In this present study, we examined the BMI (as a criterion for assessing under-nutrition) (
9), and socio-demographic characteristics of the patients before and after 8 weeks of MMT. The results showed that the majority of patients had achieved an appropriate nutritional status evaluated by their BMI, before treatment only 50.9% had a normal BMI at baseline. This is consistent with previous studies (
13-
15). The prevalence of underweight patients (BMI < 18.5 kg/m
2) was found more often than overweight (BMI 25 - 29.9 kg/m
2), and obesity (BMI ≥ 30 kg/m
2), among the examined patients. During the 8 weeks of MMT, a significant increase in BMI was observed. More of the patients had a normal BMI, particularly in the male group. The same was true for body weight which increased significantly, and this result is similar to several previous studies (
16-
18), but unlike the Forrester et al. study (
19). The findings of our study demonstrate that MMT improves nutritional status. Weight gain in methadone-maintenance patients has been documented in previous studies, and this may be derived from increasing fat body mass (
14,
18). It might also partly be due to adipose tissue-derived hormones, such as leptin, which are related to body fat content (
1). The relationship between education level, employment, marital status and BMI has been reported in earlier studies (
2,
15), but our study differed from the results of Saeland et al. (
5). In our study, the mean levels of weight and BMI were higher in educated subjects who lived with a partner, compared to the others, while employment status showed no significant difference between the two groups (data not shown). Usually, the presence of someone in the house who prepares meals seems to help the patient’s motivation to eat. So, healthcare professionals should pay more attention to the social problems of these patients (
1). Although there was some evidence concerning the association between anthropometric and socio-demographic characteristics with drug use and MMT, so far only a little data has been made available on the particular factors of MMT. Thus, future studies will be necessary to assess the impact of other factors, such as food behavior, dietary intake, carbohydrate craving, exercise, adipocyte-derived hormones and non-dietary determinants of nutritional status in the opioid-using population. Opioid abuse was associated with increased numbers of underweight patients. Substitution treatment of Opioid dependency with methadone led to improvements in the nutritional status by means of decreasing the numbers who were underweight. Limitations of this study which need to be given more attention in the future include: 1) Longer study duration, this may give a much better therapeutic evaluation of the intervention. 2) Measurement of adipose tissue-derived hormones, which are related to body fat content such; as leptin and adiponectin. 3) Evaluation of nutritional status based on nutrient intake and, 4) the selection of a control group.