How to control weight gain when prescribing antidepressants

Table 2

Antidepressants’ relative long-term effects on body weight

Table 3

Using antidepressants in patients at metabolic risk for weight gain

Dietary measures

If weight gain has occurred, a safe initial goal for patients is to lose 0.5% to 1% initial body weight per week—or 5% to 10% of weight across several months. Diet and exercise produce maximal benefit but require commitment and motivation, which are often difficult or impossible for depressed patients. Encouraging the patient’s efforts is worthwhile; if intervention is postponed until remission is achieved, weight gain may be substantially higher and more difficult to treat.

Cutting fat and calories. The first step in losing weight is to restrict high-fat and high-calorie foods and eat smaller portions. If this fails, then switch the patient to a low- or very-low-calorie diet, which provides a quick initial weight loss. This can motivate the patient but should be tried only under a physician’s supervision.

Many patients benefit from structured commercial weight-loss programs, but the likelihood of regaining the weight is high if stopped. These programs typically recommend 1,200 kcal/day for women and 1,800 kcal/day for men, with 55% of calories from carbohydrates, about 25% to 35% from protein, and 10% to 25% from fat.

In a study of 100 patients, those on 2 liquid meal replacements per day plus snacks and 1 low-fat meal (approximately 1,200 to 1,500 kcal/day) lost considerable weight in the first 3 months but regained some weight later. Many maintained weight loss on 1 liquid meal replacement per day plus snacks and 2 low-fat meals.²⁶

Low- and very-low-calorie diets are indicated for patients with BMI >35 kg/m²:

• in whom conservative treatment (a portion-controlled, low-fat diet) has failed
• and who are willing to maintain at least 1 year of treatment and major lifestyle changes.

A low-calorie diet provides ≥1,000 kcal/day; very low-calorie diets may provide ≤800 kcal/day and rely mostly on liquid meal replacements. This semi-starvation can produce fatigue, weakness, lightheadedness, and changes in vital signs, including blood pressure, heart rate, and respiratory rate. For this reason, extreme diets require a team approach with the primary care clinician and a dietitian.

Among mentally healthy patients following very-low-calorie diets in clinical trials, 90% lose ≥10 kg and 50% lose ≥20 kg in the first 4 to 6 months.²⁷ Most weight loss occurs in the first 12 to 16 weeks, after which an ad libitum low-fat, high-fiber diet can be used.

Exercise has physiologic and psychological benefits, including inhibiting food intake and promoting a sense of self-control. Physical exercise increases insulin sensitivity and reduces the risk of secondary medical problems, such as heart disease. Walking ≥40 minutes daily produces maximal benefit, but walking even 30 minutes 3 times a week can help maintain weight.

CBT. Eating habits can be changed through identifying lifestyle behaviors to be modified, setting goals, modifying triggers of excessive eating, and reinforcing desired behavior with CBT. Gradual but consistent behavior change leads to healthier eating habits, exercise, and weight loss. Behavior modification alone can generate a weight loss of 0.5 kg to 0.7 kg per week.²⁸

A study of 6 schizophrenia patients (mean age 37) examined CBT effects on weight gain associated with clozapine (n=4) or olanzapine (n=2). Mean BMI decreased from 29.6 kg/m² to 25.1 kg/m² after 7 to 9 sessions of individual CBT, followed by 16 biweekly group sessions that focused on weight reduction and weight maintenance. A dietician provided detailed counseling.²⁸