I do weight watchers and I find cycling very hard to track. Always go on the low end. I track my rides as low intensity, even though, realistically, they are medium based on HR and sweat loss. I try not to eat my exercise points, unless it was a long ride day. Eating healthier, like avoiding soda, drinking more water and picking better snacks (string cheese, handful of nuts, fruit, yogurt) has made the biggest difference in my weight loss. Cycling alone doesnt keep it off (for me). It is a motivating factor--losing weight and eating healthier give me more energy for riding--and riding makes me feel like eating healthier 
Good luck on your goals
"Well-behaved women seldom make history." --Laurel Thatcher Ulrich
'09 Trek WSD 2.1 with a Brooks B-68 saddle
'11 Trek WSD Madone 5.2 with Brooks B-17