The first thing to do is drink at least 2 litres of pure water each day (not juice, squash, tea or coffee - just good old water). Water flushes out toxins and you lose at least 2 litres a day from perspiration alone, so this needs to be replaced. Don't drink more than 3 litres of water a day however, as the body needs essential salts which can be depleted by over-hydration. Cut down on tea and coffee which are often dehyrating, especially if they contain caffeine.
Next thing is to eat more green foods such as broccoli, spinach, avocados, green beans and celery. These are packed full of vitamins, iron and are water-rich. They are also full of fibre (see below). Too much fruit can cause acid reflux, so replace some fruit with greens (as above).
Eat at least 25g of fibre a day. Fibre is only found in plants and fruits, not animal flesh or fish. Fibre helps you feel fuller for longer and helps keep your system moving.
Cut down your consumption of unhealthy fats (those that are solid at room temperature). Eat more healthy fats as found in oily fish, olive oil and avocados. These fill you up and are nutitious and energy-giving.
Eat less processed food, such as ready meals which contain toxins in the form of preservatives. Consumption of toxins causes you to hold onto fat. Once consumption of toxins reduces, the body no longer has to worry about shipping toxins out of the system and can metabolise away fat instead. Eat more fresh foods instead; alive foods are packed with energy which you can use.
Get some regular exercise - it's hard to lose weight without it and there are lots of side-benefits, such as boosting your mood and sleeping better. Housework and a brisk walk with the pushchair do count. Aim for 30 mins of sensible exercise 4 times a week. Contrary to popular belief, over-exercise can cause you to hold on to fat around the middle (when the body releases the stress hormone cortisol)
I did exactly these things to lose 45lbs in 5 months and have kept the weight off since. It's all about getting healthy in order to lose weight, rather than losing weight in order to get healthy. This benefits your overall health and mood as well as your babies long-term health, especially if breast-feeding. It also means an end to the misery and frustration of yo-yo dieting.
The best bit was that I didn't feel hungry once and neither did I have to stop eating my favourite foods.