In fact, if your are nearing the end of your diet cycle or have finished it, now is the most important time of your diet. Wouldn't it all feel like a waste of time if you gained all that weight back? What about half of it?? You've worked HARD to lose that weight, now keep it off!!!
Because your body has gone through such a traumatic experience (losing weight makes your body feel like you're starving, which is bad), it's gonna do nearly whatever it can to "help" you gain that weight back.
Anybody remember the show The Biggest Loser...? It was an American show where large or obese individuals would compete to lose the most amount of weight in the smallest amount of time. They had this ridiculous scale where they'd have each member of the other team stand on one side all as a group to see who lost the most amount of weight.
Interestingly enough, as thousands of viewers tuned in to watch obese people lose an unGodly amount of weight, others started to notice something peculiar; a contestant might lose upwards of 200lbs on the show but once the show was over they'd gain most of it back (if not more). It seemed as though their strenuous high-intensity-interval-training, low calories and excess cardio proved little effect on their overall health.
Why did/does this happen??
As many people tend to forget (myself included) is that although weight loss (more specifically fat loss) may be your current goal, nobody wants to immediately gain that weight back. But if you go back to the diet and lifestyle you were living BEFORE the diet, that's exactly what will happen, and it only makes sense! You changed your diet and lifestyle just to lose the weight and now you're going back to the same weight gaining foods??
The Importance of Maintenance
To avoid gaining back all that unsightly weight/fat, it's paramount that one not eat their "maintenance" calories right away. That is to say, don't eat how many calories you've calculated to be your maintenance right after ending a diet because your body has adapted to be in a caloric deficit. What this means is your metabolism has slowed down along with a host of other bodily functions that make your actual maintenance caloric requirement lower than usual. Typically one should calculate their maintenance caloric requirement (14-16 calories per pound of body weight), then subtract 10% and eat that for a week or so.
I'm 130lbs., 130*14= 1,820. 10% of 1,820 is 182. 1,820-182= 1,638 calories. I'd eat that for about a week before upping it to 1,800 then maybe to 2,000 depending on how my body reacts.
Many people react differently after being on a diet for a long time. For example, I know many people who transition flawlessly whereas I want to eat everything in site. Be ready for this!!!