This is a little early for you, but…
There are at least two keys to maintenance of weight loss:
1. Regular physical activity
2. Restrained eating
Key #1 is documented, for example, in Anne Fletcher’s book, “Thin For Life.” Key #2 means you never really go back to your old ways of eating, or you’ll go back to your old weight. Most successful losers have to make a concious decision to limit what, and how much, they eat. Pretty much forever.
These comments target the typical dieter who has carried 30 to 100 pounds of excess weight in adulthood for years, having tried and ultimately failed several diets.