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From a health perspective it may be good that green tea does not contain all-too much caffeine. From a fat loss perspective, it clearly lacks caffeine.

When it comes to dietary supplements, people like to pay tons of money for unproven ingredients with funky names and dubious or non-existent safety profiles; agents that have been scientifically proven to work, are save and cheap, on the other hand, are non-sellers or at least considered to be non-effective.

Obviously, I cannot really explain why that is the case (I suspect it is because people effect drug-like effects without drug-like side-effects from supps and are thus always on the lookout for the "next big"... hoax), I can tell you, though, that a recent study that is going to be published in one of the upcoming issues of the Journal of Strength and Conditioning Research (Jo. 2015) shows that caffeine and green tea, two supplements that belong to the previously described category, are everything but useless.
In said study, Edward Jo and colleagues investigated the effects of a caffeine + green tea polyphenol mix (250mg caffeine + 400mg of a green tea extract with 50% EGCG and 5mg of caffeine per serving) on (a) metabolic rate and fat oxidation at rest, as well as following a bout of sprint interval exercise (SIE) and (b) the performance during a standardized sprint-interval test.

The study was a double-blind, randomized, placebo-controlled, crossover study that involvd 12 subjects (male: n=11; female:1 n=1) whose antroprometric data, i.e "body mass=76.1±2.2 kg; height= 169.8±1.6 cm; BMI= 22.7±3.0 kg/m2; body fat %= 21.6±2.0% [DXA data]" (Jo. 2015), already tell you that they were healthy recreationally active, but not necessarily athletic (it may be worth mentioning that they were relatively stim-naive with an intake of < 201mg of caffeine per day).

Figure 1: Energy expenditure (kcal/h) and fat oxidation (g/day) measure before (at rest) and during (during SIE) the sprint interval exercise 10 and 55 minutes after the ingestion of caffeine + GTE or placebo (Jo. 2015).

During the two testing sessions at the Human Performance Research Laboratory of the California State Polytechnic University, the subjects' resting energy expenditure (REE) was measured for 45 minutes starting 10 minutes after the ingestion of the aforementioned caffeine + polyphenol mix - a mix that was consumed on an empty stomach after an 8-h overnight fast (don't be fooled by the way the scientists report their data in "g/day" and kcal/day - I changed the latter, already but the values for fat in g would have become to small - we are talking about 45 + 30 min and a 24h measurement here).
After the initial 45-minutes, during which the subjects' resting energy expenditure had been measured, the subjects were placed on a computer-integrated cycle ergometer on which they performed a standardized 30 minute sprint interval exercise (SIE) protocol., the scientists describe as follows:

"Sprint-Interval Exercise Protocol. The SIE protocol was performed on the Velotron DynaFit Pro cycle ergometer and comprised of four 30-second maximal effort intervals each separated by 5 minutes of low-intensity, constant workload cycling (Figure 2). First, the ergometer was properly adjusted for the subject. Adjustment specifications for each subject was recorded during their familiarization visit and repeated for all experimental trials. Subjects initiated the SIE protocol with a 5-minute interval of low-intensity cycling at a constant workload of 75W. Immediately after, subjects cycled with maximal effort for 30 seconds against an added resistance that is 7.5% of BW for males and 7.2% for females. These two intervals were repeated three additional times. After the last 30-second sprint interval, the subjects performed an additional low-intensity 75W interval plus an extra 3 minutes of cool-down at a constant workload of 30W. The total duration of the SIE protocol was 30 minutes" (Jo. 2015).

A workout that had little effect on the effect of the caffeine + green tea combo which did, as you can see, when you compare the "at rest" and "during SIE" values in Figure 1, increase the energy at rest and during sprint interval training to a similar extent. More specifically, the increase in energy expenditure and fat oxidation was - within the margin of inter-individual variability - in the range of +10% during both conditions.

Figure 2: Illustration of the sprint interval exercise test performed 55 min after ingesting the supplement (Jo. 2015).

