Nightly cup of tea

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Every night after dinner I have a cup of tea and something sweet, for me that seems to work to stop my late night snacking. So I stop eating about 9pm. But I have noticed something, if I'm up really late and I have another cup of tea about 12midnight I will more than likely loose weight the next day as long as my diet for the day wasn't bad. Is there anything behind this or is it all in my head? Is a reason this happens?

BTW I have my tea black with 1tsp of sugar substitute

Any info would be wonderful