Risk factors for weight gain during methadone maintenance treatment

Weight gain was reported during methadone maintenance treatment (MMT). However, its relation to eating habits and specific risk factors, including methadone dose or serum level, was limited. The aims of this study were to characterize risk factors for weight gain and to study current eating habits, food preferences, and nutrition knowledge.

Patients with available measures of weight and height (body mass index [BMI]) at admission to MMT and at follow-up, when methadone serum levels were determined (after 1 year or when stabilized) (N = 114), were studied (using the Addiction Severity Index [ASI], drugs in urine, methadone doses, and serum levels). In addition, 109 current patients with available earlier (5.8 ± 2.6 years earlier) BMI completed eating behavior rating and nutrition knowledge questionnaires, and their current and earlier BMI were compared.

The BMI of 114 newly admitted patients increased from 22.5 ± 3.8 to 24.4 ± 4.3 (P < .0005). Once stabilized on methadone, BMI increased further (24.3 ± 4.5 to 25.6 ± 5.0; P < .0005; n = 74), with no change in methadone doses (125.6 ± 32.5 to 128.0 ± 34.1; F = 1.4, P = .2) or serum levels (495.6 ± 263.7 to 539.8 ± 306.2; F = 1.3, P = .2). Repeated-measures analyses revealed that BMI elevation was higher among 45 hepatitis C virus seronegative and 46 non-benzodiazepine-abusing on-admission patients. Those who scored lower on knowledge about healthy diet and showed a higher sweet-foods preference had a higher BMI.

BMI increased over time, but independent of methadone dosage and blood levels. As expected, worse diet habits and a desire for sweet foods are related to higher BMI. Paradoxically, healthier status (i.e., hepatitis C seronegative, no benzodiazepine abuse) at admission is predictive of greater weight gain during MMT. Education about nutrition habits is recommended.