The UK Food Standards Agency Website has this to say:

"It's not a good idea to try to lose weight while you're breastfeeding because you need to keep up your energy levels and you might miss out on the nutrients that you and your baby need.

"The good news is that the extra fat laid down in pregnancy is used to make breast milk, so breastfeeding will help you get back into shape quicker.

"If you eat a healthy balanced diet, limit the amount of fat and sugar you eat, and are physically active, this will help you to lose any extra weight you put on during pregnancy."

However, we at Infant Feeding Information recognise that some mothers find it hard to hang on to weight they would rather not have, and would prefer to use some structured weight loss programme to help shed some fat. We also understand that if breastfeeding mothers are told they mustn't 'diet' while breastfeeding, this could be the breaking point for ongoing breastfeeding for some, so we have provided some information about four main diets, and their speificis for the breaastfeeding mother.

Breastfeeding uses at least 500 calories a day. Much of this energy can be derived from fat stores laid down in pregnancy, but many women also experience an increase in their appetite.
Sensations of hunger and thirst are particularly intense during this period, and new mums should be encouraged to respond to these signals. It?s important to eat regularly so have small snacks in between meals. The stress and tiredness of early motherhood, as well as the demands of breastfeeding, mean this is not a good time to diet or limit your food intake.

It's important that this increased appetite is satisfied with foods of a high nutritional quality, not fatty and sugary foods alone. Requirements for protein, calcium, folate and vitamins C and A increase significantly while breastfeeding. This necessitates a balanced intake of foods. Sufficient fluid is also vital, see above.

All lactating women should drink more than usual (at least eight glasses of fluids a day) and shouldn't ignore thirst; it's often the first sign of dehydration. Caffeine (from tea, coffee and some soft drinks) and alcohol are excreted in breastmilk, so excessive quantities should be avoided.

This website does not advocate the use of slimming shakes, and urges breastfeeding mothers, expecially those mothers of young babies, to use caution when embarking on a weight loss programme, and to carefully monitor both their own weight loss and well being, and that of their baby too.

Weightwatchers
Breastfeeding mums are able to join WW but only if they attend the meetings: there is no way to do WW online as a BF mum. BF Mums should add 10 points to their allowance if their baby is still exclusively BF, and 5 if the baby is on solids or is mixed-fed. Unfortunately no provision is made for BF mums who want to follow a sensible eating programme online.

They have a leaflet which your group leader will supply you with which stresses that you should have had your 6 week check and spoken to your doctor about starting to lose weight while BF etc.

If you have attended WW before and reached goal weight, you will have been given 'Gold Memebership': this entitles you to free meetings for 6 months after your baby is born. It is ssaid to be best to wait till baby is 3 months aold but you can start at any time.

Slimming World

Your consultant should give you a booklet called 'advice on pregnancy and breastfeeding'. You get extra healthy extras but the amount depends on the baby's age.
Up to 2 months - 3 extra
2 to 4 months - 4 extra
4 to 6 months (if starting to wean) - 3 extra
4 to 6 months (if breast milk is the only source of nutrient for your baby - 4 extra
Over 6 months (when weaning) - 1 extra
It also recommends thast you have the full 15 syns a day.
SW also advise that at least 1 and preferably 2 of the additional healthy extras are (A) choices which are rich in calcium as you should increase the recommended daily intake of calcium from 700mg to 1250mg per day.

The GI Plan

It is not advisable for pregnant or breastfeeding women to follow a weight loss programme of any kind, but it would be fine to follow a low GI way of eating at both times.
General recommendations for nutrition during pregnancy are to include at least 5 portions of fruit and veg, 3 servings of dairy products and 2 servings of protein foods every day. Your energy requirements only increase in the last trimester of pregnancy - with calorie requirements being around the 2000 mark for the first 6 months of pregnancy, increasing by 200 cals per day in the last three months. This would continue after delivery, with the average additonal calorific need being c. 500cals per day in a fully breastfeeding mother.

Atkins Nutritional Approach

Here are two useful links
Low Carbohydrate Diets and the Breastfeeding Mother La Leche League FAQ
http://www.lalecheleague.org/FAQ/lowcarb.html
Are ketones in breastmilk a problem? comments by Thomas Hale, PhD
http://neonatal.ama.ttuhsc.edu/discus/messages/53/187.html?1052170264

The main concern would not be the ketones but the toxins excreted as you break down fats in the body - toxins such as perfumes, cadmium, lead, DDT and other pesticides - all stored in the fat deposits of adults - and excreted by you into your breastmilk when you diet severely during BF. It is for this reason that crash dieting is not recommended during BF but in an older baby, perhaps one now taking solids, there is not so much risk from this (food and formula both potentially contains toxins too of course).

It is certainly not recommended to follow a low carb diet (whether Atkins or any other) for a short period of time, followed by a return to previous ways of eating - because it messes with your metabolism, as frequent crash dieting or long term low cal dieting does, and so affects your long term health, weight, fitness etc. The thing about Atkins is that it changes your way of eating for life, and if you do it properly, you feel no sacrifice after the first couple of weeks because you can eat so much gorgeous, tasty and varied food and never feel hungry, whilst maintaining your weight and looking and feeling better than in years. The most important aspect of this diet, especially for those with only a little to lose, is not the two week detox at the beginning, but the long term pre-maintenance and Maintenance bits - keeping the weight off and eating healthily for life.

You have to stick with it and there are 4 stages of Atkins for you to eat throughout your life.

Here are some links you need to know a bit more about this way of eating. Read these articles - and maybe print out the 'Acceptable Foods' list and stick it to your fridge!

Rules of Induction

Acceptable Foods for Induction

Ongoing Weight Loss

The Atkins Nutritional Approach Food Pyramid

The Crucial Phase of Pre-Maintenance

How to Do Lifetime Maintenance Correctly