Everyone has a different potential or ability to change their weight. Of the many aspects of weight management, those that can be modified are exercise, food (portions, type, timing of meals, etc.), relationship with food, stress levels and sleep. Many people forget that all of these influence weight and lifestyle choices -- it is NOT just about food and exercise.
Be mindful of portion size but think mostly in terms of quality, not calories. An energy-equivalent portion of kale and processed fast foods are not equivalent in any other way, as the cruciferous kale is akin to a warehouse of nutrition with anti-inflammatory, anti-oxidative and anti-carcinogenic health benefits.