People gain weight when they consume more calories than they expend.
This holds true whether the calories are coming from fats, carbohydrates, or even non-fat foods. A simple key to losing body fat is to use up more calories than you consume daily by increasing the amount of exercise you get each day, and reducing the amount of fat in your diet. Water retention can also pass for weight gain, so watch your sodium. Try to catch a weight gain when it is most manageable, such as a weight gain of five pounds or less. For more information on nutrition, contact your health care professional.