From the Guidelines
Fluoxetine is not typically associated with increased appetite, and it may even lead to weight loss due to its appetite-suppressing effects, especially during the initial stages of treatment. As a selective serotonin reuptake inhibitor (SSRI), fluoxetine works by increasing serotonin levels in the brain, which often leads to reduced hunger and sometimes weight loss, especially during the first few months of treatment 1. The standard dosage ranges from 20-80 mg daily, usually starting at 20 mg and adjusting as needed.
Key Points to Consider
- While appetite suppression is common, individual responses vary significantly - some patients experience no change in appetite, and a minority may actually experience increased appetite, particularly with long-term use.
- The appetite-suppressing effect occurs because serotonin plays a key role in regulating satiety signals and food intake.
- This effect is often most pronounced during the initial weeks of treatment and may diminish over time as your body adjusts to the medication.
- If you're taking fluoxetine and concerned about appetite changes, it's essential to monitor your weight and eating patterns.
Clinical Implications
- Fluoxetine and sertraline, another SSRI, have been associated with weight loss with short-term use and weight neutrality with long-term use 1.
- In contrast, other antidepressants like paroxetine and amitriptyline are associated with a greater risk for weight gain 1.
- The choice of antidepressant should be guided by the individual patient's circumstances, considering factors like the type of depression, potential side effects, and the patient's medical history.
From the FDA Drug Label
Altered Appetite and Weight — Significant weight loss, especially in underweight depressed or bulimic patients may be an undesirable result of treatment with Prozac. In US placebo–controlled clinical trials for major depressive disorder, 11% of patients treated with Prozac and 2% of patients treated with placebo reported anorexia (decreased appetite). In US placebo–controlled clinical trials for OCD, 17% of patients treated with Prozac and 10% of patients treated with placebo reported anorexia (decreased appetite) In US placebo–controlled clinical trials for bulimia nervosa, 8% of patients treated with Prozac 60 mg and 4% of patients treated with placebo reported anorexia (decreased appetite).
Fluoxetine (Prozac) does not increase appetite. In fact, it is associated with decreased appetite (anorexia) in a significant number of patients, particularly those with major depressive disorder, OCD, and bulimia nervosa 2.
From the Research
Effects of Fluoxetine on Appetite
- Fluoxetine is thought to affect weight control through appetite changes, resulting in decreased food intake and normalization of unusual eating behaviors 3.
- However, a case study reported an unusual coincidence of weight loss with increased appetite and food intake in a patient treated with fluoxetine, suggesting that the effects of fluoxetine on appetite and weight may be mediated by partially distinct mechanisms 4.
- A study on the changes in weight during a 1-year trial of fluoxetine found that weight gain during continuation treatment was related to improvement in appetite after recovery from depression 5.
Weight Changes Associated with Fluoxetine
- Fluoxetine has been associated with weight loss during acute treatment, with a mean absolute weight decrease of 0.4 kg observed during the initial 4 weeks of therapy 5.
- However, after remission of depressive symptoms, weight gain for patients taking fluoxetine for longer periods was not different from that for patients taking placebo 5.
- A meta-analysis of 19 randomized controlled trials found that fluoxetine decreased weight compared with placebo, with a mean difference of -2.7 kg 3.