As the prevalence of obesity in America approaches epidemic proportions, researchers are scrambling to learn more about how the body stores fat, how fat tissues affect body systems and the role body fat plays in determining one's risk of chronic diseases.
What researchers have learned is that fat is much more than an extra layer of insulation. It actually works as an endocrine organ that secretes dozens of proteins that affect the inner workings of the body.
One such protein is leptin. Discovered in 1994, leptin is released by fat cells. One of its functions is to send signals to the brain to boost or curb appetite. As a person gains weight, their fat cells release more leptin, which in theory should cause a decrease in appetite and an increase in the number of calories burned. However, researchers have found that obese people often are not sensitive to leptin; thus, it has little effect on their appetite and calorie usage. What's more, leptin may work against people trying to lose weight because, as a person loses weight, the body tends to release less leptin, potentially contributing to a boost in appetite and reduction in the number of calories burned at a given activity level.
Another key protein secreted by fat cells is adiponectin. Adiponectin helps insulin move sugar from the bloodstream into the body's cells where it can be used either for fuel or stored. People who are overweight, and especially those who are insulin resistant, have low levels of adiponectin, which may raise the risk for diabetes and heart disease.
Larger fat cells also cause the release of a variety of inflammatory proteins that result in low-level inflammation throughout the body. While the inflammation does not cause symptoms such as fever or pain, it can reduce the ability of insulin to move glucose out of the blood, thus leading to the development of plaque in the arteries and increased risk for heart attack or stroke.
In addition to their biochemical influences, the location of fat cells seems to be important. People who gain weight around the middle (so-called apples) have been shown to be at higher risk for heart disease and diabetes than those who gain their weight in their hips and thighs (so-called pear shapes). Men are more likely to be apple-shaped, and women pear-shaped, at least in their younger years. Older women become more apple shaped as their weight shifts following menopause. Fat stored under the skin (subcutaneous fat) seems to have less influence on the development of chronic diseases than fat stored deep in the abdomen or near the heart and liver.
While scientists have learned much about fat over the last decade, there is still more research to be done. Discovering that fat cells are capable of sending signals to the body and learning how the body stores fat are just the tip of the iceberg. Researchers now are working to determine how diet, exercise and other changes within the body affect the storage and regulation of fat tissue. In so doing, researchers hope to uncover more effective ways to treat obesity.
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Friday, February 04, 2005
GREEN TEA EXTRACT BOOSTS EXERCISE ENDURANCE 8-24%
Dose-related improvement utilizes fat as energy source
BETHESDA, Md. (Jan. 27, 2005) – Now that even baseball players may need to seek new, more natural performance aids, will Japanese green tea sets become standard in dugouts and athletic training tables around the world?
A new study tested the effect of regularly taking green tea extract (GTE) and found that over 10 weeks, endurance exercise performance was boosted up to 24% with 0.5% GTE supplementation, and 8% with 0.2% by-weight addition to food.
Reporting in the online edition of the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology researchers at the Biological Sciences Laboratories of Kao Corp., Tochigi, Japan, said the 8-24% increase in swimming time-to-exhaustion was “accompanied by lower respiratory quotients and higher rates of fat oxidation.”
The results “indicate that GTE is beneficial for improving endurance capacity and support the hypothesis that the stimulation of fatty acid utilization is a promising strategy for improving endurance capacity,” according to the study entitled, “Green tea extract improves endurance capacity and increases muscle lipid oxidation in mice.” Research was conducted by Takatoshi Murase, Satoshi Haramizu, Akira Shimotoyodome, Azumi Nagasawa and Ichiro Tokimitsu, working at Kao Corp., a Japanese maker of healthcare products, including green tea beverages.
Results came from the equivalent of about 4 cups of tea a day
Although it’s difficult to extrapolate from mice eating GTE as a food supplement to a major leaguer or Olympic swimmer sipping green tea, the study’s lead author, Takatoshi Murase said: “We estimate that an athlete weighing 75 kilograms (165 pounds) would have to drink about four cups (0.8 liter) of green tea daily to match the effect in our experiments.”
“One of our important findings,” Murase pointed out, “was that a single high-dose of GTE or its active ingredients didn’t affect performance. So it’s the long-term ingestion of GTE that is beneficial.” (Murase based his calculations of mouse-to-human tea/GTE consumption equivalents on work his lab is doing on the anti-obesity effects of GTE on mice and humans.)
In an era when professional and amateur athletes are always looking for ways to improve performance, and most people want to improve their health and exercise capabilities, “the efficacy of dietary interventions is still controversial,” the authors acknowledge. They note that green tea and cacao contain a class of polyphenols called catechins, which consist mainly of epigallocatechin gallate (EGCG), epicatechin gallate and gallocatechin gallate. Catechins have been reported to have various physiological and pharmacological properties over the years.
