I lost 2kg during my last pg due to gestational diabetes and having to follow a low gi diet. I alsoended up on insulin so was quite strict with myself.

I am going to be following the same diet this time and hopefully keep my bmi under 35.

My diet basically consisted of
Cereal, cup of tea for breakfast
Sandwich on low gi grainy bread for lunch
Meat and veg/ stir fries for dinner.
Apples were the main fruit I ate as everything else sent my levels up.
My one treat I allowed myself maybe twice a week was a spoonful of Milo in a glass if milk and that's it.
As for exercise, I walked 2-3 times per day for 10 minutes until 3rd Tri when my spd was really giving me grief.

I was diagnosed with gd at 17 weeks, so it was a long hard road but I reached my goal and didn't put on any extra weight.