Does Green Tea Accelerate Weight Loss?
Green tea is a beverage made from the unfermented, lightly steamed leaves of the tea plant, Camellia sinensis. It has been one of the most popular beverages in Asia since its discovery some 5000 years ago by Shen Nung, the emperor of China whose name meant “Divine Farmer.” Shen Nung taught his subjects to cultivate grain, developed acupuncture and personally tasted hundreds of herbs to discover their healthful qualities. Some of the herbs were poisonous, so it was fortunate that he discovered the detoxifying properties of green tea. Since the emperor’s reign, green tea has been shown to have a broad range of healthful properties, leading a pharmacist of the Tang Dynasty to call it “the medicine for all diseases.” 
Green tea’s ability to eliminate fat was first noted by Wang Ang, a Chinese pharmacist born in 1615. Western medicine’s clinical evaluation of green tea’s anti-obesity properties was not begun until more than three centuries later, in 1995. Since that time, evidence has been collected proving green tea’s ability to guard against cancer, heart disease, type 2 diabetes and obesity.
Obesity is considered by the CDC (Centers for Disease Control) to be an epidemic which now afflicts one out of every four Americans and costs the United States over $100 billion in medical spending each year due to resultant health problems. The condition is caused by an imbalance between energy intake and energy expenditure. In order tolose weight, a negative energy balance must be achieved, either through reduced caloric intake or increased expenditure of energy.
How Does Green Tea Promote Weight Loss?
Camilla sinensis contains a type of flavonoid called a catechin, which has been shown in scientific studies to be the active ingredient central to green tea’s weight loss effect. Catechins are altered by heat. In order to be effective, green tea must be steeped in water that is hot, but not boiling.
A human interventional study is an experiment performed on two groups of human subjects that are subjected to different diets. One such study was conducted on 240 obese Japanese men in 2005. The subjects, who drank catechin-enriched green tea once daily for 12 weeks, showed a significant decrease in body weight, visceral fat, waist circumference and LDL (bad) cholesterol . Other studies have produced similar results. The studies’ subjects did not alter their customary dietary intake or level of physical activity.
An epidemiological study is conducted on human populations with the goal of linking human health effects to a specific cause. In 2003, one such study was conducted on 1103 adults in Taiwan with the objective of discovering the relationship between habitual tea consumption and human body fat distribution. The findings showed that habitual tea drinkers, defined as those who consumed tea at least once a week for longer than ten years, had slimmer waistlines and 20% less body fat than people who did not drink tea on a regular basis .
Observational studies note effects in the world without manipulating them. Longitudinal studies are observational studies that take place over a long period of time. Cohort studies are composed of people who share common characteristics or experiences. A longitudinal cohort study in The Netherlands analyzed data collected on 4280 adults over a 14-year period and discovered an inverse relationship between BMI (body mass index) and catechin consumption .
These findings suggest that consumption of green tea that contains a high level of catechins can promote weight loss.
Green Tea Prevents Fat Storage
The size and quantity of a person’s adipocytes (fat cells) will determine that person’s ability to store body fat. If there are few fat cells, fat storage potential is limited. Adipocytes are created by pre-adipocytes via a process known as adipogenesis.
The constant generation of adipocytes is necessary for adipose tissue formation, which allows the body to store energy as fat. Fat cells are constantly dying and new ones are generated to take their place.
Cell studies have demonstrated that green tea inhibits adipogenesis, preventing new fat cells from being generated . It appears that the daily consumption of green tea results in fewer fat cells and a subsequent diminished capacity for fat storage.
Green Tea Increases Energy Expenditure
The body expends energy even during sleep. The number of calories burned while inactive is known as the Resting Energy Expenditure or REE. It is also known as the basal metabolic rate. A portion of REE is dedicated to heat production, or thermogenesis, which maintains constant body temperature. Thermogenic foods are substances that can increase the body’s heat production, thereby causing the body to utilize more calories while in a state of rest.
A 1999 French interventional study had the objective of determining whether green tea extract could increase REE in human subjects . In three separate tests, 10 healthy male subjects were administered a capsule at each meal. In the first test, the capsule contained green tea extract. The next occasion tested caffeine and finally, a placebo. The results showed a 4% increase in REE during the green tea extract test. There was no significant basal metabolism rate increase with either caffeine or the placebo.
In a similar study conducted at Switzerland’s Lausanne University School of Medicine, 31 male and female subjects were administered 3 servings daily of a green tea beverage. After 3 days, REE was measured and was found to have increased by 4 to 8%. This equates to an additional 100 calories per day burned at the basal metabolic rate. The findings suggest that green tea can assist in weight control by increasing REE.
Green Tea Locks In Weight Loss
As a person loses weight, there is a reduction in the basal metabolic rate (BMR). This is because REE rises in conjunction with body weight.
The weight loss plateau that dieters soon encounter after initially losing pounds is due to this decrease in BMR. This also accounts for the difficulty dieters experience in maintaining lower weight once the pounds have been shed. Studies have shown that daily consumption of green tea enables weight maintenance by increasing the basal metabolic rate.
Green Tea Inhibits Fat Absorption From Food
In order to be absorbed by the intestines, lipids (the fat content of food) must undergo two transformations:
1. Emulsification by bile salts. Lipids are not water-soluble and therefore cannot be absorbed by the intestines until they have been emulsified. Bile salts bind fat molecules and turn them into micelles. Micelles are water-soluble domes that provide transport of lipids into the bloodstream.
2. Digestion by lipases. Lipases are enzymes secreted in the stomach and small intestine that break down lipids.
The catechins in green tea decrease lipid absorption in the intestines . The most abundant and powerful catechin found in green tea is EGCG, which inhibits the formation of micelles and blocks lipase in the stomach and the pancreas. By inhibiting lipid absorption, green tea decreases the caloric value of fatty foods. The inhibition of fat absorption becomes evident as excess lipid excretion.
Green Tea Hinders The Creation Of Fat
Food is composed of three macronutrients: protein, carbohydrates and fats. When eaten, these macronutrients are transformed into micromolecules to enable absorption by the intestines. Proteins are broken down into amino acids; carbohydrates are turned into sugar; and dismantled fats become fatty acids. Once these micromolecules are absorbed, they are put to use for a variety of biological processes.
Any calories consumed beyond what is used immediately for energy will be turned into fat (because adipocytes can only store fat) through a process called lipogenesis, which is performed by lipogenic enzymes. The activity of these enzymes and the subsequent synthesis and storage of fat is hindered by green tea .
Recent scientific studies have proven what the ancient world already knew – that green tea confers many health benefits. Through several mechanisms – inhibiting fat cell formation, blocking lipid storage and increasing the basal metabolic rate – green tea initiates weight loss, maintains weight loss and prevents obesity, especially when combined with a healthy diet and exercise regimen. However, even when there is no significant change in lifestyle, catechins still promote weight loss by enhancing REE, resulting in a ‘free burn’ of about 100 calories per day. Now that obesity has reached epidemic proportions, this ancient remedy has more relevance than ever before.