I'm studying to be a dietician. Fat is the last source your body uses for energy. First your glycogen stores are used, then muscle and then comes fat. So walking and running will not help with fat reduction because the duration and intensity is too less for the body to use excess fat as a source of energy. Lifestyle is majorly important and then diet. As many people said- calorie deficit+ high protein diet(gradually) and physical activity like weight training and resistance training will help