From my (very limited) observation most people who report that they gain weight but eating very little forget that they eat a gallon of ice cream every night or similar. The overweight people I know all without exception eat way more than I do. They may eat a salad for dinner but then they drink 3 glasses of wine or eat a ton of dessert.

To me the main effect of exercising is that it balances food cravings. I often eat less when I hike the whole day than when I am in the office.