A study conducted by the University of Western Ontario recently found that green tea can trick your brain into thinking it is burning more calories than it actually is, allowing you to burn up to 50 extra calories a day. If you’re drinking three to four cups of green tea every day, this could lead to around 10 pounds lost over the course of a year.
Study in rats shows that green tea and caffeine supplementation prevents diet-induced body fat accumulation via carbohydrate metabolism…
The Journal of Nutrition”Evidence is limited as to the usefulness of green tea catechins for weight loss,” comment Solomon et al. “Although a handful of studies have shown promising results, the majority have proven inconclusive.”
To investigate the effects of green tea and caffeine supplementation on weight loss, Solomon et al. assigned obese adults (average BMI = 36 kg/m2 ) to one of four groups for six months: control (no intervention), low-dose green tea extract (150 mg of catechins and 50 mg of caffeine), high-dose green tea extract (450 mg of catechins and 100 mg of caffeine) or a placebo. The extracts were administered in capsules, twice daily with meals.
The low dose of green tea was about what you would get from drinking three to four cups a day; the high dose is comparable to 6-7 cups.
The participants were not asked to follow any specific diet, although they were counseled to restrict their calorie intake by 250-500 kcal/day and increase physical activity.
In addition, the researchers measured body weight, waist circumference, fat mass and percentage of body fat at baseline and after three and six months. After six months, both green tea groups had reduced their waist circumference and body fat mass compared to the control group. The high-dose green tea extract also resulted in a greater reduction of body fat percentage than the low dose. However, neither dose resulted in significant weight loss at any time point compared to baseline.
The researchers acknowledge that participants did not receive dietary counseling until after three months, when the participants’ waist circumferences had started to decrease. Hence, they do not know whether more weight loss might have been observed if dietary counseling was given from the start. In addition, only four capsules were taken twice a day and thus compliance may have been an issue.
The authors conclude that “green tea extract and caffeine supplementation for 6 months may prevent body fat accumulation in healthy adult men and women at risk for obesity.”
The authors also highlight a few study limitations: only healthy adults were included; no control group was used to show that any significant weight loss would have occurred without supplementation; participants consumed a small number of capsules twice daily, which may not be enough to influence weight loss; and dietary counseling was delayed until after three months, when the study participants’ waist circumferences began to decrease.
“Weight management products are often sold with unsubstantiated claims that they aid weight loss,” write the authors. “Green tea is widely marketed as a weight loss supplement, although evidence of its effectiveness has been limited.”
In a Perspective article published in JAMA, Melinda Manore concludes that “although there is encouraging evidence of weight loss with combined green tea and caffeine supplement use, further randomised clinical trials are warranted before green tea can be recommended routinely for use as an obesity intervention.”
“More information on the potential adverse effects of long-term green tea consumption and how much weight loss can be attributed to green tea is needed before it is ready for prime time as a weight-loss product,” she adds.
“Whether the effects of caffeine, green tea catechins, or both are responsible for [weight loss], these results show that adverse side effects do not occur with green tea extract consumption up to at least 900 mg per day in healthy adults, and thus the risks of supplementation are low,” Solomon states.
She concludes that “combining green tea extract and caffeine is a safe weight-loss strategy, even without lifestyle intervention.”