研究表明绿茶结合运动对减肥、降低血糖有显著效果
据宾夕法尼亚州立大学农业科学学院的研究人员称，高脂肪饮食的小鼠摄入无咖啡因的绿茶提取物，并经常锻炼，最终体重显著下降，健康状况显著改善。
16周后，高脂肪喂养的小鼠定期运动，摄入绿茶提取物，平均体重减少27.1%，腹部脂肪平均减少36.6%。
摄入绿茶提取物和运动疗法的小鼠空腹血糖降低了17%，血浆胰岛素水平降低了65%，胰岛素抵抗降低了65%——这些都是与糖尿病健康相关的显著改善。
该研究的首席研究员、食品科学副教授乔舒亚·兰伯特(Joshua Lambert)指出，摄入绿茶提取物但不锻炼或不锻炼但饮用绿茶提取物的老鼠体重和健康状况的变化幅度较小。
他说:“这项研究的重要之处在于，我们首次报告，与绿茶提取物联合使用绿茶提取物能减轻代谢综合征的症状，并使高脂肪喂养的老鼠的肥胖引起的肥胖比单独治疗更显著。”“体重和身体脂肪的变化可能是由于脂肪代谢增加和脂肪合成减少所致。”绿茶似乎调节了与能量代谢有关的基因。
白老鼠在车轮上奔跑
运动的和去咖啡因的绿茶提取物的小鼠的体重发生了更显著的变化。
代谢综合征是一组危险因素的名称，比如腰围增加、甘油三酸酯升高、高密度脂蛋白胆固醇降低、血压升高、空腹血糖升高，从而增加患心脏病和其他严重健康问题的几率，如糖尿病和中风。
兰伯特指出，这项研究于2013年12月在《分子营养食品研究》(Molecular Nutrition Food research)网站上发表，并将于今年春季发表在《华尔街日报》(journal this spring)杂志上，表明人们也可以实现类似的好处。
“当我们设计动物模型试验时，我们尽量模仿人类的情况，因此在这个研究中使用的不含咖啡因的绿茶尽可能多，相当于一天8至10杯绿茶, 对某些人这是一个很大的量。但有很多人是喝很多茶的。
茶富含儿茶素，多酚是天然的抗氧化剂。许多动物研究表明绿茶多酚对肥胖的预防作用。最近的一项对11项人体试验的分析表明，与对照组相比，干预组的平均体重减轻了1.31公斤。
在美国，大约34%的成年人属于肥胖。肥胖是代谢综合征的危险因素。兰伯特解释说，应对肥胖和代谢综合征的最有效的方法是改变生活方式，并补充说，如果人们真的想减肥，他们需要锻炼更多来燃烧更多的卡路里，他们需要少吃。
兰伯特说:“但我们的研究结果表明，没有咖啡因的绿茶能增强运动的效果。”“运动的和无咖啡因的绿茶提取物对体重有更显著的改变，他们的血糖和血浆胰岛素水平都较低。”它看起来像是运动和脱咖啡因的绿茶的结合增强了身体使用能量的能力。
兰伯特指出，脱咖啡因可能对研究并不重要，但他不希望茶中含有咖啡因，从而使结果模糊不清。研究人员把注意力集中在脱咖啡因的绿茶上，因为研究表明咖啡因有刺激作用。如果老鼠或人摄入咖啡因，它会增加基础代谢率，并在提高能量利用率和降低体重方面发挥作用。
此外，由于部分人群对咖啡因对健康的影响持怀疑态度，兰伯特将其排除在研究之外。
在研究中使用的老鼠是预先被挑选出来的。像人一样，有些老鼠根本不愿意跑; 兰伯特说，其他人愿意不断地跑。装有计数器的轮子被放在笼子里，老鼠自愿跑。
尽管先前的研究已经表明，强迫跑步或与茶提取物结合在一起游泳可以减轻小鼠的肥胖，但之前没有关于绿茶对高脂肪喂养小鼠的肥胖和代谢综合症的影响的报道。兰伯特说，强迫运动将其他健康问题引入研究。
他说:“我们研究自愿运动的理由是，那些对减轻体重和治疗糖尿病，或类似的事情感兴趣的人，确实有很高的动机。然而，大多数人并没有被迫去锻炼。只是被支持或鼓励，是的，但强迫，不。”
兰伯特强调，将绿茶的饮用和运动结合起来，可以很好地帮助人们——比如老鼠——减轻体重，但在对人类进行研究之前，没有任何方法可以确定。
他说:“这看起来对人们来说很有希望，但总得有人来做这个实验，让人们明确地证明绿茶和锻炼对人类有好处。”
参考文献：
Research suggests that green tea exercise boost weight loss, health
By Jeff Mulhollem
April 2, 2014
UNIVERSITY PARK, Pa. -- Mice on a high-fat diet that consumed decaffeinated green tea extract and exercised regularly experienced sharp reductions in final body weight and significant improvements in health, according to researchers in Penn State's College of Agricultural Sciences, who suggest that similar results could be realized by people.
