skeletal muscle lipid content and lipolytic protein expression were also investigated.

RESULTS

Our data show that exercise training reduced IMTG content by 42% (P < .01) and increased skeletal muscle oxidative capacity, whereas no change in total diacylglycerol content and glucose oxidation was found. Exercise training up-regulated adipose triglyceride lipase, perilipin (PLIN) 3 protein, and PLIN5 protein contents in skeletal muscle despite no change in mRNA levels. Training also increased hormone sensitive-lipase Ser660 phosphorylation. No significant changes in comparative gene identification 58, G₀/G₁ switch gene 2, and PLIN2 protein and mRNA levels were observed in response to training. Interestingly, we noted a strong relationship between skeletal muscle comparative gene identification 58 and mitochondrial respiratory chain complex I protein contents at baseline (r = 0.87, P < .0001).

CONCLUSIONS

Endurance exercise training coordinately up-regulates fat oxidative capacity and lipolytic protein expression in skeletal muscle of obese subjects. This physiological adaptation probably favors fat oxidation and may alleviate the lipotoxic lipid pressure in skeletal muscle. Enhancement of IMTG turnover may be required for the beneficial metabolic effects of exercise in obesity.

The anaerobic threshold: over-valued or under-utilized? A novel concept to enhance lipid optimization!

PURPOSE OF REVIEW

The purpose of this article is to assess the value of the anaerobic threshold for use in clinical populations with the intent to improve exercise adaptations and outcomes. The anaerobic threshold is generally poorly understood, improperly used, and poorly measured. It is rarely used in clinical settings and often reserved for athletic performance testing.

RECENT FINDINGS

Increased exercise participation within both clinical and other less healthy populations has increased our attention to optimizing exercise outcomes. Of particular interest is the optimization of lipid metabolism during exercise in order to improve numerous conditions such as blood lipid profile, insulin sensitivity and secretion, and weight loss. Numerous authors report on the benefits of appropriate exercise intensity in optimizing outcomes even though regulation of intensity has proved difficult for many. Despite limited use, selected exercise physiology markers have considerable merit in exercise-intensity regulation. The anaerobic threshold, and other markers such as heart rate, may well provide a simple and valuable mechanism for regulating exercising intensity.

SUMMARY

The use of the anaerobic threshold and accurate target heart rate to regulate exercise intensity is a valuable approach that is under-utilized across populations. The measurement of the anaerobic threshold can be simplified to allow clients to use nonlaboratory measures, for example heart rate, in order to self-regulate exercise intensity and improve outcomes.

Comparison of substrate oxidation during walking and running in normal-weight and overweight/obese men

OBJECTIVE

The aim of the present study is to examine the differences in fat and carbohydrate (CHO) oxidation during walking and running between normal-weight and overweight/obese young adult men.

METHODS

19 healthy, normal-weight (age = 21.9 ± 0.7 years, BMI = 22.6 ± 0.4 kg, n = 10) and overweight (age = 21.4 ± 0.6 years, BMI = 31.6 ± 1.1, n = 9) young men volunteered to participate in this study. Body composition was assessed by bioelectrical impedance. Maximal oxygen uptake and maximal fat oxidation rate were determined with indirect calorimetry by using an incremental exercise test on a motor-driven treadmill. The participants' individual preferred transition speeds between walking and running were determined. Indirect calorimetry was used to calculate fat and CHO oxidation during the resting, walking and running tests.

RESULTS

Maximal fat oxidation rates during the graded exercise test were not significantly different between the groups. Changes in CHO and fat oxidation in the resting, walking and running tests were similar in the normal-weight and overweight groups.

CONCLUSION

The study results suggest that with regard to changes in CHO and fat oxidation, normal-weight and overweight/obese individuals have similar responses to walking and running at preferred speeds, despite significant differences in oxygen uptake during activity and body composition.

Does exercise duration affect Fatmax in overweight boys?

