Between 1900 and 1950, with the help of modern scientific medicine, the life expectancy of Americans leaped more than 200% from 47 to 68 years. The second half of the 20th century saw life expectancy continue to rise, albeit at a somewhat slower pace. By the year 2000, people could expect to live, on average, for 77 years, a growth rate of about 75%. One would think that, with continued improvements in medicine, nutrition, health awareness, and life style, by 2050 we might expect to be breaking 100.1
One would think that…but we may actually be facing something quite different — the first decline in human life expectancy in hundreds of years! The reason: our ever-expanding waistlines. It's well documented: As body mass goes up, life expectancy goes down.
"My colleagues and I believe that within the next 50 years, life expectancy at birth will decline as a result of the obesity epidemic that will creep through all ages like a human tsunami," said Professor Jay Olshansky, an expert on the epidemiology of aging and the biodemography of survival at the University of Illinois, Chicago. "There has been a dramatic increase in obesity among the younger generation; it is a storm that is approaching," he added.
Dr. Olshansky's conclusions are supported by recent research from the Rand Corporation, which found that one in five US adults classified themselves as obese, which is bad enough, but when their weight was measured objectively, one in three was actually considered obese.
Obesity triples the risk of heart disease and raises the risk of developing diabetes by a factor of 10. It not only shortens lifespan, it is linked to higher health care costs than smoking or drinking and plays a principal role in disability at all ages.2
Of course, the first level of protection against the "obesity tsunami" must be sensible diet and lifestyle measures. Unless we have extraordinarily good genetic luck, we can't expect much from a fast-food diet and a couch-potato existence. On top of these, there are important nutritional steps we can take to reduce body fat while adding years to our lives. Key among these is a food that is widespread across Asia, but much less well known in the West: green tea.
Controlling Body Fat
Green tea is probably best known for its potent antioxidant activity, which offers significant protection against cancer and heart disease. However, new evidence confirms that ingesting green tea can also help reduce body fat and promote beneficial levels of lipids (e.g., cholesterol), blood sugar, and insulin.3
The most recent scientific confirmation comes from Japan, where (along with China) green tea is the second only to water as a popular drink. In a double-blind, controlled study, 38 healthy Japanese men (aged 24—46 years) were randomly assigned to one of two groups: Group 1 ingested oolong tea containing 690 mg of a green tea extract known as catechins; Group 2 received ordinary oolong tea, containing just 22 mg of catechins.
Green Tea Lowers Body Fat Levels:
Results After 12 Weeks
After 12 weeks, during which both groups ate the same diet, the green tea group wound up with significantly lower body weight, body mass index (BMI), waist size, and visceral, subcutaneous, and total fat levels (see figure). These changes were associated with a more beneficial blood lipid profile.4 While dietary measures and ordinary tea reduced the body fat measures by only about 2% to 3% across the board, ingesting green tea trimmed fat levels by as much as 10% to 12%.
The key ingredients in green tea are chemicals known as catechins, of which scientists have identified several varieties (isomers). These include catechin, catechin gallate (Cg), gallocatechin, gallocatechin gallate (GCg), epicatechin, epicatechin gallate (ECg), epigallocatechin, and epigallcatechin gallate (EGCg).
Of these, EGCg seems to be the most important. Many studies have shown that, once ingested, EGCg is quickly absorbed and widely distributed all over the body, where it performs its antioxidant, antiviral, antiplaque-forming, and anticancer feats. Also well documented is its ability to lower blood pressure and blood sugar, two important elements of the metabolic syndrome," also known as "syndrome X." This silent killer starts as a general derangement of the body's metabolic functions, including obesity, high blood pressure, elevated cholesterol and triglycerides, insulin resistance, and high blood glucose levels. Over many years, these metabolic disruptions can develop into heart disease, diabetes, and kidney failure.5-10 Now we know that the EGCg and the other catechins in green tea significantly reduce the accumulation of body fat and help normalize blood lipid levels and other aspects of this syndrome.4
There are really only two ways to reduce body fat: either we make less fat or burn more. It's as simple as that. But as we all know, getting it done is not so simple. There is one simple strategy that offers substantial benefits, not only for losing fat but also for a wide range of other important health benefits. We're talking, of course, about ingesting green tea.
