LisaS
06-07-2006, 01:28 AM
Effect of resistance exercise on postprandial lipemia
J Appl Physiol 94: 694-700, 2003
full text found here:
http://jap.physiology.org/cgi/search?sortspec=relevance&author1=&fulltext=&pubdate_year=2003&volume=94&firstpage=694
This was another interesting study. It looked at postprandial lipemia - that is, your blood lipids after a meal. Since most of your waking day is postprandial, the authors speculated that your TG might be elevated for most of the day. They state that reducing postprandial lipemia "is believed to lower the risk of hear disease by improving TG metabolism".
According to the authors, aerobic exercise performed on one day is known to decrease the insulin response to a meal the next day and attenuate the blood lipid response. The energy expended (EE) in this effort seems to effect the lipid response - that is a longer period of walking (more energy burned) will have a greater effect on TG levels. At the same EE level, there does not seem to be a difference between low-intensity and moderate intensity aerobic exercise and the effect on TG - though both have a significant effect compared to controls.
This study compared strenuous resistance exercise (weight training) and aerobic exercise designed to have the same EE levels and looked at effects on postprandial TG, insulin response, fat oxidation and blood glucose. They suspected RE would have better results on these factors. This was an intense RE program: 3x10 of 10 exercises at the subjects 10RM - a whole body workout - 2 mins rest between sets for an 88 min workout. Their EE was actually measured during the workout and that number used to design their AE program for comparison. The subjects were healthy men and women, 21-40 who were accustomed to weight training. The gross EE was 1.7 +/- 0.1 MJ for RE and 1.6 +/- 0.1 MJ for AE. This is important to note for the discussion section.
The subjects trained on day one and reported back the next day, 15 hours later, while on a 12 hr (overnight fast). After more bloodwork, a breakfast was consumed within 15 mins (89g fat, 74g CHO, 32g Pro, give or take). The meal was standardized to be a high-fat meal, 1.2g fat/kg body mass. More blood every 1/2 hour for 6 hours.
From the discussion :D
The major finding of this study is that a single session of strenuous resistance exercise completed ~16 h before meal ingestion decreases baseline TGs as well as the total serum TG response to a high-fat meal. Furthermore, resting fat oxidation was significantly increased 15 h after RE. Our findings are in agreement with studies using aerobic exercise; however, the EE of the RE was much less than that for the AE that has been shown to attenuate the postprandial TG response in the literature.
We did not find an attenuated postprandial lipemic response after acute aerobic exercise expending ~1.7 MJ. This finding appears consistent with the literature. Studies by Tsetsonis and Hardman (35, 36) suggest that the effect of aerobic exercise on the postprandial TG levels is related to the EE of the prior exercise. The mean EE in 13 published studies that examined the effect of prior exercise on postprandial lipemia averaged 3.4 MJ (range 1.6-7.2 MJ) with a value for d of -0.57, a moderate effect size according to Cohen (4). The relationship between EE and the reduction in the postprandial AUC relative to control for those studies is moderately strong (r = 0.62), indicating that as the EE increases, the decrease in postprandial lipemia becomes greater. Tsetsonis and Hardman (35) reported that 90 min of moderate-intensity exercise (expending ~3.5 MJ) significantly reduced the postprandial lipemic response to a meal, whereas low-intensity exercise (expending ~1.7 MJ) for the same duration did not. On the basis of subsequent findings (36), the decrease in postprandial TG levels was presumably a function of the EE of the exercise and not the exercise intensity.
In contrast, the resistance exercise used in this study reduced the postprandial lipemic response despite the relatively low energy expended during the exercise bout (1.7 MJ). The strong effect size (d = -0.78), on the basis of adjusted means, indicates that the reduction in postprandial lipemia after resistance exercise is similar to reductions observed after aerobic exercise with an EE during exercise approximately double that observed in this study. This suggests that the response after resistance exercise may not be related to the energy expended during exercise but to some other factor linked to the strenuous muscle contraction associated with weight lifting.
