Effect of Tea Consumption on Weight Loss and Obesity

Effect of tea Consumption on Weight Loss and Obesity

Worldwide, obesity has more than doubled since 1980 and has become an important global health issue. Excess weight and obesity are major risk factors for a number of chronic diseases, including diabetes, cardiovascular diseases and cancer. Therefore, any strategy for weight reduction would be very important. Research has demonstrated that tea consumption could contribute to weight loss and weight maintenance. A cup of tea, without milk or sugar, contain almost zero calories. Therefore, consumption of a cup of plain tea between main meals, instead of any other snacks, would significantly contribute to weight maintenance. Further, research has shown that tea consumption could contribute to weight reduction through many other mechanisms. These include reduced fat absorption from the diet, alterations in fat metabolism resulting in lower storage of fat and increased energy expenditure resulting in increased use of fat. Many human clinical studies and population studies, involving large numbers of individuals, also have confirmed that tea consumption contributes to reduced obesity and weight maintenance.

Excess weight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health. Obesity is measured using the body mass index (BMI), a person’s weight (in kilograms) divided by the square of his or her height (in metres). A person with a BMI of 30 or more is generally considered obese. A person with a BMI equal to or more than 25 is considered overweight.

Excess weight and obesity are major risk factors for a number of chronic diseases, including diabetes, cardiovascular diseases and cancer. Worldwide, obesity has more than doubled since 1980. In 2014, more than 1.9 billion adults were overweight and over 600 million of them were obese. Total overweight population was 39% of the adult population and 13% of the total population were obese. Once considered a problem only in high income countries, Excess weight and obesity are now dramatically on the rise in low and middle income countries, particularly in urban areas.

Obesity among children is also increasing at an alarming rate. According to WHO in 2013, 42 million infants and young children were overweight or obese globally. The rate of increase is 30% higher in low and middle income countries, than that of developed countries. If current trends continue 70 million young children will be overweight or obese by 2025.

The fundamental cause of obesity and excess weight is an energy imbalance between calories consumed and calories used. Globally, there has been an increased intake of energy-dense foods that are high in fat, accompanied by a drift towards physical inactivity, due to the increasingly sedentary nature of many forms of work, changing modes of transportation, and increasing urbanization. These have contributed to obesity.

Raised BMI is a major risk factor for noncommunicable diseases (NCD’s) such as cardiovascular diseases (mainly heart disease and stroke), diabetes, cancer and musculo-skeletal disorders, such as osteoarthritis, which is a highly disabling degenerative disease of the joints.

The risk for these NCD’s increases, with increases in BMI.

Childhood obesity is associated with a higher propensity to obesity, premature death and disability in adulthood. But in addition to increased future risks, obese children experience breathing difficulties, increased risk of fractures, hypertension, early signs of cardiovascular disease, insulin resistance and psychological effects.1, 2

The role of tea consumption on obesity and weight loss has been extensively studied since 1900s. Polyphenols and caffeine in tea have been identified as responsible for the prevention of obesity and the interaction between these compounds also has been studied.

Mechanisms of Weight Reduction by Components of Tea

A cup of tea, without milk or sugar, contain almost zero calories (see chapter 2 for details). Therefore, when a person has a yearning to have a snack between main meals, if a cup of plain tea

is consumed, it would significantly contribute to weight maintenance. Habit of consuming tea instead of snacks could be developed over time by choosing a high quality tea according to taste preferences.

Research has shown that tea consumption could contribute to the weight reduction through several other mechanisms too.

Absorption of Nutrients from the Digestive Tract

Fat in the diet is present as triglycerides which cannot be absorbed directly from the digestive tract. Triglycerides are first digested, or broken down, to fatty acids by an enzyme called lipase, secreted by the pancreas. Fatty acids are then absorbed from the digestive tract and circulated through the blood stream. Several research studies have shown that tea polyphenols could inhibit the pancreatic lipase enzyme and reduce the fatty acid absorption.3, 4

Microorganisms in the Digestive Tract and Fat Absorption

Large populations of microorganisms that live in the digestive tract also help in the digestion and absorption of fat and other nutrients. Research studies have shown that tea consumption could alter the populations of these microorganisms. Tea polyphenols could reduce the microorganisms which contribute to digestion and absorption of fat, thus reducing absorption of fat from the digestive tract. 5, 6

Effect of Tea on Fat Metabolism in the Human Body

A complicated signalling system and enzymes control the synthesis of fat, usage of fat and storage of fat in the human body. Research studies have shown that tea polyphenols could interfere with this signalling mechanism, resulting in a reduction of synthesis and storage of fat while increasing the breakdown of fat. These research studies have demonstrated that this mechanism induced by tea polyphenols significantly contributes to weight reduction in humans. 6, 7

Effect of Tea on Energy Expenditure

The stimulating effect of tea is due to caffeine which acts on the human Central Nervous System (CNS). Research has found that in addition to the stimulation effect, caffeine could also increase the energy expenditure in the body. Tea polyphenols also contribute to the increased energy expenditure by synergistically acting with caffeine. This will result in increased use of energy, or burning more calories, after a cup of tea, which contributes to weight reduction. However, research studies carried out so far indicate that the contribution of this mechanism to weight reduction is relatively low compared to the above two mechanisms.8

Population Studies

Many human clinical studies have been conducted to examine the effect of tea consumption on obesity. These studies have shown that tea consumption contributes to weight reduction and reduces the risk of obesity. Early studies have established that tea and polyphenolic extracts from tea have the ability to reduce body weight and body fat.