In view of the fact that we may safely assume that this effect should last for at least 2-3h this can be a practically relevant effect if it is complemented by a reduced energy intake and a caloric deficit. If the latter is not present, even the extremest increases in fat oxidation and energy expenditure will fizzle out and be as irrelevant as the effect of the caffeine + green tea combination on exercise average and peak power (W) during the sprint training, Jo et al. observed in their study... and "Yes!", that is disappointing, but in view of the low dose of caffeine and the non-existent effects of green tea on performance during a test like this not really surprising.
References:

• Jo et al. "Dietary Caffeine And Polyphenol Supplementation Enhances Overall Metabolic Rate And Lipid Oxidation At Rest And After A Bout Of Sprint Interval Exercise." Journal of Strength & Conditioning Research: Post Acceptance: November 23, 2015. doi: 10.1519/JSC.0000000000001277

Green tea smoothies - If you don't want to waste more than 60% of green tea's precious EGCG content, you better don't blend it with too much other stuff

While the previously discussed effect of milk on the bioavailability of the polyphenols from green tea (the beverage) is probably negligible, a recent study from the University of Cranberra suggests that the inhibitory effect of food on the absorption of the major catechins in green tea may be significant enough to say that it's important to take them away from food.

To assess the effects of different food matrices on the bioavailability of capsulated green tea supplements, Naumovski et al. came up with a systemic absorption test healthy fasted humans.
On three separate days, their four healthy, normal-weight participants (3 males and 1 female aged 18-64 years) had to come to the clinic fasted (10h of fasting minimum). At the laboratory, the participants ingested 500 mg of EGCG given either as

• two capsules (2 × 250 mg) with 100 mL of water only (without any breakfast), 
• two capsules (2 × 250 mg) provided with 50 g of Special K breakfast cereal (Kellogg’s, Pagewood, NSW, Australia), or
• in form of 200 mL of full cream milk or EGCG (500 mg) that had been incorporated in 200 g of strawberry sorbet 

All treatments were ingested within 5 min and no additional food was taken for a further 4 h. All participants were provided with a lunch and a drink three hours after ingesting the EGCG, which consisted of a sandwich (bread, ham, cheese, tomato, lettuce) and 200 mL of orange juice.
To determine the effect of the different food items on the absorption of EGCG, the scientists used blood samples that were taken before the ingestion of the capsules / sorbet, 30min, 1h, 2h, 3h, 5h, and 8h afterwards by the means of a previously installed intravenous catheter (BD, North Ryde, NSW, Australia).

Figure 1: The mean plasma EGCG concentration-time curves for the three different methods of oral delivery: capsules without breakfast (green), capsules with breakfast (purple) and strawberry sorbet (red). The values are means ± the standard error of the means for the four participants (n = 4 | Naumovski. 2015).

As the data in Figure 1 shows the amount of EGCG that actually made it into the blood of the study participants was significantly (and practically relevantly) reduced when the capsulse were ingested with food or the EGCG was incorporated into the sorbet.
References:

• Naumovski, Nenad, Barbara L. Blades, and Paul D. Roach. "Food Inhibits the Oral Bioavailability of the Major Green Tea Antioxidant Epigallocatechin Gallate in Humans." Antioxidants 4.2 (2015): 373-393.

Tea catechins (which can also be found in black and jasmin tea | see Figure 3) can help you keep particularly unhealthy abdominal fat (Després. 2012) at bay.

It is one thing to have in-vitro and rodent data that green tea can inhibit the digestion of dietary fat (reported previously in the waredownloadsoft Facebook News); it is another thing, however, to have a human study like the one Makoto Kobayashi and colleagues are about to publish in the peer-reviewed scientific journal Food & Function that shows that the "[i]ngestion of a green tea beverage enriched with catechins with a galloyl moiety (THEA-FLAN 90S) during a high-fat meal reduces body fat in moderately obese adults" (Kobayashi. 2015).

Ok, the abdominal fat loss does not, as the previous quote from the conclusion appears to suggest, occur instantly right after you've consumed your first tea w/ a single meal.
Rather than that, 124 subjects (two of the initially 126 subjects 2 dropped out for personal reasons unrelated to the trial), 53 men, 71 women, who consumed similar, albeit non-standardized diets (see Figure 1 | note: physical activity was also identical) and began the study with body fat levels of ca. 31-35% had to consume the previously mentioned tea beverage that contained tea catechins (250 mL with 215.3 mg green tea catechins containing 211.0 mg green tea catechins with a galloyl moiety) twice or three times daily during mealtimes for 12 weeks, before the significant reduction in body fat became visible.

