Exercise has no impact on milk composition with the exception of a temporary rise in milk lactate after prolonged, heavy exercise (Larson-Meyer, 2002; Prentice, 1994).
It is the mum’s health and wellbeing that will suffer from being in a calorie deficit and over-exertion due to exercise in the postpartum period, long before the nutrient profile of breastmilk is impacted. And we can see this clearly in countries where food insecurity is rife – women are still able to breastfeed their babies long into childhood.
As a lactation consultant I would not recommend any mother partakes in any heavy physical activity in the first 6-12 weeks postpartum, much longer if there was anything like a postpartum haemorrhage, c-section, episiotomy, or if they have a premature or sick infant or other ongoing health concerns.
Speaking to a qualified personal trainer about your wants and needs with regard to fitness is important. But also ensuring you have spoken to a GP or your consultant if you have ongoing health issues to ensure you have the right training plan in place.
Ultimately, we know exercise can make us feel great by releasing endorphins. Lots of parents feel great exercising because they get a bit of time child-free to process their thoughts, wind down, let off steam, socialise with other adults, etc.
And if you don’t feel good about leaving your baby at home, loads of gyms are now set up to welcome children and are the perfect place to start training again in the postpartum period – you can bring your baby and a helper, and if your baby needs feeding you are right there to do so, and you don’t need to suffer the anxiety of leaving them at at home, or feel trapped and overwhelmed by trying to exercise at home!