Pristiq, also known as desvenlafaxine, is an antidepressant used in treating depression and anxiety. Pristiq is in a class of medications called selective serotonin and norepinephrine reuptake inhibitors. Although Pristiq is effective for treating depression for many people, the drug does have some side effects. Nausea, dizziness, sweating and constipation are the most common side effects. Weight gain is not listed as a common side effect of Pirstiq, but the Mayo Clinic says weight gain is a possible result of any antidepressant. Losing weight while taking Pristiq is similar to the weight-loss process under other circumstances.
Keep a food diary for several days, writing down everything you eat and drink. According to the Mayo Clinic, some people eat less while depressed, and antidepressant treatments can cause the appetite to return. This can result in unexpected weight gain if you do not notice that you are eating more.
Reduce your calorie intake. It takes 3,500 calories to gain or lose a pound, and the recommended amount of weight you can lose each week is 1 to 2 pounds. This requires you to cut 500 to 1,000 calories each day. You can cut these calories by reducing portion size, eating low-fat foods and avoiding high-calorie beverages. The Mayo Clinic says that antidepressants often cause carbohydrate cravings, so it is especially important to watch your carbohydrate intake.
Engage in a total of 150 minutes of aerobic exercise each week. The National Institutes of Health recommends 2 1/2 hours of moderate intensity aerobic exercise weekly, which can be broken down into intervals of at least 10 minutes. Examples of moderate intensity aerobic exercise include brisk walking, swimming, dancing or tennis. You should also do strength training twice a week, in the form of resistance training, weight lifting or Pilates. Strength training builds muscle, and muscle burns more calories than fat.