To compare the assessment of Fat(max) using a single graded exercise test with 3 min stages against 30 min prolonged exercise bouts in overweight boys. Ten overweight boys (8-12 years) attended the laboratory on seven separate occasions. On the first visit, body anthropometrics and peak aerobic capacity ([Formula: see text]O(2peak)) were assessed. Following this, each participant attended the laboratory after an overnight fast for six morning cycling sessions. During the first session, participants completed a continuous, submaximal graded exercise protocol with seven 3 min stages (GRAD) at 35, 40, 45, 50, 55, 60 and 65% [Formula: see text]O(2peak). The final five visits consisted of a 30 min bout of prolonged exercise (PROL) performed in a counterbalanced order at 40, 45, 50, 55 and 60% [Formula: see text]O(2peak). There was no effect of exercise duration on Fat(max) or the absolute rate of fat oxidation during PROL (p > 0.05). At the group level, GRAD and PROL provided similar estimates of Fat(max) (GRAD: 53 ± 10% [Formula: see text]O(2peak); PROL: 53 ± 10% [Formula: see text]O(2peak); p = 0.995); however, individual variation between the two protocols is shown by a systematic bias and residual error of 0 ± 11% [Formula: see text]O(2peak). Fat oxidation rates remained stable across 30 min of steady-state exercise in overweight boys. Furthermore, Fat(max) was similar at 3, 10, 20 and 30 min of exercise, suggesting that for exercise lasting ≤ 30 min, exercise duration does not affect Fat(max). However, Fat(max) determined with GRAD may need to be interpreted with caution at the individual level given the variation in Fat(max) between protocols.

Energy expenditure and metabolism during exercise in persons with a spinal cord injury

Resting energy expenditure of persons with a spinal cord injury (SCI) is generally lower than that seen in able-bodied (AB) individuals due to the reduced amounts of muscle mass and sympathetic nervous system available. However, outside of clinical studies, much less data is available regarding athletes with an SCI. In order to predict the energy expenditure of persons with SCI, the generation and validation of prediction equations in relation to specific levels of SCI and training status are required. Specific prediction equations for the SCI would enable a quick and accurate estimate of energy requirements. When compared with the equivalent AB individuals, sports energy expenditure is generally reduced in SCI with values representing 30-75% of AB values. The lowest energy expenditure values are observed for sports involving athletes with tetraplegia and where the sport is a static version of that undertaken by the AB, such as fencing. As with AB sports there is a lack of SCI data for true competition situations due to methodological constraints. However, where energy expenditure during field tests are predicted from laboratory-based protocols, wheelchair ergometry is likely to be the most appropriate exercise mode. The physiological and metabolic responses of persons with SCI are similar to those for AB athletes, but at lower absolute levels. However, the underlying mechanisms pertaining to substrate utilization appear to differ between the AB and SCI. Carbohydrate feeding has been shown to improve endurance performance in athletes with generally low levels of SCI, but no data have been reported for mid to high levels of SCI or for sport-specific tests of an intermittent nature. Further research within the areas reviewed may help to bridge the gap between what is known regarding AB athletes and athletes with SCI (and other disabilities) during exercise and also the gap between clinical practice and performance.

Lipid oxidation in overweight men after exercise and food intake

Fat oxidation (FO) is optimized during low- to moderate-intensity exercise in lean and obese subjects, whereas high-intensity exercise induces preferential FO during the recovery period. After food intake during the postexercise period, it is unknown if FO differs according to the intensity exercise in overweight subjects. Fat oxidation was thus evaluated in overweight men after low- and high-intensity exercise during the recovery period before and after food intake as well as during a control session. Ten healthy, sedentary, overweight men (age, 27.9 +/- 5.6 years; body mass index, 27.8 +/- 1.3 kg m(-2); maximal oxygen consumption, 37 +/- 3.9 mL min(-1) kg(-1)) exercised on a cycloergometer (energy expenditure = 300 kcal) at 35% (E35) or 70% (E70) maximal oxygen consumption or rested (Cont). The subjects were fed 30 minutes after the exercise with 300 kcal (1256 kJ) more energy in the exercise sessions than in the Cont session. Respiratory quotient and FO were calculated by indirect calorimetry. Blood samples were analyzed to measure plasma glycerol, nonesterified fatty acid, glucose, and insulin. During exercise, mean respiratory quotient was lower (P < .05) and FO was higher (P < .01) in the E35 than in the E70 session (FO [in mg min(-1)]: E35 = 290 +/- 12, E70 = 256 +/- 38, and Cont = 131 +/- 7). Conversely, FO was higher in the E70 than in both the E35 session and the Cont session during the immediate recovery as well as during the postprandial recovery period (P = .005 for all; FO from the end of the exercise to the end of the session [in grams]: E70 = 45.7 +/- 8.9, E35 = 38.2 +/- 6.8, and Cont = 36.0 +/- 4.3). Blood parameters did not differ between the 3 sessions but changed according to the absorption of the nutrients. In overweight subjects, high-intensity exercise increased FO during the postexercise period even after food intake compared with the low-intensity exercise and the control session.