The Kao lab “recently demonstrated that the long-term consumption of tea catechins was beneficial in counteracting the obesity-inducing effects of a high-fat diet, and that their effects may be attributed, at least in part, to the activation of hepatic lipid catabolism” in mice. “Overall,” the authors said, “observations so far suggest that thermogenesis and fat oxidation are stimulated by the intake of catechins.”
Working hypothesis and study methods
“To confirm our hypothesis that catechins affect endurance exercise capacity (i.e. time to exhaustion) by increasing lipid utilization, in this study we examined the effect of catechin-rich GTE intake on the endurance capacity of Balb/c mice swimming in an adjustable-current water pool. We also analyzed changes in energy metabolism, especially lipid metabolism. We demonstrated that GTE intake improved endurance capacity and this was accompanied by an increase in lipid catabolism. Our results support the hypothesis that stimulation of lipid metabolism is a promising strategy for improving the capacity for endurance training.”
The ideas for the experiment come from the fact that “skeletal muscles utilize carbohydrates, lipids and amino acids as energy sources, but the ratio in which they are used varies with the intensity of exercise and the level of fitness” as well as the type of exercise involved. For instance “during endurance exercise, excess glucose is undesirable because it induces insulin secretion, which in turn simultaneously inhibits lipid metabolism and stimulates lactate production. Conversely, enhanced availability and utilization of free fatty acids are considered to reduce carbohydrate utilization, which in turn spare glycogen and suppresses lactate production and results in an increase in endurance.”
To test what effects GTE and its components would have on endurance exercise, the researchers ran two experiments. In the first, swimming endurance capacity was measured at eight weeks of age and the mice were divided into four groups of 10 each. All subjects had unlimited access to water for exercise. For 10 weeks, controls ate a standardized diet only, while experimental animals had this diet supplemented with 0.2% and 0.5% GTE by weight. During this period experimental mice were exercised in a pool twice a week, but non-exercise mice weren’t.
The second experiment was similar to the first but the experimental groups received a diet containing 0.1% to 0.5% EGCG for 10 weeks.
At the beginning of the experiment, the mice swam about 26 minutes until they were exhausted. After 10 weeks on the training regimen, the time-to-exhaustion for the exercise-control mice (no GTE or EGCG supplement) rose to about 33 minutes, showing the effects of unaided practice on endurance capacity. From the first week of the experiment, the mice on GTE showed greater improvement compared with the exercise-controls. By week eight, the improved performance of mice on 0.5% GTE was significantly better (39 minutes) than the exercise-controls (33 minutes) at a 0.05 level, while improvement in weeks 9 and 10 (40 minutes vs. 33 minutes) were significant at the 0.01 level.
GTE effects not matched by EGCG alone suggesting other additional influences
In the global search for enhanced athletic performance (and health and fitness), the Kao team said they “have shown that GTE improved endurance capacity and that the improvement was dose-dependent. A similar effect was observed in mice fed EGCG, a major constituent of GTE, suggesting that the effects of GTE were mediated at least in part by EGCG.
“However, because the effects of EGCG appear weak compared with those of GTE, we cannot rule out a possible contribution from other components of GTE. Although long-term intake of GTE enhanced endurance capacity, no marked effects were observed after a single dose of GTE, suggesting that some biochemical changes induced by habitual GTE intake, such as up-regulation of muscular beta-oxidation, contributed to the improvement in endurance capacity.”
The study found that plasma NEFA (non-esterified fatty acid) measured immediately after exercise slightly, but significantly, increased in mice fed tea catechins. Though they concede that the effect of plasma fatty acid level on endurance capacity is controversial, they say that increased supply of circulating fatty acids would “induce the uptake of fatty acids, and thereby stimulate lipid metabolism in muscle.”
Indeed, lab results showed that muscular beta-oxidation was higher in GTE-fed mice (compared with non-exercise and exercise-control mice), “suggesting that GTE enhanced the capacity of muscle to catabolize lipids and utilize fatty acids as an energy source.” Conversely, GTE lowered plasma lactate concentrations, which would be raised by glycogen breakdown and glycolytic flux, they note.
Taken together the experimental results “suggest that habitual exercise and the intake of GTE enhance fatty acid availability, catabolism and utilization in muscle, and this is accompanied by a reduction in carbohydrate use, which together result in prolonged swimming times to exhaustion.”
Controlling for caffeine
Kao researchers controlled for possible influences of caffeine and possible weight-fat changes that might affect buoyancy.