Figure 1: Macronutrient composition (in g an % of energy) of the non-energy reduced diets the subjects consumed; the values in the left pie chart represent a group average of all three intervention groups. Since the data is based on food records with photographs, it is probably more reliable than in your average diet study (Kobayashi. 2015).

Now, in view of the fact that this is not the first study to demonstrate weight loss effects in overweight subjects consuming green tea or, as in most other studies, green tea extracts, the word "during" and thus the fact that the green tea beverage was consumed with at least two of the three meals per day should be highlighted as a specific feature of the study at hand that is highly relevant to its interpretation.

Figure 2: Detailed analysis of the rel. change in fat area in the abdominal depot of the subjects (Kobayashi. 2015)

It is after all the requirement that the green tea beverage had to be consumed with a (preferable high fat) meal that allows the authors to conclude that the significant fat loss Kobayashi et al. measured by the means of computer tomography predominantly in the abdominal area are the result of an inhibition or slowing of the intestinal fat absorption and thus warrant the conclusion that "the ingestion of green tea beverages enriched with CGM together with high-fat meals may be an effective strategy for reducing body fat in moderately obese adults" (Kobayashi. 2015) - an observation of which I would like to add that the underlying mechanism is not 100% certain.
The authors base their conclusion that it is "unlikely that absorbed green tea CGM leads to increased energy expenditure, followed by reduced abdominal body fat area" (Kobayashi. 2015) on two reasonable, but experimentally (in this study) not confirmed assumptions which are that little to no catechins actually made it into the bloodstream, because ...

1. the low caffeine content of the beverage limits the bioavailability of EGCG & co (caffeine enhances its bioavailability | Nakagawa. 2009) and
2. the ingestion of the beverage with a meal has been shown to significantly reduce the bioavailability of green tea catechins in comparison to the fasted state (Chow. 2005).

The assumption that its just a blockade of the digestion of fat becomes even more questionable, if you (re-)read my 2014 article on the carb blocking effects of tea... Well, eventually, though, you may argue that it does not matter if the reduction in abdominal fat was due to thermogenic effects, thermogenic and fat-blocking effects or, as the scientists believe, mediated exclusively an "inhibit[ion] or slowing [of the subjects'] intestinal fat absorption" (Kobayashi. 2015). And let's be honest, I guess you're right. What matters is that there were significant reduction ins abdominal fat (visceral, subcutaneous and total abdominal fat area). Reduction of which the data in Figure 2 tells you that ...

1. Table 1: Catechin composition of the test beverages.

   the fat loss in the abdominal area was dose dependent - even if the differences between the low and high dose group did not reach statistical significance (for the exact catechin composition see Table 1 on the right) - and that 
2. roughly 50% of the benefits were lost within only 5 weeks when the subjects stopped consuming the green tea beverage, even though their diet didn't change at all (in fact, they consumed minimally less energy in the withdrawal phase from week 12-17).

References:

• Bronner, W. E., and G. R. Beecher. "Method for determining the content of catechins in tea infusions by high-performance liquid chromatography." Journal of Chromatography A 805.1 (1998): 137-142.
• Chow, HH Sherry, et al. "Effects of dosing condition on the oral bioavailability of green tea catechins after single-dose administration of Polyphenon E in healthy individuals." Clinical Cancer Research 11.12 (2005): 4627-4633.
• Després, Jean-Pierre. "Body fat distribution and risk of cardiovascular disease an update." Circulation 126.10 (2012): 1301-1313.
• Kobayashi, Makoto, et al. "Green tea beverages enriched with catechins with a galloyl moiety reduce body fat in moderately obese adults: a randomized double-blind placebo-controlled trial." Food & Function (2016).
• Nakagawa, Kiyotaka, et al. "Effects of co-administration of tea epigallocatechin-3-gallate (EGCG) and caffeine on absorption and metabolism of EGCG in humans." Bioscience, biotechnology, and biochemistry 73.9 (2009): 2014-2017.