So, there seems to be something about using your muscles in weight training that has a specific effect, and not just the energy used while working out.
later in the discussion:
In addition, the RE in this study did not alter insulin and glucose concentrations compared with Con. Some previous studies have found no change in fasting insulin levels 22-24 h after the last bout of resistance exercise in trained persons (18, 27), whereas others report that resistance training decreases insulin levels (24) or that resistance-trained persons have lower absolute insulin levels than untrained persons (25). Kraemer et al. (18) examined insulin levels on three consecutive days before and after a bout of resistance exercise performed on each day in resistance-trained men. They found no differences in insulin levels on each day and no differences between days. Similarly, discrepant findings exist concerning the effect of an acute bout of aerobic exercise on insulin levels. Tsetsonis et al. (37) found a significantly lower insulin response to a meal 16 h after aerobic exercise in trained women compared with untrained women as well as to a control trial in the absence of prior exercise. The untrained women, however, did not exhibit the insulin attenuation in response to prior exercise. Gill et al. (8) found that despite reductions in fasting and postprandial TG and insulin levels the day after 90 min of aerobic exercise at 60% VO2 max, there were no relationships between the exercise-induced changes in fasting or postprandial TGs and the exercise-induced changes in insulin, suggesting that changes in markers of insulin sensitivity after acute aerobic exercise were not the primary factor mediating changes in postprandial TGs. Although we did not directly measure insulin sensitivity, the lack of changes in fasting and postprandial glucose and insulin in our study also suggest that postprandial changes in TGs caused by RE are unlikely to be mediated by altered insulin sensitivity.
So - whatever it was about RE that helped TG was independent of any insulin sensitivity changes. They theorize about various mechanisms that might have been involved.
and they conclude:
Interestingly, Tikkanen et al. (33) found a 65% increase in skeletal muscle LPL activity after 12 mo of increased leisure-time physical activity. The physical activity was of lower intensity exercise than that used in previous studies, yet LPL activity more than doubled in skeletal muscle. If an increase in LPL activity is the mechanism for the reduced postprandial lipemia after exercise, it appears that various types of exercise can be utilized to initiate this effect. Additionally, the reduced postprandial lipemia has been shown after both continuous and intermittent aerobic exercise (9), supporting the Centers for Disease Control and American College of Sports Medicine 1995 position stand that to achieve health benefits, at least 30 min of activity should be accumulated on most days of the week (22). The more recent American College of Sports Medicine position stand (26) also recommends that "resistance training should be an integral part of an adult fitness program" and that "the inclusion of resistance training ... should be effective in the development and maintenance of muscular strength and endurance, [fat-free mass], and [bone mineral density]." On the basis of findings in this study, reduced postprandial lipemia is an additional health benefit of resistance exercise.
In summary, these results suggest that resistance exercise of the type used in this study attenuates baseline TG concentrations as well as the total postprandial TG response and increases resting fat oxidation 15 h after exercise. Resistance exercise may provide health benefits other than those traditionally associated with this type of exercise.
So - don't forget to hit the weights.
J Appl Physiol 94: 694-700, 2003
full text found here:
http://jap.physiology.org/cgi/search?sortspec=relevance&author1=&fulltext=&pubdate_year=2003&volume=94&firstpage=694
This was another interesting study. It looked at postprandial lipemia - that is, your blood lipids after a meal. Since most of your waking day is postprandial, the authors speculated that your TG might be elevated for most of the day. They state that reducing postprandial lipemia "is believed to lower the risk of hear disease by improving TG metabolism".
According to the authors, aerobic exercise performed on one day is known to decrease the insulin response to a meal the next day and attenuate the blood lipid response. The energy expended (EE) in this effort seems to effect the lipid response - that is a longer period of walking (more energy burned) will have a greater effect on TG levels. At the same EE level, there does not seem to be a difference between low-intensity and moderate intensity aerobic exercise and the effect on TG - though both have a significant effect compared to controls.
This study compared strenuous resistance exercise (weight training) and aerobic exercise designed to have the same EE levels and looked at effects on postprandial TG, insulin response, fat oxidation and blood glucose. They suspected RE would have better results on these factors. This was an intense RE program: 3x10 of 10 exercises at the subjects 10RM - a whole body workout - 2 mins rest between sets for an 88 min workout. Their EE was actually measured during the workout and that number used to design their AE program for comparison. The subjects were healthy men and women, 21-40 who were accustomed to weight training. The gross EE was 1.7 +/- 0.1 MJ for RE and 1.6 +/- 0.1 MJ for AE. This is important to note for the discussion section.
The subjects trained on day one and reported back the next day, 15 hours later, while on a 12 hr (overnight fast). After more bloodwork, a breakfast was consumed within 15 mins (89g fat, 74g CHO, 32g Pro, give or take). The meal was standardized to be a high-fat meal, 1.2g fat/kg body mass. More blood every 1/2 hour for 6 hours.
From the discussion :D
The major finding of this study is that a single session of strenuous resistance exercise completed ~16 h before meal ingestion decreases baseline TGs as well as the total serum TG response to a high-fat meal. Furthermore, resting fat oxidation was significantly increased 15 h after RE. Our findings are in agreement with studies using aerobic exercise; however, the EE of the RE was much less than that for the AE that has been shown to attenuate the postprandial TG response in the literature.