Aware that previous studies were criticized by the possible role of caffeine on fatty acids and exercise, the Kao researchers reduced the amount of caffeine in supplements. “In addition, we observed no changes in plasma NEFA level under resting conditions, suggesting that caffeine-stimulated lipolysis did not occur under these conditions. Thus our results overall suggest that the effects observed in this study are not attributable to caffeine. In particular, our findings that purified EGCG improved endurance capacity supports this conclusion.”
Next steps
The “precise molecular mechanism by which GTE stimulates fatty acid metabolism is unclear at present (and) remains to be elucidated.”
For instance, the researchers wrote, “it is possible that the anti-oxidant properties of tea catechins mediate their effects on endurance capacity.”
And finally they noted: “Although the clinical efficacy of GTE has not yet been confirmed in human studies, our results suggest that GTE may be a useful tool for improving endurance capacity.”
Contact: Mayer Resnick
Office: 301-634-7209
Cell: 301-332-4402
mresnick@the-aps.org
Body Perfect Fitness- The most comprehensive fitness and health resource online, dedicated to helping improve everyone’s overall
Body Perfect Fitness and Health!!
My Private Coach - Because, if not now... WHEN?
Get your FREE Coaching Session TODAY!
BETHESDA, Md. (Jan. 27, 2005) – Now that even baseball players may need to seek new, more natural performance aids, will Japanese green tea sets become standard in dugouts and athletic training tables around the world?
A new study tested the effect of regularly taking green tea extract (GTE) and found that over 10 weeks, endurance exercise performance was boosted up to 24% with 0.5% GTE supplementation, and 8% with 0.2% by-weight addition to food.
Reporting in the online edition of the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology researchers at the Biological Sciences Laboratories of Kao Corp., Tochigi, Japan, said the 8-24% increase in swimming time-to-exhaustion was “accompanied by lower respiratory quotients and higher rates of fat oxidation.”
The results “indicate that GTE is beneficial for improving endurance capacity and support the hypothesis that the stimulation of fatty acid utilization is a promising strategy for improving endurance capacity,” according to the study entitled, “Green tea extract improves endurance capacity and increases muscle lipid oxidation in mice.” Research was conducted by Takatoshi Murase, Satoshi Haramizu, Akira Shimotoyodome, Azumi Nagasawa and Ichiro Tokimitsu, working at Kao Corp., a Japanese maker of healthcare products, including green tea beverages.
Results came from the equivalent of about 4 cups of tea a day
Although it’s difficult to extrapolate from mice eating GTE as a food supplement to a major leaguer or Olympic swimmer sipping green tea, the study’s lead author, Takatoshi Murase said: “We estimate that an athlete weighing 75 kilograms (165 pounds) would have to drink about four cups (0.8 liter) of green tea daily to match the effect in our experiments.”
“One of our important findings,” Murase pointed out, “was that a single high-dose of GTE or its active ingredients didn’t affect performance. So it’s the long-term ingestion of GTE that is beneficial.” (Murase based his calculations of mouse-to-human tea/GTE consumption equivalents on work his lab is doing on the anti-obesity effects of GTE on mice and humans.)
In an era when professional and amateur athletes are always looking for ways to improve performance, and most people want to improve their health and exercise capabilities, “the efficacy of dietary interventions is still controversial,” the authors acknowledge. They note that green tea and cacao contain a class of polyphenols called catechins, which consist mainly of epigallocatechin gallate (EGCG), epicatechin gallate and gallocatechin gallate. Catechins have been reported to have various physiological and pharmacological properties over the years.
The Kao lab “recently demonstrated that the long-term consumption of tea catechins was beneficial in counteracting the obesity-inducing effects of a high-fat diet, and that their effects may be attributed, at least in part, to the activation of hepatic lipid catabolism” in mice. “Overall,” the authors said, “observations so far suggest that thermogenesis and fat oxidation are stimulated by the intake of catechins.”
Working hypothesis and study methods
“To confirm our hypothesis that catechins affect endurance exercise capacity (i.e. time to exhaustion) by increasing lipid utilization, in this study we examined the effect of catechin-rich GTE intake on the endurance capacity of Balb/c mice swimming in an adjustable-current water pool. We also analyzed changes in energy metabolism, especially lipid metabolism. We demonstrated that GTE intake improved endurance capacity and this was accompanied by an increase in lipid catabolism. Our results support the hypothesis that stimulation of lipid metabolism is a promising strategy for improving the capacity for endurance training.”
