I'm not a dietician, but I am a personal trainer, and I'd say that you should just stick to healthy food and exercise whilst you're breastfeeding. I don't know the scientific background, but I'd expect that restrictive diets (where you're eating less calories than you need, so you burn fat) may adversely impact your breastfeeding, both in terms of quantity of milk and the nutrients you/your baby receive. Plus, it is a fact that restrictive diets do not tend to work in the long term, as your body simply adjusts its metabolic rate to take into account the reduced calorie intake. Indeed, a lot of people who use restrictive diets end up heavier than they started, after they stop the diet.

As others have said, you are not overweight, especially given you've just had a baby. I can understand you wanting to lose a few kilo's - I had my baby 6 months ago, and I've been sweating it out at the gym to try and get back to my pre-baby body! Unfortunately, whilst I'm still breastfeeding, it looks like my body will hang onto a few kilo's of fat (so much for it all dropping off if you breastfeed!)