A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN HUMAN NUTRITION OF SOKOINE UNIVERSITY OF AGRICULTURE. MOROGORO, TANZANIA.Obesity is a condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy. It is one of the most serious public health problems of the 21st century. This study was carried out to determine diet quality and dietary diversity among overweight and obese adults aged 40 years and above working in public and private institutions in Morogoro Municipality. A cross sectional study was conducted in which data were collected once to determine the diet quality and dietary diversity in 288 individuals. Dietary diversity was determined by using a validated 24 hours recall method. Anthropometric measurements of weight and height were measured by using Salter scale and stadiometer, respectively, while waist and hip circumferences were measured by using non-stretchable tape measure. Structured questionnaire was used to collect social-economic and demographic information of the subjects. Data were coded and analyzed by IBM Statistical Product for Service Solution (SPSS) program, version 20. Results showed that, prevalence of overweight was higher (P=0.005) among males (41%, n = 118) than females (22.1%, n = 64) while prevalence of obesity was higher (P = 0.005) among females (26.7%, n = 77) than males (10.1%, n = 29). The average dietary diversity score for the study sample was 5.51 ± 1.056 and no significant association was observed between Dietary Diversity Score (DDS) and Body Mass Index (BMI) of the respondents (P = 0.280). Dietary quality score of the subjects using Diet Quality Index-Revised (DQI-R) was low since they were related to high fat consumption, low fruits and vegetable intakes, and low iron and calcium intakes. There was a strong association (P = 0.000) between diet quality index and BMI of the respondents. Most of the participants in the study (> 80%) had daily energy intakes ranging from 1634.73 to 3598.00 kcal. The average energy intake for both males and females was 2318.18 kcal. Despite most subjects being literate, majority of them were not aware of dietary diversity, diet quality and the health problems that could result from poor dietary diversity. It was concluded from the study that overweight and obesity together with unhealthy eating practices may play a major role in the future risk for cardio vascular diseases, therefore should be discouraged, also dietary diversity should be encouraged but limiting diets that offer a greater variety of energy-dense foods because could increase food intake and body weight. It was recommended from the study that people should be encouraged to eat healthier foods that are high in energy and nutrients from different food groups such as fruits, vegetables, and or non-refined grain. While discouraging the practice of eating highly refined foods, high sugar confectionery foods such as cakes, biscuits and high fat and low fibre foods.