Corticosteroids are often called steroids. These prescription drugs are used to treat inflammation. One of the side effects of these drugs is weight gain due to an increased appetite caused by the drugs, according to the Radiation Oncology Online Journal (ROOJ). It is, however, possible to lose weight when on prescription steroid treatment.

Plan your meals. Because steroids will make you hungry, you should opt to eat a small meal every two to four hours, with the first meal of the day being breakfast shortly after you wake up.

Eat a healthy diet. Your diet while on steroids should be a reduced-calorie diet that is low in sugar. Lean protein, milk, vegetables, grains, fruits and oils should be included in your daily diet.

Limit the amount of sugar you eat. Chemocare.com states that corticosteroids can cause an increase in blood sugar. Choose complex carbohydrates, such as whole grains like oatmeal or brown rice, instead of simple sugars like candy or cake. Limit the amount of sugar you put into drinks, and limit the amount of starchy vegetables, like potatoes or corn, that you eat daily.

Drink at least 8 to 10 glasses of water daily to control the amount of steroid-related water retention you suffer from. Water retention can lead to weight gain. Carry a bottle of water around with you so you can drink often.

Exercise at least 60 to 90 minutes per day at a moderate level of exercise. This is the amount of exercise recommended by the American College of Sports Medicine (ACSM). Walking at a brisk pace and swimming are both suitable exercises. When you exercise, you should be able to talk, but you should be sweating.

Tips
Certain foods, such as strong spices, carbonated beverages and acidic foods, such as tomatoes or citrus fruits, may irritate your stomach. Plan your meals with this in mind.

Warnings
Don't take any weight-loss supplements when you are taking steroids unless your doctor approves the supplements. Many supplements and medications won't work properly when you are taking steroids, and some may affect the way the steroids work.