In one of the blog posts for new runners, a frustrated woman commented "And everyone said the weight would fall off when I started to run. Not true!"
I agree. Most novice runners start their exercise program believing undesired body fat will melt away. Not the case. If running contributes to a calorie deficit, body fat does dwindle away. But all too often, new runners eat a little bit more than usual, either because they are hungrierexercise can stimulate the appetite for women (more so than for men)or because they believe they deserve a reward of a cookie or two. The combination of hunger + desire for a reward = no fat loss, and often fat gain.
The other thing you have to look at is 24-hour energy expenditure. That is, some new runners become less active in the other parts of their day ("I ran today, so I'll sit and read instead of clean the house.) A study with middle-aged people who added on an hour of brisk walking each day indicated they did they eat more, nor did they lose weight. They simply napped and slept more In 24-hours, they did not burn additional calories.
I recommend you run for health and fitness, and pay attention to eating smaller portions at dinner to lose undesired body fat. Just chip off 100 to 200 fewer calories at night. For information on how to lose fat and maintain energy to exercise, you might want to read my Food Guide for New Runners: Getting It Right From the Start.
Regardless of weight, enjoy feeling proud of your running accomplishments!