Green Tea Fights Fat
Green tea appears to fight body fat at both ends: First, it reduces the accumulation of fat by regulating fat-producing mechanisms in the liver and other locations in the body. In-vitro studies show that green tea catechins markedly inhibit digestive enzymes (lipases) that break down triglycerides, which could translate into reduced fat digestion in humans.11, 12
Second, it turns up the body's metabolic engines, which literally burn fat for energy.11, 13, 14 This latter process is known as thermogenesis. Burning fat faster means there is less fat left to inflate that spare tire.
A recent randomized, double-blind Swiss study demonstrated that green tea generates a significant thermogenic effect.13 The subjects were 10 healthy young men, aged 24 to 26 years, who ranged from lean to mildly obese (8% - 30% body fat). Their typical daily energy intake included 35% to 40% fat, in other words, the typical Western diet. The treatments consisted of: 1) a powdered green tea extract (roughly equivalent to 4 cups of tea); 2) caffeine (which is known to be thermogenic) in an amount equal to that found naturally in the green tea extract, and 3) a placebo. Each subject experienced each of the treatments on a rotating basis. During the 56-weeks of the study, the men were restricted to a standard weight-maintenance diet consisting of about 13% of energy intake as protein, 40% as fat, and 47% as carbohydrate.
Compared with placebo and caffeine, the green tea extract produced a significant increase in total energy expenditure of about 4%. That may not sound like much, but, like interest compounded in a bank account, a small effect continued day after day for an extended period adds up. Also, this 4% increase corresponds to a large increase in the thermogenic component of total energy expenditure: about 35% to 43%. The men taking the green tea extract burned 266 more calories per day than those taking the placebo. The authors concluded that "…oral administration of the green tea extract stimulated thermogenesis and fat oxidation and thus has the potential to influence body weight and body composition…"
Fat doesn't shorten our life spans by itself. It usually contributes to the breakdown of other systems in the body. For example, excessive body fat accumulation is closely linked to heart disease and diabetes, two of the most common potentially fatal chronic diseases. Fortunately, green tea can come to the rescue in both these conditions, and helping control body fat is only part of the story.
Reducing Heart Disease
Heart disease is much less prevalent in Japan, where people drink lots of green tea, than it is in the US. In one recent study, Japanese green tea drinkers had a 30% risk of suffering a heart attack compared with 45% for non-drinkers.15
Green tea catechins contribute to cardiovascular health at least partly through their antioxidant activity. They combine with other powerful antioxidants, such as vitamins C and E and the enzymes superoxide dismutase (SOD) and catalase, to prevent free-radical-induced damage to the vascular endothelium, the delicate lining of blood vessels where atherosclerotic plaque can form. By preventing the oxidation of other antioxidants, catechins may increase the concentration of vitamin E in low-density lipoprotein (LDL — "bad") cholesterol, thus helping protect LDL from peroxidation, an early stage in plaque formation.
