How Green Tea Targets Fat and Protects Muscles During Weight Loss

Green tea is an ancient beverage known for its medicinal and antioxidant benefits. It has been extensively researched for its positive effects on metabolic diseases like obesity and type 2 diabetes. Recent FAPESP-funded investigations (19/10616-5, 21/08498-4, and 23/11295-3) have increased our understanding of the mechanisms of action of this infusion, revealing that green tea therapy lowered weight while dramatically improving glucose sensitivity and insulin resistance in obese mice (1^✔ ✔Trusted Source
Does Green Tea Ameliorate Obesity in Mice Kept at Thermoneutrality by Modulating Skeletal Muscle Metabolism?

Go to source). These findings support the beverage's potential role as an adjuvant in the treatment of obesity in humans. Rosemari Otton led studies from the Interdisciplinary Graduate Program in Health Sciences at Cruzeiro do Sul University in São Paulo, Brazil. The scientist, who has spent more than 15 years researching green tea, says her original motivation stemmed from curiosity about the truth behind the popular assumption that the drink aids in weight loss. The findings of her most recent work were published in the journal Cell Biochemistry and Function.

Effects of Green Tea on Obesity

To investigate the effects of green tea on obesity, the researchers fed mice a high-calorie meal rich in fat as well as a "cafeteria diet," which is similar to the Western diet.

Following the initial phase, the animals participated in the green tea trial for an additional 12 weeks. During this time, they maintained their high-calorie diet, but some of them began receiving standardized green tea extract at a dose of 500 mg per kilogram of body weight, given intragastrically (by gavage).

"It's a strategy that ensures everyone gets the exact dose we want to examine. "If we put it in water, for example, we wouldn't know how much the animal ingested," explains the researcher. For humans, this amount is similar to drinking three cups of green tea per day.

Using Green Tea Extract For Weight Loss

According to the researcher, not all commercial green tea satisfies the required quality criteria. "Pre-made tea bags may not always ensure the quantity or quality of the compounds. The ideal for intake would be to utilize standardized green tea extract, such as those available at compounding pharmacies. "This is a concentrated way of using the plant, with a guarantee of the presence of flavonoids, which are health-beneficial compounds found in the green tea plant," Otton says.

The study had one methodological difference: the controlled room temperature. The animals were kept in a temperature-neutral environment (28 °C) throughout the trial. Animal facilities typically maintain an average temperature of 22 °C, which is considered chronic cold for mice. "Excessive cold triggers compensatory regulatory mechanisms in animals' bodies, causing them to expend extra energy to stay warm. This can obscure the true effects of any substance," explains the researcher. "If the animals are in a cooler environment, the tea's effect is augmented by the activation of energy expenditure caused by the cold. But by remaining thermoneutral, we were able to observe the effects of green tea in a 'clean' manner, free of environmental disturbance," she explains.

A previous study, published in August 2022 in the European Journal of Nutrition, indicated that obese mice treated with green tea lost up to 30% of their total weight (2^✔ ✔Trusted Source
Effects of Different Green Teas on Obesity and Non-Alcoholic Fatty Liver Disease Induced by a High-Fat Diet in Mice

Go to source). "Losing 5% to 10% of one's body weight is a significant amount. So this result in animals is very significant," adds the professor.

Green Tea Reduces Muscle Atrophy During Weight Loss

Another notable aspect of the most recent study was the preservation of muscle morphology. Obesity normally reduces muscle fiber diameter, but green tea reduces muscular atrophy. "Fiber diameter is one method for assessing muscle function. If it rises, we have more active muscle components. Green tea was able to maintain this width, demonstrating that it protects muscle from the negative effects of fat," Otton says.

In addition to morphological data, the researchers assessed the expression of genes involved in glucose metabolism. Green tea treatment enhanced the expression of genes involved in glucose absorption and usage in muscles, including Insr, Irs1, Glut4, Hk1, and Pi3k. Lactate dehydrogenase (LDH), a key enzyme in glucose metabolism, was also recovered.

Green Tea Targets Extra Body Fat

According to Otton, there is evidence that green tea does not influence the weight of lean animals, implying that it targets extra body fat. "It causes fat animals to lose weight while keeping lean animals at the same weight. This demonstrates that the tea appears to require an environment rich in nutrients to function, supporting the concept that it acts directly on fat cells."

The team also looked into how the chemicals worked in isolation. "Green tea is a complex matrix containing dozens of bioactive compounds." We attempted to separate these chemicals and examine their effects separately, but the combined extract was always more effective. "There is a synergy between the compounds that we cannot replicate when they are isolated," she explains.

According to the expert, one explanation for how green tea affects obesity involves adiponectin, a protein generated by adipocytes with anti-inflammatory and metabolic control capabilities. "We did a study using adiponectin-knockout mice, who do not manufacture it. Green tea did not have any effect on these animals. This indicates that adiponectin plays an important role in the tea's mechanism of action."

Why Long-Term Green Tea Consumption Matters More Than Quick Fixes

Despite the hopeful results of the mice study, Otton notes that a safe and effective dose of green tea for humans has yet to be determined. This is mostly due to the variety of the extracts and the fact that each person behaves uniquely. "The ideal is chronic consumption, as observed in Asian countries. In Japan, for example, people drink green tea every day of their life, and obesity rates are low. But this isn't the same as sipping tea for five months and expecting amazing weight loss results," she muses.

The researcher contends that natural and accessible remedies should gain traction in the fight against obesity, particularly as alternatives to costly pharmaceuticals that frequently cause negative effects. "The goal is to produce safe, natural, effective, and high-quality substances. The Camellia sinensis plant provides this. We're still researching all of the components involved, but there's no denying that green tea, as a plant matrix rich in flavonoids, has significant medicinal promise."

The researcher argues that science strives to offer practical solutions. "What we observe in animals does not necessarily translate into human behavior. However, if we wish to use this translation in real life, we must consider all of the factors, including ambient temperature. These procedures strengthen the validity of our data. We don't have all the answers yet, but we're getting closer."

References:

1. Does Green Tea Ameliorate Obesity in Mice Kept at Thermoneutrality by Modulating Skeletal Muscle Metabolism? - (https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/cbf.70094)
2. Effects of Different Green Teas on Obesity and Non-Alcoholic Fatty Liver Disease Induced by a High-Fat Diet in Mice - (https://pubmed.ncbi.nlm.nih.gov/35811941/)

Source-Medindia