The new conventional wisdom I have seen starting to appear (at least in Norwegian journals) is that dropping weight fast, in contrast to very gradual, is not a bad thing anymore.
The real struggle (which we all know) is maintaining your goal weight
after reaching it. But if you have the right plan you can do it.
Shortly summarized:
Diet:
Person (male or female) goes on a 800-1000kcal diet (3300-4200kj) with a focus on healthy calories. This will result in a weekly drop of 1-2kg (2.2-4.4pounds), the very first week is usually double that (water etc.).
They do this for a maximum of three months.
Training regularly gives a nice additional boost but this becomes much more important after the diet is complete.
PS. The third or fourth day is the hardest.
Having reached your goal:
The bodies of people who have been previously fat and for good portions of their life will always strive to regain that weight. Using the Rule of Thumb (see below) to find your daily energy usage, you should on average expect that after weight-loss your daily energy usage will be ~400kcal lower than even that due to your body using energy more effectively aka "starvation mode" or whatever (so for a 70kg person who has previously been fat: 2100kcal minus 400kcal on average is your new life).
The older conventional wisdom sais that this effect lasts a year after reaching your new goal but the new conventional wisdom (research backed in Norwegian journals) sais that this is for the rest of your life... which sucks majorly. People who have had optimal weight their whole life don't have this problem... And this problem is the same for both those who dropped weight fast or those who did it very gradually (so why draw out the pain w/sleep problems, counting calories and so forth). The research pointed out that those who dropped fast were however much more successful in maintaining their new weight over the years following (w/post-goal plan).
So the hard part is to live your life with your body having this saving-effect turned-on permanently.
You can however greatly reduce or nullify this effect by making sure you regularly exercise. The recommendation is whatever equals 1 hour of walking every day (hence exercise becoming much more important
after reaching your goal).
And of course eating consciously.
Rule of thumb:
Your weight in KG x 30 = kcal needed daily to sustain your weight.
I.e. 70kg x 30 = 2100kcal needed per day.
I found one english-language article backing up the Norwegian research articles I have read:
http://www.latimes.com/science/sciencenow/la-sci-sn-rapid-vs-gradual-weight-loss-20141016-story.html
