Any diet that loses you weight dramatically will not stay off. Finding a plan that suits you first would be best... slimming world was a GREAT starter for me. You want to change your eating habits and lifestyle.
There are a lot of things to consider and factors into how quickly you lose weight. I lost more per week while at my biggest but as the scales went down my weight loss got less per week, this is normal. I lost around 60lbs in 2013.
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