Ready, set... DIET!

Allright, this last week I've been keeping it pretty fine, I'm already sticked on my old-good-habits routine (more or less), So, the other day I was thinking and... I realised I eat SO much. So I started a drastic diet that is going to last 3 weeks (the time where your body and mind get sticked into a routine). The diet pretty much consists of eating 700 calories on 5 meals a day (because I don't want to ralentise too much my metabolism). So, more or less this is my day:
-Breakfast: Apple + Yogurt (more or less 80 calories)
-Morning snack: Mandarin Orange (45 calories)
-Lunch: 1/2 margarin and ham sandwich (more or less 120 calories)
-Afternoon snack: Tea or coffee with milk and sugar (60 calories)
-Dinner: whatever my hostfamily has cooked for me.
 Ok, so dinner is my biggest deal because is obviously so bad for my health and metabolism to eat that much when I'm eating that little the rest of the day. But I've nothing to do with it because as you know my hostparents cook the dinner and also serve it. And I don't want to say things like "I'm on a diet" because I don't want to worry them. So all I can do it's to try to eat as little as I can during the dinner.
 I actually started this diet on saturday and since that everyday I feel less and less hungry. And I've also lost more than 1kg! So yes, I'm pretty happy with it. I'm supposed to be making some exercise- to boost my metabolism because the fast is ralentising it- but as this week I'm on my work experience and I finish everyday at 6 o'clock in the evening, I'm not able to go to the gym- any day. So all I can do it's to look for some video-home-workouts and things like that. Wich I find pretty boring- but I don't have any other chance!
 To fight hunger and craving I'm drinking loads (and when I say loads I mean loads) of water, green tea as much as I can, looking at my phone's thinspo wallpaper or reading motivational texts.
This is my first time in such a drastic diet. Have you been in any diets? Did they worked? Did you regained everything after them?
xoxo
Elisa
PS. Alright, I'm not a doctor, and I've NO IDEA if what I'm doing is healthy or not. So please, PLEASE, if you follow me at this diet, you have to be responsable of the changes that it will produce at your body. I don't want anyone to sue me!!