After 16 weeks, high-fat-fed mice that exercised regularly and ingested green tea extract showed an average body mass reduction of 27.1 percent and an average abdominal fat mass reduction of 36.6 percent.
The mice on the green-tea-extract-and-exercise regimen also experienced a 17 percent reduction in fasting blood glucose level, a 65 percent decrease in plasma insulin level and reduction in insulin resistance of 65 percent -- all substantial improvements related to diabetic health.
Mice that ingested green tea extract but did not exercise or those that exercised but were not given green tea extract experienced less significant changes in weight and health measurements, noted lead researcher Joshua Lambert, associate professor of food science.
"What is significant about this research is that we report for the first time that voluntary exercise in combination with green tea extract reduced symptoms of metabolic syndrome and diet-induced obesity in high-fat-fed mice more significantly than either treatment alone," he said. "The changes in body weight and body fat may result from increased fat metabolism and decreased fat synthesis. Green tea seems to modulate genes related to energy metabolism."
white mouse running in wheel
The mice that exercised and had decaffeinated green tea extract had a more significant change in body weight.
Image: NIH.gov
Metabolic syndrome is the name for a group of risk factors -- such as increased waist circumference, elevated triglycerides, reduced HDL-cholesterol, increased blood pressure and increased fasting blood glucose -- that increase the chance of developing heart disease and other serious health problems, such as diabetes and stroke.
The research, which was published online in Molecular Nutrition Food Research in December 2013 and will appear in an issue of the journal this spring, indicates that people could realize similar benefits, Lambert pointed out.
"I think we can make that leap," he said. "When we put together our animal model experiments, we try to mimic the human situation as much as possible, so the dose of decaffeinated green tea that we used in this study is the equivalent of 8 to 10 cups of green tea a day, which is a lot for some people. But there are many people out there who are heavy, regular tea consumers."
Tea -- Camellia sinensis -- is rich in catechins, polyphenols that are natural antioxidents. A number of animal studies show the preventive effects of green tea polyphenols against obesity. A recent analysis of 11 human trials with green tea preparations reported a 1.31 kilogram average body weight loss in intervention groups compared to control groups.
Approximately 34 percent of adults in the United States are classified as obese. Obesity is a risk factor for metabolic syndrome. The most effective way to deal with the development of obesity and metabolic syndrome is lifestyle change, Lambert explained, adding that if people really want to lose weight, they need to exercise more to burn more calories, and they need to eat less.
"But our findings suggest that green tea in the absence of caffeine can enhance the effects of exercise," Lambert said. "The mice that exercised and had decaffeinated green tea extract had a more significant change in body weight, and they had better outcomes as far as lower blood glucose and lower plasma insulin levels. It looks like a combination of exercise and decaffeinated green tea enhances the body's ability to use energy that is taken in."
Decaffeination may not be crucial to the study, Lambert noted, but he did not want the presence of caffeine in the tea to blur the results. Researchers focused on decaffeinated green tea because the literature shows that caffeine has a stimulatory effect. If mice or people ingest caffeine, it increases their basal metabolic rate and plays a role in increasing energy utilization and decreasing body weight.
Also, because a segment of the population remains skeptical of caffeine's effect on health and avoids it, Lambert eliminated it from the research.
The mice used in the research were preselected for their propensity to run. Like people, some mice aren't willing to run at all; others are willing to run constantly, Lambert said. Running wheels equipped with counters were placed in the cages and the mice ran voluntarily.
Although previous studies have shown that forced running or exhaustive swimming in combination with tea extract attenuate obesity in mice, there have been no previous reports on the effects of green tea in combination with voluntary exercise on obesity and metabolic syndrome in high-fat-fed mice. Forced exercise introduces other health problem into studies, Lambert said.
"Our rationale for looking at voluntary exercise as opposed to forced exercise is that people who are interested in reducing body weight and dealing with diabetes and that sort of thing do have a high level of motivation," he said. "However, most people aren't in a situation where they are being forced to exercise. Supported or encouraged, yes, but forced, no."
Combining green-tea drinking and exercise may well help people -- like mice -- lose weight, but until research is done with humans, there is no way to be certain, Lambert stressed.
"It looks promising for people, but somebody will have to do this experiment with people to definitively show that green tea and exercise together have a beneficial effect in humans," he said.
The National Institutes of Health supported this work.
