The anti-obesity effects of green tea in human intervention and basic molecular studies

Abstract

Many researchers have reported that obesity is a major risk factor for diabetes, cardiovascular diseases, several forms of cancer (such as breast, colon and prostate), pulmonary, osteoarticular and metabolic diseases in the past decades. Recently, the hypolipidemic and anti-obesity effects of green tea in animals and humans have slowly become a hot topic in nutritional and food science research. This review will up-date the information of the anti-obesity effects of green tea in human intervention and animal studies. During recent years, an increasing number of clinical trials have confirmed the beneficial effects of green tea on obesity. However, the optimal dose has not yet been established owing to the very different results from studies with a similar design, which may be caused by differences in the extent of obesity, dietary intake, physical activity intensity, the strength of subjects' compliance to test instruction, the genetic background of populations, body composition and dietary habits. Therefore, further investigations on a larger scale and with longer periods of observation and tighter controls are needed to define optimal doses in subjects with varying degrees of metabolic risk factors and to determine differences in beneficial effects among diverse populations. Moreover, data from laboratory studies have shown that green tea has important roles in fat metabolism by reducing food intake, interrupting lipid emulsification and absorption, suppressing adipogenesis and lipid synthesis and increasing energy expenditure via thermogenesis, fat oxidation and fecal lipid excretion. However, the exact molecular mechanisms remain elusive.

Does green tea extract enhance the anti‐inflammatory effects of exercise on fat loss?

“…Green tea, made from the leaves of Camellia sinensis , contains catechins (such as epigallocatechin‐3‐gallate) as well as quercetin, thearubigins, theaflavins, theanine, caffeine, chlorogenic acid and gallic acid . The effect of green tea on obesity and body weight loss has been extensively described in nutritional research . Although considerable research has been conducted on the effects of green tea on obesity and its complications, the effectiveness of green tea on weight loss is unclear …”

“…Multiple mechanisms have been proposed for the weight loss caused by green tea. These mechanisms include reducing food intake, interrupting lipid emulsification and absorption, suppressing adipogenesis and lipid synthesis and increasing energy expenditure via thermogenesis, fat oxidation and faecal lipid excretion . Additionally, previous clinical and laboratory studies suggest that dietary polyphenols have anti‐inflammatory effects .…”

The safety of green tea extract supplementation in postmenopausal women at risk for breast cancer: results of the Minnesota Green Tea Trial

“…Green tea is one of the world’s most popular beverages and has been associated with a number of health benefits, including prevention of obesity (Huang et al 2014), cardiovascular disease (Hodgson and Croft 2010), neurodegenerative diseases (Andrade and Assuncao 2012), and several site-specific cancers, including breast cancer (Yuan 2013). These beneficial effects are primarily attributed to the chemical properties of tea catechins, of which (-)-epigallocatechin-3-gallate (EGCG) is the most abundant (50-75% of total catechin content) and biologically active form (Kao, Hiipakka, Liao 2000).…”

Dietary Strategies Implicated in the Prevention and Treatment of Metabolic Syndrome

“…The mechanisms of action suggested to explain these beneficial effects on body weight are: increasing energy expenditure and fat oxidation, and reducing fat absorption [177]. It is thought that energy expenditure is enhanced by catechol- O -methyltransferase and phosphodiesterase inhibition, which stimulates the sympathetic nervous system causing an activation of the brown adipose tissue [178].…”