you can and it doesn't have to be slimming world or weight watchers, the main thing to keep in mind is if dieting while BF you cannot go below 1500 calories a day and many women will need closer to 1800 calories a day to maintain good milk supply, the larger you are the more calories you may need as your basal metabolic rate will be higher. I am doing diet chef which is a delivered diet but I think after my three month deal on it is up I will just do lower calorie under my own steam as there is no need to do any set diet plan when BF and I feel more confident now; but its been really good as it has a lot of dairy foods, nuts and seeds, beans and other veggie protein as part of the diet foods-they are really just normal foods with full fat dairy etc in but very carefully measured portions. Almost all the breakfast and snack options contain wholegrain oats as well-which is fab for milk supply. They also advise drinking at least 250ml of semi-skimmed milk a day as well as at least one extra protein portion a day. I have lost over a stone and feel so much more energetic and healthy now xx