In 2005 a study had been carried out in Tokyo, using 38 healthy males, aged 24 - 46 years, whose body weights ranged from normal to overweight. They were given a tea extract containing 690 mg of catechins per day for 12 weeks and compared with a control group consuming a low catechin extract (22 mg per day). After the 12 week period, body weight, body mass index (BMI), waist circumference, body fat mass and subcutaneous fat area were significantly lower in the high catechin group compared to low catechin control group.9

A similar study had been carried out to find the effect of high catechin intake on obese or nearobese Japanese children. One group was given 576 mg of catechins per day and compared with a low catechin group (75 mg per day) after 24 weeks. In addition to assessing the effect on weight reduction, cardiovascular risk factors were also monitored. It was concluded that ingestion of catechin-rich beverages ameliorates serious obesity and cardiovascular disease risk factors.10

Another interesting area of research was whether tea has any additive effect on exercise induced weight loss programs. In such a study carried out in US, 132 overweight or obese adult participants were randomly assigned to receive tea containing 625 mg of catechins with 39 mg caffeine or a control beverage (39 mg caffeine, no catechins) for 12 weeks. Findings of the study was that

tea catechin consumption enhances exerciseinduced reduction in abdominal fat. Further, this experiment proves that catechins in the absence of caffeine also could contribute to the reduction of fat.11

Another similar research had focused on the effect of tea on body fat reduction in women. This study investigated the effects of green tea consumption, combined with exercise program on body composition in women, who were overweight or obese. Thirty six women were divided into four groups (group 1 green tea; group 2 placebo; group 3 green tea plus resistance training; group 4 placebo plus resistance training). After eight weeks the groups receiving tea had reduced body fat and waist circumferences compared to respective control group. Further, the third group receiving tea and resistance training had the highest increase in lean body mass (body weight minus body fat) and muscle strength.12

Population studies using large number of individuals also have proven the effect of tea on weight reduction.

A study carried out in US, examined the association between tea consumption and weight status of a sample of 6,472 adults who participated in the 2003 - 2006 National Health and Nutrition Examination Surveys (NHANES). According to the results, hot tea consumption was inversely associated with obesity and tea consumers had lower mean waist circumference and lower body mass indices. However, for iced tea consumers, the association was reversed and increased iced tea consumption was associated with higher body mass index and greater waist circumference.

Most of the iced teas available in the market contain significantly low polyphenolic content compared to a hot cup of tea. Further, most iced teas were sweetened with high amounts of sugar. Findings of this research study demonstrate that the health benefits of tea consumption may occur only when tea is consumed in the traditional manner, and iced tea may provide no health benefit to consumers, especially when sweetened.13

A research study carried out in Netherlands investigated the association between flavonoid intake and body mass index, over a 14 year period, in 4280 individuals aged 55 - 69 years. Findings revealed that body mass index of women with the lowest intake of flavonols/flavones and total catechins increased by 0.95 and 0.77, respectively, after 14 years. Women with the highest intake of total flavonols/flavones and total catechins experienced a significantly lower increase in BMI of 0.40 and 0.31, respectively. The conclusion was that flavonoid and catechin intake may contribute to maintaining body weight in the general female population.14

Results from the research studies on weight loss by green tea had been reviewed by scientists in the Maastricht University, Netherlands. Results of 11 studies reviewed revealed that Catechins or catechin-caffeine mixture have a positive effect on weight loss and weight maintenance.15

Conclusions

Tea, without milk and sugar, contains almost zero calories. Therefore, consumption of a plain cup of tea between main meals instead of snacks could significantly contribute to maintain weight and weight reduction. Flavonoids in tea assists weight maintenance through several mechanisms. These include reduced fat absorption from the digestive tract, increased energy expenditure by increasing the rate of metabolism and also alterations in fat metabolism resulting in reduced synthesis and storage. Population studies involving large numbers of individuals also indicate that regular tea consumption has a positive effect on weight maintenance. Further, research on consumption of tea while undergoing an exercise regime for weight reduction had shown synergistic effects on weight maintenance. • Obesity and excess weight have become a significant global problem as it could lead to non-communicable diseases such as heart disease, stroke, diabetes and cancer. • A cup of tea, without milk and sugar, contains almost zero calories. Therefore, a cup of plain tea instead of any other food could significantly contribute to weight reduction and weight maintenance. • Tea components, especially flavonoids, could contribute to weight reduction by reducing fat absorption from the digestive tract and altering the fat metabolism in the human body. • Research on individuals following an exercise regime for weight reduction has shown that tea consumption has an additive effect on the weight loss. • Human clinical trials and also population studies in several countries involving large numbers of individuals, had demonstrated that tea consumption could contribute to weight reduction and weight maintenance.

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