The ideas for the experiment come from the fact that “skeletal muscles utilize carbohydrates, lipids and amino acids as energy sources, but the ratio in which they are used varies with the intensity of exercise and the level of fitness” as well as the type of exercise involved. For instance “during endurance exercise, excess glucose is undesirable because it induces insulin secretion, which in turn simultaneously inhibits lipid metabolism and stimulates lactate production. Conversely, enhanced availability and utilization of free fatty acids are considered to reduce carbohydrate utilization, which in turn spare glycogen and suppresses lactate production and results in an increase in endurance.”
To test what effects GTE and its components would have on endurance exercise, the researchers ran two experiments. In the first, swimming endurance capacity was measured at eight weeks of age and the mice were divided into four groups of 10 each. All subjects had unlimited access to water for exercise. For 10 weeks, controls ate a standardized diet only, while experimental animals had this diet supplemented with 0.2% and 0.5% GTE by weight. During this period experimental mice were exercised in a pool twice a week, but non-exercise mice weren’t.
The second experiment was similar to the first but the experimental groups received a diet containing 0.1% to 0.5% EGCG for 10 weeks.
At the beginning of the experiment, the mice swam about 26 minutes until they were exhausted. After 10 weeks on the training regimen, the time-to-exhaustion for the exercise-control mice (no GTE or EGCG supplement) rose to about 33 minutes, showing the effects of unaided practice on endurance capacity. From the first week of the experiment, the mice on GTE showed greater improvement compared with the exercise-controls. By week eight, the improved performance of mice on 0.5% GTE was significantly better (39 minutes) than the exercise-controls (33 minutes) at a 0.05 level, while improvement in weeks 9 and 10 (40 minutes vs. 33 minutes) were significant at the 0.01 level.
GTE effects not matched by EGCG alone suggesting other additional influences
In the global search for enhanced athletic performance (and health and fitness), the Kao team said they “have shown that GTE improved endurance capacity and that the improvement was dose-dependent. A similar effect was observed in mice fed EGCG, a major constituent of GTE, suggesting that the effects of GTE were mediated at least in part by EGCG.
“However, because the effects of EGCG appear weak compared with those of GTE, we cannot rule out a possible contribution from other components of GTE. Although long-term intake of GTE enhanced endurance capacity, no marked effects were observed after a single dose of GTE, suggesting that some biochemical changes induced by habitual GTE intake, such as up-regulation of muscular beta-oxidation, contributed to the improvement in endurance capacity.”
The study found that plasma NEFA (non-esterified fatty acid) measured immediately after exercise slightly, but significantly, increased in mice fed tea catechins. Though they concede that the effect of plasma fatty acid level on endurance capacity is controversial, they say that increased supply of circulating fatty acids would “induce the uptake of fatty acids, and thereby stimulate lipid metabolism in muscle.”
Indeed, lab results showed that muscular beta-oxidation was higher in GTE-fed mice (compared with non-exercise and exercise-control mice), “suggesting that GTE enhanced the capacity of muscle to catabolize lipids and utilize fatty acids as an energy source.” Conversely, GTE lowered plasma lactate concentrations, which would be raised by glycogen breakdown and glycolytic flux, they note.
Taken together the experimental results “suggest that habitual exercise and the intake of GTE enhance fatty acid availability, catabolism and utilization in muscle, and this is accompanied by a reduction in carbohydrate use, which together result in prolonged swimming times to exhaustion.”
Controlling for caffeine
Kao researchers controlled for possible influences of caffeine and possible weight-fat changes that might affect buoyancy.
Aware that previous studies were criticized by the possible role of caffeine on fatty acids and exercise, the Kao researchers reduced the amount of caffeine in supplements. “In addition, we observed no changes in plasma NEFA level under resting conditions, suggesting that caffeine-stimulated lipolysis did not occur under these conditions. Thus our results overall suggest that the effects observed in this study are not attributable to caffeine. In particular, our findings that purified EGCG improved endurance capacity supports this conclusion.”
Next steps
The “precise molecular mechanism by which GTE stimulates fatty acid metabolism is unclear at present (and) remains to be elucidated.”
For instance, the researchers wrote, “it is possible that the anti-oxidant properties of tea catechins mediate their effects on endurance capacity.”
And finally they noted: “Although the clinical efficacy of GTE has not yet been confirmed in human studies, our results suggest that GTE may be a useful tool for improving endurance capacity.”
Contact: Mayer Resnick
Office: 301-634-7209
Cell: 301-332-4402
mresnick@the-aps.org
Body Perfect Fitness- The most comprehensive fitness and health resource online, dedicated to helping improve everyone’s overall
Body Perfect Fitness and Health!!
My Private Coach - Because, if not now... WHEN?
Get your FREE Coaching Session TODAY!
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