Therapeutic usage of natural herbal supplements is rapidly growing. One of these supplements is a Green tea–Caffeine mixture (epigallocatechin gallate plus caffeine). This mixture is claimed to increased thermogenesis and fat oxidation which may help you get peeled faster [1-3].
A green tea-caffeine mixture contains caffeine that may stimulate thermogenesis and fat oxidation through inhibition of phosphodiesterase. Dulloo et al.  showed that the effect of a green tea-caffeine mixture was greater than could be attributed to its caffeine content. They noted that: “Green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both.”
Margriet S. and colleagues  hypothesized that a green tea-caffeine mixture would reduce body weight regain in humans after weight loss, possibly through a thermogenic effect. They divided seventy-six subjects into either habitual low caffeine consumers (n = 38; caffeine consumption < 300 mg/d) or habitual high caffeine consumers (n = 38; caffeine consumption > 300 mg/d). Habitual caffeine intake was sustained during the study. All subjects followed a very low energy diet (VLED) for 4 weeks to lose weight. High caffeine intake groups lost significantly more weight than the low caffeine intake groups.
During weight maintenance period, the subjects received a green tea-caffeine mixture (270 mg epigallocatechin gallate + 150 mg caffeine per day) or placebo. Surprisingly, in the low caffeine intake group who consumed the green tea-caffeine mixture, body weight maintenance after body weight loss was considerably greater. In fact, green tea still reduced body weight in the low caffeine consumers during weight maintenance.
What is interesting (as seen in pic below) is that high caffeine group which also ingested green tea-caffeine mixture in the weight maintenance phase regained weight faster than all other groups.
Pic. – BMI of men (n = 23) and women (n = 53) over time. Month 1: after the VLED; month 4: after 3-month follow-up; CL, habitual low caffeine intake; CH, habitual high caffeine intake; GT, green tea during follow-up; P, placebo during follow-up.
Margriet S. and colleagues  explained that : “The high caffeine intake group had become nonresponders to the green tea-caffeine mixture, probably because of a ceiling effect.”
Dulloo, A. G., J. Seydoux, and L. Girardier. “Potentiation of the thermogenic antiobesity effects of ephedrine by dietary methylxanthines: adenosine antagonism or phosphodiesterase inhibition?.” Metabolism 41.11 (1992): 1233-1241.
Dulloo, A. G., et al. “Normal caffeine consumption: influence on thermogenesis and daily energy expenditure in lean and postobese human volunteers.” The American journal of clinical nutrition 49.1 (1989): 44-50.
Dulloo, Abdul G., et al. “Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.” The American journal of clinical nutrition 70.6 (1999): 1040-1045.
WesterterpPlantenga, Margriet S., Manuela PGM Lejeune, and Eva MR Kovacs. “Body weight loss and weight maintenance in relation to habitual caffeine intake and green tea supplementation.” Obesity research 13.7 (2012): 1195-1204.