Green tea catechins may also help prevent the formation of atherosclerotic plaque by decreasing the absorption of triglycerides and cholesterol. Studies show that at high doses, green tea ingestion decreases LDL cholesterol and increases high-density lipoprotein (HDL — "good") cholesterol.16
Controlling Blood Sugar
The anti-diabetic properties of tea catechins have a long history in number of ancient folk medicine traditions, especially the Chinese. United States Department of Agriculture research has confirmed the health benefits of green tea, demonstrating that, like its two-pronged attack against fat, tea also takes on blood sugar from two different directions. First, it helps control blood sugar indirectly by enhancing insulin activity (in vitro) by more than 15 fold.17
Second, green tea catechins can also directly suppress blood sugar levels. When humans in a clinical trial ingested tea catechins (200 mg — 500 mg) before consuming 50 g of starch (which is converted to glucose by digestive enzymes), glucose production was suppressed, apparently because the catechins inhibited the enzyme action. It has also been found that green tea catechins markedly suppress the uptake of glucose via the intestines for transfer to the bloodstream.17
Some physicians recommend 4 to 6 cups of green tea a day; others recommend 8 to 10 cups (the average in Far Eastern societies is about 5 to 10 cups a day). That's a challenging amount for even tea lovers to imbibe on a daily basis. Fortunately, researchers have concluded that it's just as effective to take green tea extract supplements, which contain the equivalent amount of catechins in a couple of easy-to-swallow capsules.
- Arias E. United States Life Tables, 2002. National Vital Statistics Report.2004;53:1-39.
- The Rand Corporation. Obesity and Disability: The Shape of Things to Come. http://www.rand.org/publications/RB/RB9043/. 2004;Accessed Feb 9, 2005.
- Crespy V, Williamson G. A review of the health effects of green tea catechins inin-vivo animal models. J Nutr. 2004;134:3431S-3440S.
- Nagao T, Komine Y, Soga S, et al. Ingestion of a tea rich in catechins leads to a reduction in body fat and malondialdehyde-modified LDL in men. Am J Clin Nutr. 2005;81:122-129.
- Nakagawa K, Miyazawa T. Absorption and distribution of tea catechin, (-)-epigallocatechin-3-gallate, in the rat. J Nutr Sci Vitaminol (Tokyo). 1997;43:679-684.
- Nakayama M, Suzuki K, Toda M, Okubo S, Hara Y, Shimamura T. Inhibition of the infectivity of influenza virus by tea polyphenols. Antiviral Res. 1993;21:289-299.
- Hattori M, Kusumoto IT, Namba T, Ishigami T, Hara Y. Effect of tea polyphenols on glucan synthesis by glucosyltransferase from Streptococcus mutans. Chem Pharm Bull (Tokyo). 1990;38:717-720.
- Katiyar SK, Mukhtar H. Tea consumption and cancer. World Rev Nutr Diet. 1996;79:154-184.
- Henry JP, Stephens-Larson P. Reduction of chronic psychosocial hypertension in mice by decaffeinated tea. Hypertension. 1984;6:437-444.
- M C, K S, Kuttan R. Anti-diabetic activity of green tea polyphenols and their role in reducing oxidative stress in experimental diabetes. J Ethnopharmacol.2002;83:109-116.
- Dulloo AG, Seydoux J, Girardier L, Chantre P, Vandermander J. Green tea and thermogenesis: interactions between catechin-polyphenols, caffeine and sympathetic activity. Int J Obes Relat Metab Disord. 2000;24:252-258.
- Juhel C, Armand M, Pafumi Y, Rosier C, Vandermander J, Lairon D. Green tea extract (AR25®) inhibits lipolysis of triglycerides in gastric and duodenal medium in vitro. J Nutr Biochem. 2000;11:45-51.
- Dulloo AG, Duret C, Rohrer D, et al. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr. 1999;70:1040-1045.
- Chaudhari P, Hatwalne V. Effect of epicatechin on liver lipids of rats fed with choline deficient diet. Ind J Nutr Diet. 1977;14:136-139.
- Hirano R, Momiyama Y, Takahashi R, et al. Comparison of green tea intake in Japanese patients with and without angiographic coronary artery disease. Am J Cardiol. 2002;90:1150-1153.
- Yokozawa T, Nakagawa T, Kitani K. Antioxidative activity of green tea polyphenol in cholesterol-fed rats. J Agric Food Chem. 2002;50:3549-3552.
- Anderson RA, Polansky MM. Tea enhances insulin activity. J Agric Food Chem.2002;50:7182-7186.