I am a 26 year old lean person. I think I have less weight than the normal person of the same age. I know about the use of green tea for loosing weight. I want to ask if I start drinking green tea, will it reduce my weight? And, can it really cause another side effects like acidity and iron deficiency?
Green tea contains caffeine, that has been proven to increase your metabolic rate (http://ajcn.nutrition.org/content/33/5/989.short) and to help with the release of fat from your body fat reserves (http://ajcn.nutrition.org/content/79/1/40.abstract) - but bear in mind that you still have to burn away those released fatty acids, or they will simply return to where they came from. So the first thing you need to decide, is whether or not you're even ok with consuming caffeine - which is a substance classified as a drug.
Another study (http://ajcn.nutrition.org/content/70/6/1040.short) has confirmed green tea has an additional effect on the rate at which we burn our body fat when compared to caffeine alone. The chemicals in green tea that are believed to boost the calorie-burn rate are called polyphenols. All-in-all they measured a 4% increase in a 24-hour energy expenditure...so if you normally spend 2000 calories throughout the day, you can count on green tea to add another 80 to that (roughly).
And as far as the safety is concerned, some cases of liver damage have been reported (http://www.leanhigh.com/weight-loss/supplement-reviews/can-green-tea-help-you-lose-weight-without-damaging-your-liver), but the evidence on that does not seem to be conclusive.
Science Based Medicine did a review of the literature along with another 14 "super-foods" espoused by Dr. Oz.
Dr. Oz claims: Contains EGCG (epigallocatechin gallate) that “increases the hormone responsible for making you feel satiated”; “can help prevent storage of excess fat”, “improve your appetite-regulating hormones” and will change how your body handles cravings and metabolizes food.
Reality check: Green tea is brewed from the non-fermented leaves of the Camellia sinensis plant. It contains a number of biologically active ingredients which are believed (though not established) to be a panacea for nearly everything. With respect to weight loss, a systematic review of green tea for obesity concluded that green tea has no meaningful effects, and a Cochrane review concluded that any effects are “not likely to be clinically important”.