atkins and ketosis (which is starvation) will only make you thinner for the short term, as soon as you start eating normal (carbs) again the weight (plus some) comes back.
Also, Ketosis (Atkins, no carbing etc.) is very unhealthy and bad for your kidneys, your heart (all that cholesterol).
I know most people love it though, as it`s a quick fix.
Doing something more sensible like normally, but more healthily and smaller portions, is the best way IMHO. Something like the GI diet (where you cut out suger and refined starch, but eat wholewheat stuff, porridge, and other whole grains, low fat fish, meat dairy and fruit and veg)
I think all diets are a con. Apart from the GI one as that just teaches you about more sensible eating without the dreaded ketosis.
Personally, I need carbs for my brain and body to function properly.
So start the day with porridge (skim milk), wholewheat toast or similar. Maybe a poached egg too! Soup and brown bread fo lunch, and nice fish and rice and salad for tea.
And cut out any soda`s, cakes etc.
I think you should eat carbs, just not too much of the bad ones (like sugar).
I lost 2 stone like this after pregnancy, but it took a year. it stayed off though.
I hate seeing people tout ketosis (starvation through no carbs) as a good thing. It messes up your metabolism, and you`ll most likely end up a yoyo dieter...