During first 6 weeks after the delivery you would need to heal and restore nutrients depleted during your pregnancy, it is not the right time for restrictions.
If you are breastfeeding, that alone can help you losing weight to the pre pregnancy level. Tricky task is to keep the weight off after you stop breastfeeding as your daily energy need will be at least 500kcal lower. Start a weight loss diet during the weaning process gradually reducing number of breastfeeds and energy intake.
If you are not breastfeeding, you may start your weight loss diet 6 weeks after the childbirth. Be attentive to nutrients deficiencies, consult your doctor if you feel tiered. You may need to supplement your diet with natural iron supplements.