We did not find an attenuated postprandial lipemic response after acute aerobic exercise expending ~1.7 MJ. This finding appears consistent with the literature. Studies by Tsetsonis and Hardman (35, 36) suggest that the effect of aerobic exercise on the postprandial TG levels is related to the EE of the prior exercise. The mean EE in 13 published studies that examined the effect of prior exercise on postprandial lipemia averaged 3.4 MJ (range 1.6-7.2 MJ) with a value for d of -0.57, a moderate effect size according to Cohen (4). The relationship between EE and the reduction in the postprandial AUC relative to control for those studies is moderately strong (r = 0.62), indicating that as the EE increases, the decrease in postprandial lipemia becomes greater. Tsetsonis and Hardman (35) reported that 90 min of moderate-intensity exercise (expending ~3.5 MJ) significantly reduced the postprandial lipemic response to a meal, whereas low-intensity exercise (expending ~1.7 MJ) for the same duration did not. On the basis of subsequent findings (36), the decrease in postprandial TG levels was presumably a function of the EE of the exercise and not the exercise intensity.
In contrast, the resistance exercise used in this study reduced the postprandial lipemic response despite the relatively low energy expended during the exercise bout (1.7 MJ). The strong effect size (d = -0.78), on the basis of adjusted means, indicates that the reduction in postprandial lipemia after resistance exercise is similar to reductions observed after aerobic exercise with an EE during exercise approximately double that observed in this study. This suggests that the response after resistance exercise may not be related to the energy expended during exercise but to some other factor linked to the strenuous muscle contraction associated with weight lifting.
So, there seems to be something about using your muscles in weight training that has a specific effect, and not just the energy used while working out.
later in the discussion:
In addition, the RE in this study did not alter insulin and glucose concentrations compared with Con. Some previous studies have found no change in fasting insulin levels 22-24 h after the last bout of resistance exercise in trained persons (18, 27), whereas others report that resistance training decreases insulin levels (24) or that resistance-trained persons have lower absolute insulin levels than untrained persons (25). Kraemer et al. (18) examined insulin levels on three consecutive days before and after a bout of resistance exercise performed on each day in resistance-trained men. They found no differences in insulin levels on each day and no differences between days. Similarly, discrepant findings exist concerning the effect of an acute bout of aerobic exercise on insulin levels. Tsetsonis et al. (37) found a significantly lower insulin response to a meal 16 h after aerobic exercise in trained women compared with untrained women as well as to a control trial in the absence of prior exercise. The untrained women, however, did not exhibit the insulin attenuation in response to prior exercise. Gill et al. (8) found that despite reductions in fasting and postprandial TG and insulin levels the day after 90 min of aerobic exercise at 60% VO2 max, there were no relationships between the exercise-induced changes in fasting or postprandial TGs and the exercise-induced changes in insulin, suggesting that changes in markers of insulin sensitivity after acute aerobic exercise were not the primary factor mediating changes in postprandial TGs. Although we did not directly measure insulin sensitivity, the lack of changes in fasting and postprandial glucose and insulin in our study also suggest that postprandial changes in TGs caused by RE are unlikely to be mediated by altered insulin sensitivity.
So - whatever it was about RE that helped TG was independent of any insulin sensitivity changes. They theorize about various mechanisms that might have been involved.
and they conclude:
Interestingly, Tikkanen et al. (33) found a 65% increase in skeletal muscle LPL activity after 12 mo of increased leisure-time physical activity. The physical activity was of lower intensity exercise than that used in previous studies, yet LPL activity more than doubled in skeletal muscle. If an increase in LPL activity is the mechanism for the reduced postprandial lipemia after exercise, it appears that various types of exercise can be utilized to initiate this effect. Additionally, the reduced postprandial lipemia has been shown after both continuous and intermittent aerobic exercise (9), supporting the Centers for Disease Control and American College of Sports Medicine 1995 position stand that to achieve health benefits, at least 30 min of activity should be accumulated on most days of the week (22). The more recent American College of Sports Medicine position stand (26) also recommends that "resistance training should be an integral part of an adult fitness program" and that "the inclusion of resistance training ... should be effective in the development and maintenance of muscular strength and endurance, [fat-free mass], and [bone mineral density]." On the basis of findings in this study, reduced postprandial lipemia is an additional health benefit of resistance exercise.
In summary, these results suggest that resistance exercise of the type used in this study attenuates baseline TG concentrations as well as the total postprandial TG response and increases resting fat oxidation 15 h after exercise. Resistance exercise may provide health benefits other than those traditionally associated with this type of exercise.
So - don't forget to hit the weights.